From 9300ffec887a766b1ccf27198f69f7e5d5e3fb84 Mon Sep 17 00:00:00 2001
From: Valery Kharseko <vharseko@3a-systems.ru>
Date: Tue, 15 Sep 2026 07:24:43 +0000
Subject: [PATCH] [#956] Tell a failed entryUUID search apart from an entry which is not there (#968)

---
 opendj-server-legacy/src/test/java/org/opends/server/replication/plugin/ReplayDuringImportTest.java |  385 ++++++++++++++++
 opendj-server-legacy/src/test/java/org/opends/server/replication/plugin/NamingConflictTest.java     |  555 +++++++++++++++++++++++
 opendj-server-legacy/src/messages/org/opends/messages/replication.properties                        |    4 
 opendj-server-legacy/src/main/java/org/opends/server/replication/plugin/LDAPReplicationDomain.java  |  396 ++++++++++++++--
 opendj-server-legacy/src/test/java/org/opends/server/plugins/ShortCircuitPlugin.java                |   85 +++
 5 files changed, 1,360 insertions(+), 65 deletions(-)

diff --git a/opendj-server-legacy/src/main/java/org/opends/server/replication/plugin/LDAPReplicationDomain.java b/opendj-server-legacy/src/main/java/org/opends/server/replication/plugin/LDAPReplicationDomain.java
index 537e70c..fb908f8 100644
--- a/opendj-server-legacy/src/main/java/org/opends/server/replication/plugin/LDAPReplicationDomain.java
+++ b/opendj-server-legacy/src/main/java/org/opends/server/replication/plugin/LDAPReplicationDomain.java
@@ -496,6 +496,23 @@
   private final InternalClientConnection conn = getRootConnection();
   private final AtomicBoolean shutdown = new AtomicBoolean();
   private volatile boolean disabled;
+  /**
+   * Whether the data of this domain is being replaced by a total update into this replica:
+   * the import streams over the session of this domain, on its listener thread, and the
+   * backend the replay would apply a change to is deregistered for the length of it.
+   * <p>
+   * It is what {@link #disabled} is for an import or a restore run on this server, on the
+   * one road which does not set that flag: {@link #preBackendImport(LocalBackend)} takes
+   * the backend away without disabling the domain, because the domain can not stop the
+   * session it is importing over. The replay threads read it where they read
+   * {@link #disabled}: an attempt made meanwhile is made into no backend, and whatever it
+   * decided is overwritten by the import, so the change is given back instead - without a
+   * session restart, which {@link #sessionHasAnOwner()} refuses for the whole of the total
+   * update. It is set for the length of {@link #importBackend(InputStream)}, so it covers
+   * the reload of the ServerState and the reset of the pending changes which follow the
+   * import.
+   */
+  private volatile boolean importingData;
 
   /**
    * This list is used to temporary store operations that needs to be replayed
@@ -1849,7 +1866,16 @@
        * this operation has already been replayed in the past.
        */
       String uuid = ctx.getEntryUUID();
-      if (findEntryDN(uuid) != null)
+      final DN replayedEntryDN;
+      try
+      {
+        replayedEntryDN = findEntryDN(uuid);
+      }
+      catch (SearchFailedException e)
+      {
+        return searchDidNotRun(ctx.getCSN(), e);
+      }
+      if (replayedEntryDN != null)
       {
         return new SynchronizationProviderResult.StopProcessing(
             ResultCode.NO_OPERATION, null);
@@ -1866,7 +1892,15 @@
       {
         // There is a potential of perfs improvement here
         // if we could avoid the following parent entry retrieval
-        DN parentDnFromCtx = findEntryDN(ctx.getParentEntryUUID());
+        final DN parentDnFromCtx;
+        try
+        {
+          parentDnFromCtx = findEntryDN(ctx.getParentEntryUUID());
+        }
+        catch (SearchFailedException e)
+        {
+          return searchDidNotRun(ctx.getCSN(), e);
+        }
         if (parentDnFromCtx == null)
         {
           // The parent does not exist with the specified unique id
@@ -1894,6 +1928,28 @@
   }
 
   /**
+   * Turns down an operation being replayed whose conflict resolution could not read the
+   * data, so that the change is attempted again rather than applied on what a search
+   * which did not run seemed to say.
+   * <p>
+   * The operation is reported as unavailable, which is what it is, and the search which
+   * did not run is its error message: the change is retried in place, and left out of
+   * the ServerState and asked for again if this server keeps failing to serve the
+   * searches this phase reads the data with (issue #956). Nothing is logged here: this
+   * hook runs on every attempt in place, and the error is reported once, with the
+   * attempt which ended them, where a storage which failed to serve the operation is.
+   *
+   * @param csn the CSN of the change being replayed
+   * @param e the search which did not run
+   * @return the result which stops the operation
+   */
+  private SynchronizationProviderResult searchDidNotRun(CSN csn, SearchFailedException e)
+  {
+    return new SynchronizationProviderResult.StopProcessing(
+        ResultCode.UNAVAILABLE, e.report(csn, getBaseDN()));
+  }
+
+  /**
    * Check that the broker associated to this ReplicationDomain has found
    * a Replication Server and that this LDAP server is therefore able to
    * process operations.
@@ -2730,15 +2786,28 @@
         dependency = remotePendingChanges.checkDependencies(op, msg);
         boolean replayDone = false;
         boolean firstAttempt = true;
+        /*
+         * The search conflict resolution could not run on the last attempt, when it ended
+         * on one: the result code of the operation says nothing of it - it is the conflict
+         * the operation failed on - so the failure of the server below the loop is told
+         * here, and reported there once the attempts are spent.
+         */
+        SearchFailedException searchFailedResolvingConflict = null;
         int retryCount = IN_PLACE_REPLAY_ATTEMPTS;
         while (!dependency && !replayDone && retryCount-- > 0)
         {
           /*
-           * The flag which says this domain is going down is read before the lock as well
-           * as under it. The replay threads are a pool shared by every domain of this
-           * server, so a thread which took a change of a domain which is going down should
-           * not queue behind the wait for that domain: the changes of every other domain
-           * are behind it in the same pool.
+           * What this attempt ends on, not what an earlier one did: an attempt the server
+           * refuses before it reaches the data makes no search, and the verdict below the
+           * loop reads the attempt which spent the last of them.
+           */
+          searchFailedResolvingConflict = null;
+          /*
+           * The flags which say this domain is going down, or that its data is being
+           * replaced, are read before the lock as well as under it. The replay threads are
+           * a pool shared by every domain of this server, so a thread which took a change
+           * of a domain which is going down should not queue behind the wait for that
+           * domain: the changes of every other domain are behind it in the same pool.
            *
            * The read under the lock is the one which decides; the one above it is a
            * scheduling optimisation for the common case and nothing more. It cannot keep
@@ -2746,7 +2815,7 @@
            * between the two reads, and a reader which arrives behind a queued writer blocks
            * even on a lock which is not the fair kind.
            */
-          boolean goingDown = replayThreadShutdown.get() || shutdown.get() || disabled;
+          boolean goingDown = replayThreadShutdown.get() || shutdown.get() || disabled || importingData;
           if (!goingDown)
           {
             /*
@@ -2759,7 +2828,7 @@
             replayReadLock.lock();
             try
             {
-              goingDown = replayThreadShutdown.get() || shutdown.get() || disabled;
+              goingDown = replayThreadShutdown.get() || shutdown.get() || disabled || importingData;
               if (!goingDown)
               {
                 if (!firstAttempt)
@@ -2845,34 +2914,52 @@
                   else
                   {
                     ConflictResolution resolution = ConflictResolution.NOTHING_TO_DO;
-                    if (op instanceof ModifyOperation)
+                    try
                     {
-                      ModifyOperation castOp = (ModifyOperation) op;
-                      dependency = remotePendingChanges.checkDependencies(castOp);
-                      ModifyMsg modifyMsg = (ModifyMsg) msg;
-                      resolution = dependency ? resolution : solveNamingConflict(castOp, modifyMsg);
+                      if (op instanceof ModifyOperation)
+                      {
+                        ModifyOperation castOp = (ModifyOperation) op;
+                        dependency = remotePendingChanges.checkDependencies(castOp);
+                        ModifyMsg modifyMsg = (ModifyMsg) msg;
+                        resolution = dependency ? resolution : solveNamingConflict(castOp, modifyMsg);
+                      }
+                      else if (op instanceof DeleteOperation)
+                      {
+                        DeleteOperation castOp = (DeleteOperation) op;
+                        dependency = remotePendingChanges.checkDependencies(castOp);
+                        resolution = dependency ? resolution : solveNamingConflict(castOp, msg);
+                      }
+                      else if (op instanceof AddOperation)
+                      {
+                        AddOperation castOp = (AddOperation) op;
+                        AddMsg addMsg = (AddMsg) msg;
+                        dependency = remotePendingChanges.checkDependencies(castOp);
+                        resolution = dependency ? resolution : solveNamingConflict(castOp, addMsg);
+                      }
+                      else if (op instanceof ModifyDNOperation)
+                      {
+                        ModifyDNOperation castOp = (ModifyDNOperation) op;
+                        ModifyDNMsg modifyDNMsg = (ModifyDNMsg) msg;
+                        dependency = remotePendingChanges.checkDependencies(modifyDNMsg);
+                        resolution = dependency ? resolution : solveNamingConflict(castOp, modifyDNMsg);
+                      }
+                      // else: unknown type of operation ?! there is nothing to replay
                     }
-                    else if (op instanceof DeleteOperation)
+                    catch (SearchFailedException e)
                     {
-                      DeleteOperation castOp = (DeleteOperation) op;
-                      dependency = remotePendingChanges.checkDependencies(castOp);
-                      resolution = dependency ? resolution : solveNamingConflict(castOp, msg);
+                      /*
+                       * Conflict resolution reads the data with a search of the entryUUID, and
+                       * that search did not run: nothing was decided here, and whether the entry
+                       * is still in the data is not known. Report the failure of the server it
+                       * is rather than let a caller read "no entry" out of a search which never
+                       * answered. It is logged once the attempts in place are spent rather than
+                       * on every one of them, as a storage which failed to serve the operation
+                       * is: a backend which is down for a while fails every attempt of every
+                       * change delivered meanwhile.
+                       */
+                      searchFailedResolvingConflict = e;
+                      resolution = ConflictResolution.SEARCH_FAILED;
                     }
-                    else if (op instanceof AddOperation)
-                    {
-                      AddOperation castOp = (AddOperation) op;
-                      AddMsg addMsg = (AddMsg) msg;
-                      dependency = remotePendingChanges.checkDependencies(castOp);
-                      resolution = dependency ? resolution : solveNamingConflict(castOp, addMsg);
-                    }
-                    else if (op instanceof ModifyDNOperation)
-                    {
-                      ModifyDNOperation castOp = (ModifyDNOperation) op;
-                      ModifyDNMsg modifyDNMsg = (ModifyDNMsg) msg;
-                      dependency = remotePendingChanges.checkDependencies(modifyDNMsg);
-                      resolution = dependency ? resolution : solveNamingConflict(castOp, modifyDNMsg);
-                    }
-                    // else: unknown type of operation ?! there is nothing to replay
 
                     if (!dependency)
                     {
@@ -2886,6 +2973,19 @@
                         recordChangeResolved(csn);
                         break;
 
+                      case SEARCH_FAILED:
+                        /*
+                         * Conflict resolution could not read the data, so the change is not in
+                         * it and nothing was concluded about the entry it targets. Give it the
+                         * in-place attempts a storage which failed gets - a storage busy for a
+                         * moment must not cost a session restart - and leave it out of the
+                         * ServerState once they are spent, which the failure of the server
+                         * below the loop reports and acts on. A change which is not in the data
+                         * must not advance the ServerState (issue #889).
+                         */
+                        Thread.sleep(50);
+                        break;
+
                       case FAILED:
                         if (serverErrorResultCode.equals(result))
                         {
@@ -2980,20 +3080,31 @@
            * is the storage failing to serve the operation. The result of that attempt is
            * what decides, so that this branch reports the failure it is acting on: an
            * attempt which ended on something conflict resolution kept rewriting is the
-           * loop below, however the attempts before it ended.
+           * loop below, however the attempts before it ended. So is an attempt whose
+           * conflict resolution could not read the data, which the attempt itself says
+           * rather than its result code: that one is the conflict the operation failed
+           * on, not the search which did not run (issue #956).
            */
           if (isServerFailure(lastResult, serverErrorResultCode)
               || ResultCode.BUSY.equals(lastResult)
-              || serverErrorResultCode.equals(lastResult))
+              || serverErrorResultCode.equals(lastResult)
+              || searchFailedResolvingConflict != null)
           {
             /*
              * The server kept failing to apply the change, so the change is not in the data.
              * Leave it out of the ServerState, otherwise the replication server would never
              * send it again and this replica would silently diverge while reporting itself
              * up to date.
+             *
+             * The error reported is the operation's, unless the attempt ended on a search
+             * conflict resolution could not run: the operation then only says which conflict
+             * it failed on, and the search is what failed.
              */
+            final Object error = searchFailedResolvingConflict != null
+                ? searchFailedResolvingConflict.report(csn, getBaseDN())
+                : op.getErrorMessage();
             final LocalizableMessage message = ERR_ERROR_REPLAYING_OPERATION.get(
-                op, csn, lastResult, op.getErrorMessage());
+                op, csn, lastResult, error);
             logger.error(message);
             replayErrorMsg = message.toString();
             replayFailed = true;
@@ -3214,8 +3325,9 @@
        */
       if (replayFailed && recoverFromReplayFailure(msg.getCSN(), replayThreadShutdown))
       {
-        // The ack has been published and the change, still owned by the replication
-        // server, is being delivered again: there is nothing left to replay here.
+        // The ack has been published and the change is given back: the replication server
+        // delivers it again, now or - while a total update owns the session - after the
+        // import restarts it. There is nothing left to replay here.
         return;
       }
 
@@ -3524,13 +3636,19 @@
      */
     remotePendingChanges.replayFailed(csn);
 
-    if (shutdown.get() || disabled)
+    if (sessionHasAnOwner())
     {
       /*
        * This whole domain is going away or is being imported into: there is no session of
        * this thread's to restart. Restarting the one which is being stopped would leave a
        * broker and a listener thread behind on a domain whose alert generator, flush
-       * thread and RSUpdater are already gone.
+       * thread and RSUpdater are already gone; restarting the one an import streams over
+       * would end the import on the entries which had arrived. The change given back here
+       * is forgotten with the rest of the pending changes when the ServerState is loaded
+       * again, from the backend or from the imported data, and the session started then
+       * asks for everything that state does not cover - or, when the total update it was
+       * given back for never begins, it is asked for by the next restart
+       * (see sessionHasAnOwner()).
        */
       return true;
     }
@@ -3642,9 +3760,10 @@
   private void abandonReplay(CSN csn)
   {
     remotePendingChanges.replayFailed(csn);
-    if (shutdown.get() || disabled)
+    if (sessionHasAnOwner())
     {
-      // The domain owns its session, and it forgets its pending changes on its way down.
+      // The domain, or the import into it, owns its session, and the pending changes are
+      // forgotten with the ServerState on its way down or at the end of the import.
       return;
     }
     /*
@@ -3666,9 +3785,10 @@
     final long stoppedSession;
     synchronized (serviceStateLock)
     {
-      if (ownsItsSession())
+      if (sessionHasAnOwner())
       {
-        // The domain is going away or is being imported into: it owns its session.
+        // The domain is going away or is being imported into: the session is not this
+        // thread's to stop.
         return;
       }
       disableService();
@@ -3694,6 +3814,11 @@
          * import - in the meantime: the session this thread stopped is gone, so it has
          * nothing left to start. Every stop and every start of a session is counted, so
          * the generation alone tells one session from another.
+         *
+         * An import is not asked about here: the session it would stream over is the one
+         * this thread stopped, so none is streaming, and a total update which was asked
+         * for meanwhile needs the session started back to be answered at all - its
+         * request is what fails, and loudly, when no answer comes.
          */
         return;
       }
@@ -3782,24 +3907,79 @@
    * @param uuid the Entry Unique ID.
    * @return The current DN of the entry or null if there is no entry with
    *         the specified UUID.
+   * @throws SearchFailedException if the search did not run, so that whether there is
+   *         such an entry is not known
    */
-  private DN findEntryDN(String uuid)
+  private DN findEntryDN(String uuid) throws SearchFailedException
   {
+    if (uuid == null)
+    {
+      // A change which carries no entryUUID names no entry.
+      return null;
+    }
+    /*
+     * The entryUUID comes off the wire and nothing validates it as one, so it is looked up
+     * as the value it is rather than read as part of a filter string: a value which
+     * carried a wildcard would be read as a substring filter, and one which did not parse
+     * - a dangling escape - would be a search which never runs, for as long as the change
+     * is asked for.
+     */
+    final SearchFilter filter = SearchFilter.createEqualityFilter(
+        getServerContext().getSchema().getAttributeType(ENTRYUUID_ATTRIBUTE_NAME),
+        ByteString.valueOfUtf8(uuid));
+    final InternalSearchOperation search =
+        conn.processSearch(newSearchRequest(getBaseDN(), SearchScope.WHOLE_SUBTREE, filter));
+    if (search.getResultCode() != ResultCode.SUCCESS)
+    {
+      if (search.getResultCode() == ResultCode.NO_SUCH_OBJECT && baseEntryIsAbsentFromALiveBackend())
+      {
+        /*
+         * The backend serves the base DN and has no base entry yet: the search ran, and
+         * nothing is below a base entry which is not there. This is the empty replica
+         * about to receive it.
+         */
+        return null;
+      }
+      /*
+       * The search did not run - the backend is offline or being rebuilt, or the storage
+       * failed to serve it - so it read nothing of the data: an entry it did not report
+       * is not an entry which is not there.
+       */
+      throw new SearchFailedException(uuid, search.getResultCode().getName() + " " + search.getErrorMessage());
+    }
+    final SearchResultEntry resultEntry = getFirstResult(search);
+    return resultEntry != null ? resultEntry.getName() : null;
+  }
+
+  /**
+   * Returns whether the backend which serves the base DN of this domain is there and
+   * holds no base entry, which is the state of an empty replica.
+   * <p>
+   * A search under the base DN of such a backend answers NO_SUCH_OBJECT, which is the
+   * answer of a backend which is offline or being rebuilt as well - and no backend
+   * answers SUCCESS with no entry for a base which is not there. The backend itself
+   * tells the two apart: the search ran over a backend which is there and empty, and it
+   * did not run over one which is gone or fails to answer.
+   *
+   * @return {@code true} if the backend is there and holds no base entry
+   */
+  private boolean baseEntryIsAbsentFromALiveBackend()
+  {
+    final LocalBackend<?> backend = getBackend();
+    if (backend == null)
+    {
+      // Nothing serves the base DN: the backend is offline or being rebuilt.
+      return false;
+    }
     try
     {
-      final SearchRequest request = newSearchRequest(getBaseDN(), SearchScope.WHOLE_SUBTREE, "entryuuid=" + uuid);
-      InternalSearchOperation search = conn.processSearch(request);
-      final SearchResultEntry resultEntry = getFirstResult(search);
-      if (resultEntry != null)
-      {
-        return resultEntry.getName();
-      }
+      return !backend.entryExists(getBaseDN());
     }
     catch (DirectoryException e)
     {
-      // never happens because the filter is always valid.
+      // The storage did not answer this any more than it answered the search.
+      return false;
     }
-    return null;
   }
 
   /** Outcome of the conflict resolution attempted after a replayed operation failed. */
@@ -3809,18 +3989,61 @@
     REPLAY_AGAIN,
     /** The change is already reflected in the data: there is nothing left to replay. */
     NOTHING_TO_DO,
+    /**
+     * The search conflict resolution reads the data with did not run: nothing was
+     * decided, and the operation has to be attempted again.
+     */
+    SEARCH_FAILED,
     /** The operation failed for a reason which is not a naming conflict. */
     FAILED
   }
 
   /**
+   * Reports a search conflict resolution reads the data with and which did not run: it
+   * read nothing, so its result is no evidence about the data.
+   * <p>
+   * A search which failed and a search which found nothing look the same to a caller
+   * which only reads the entries it returned, and every caller here reads "no entry" as
+   * "the entry has been deleted": that answers {@link ConflictResolution#NOTHING_TO_DO},
+   * which records a change that was never applied as replayed, and the replication server
+   * never sends a change again which this replica reports itself past (issue #956).
+   */
+  private static final class SearchFailedException extends Exception
+  {
+    private static final long serialVersionUID = 1L;
+
+    /** The entryUUID the search which did not run was looking for. */
+    private final String entryUUID;
+
+    private SearchFailedException(String entryUUID, String cause)
+    {
+      super(cause);
+      this.entryUUID = entryUUID;
+    }
+
+    /**
+     * Describes the search which did not run for the change it was made for.
+     *
+     * @param csn the CSN of the change being replayed
+     * @param baseDN the base DN of the domain the change belongs to
+     * @return the error to report the change with
+     */
+    private LocalizableMessage report(CSN csn, DN baseDN)
+    {
+      return ERR_REPLAY_ENTRYUUID_SEARCH_FAILED.get(csn, baseDN, entryUUID, getMessage());
+    }
+  }
+
+  /**
    * Solve a conflict detected when replaying a modify operation.
    *
    * @param op The operation that triggered the conflict detection.
    * @param msg The operation that triggered the conflict detection.
    * @return the outcome of the conflict resolution
+   * @throws SearchFailedException if the data could not be read
    */
   private ConflictResolution solveNamingConflict(ModifyOperation op, ModifyMsg msg)
+      throws SearchFailedException
   {
     ResultCode result = op.getResultCode();
     ModifyContext ctx = (ModifyContext) op.getAttachment(SYNCHROCONTEXT);
@@ -3905,8 +4128,10 @@
   * @param op The operation that triggered the conflict detection.
   * @param msg The operation that triggered the conflict detection.
   * @return the outcome of the conflict resolution
+  * @throws SearchFailedException if the data could not be read
   */
  private ConflictResolution solveNamingConflict(DeleteOperation op, LDAPUpdateMsg msg)
+     throws SearchFailedException
  {
    ResultCode result = op.getResultCode();
    DeleteContext ctx = (DeleteContext) op.getAttachment(SYNCHROCONTEXT);
@@ -4403,11 +4628,12 @@
    * Waits for the replay threads which are applying a change of this domain to be done
    * with it.
    * <p>
-   * Called once {@link #disabled} or {@link #shutdown} has been set, which is what bounds
-   * the wait: a replay thread reads those under {@link #replayReadLock}, the lock this
-   * takes exclusively, so no attempt starts once this returns and what it waits for is the
-   * attempts which were running already. The lock is released before returning for the
-   * same reason - what keeps the replay out is the flag, not the lock.
+   * Called once {@link #disabled}, {@link #shutdown} or {@link #importingData} has been
+   * set, which is what bounds the wait: a replay thread reads those under
+   * {@link #replayReadLock}, the lock this takes exclusively, so no attempt starts once
+   * this returns and what it waits for is the attempts which were running already. The
+   * lock is released before returning for the same reason - what keeps the replay out is
+   * the flag, not the lock.
    */
   private void awaitReplayDrained()
   {
@@ -4936,6 +5162,16 @@
     ImportExportContext ieCtx = getImportExportContext();
     try
     {
+      /*
+       * The replay of this domain is held off before the backend is taken away, the way
+       * disable() holds it off before the backend is taken away for an import run on this
+       * server: the flag keeps the attempts which have not started from starting, and the
+       * wait is for the ones which had. What this road can not do is stop the session -
+       * it is the session the entries are about to stream over, on this very thread.
+       */
+      importingData = true;
+      awaitReplayDrained();
+
       if (!backend.supports(BackendOperation.LDIF_IMPORT))
       {
         ieCtx.setExceptionIfNoneSet(new DirectoryException(OTHER,
@@ -5001,6 +5237,25 @@
             ResultCode.OTHER,
             ERR_INIT_IMPORT_FAILURE.get(stackTraceToSingleLineString(fe))));
       }
+      finally
+      {
+        /*
+         * The ServerState in memory is the one read from the data now, and the changes
+         * listed as pending must not outlive the one they went with, as they do not when
+         * the domain is disabled: a change given back while the import ran would stay
+         * listed, uncommitted and owned by nobody, and a commit stops at the first
+         * uncommitted change - the state would never move past it, and the replication
+         * server does not send a change again which the state it is given covers. Nothing
+         * listed a change meanwhile: the listener thread is the one running this import,
+         * and the replay threads gave up every attempt while the flag was set. The restart
+         * a replay thread may have asked for before the total update owned the session
+         * goes with them: the caller starts the session again from the reloaded state.
+         */
+        remotePendingChanges.clear();
+        sessionRestartRequested.set(false);
+        consecutiveSessionRestarts.set(0);
+        importingData = false;
+      }
     }
 
     if (ieCtx.getException() != null)
@@ -5276,6 +5531,29 @@
     return shutdown.get() || disabled;
   }
 
+  /**
+   * Whether the session of this domain has an owner other than the replay thread which
+   * would restart it after a failed replay: the domain itself, when it is shutting down or
+   * disabled ({@link #ownsItsSession()}), or a total update into this replica.
+   * <p>
+   * The total update owns the session from the moment it is asked for, not from the
+   * moment its entries stream: the {@code InitializeTargetMsg} which answers the request
+   * arrives over that session, so a restart made while it is on its way loses it, and the
+   * import which follows reads its entries over the same session - stopping it ends the
+   * import on the entries which had arrived. The import starts the next session itself,
+   * from the state it loaded. A change given back while the total update owned the session
+   * is not asked for again by anyone until then; if no import follows - the request was
+   * refused, or gave up waiting - it stays listed until the next failed replay restarts
+   * the session, which has the replication server send it again with everything after it.
+   * Listed, it holds the ServerState back as well: a commit moves the state no further than
+   * the oldest uncommitted change, so the state in memory, and the one persisted from it,
+   * stop at the change until that restart.
+   */
+  private boolean sessionHasAnOwner()
+  {
+    return ownsItsSession() || importInProgress();
+  }
+
   @Override
   protected void restartService()
   {
diff --git a/opendj-server-legacy/src/messages/org/opends/messages/replication.properties b/opendj-server-legacy/src/messages/org/opends/messages/replication.properties
index fe6c496..f839681 100644
--- a/opendj-server-legacy/src/messages/org/opends/messages/replication.properties
+++ b/opendj-server-legacy/src/messages/org/opends/messages/replication.properties
@@ -686,3 +686,7 @@
  the domain is shutting down, or it is disabled for the length of a total update. The change is \
  stored and takes effect when the session is started again, which a domain left disabled by a \
  failed import or restore never does
+ERR_REPLAY_ENTRYUUID_SEARCH_FAILED_322=Could not read the data to check change %s for a conflict \
+ in domain "%s": the search of the entry with entryUUID %s did not run (%s). The change is not \
+ applied on what a search which read nothing seemed to say about the data, and is not recorded \
+ as replayed
diff --git a/opendj-server-legacy/src/test/java/org/opends/server/plugins/ShortCircuitPlugin.java b/opendj-server-legacy/src/test/java/org/opends/server/plugins/ShortCircuitPlugin.java
index f61b23d..786fce9 100644
--- a/opendj-server-legacy/src/test/java/org/opends/server/plugins/ShortCircuitPlugin.java
+++ b/opendj-server-legacy/src/test/java/org/opends/server/plugins/ShortCircuitPlugin.java
@@ -644,16 +644,18 @@
     // Check for registered short circuits.
     final String key = keyFor(operation.getOperationType(), section);
     Integer resultCode = shortCircuits.get(key);
-    if (resultCode != null)
+    if (resultCode != null && appliesTo(key, operation))
     {
       final int reached = shortCircuitCounts.computeIfAbsent(key, k -> new AtomicInteger()).incrementAndGet();
+      final int letThroughFirst = shortCircuitSkips.getOrDefault(key, 0);
       final Integer maxTimes = shortCircuitLimits.get(key);
-      if (maxTimes == null || reached <= maxTimes)
+      if (reached > letThroughFirst && (maxTimes == null || reached <= letThroughFirst + maxTimes))
       {
         return resultCode;
       }
-      // The short circuit was applied as many times as it was asked for: from now on the
-      // operations are let through, which is how a transient failure is simulated.
+      // The operations before the short circuit are let through, and so are the ones after
+      // it was applied as many times as it was asked for: this is how a transient failure
+      // which starts, or ends, part way through a sequence of operations is simulated.
     }
 
     /*
@@ -740,6 +742,23 @@
   /** How many times a registered short circuit must be applied, when it is limited. */
   private static final Map<String, Integer> shortCircuitLimits = new ConcurrentHashMap<>();
 
+  /** How many operations a registered short circuit lets through before it applies. */
+  private static final Map<String, Integer> shortCircuitSkips = new ConcurrentHashMap<>();
+
+  /**
+   * Which operations a registered short circuit is for, when it is not for every operation
+   * of its type: the ones it is not for are neither short circuited nor counted.
+   */
+  private static final Map<String, Predicate<PluginOperation>> shortCircuitFilters =
+      new ConcurrentHashMap<>();
+
+  /** Returns whether the short circuit registered under the given key is for the given operation. */
+  private static boolean appliesTo(String key, PluginOperation operation)
+  {
+    final Predicate<PluginOperation> filter = shortCircuitFilters.get(key);
+    return filter == null || filter.test(operation);
+  }
+
   /**
    * Returns how many times the short circuit registered for the given operation type and
    * plugin point was reached. A short circuit registered for a limited number of times is
@@ -765,10 +784,13 @@
   public static void registerShortCircuit(OperationType operation, String section, int resultCode)
   {
     final String key = keyFor(operation, section);
-    // This registration applies to every operation, and it counts from zero: a limit or
-    // a count left behind by a previous registration is not part of it.
+    // This registration applies to every operation, and it counts from zero: a limit, a
+    // number of operations let through or a count left behind by a previous registration
+    // is not part of it.
     shortCircuitCounts.remove(key);
     shortCircuitLimits.remove(key);
+    shortCircuitSkips.remove(key);
+    shortCircuitFilters.remove(key);
     shortCircuits.put(key, resultCode);
   }
 
@@ -783,13 +805,62 @@
    */
   public static void registerShortCircuit(OperationType operation, String section, int resultCode, int maxTimes)
   {
+    registerShortCircuit(operation, section, resultCode, 0, maxTimes);
+  }
+
+  /**
+   * Register a short circuit which lets the given number of operations through before it
+   * applies, then applies to the given number of operations, the ones which follow being
+   * let through again: this is how a transient failure which starts part way through a
+   * sequence of operations is simulated - the second search of an attempt failing while
+   * the first one ran, say.
+   *
+   * @param operation The type of operation the short circuit applies to.
+   * @param section The plugin point the short circuit applies to.
+   * @param resultCode The result code to be returned for the short circuit.
+   * @param letThroughFirst How many operations must be let through before the short
+   *                        circuit applies.
+   * @param maxTimes How many operations must be short circuited after them.
+   */
+  public static void registerShortCircuit(OperationType operation, String section, int resultCode,
+      int letThroughFirst, int maxTimes)
+  {
     final String key = keyFor(operation, section);
     shortCircuitCounts.remove(key);
+    shortCircuitFilters.remove(key);
+    shortCircuitSkips.put(key, letThroughFirst);
     shortCircuitLimits.put(key, maxTimes);
     shortCircuits.put(key, resultCode);
   }
 
   /**
+   * Register a short circuit like
+   * {@link #registerShortCircuit(OperationType, String, int, int, int)}, for some of the
+   * operations of the given type only: the ones the predicate does not accept are let
+   * through without being counted, as if the short circuit were not there.
+   * <p>
+   * The operations of one type which reach a plugin point are not all the test's: the
+   * server makes internal operations of its own on its own schedule - the ServerState flush
+   * thread of a replication domain writes the base entry with a Modify on its tick, say -
+   * and a short circuit which counts them takes a let-through, or a refusal, meant for the
+   * operation the test is driving. A test which counts its operations one by one names them.
+   *
+   * @param operation The type of operation the short circuit applies to.
+   * @param section The plugin point the short circuit applies to.
+   * @param resultCode The result code to be returned for the short circuit.
+   * @param letThroughFirst How many of the operations the predicate accepts must be let
+   *                        through before the short circuit applies.
+   * @param maxTimes How many of them must be short circuited after those.
+   * @param appliesTo Which operations of that type the short circuit is for.
+   */
+  public static void registerShortCircuit(OperationType operation, String section, int resultCode,
+      int letThroughFirst, int maxTimes, Predicate<PluginOperation> appliesTo)
+  {
+    registerShortCircuit(operation, section, resultCode, letThroughFirst, maxTimes);
+    shortCircuitFilters.put(keyFor(operation, section), appliesTo);
+  }
+
+  /**
    * Deregister a short circuit for the given operation type and plugin point.
    * @param operation The type of operation the short circuit applies to.
    * @param section The plugin point the short circuit applies to.
@@ -799,6 +870,8 @@
     final String key = keyFor(operation, section);
     shortCircuits.remove(key);
     shortCircuitLimits.remove(key);
+    shortCircuitSkips.remove(key);
+    shortCircuitFilters.remove(key);
     // The count belongs to the registration which is being removed: a test which counts
     // the operations it short circuits must not inherit the count of the previous one.
     shortCircuitCounts.remove(key);
diff --git a/opendj-server-legacy/src/test/java/org/opends/server/replication/plugin/NamingConflictTest.java b/opendj-server-legacy/src/test/java/org/opends/server/replication/plugin/NamingConflictTest.java
index cb74306..29659d1 100644
--- a/opendj-server-legacy/src/test/java/org/opends/server/replication/plugin/NamingConflictTest.java
+++ b/opendj-server-legacy/src/test/java/org/opends/server/replication/plugin/NamingConflictTest.java
@@ -18,11 +18,14 @@
 package org.opends.server.replication.plugin;
 
 import static org.assertj.core.api.Assertions.*;
+import static org.opends.messages.ReplicationMessages.*;
 import static org.opends.server.TestCaseUtils.*;
 import static org.opends.server.core.DirectoryServer.*;
 import static org.opends.server.protocols.internal.InternalClientConnection.*;
 import static org.testng.Assert.*;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.TreeSet;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -33,6 +36,8 @@
 import org.opends.server.TestCaseUtils;
 import org.opends.server.core.DirectoryServer;
 import org.opends.server.core.ModifyDNOperation;
+import org.opends.server.core.ModifyOperationBasis;
+import org.opends.server.plugins.ShortCircuitPlugin;
 import org.opends.server.replication.ReplicationTestCase;
 import org.opends.server.replication.common.CSN;
 import org.opends.server.replication.common.CSNGenerator;
@@ -40,8 +45,11 @@
 import org.opends.server.replication.protocol.DeleteMsg;
 import org.opends.server.replication.protocol.LDAPUpdateMsg;
 import org.opends.server.replication.protocol.ModifyDNMsg;
+import org.opends.server.replication.protocol.ModifyMsg;
+import org.opends.server.replication.protocol.OperationContext;
 import org.opends.server.replication.protocol.UpdateMsg;
 import org.opends.server.types.Entry;
+import org.opends.server.types.OperationType;
 import org.testng.annotations.AfterMethod;
 import org.testng.annotations.BeforeMethod;
 import org.testng.annotations.Test;
@@ -52,6 +60,10 @@
 {
   private static final AtomicBoolean SHUTDOWN = new AtomicBoolean(false);
 
+  /** The monitor attributes which count the naming conflicts a domain solved, and did not. */
+  private static final String RESOLVED_NAMING_CONFLICTS = "resolved-naming-conflicts";
+  private static final String UNRESOLVED_NAMING_CONFLICTS = "unresolved-naming-conflicts";
+
   private DN baseDN;
   private LDAPReplicationDomain domain;
   private CSNGenerator gen;
@@ -245,6 +257,531 @@
   }
 
   /**
+   * Test case for [Issue 956]: conflict resolution reads the data with a search of the
+   * entryUUID, and a search which did not run is no evidence about the data - the entry
+   * it did not report is not an entry which was deleted.
+   * <p>
+   * The change replayed here was made on the master under a DN this replica does not
+   * have: the entry lives under another one, the way it does after a rename which was
+   * replayed first, and only the entryUUID search finds it. So the change is applied
+   * only if that search is given another chance once the storage serves it again.
+   * Reading its failure as "the entry has been deleted" answers NOTHING_TO_DO, which
+   * records the change as replayed and loses it for good - the replication server never
+   * sends a change this replica reports itself past.
+   */
+  @Test
+  public void modifyIsRetriedWhileTheEntryUUIDSearchCanNotRun() throws Exception
+  {
+    final Entry entry = createAndAddEntry("modifyWhoseSearchCanNotRun");
+    final String entryUUID = getEntryUUID(entry.getName());
+    final String phoneNumber = "01 02 45";
+
+    // The DN the change carries is the one the entry had on the master. Here the entry
+    // is the one which was just added, which only the entryUUID search finds.
+    final DN staleDN = DN.valueOf("cn=movedAway," + TEST_ROOT_DN_STRING);
+    final CSN csn = gen.newCSN();
+
+    /*
+     * The storage does not serve the search for the first attempts and serves it after
+     * them: a failure which lasts less than the attempts made in place, the way a
+     * backend which is being rebuilt or a connection which was lost does. The short
+     * circuit is put in force right before the replay and dropped right after it - it
+     * applies to every search of this server while it is registered, and the replay
+     * here runs on this thread.
+     */
+    ShortCircuitPlugin.registerShortCircuit(
+        OperationType.SEARCH, "PreParse", ResultCode.UNAVAILABLE.intValue(), 2);
+    try
+    {
+      replayMsg(new ModifyMsg(csn, staleDN, generatemods("telephonenumber", phoneNumber), entryUUID));
+      assertShortCircuitSpentBy(2);
+    }
+    finally
+    {
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.SEARCH, "PreParse");
+    }
+
+    final Entry replayedEntry = DirectoryServer.getEntry(entry.getName());
+    assertEquals(replayedEntry.parseAttribute("telephonenumber").asString(), phoneNumber,
+        "the change was not applied: a search which could not run was read as a deleted entry");
+    assertTrue(domain.getServerState().cover(csn),
+        "a change which was applied must be recorded as replayed");
+  }
+
+  /**
+   * Test case for [Issue 956]: the entryUUID searches which check a replayed Add for a
+   * conflict read the data the same way, and a search which did not run is no evidence
+   * about it either. The first of them checks whether the Add was replayed here already.
+   * <p>
+   * The Add is delivered a second time - the replication server sends again what a
+   * replica does not report itself past - and the entry was renamed here since it was
+   * added: only the entryUUID search finds it. An entry that search did not report is
+   * not an entry which is not there: reading it that way adds the entry a second time,
+   * under its former DN, and the data holds one entryUUID twice.
+   */
+  @Test
+  public void addIsNotReplayedTwiceWhileTheEntryUUIDSearchCanNotRun() throws Exception
+  {
+    final Entry entry = createAndAddEntry("addWhoseSearchCanNotRun");
+    final String entryUUID = getEntryUUID(entry.getName());
+    final RDN renamedRDN = RDN.valueOf("cn=renamedAfterTheAdd");
+    final ModifyDNOperation rename =
+        getRootConnection().processModifyDN(entry.getName(), renamedRDN, true);
+    assertEquals(rename.getResultCode(), ResultCode.SUCCESS);
+    final CSN csn = gen.newCSN();
+
+    // The first attempt fails its first search; the second attempt has it served.
+    ShortCircuitPlugin.registerShortCircuit(
+        OperationType.SEARCH, "PreParse", ResultCode.UNAVAILABLE.intValue(), 1);
+    try
+    {
+      replayMsg(addMsg(entry, csn, getEntryUUID(baseDN), entryUUID));
+      assertShortCircuitSpentBy(1);
+    }
+    finally
+    {
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.SEARCH, "PreParse");
+    }
+
+    assertFalse(entryExists(entry.getName()),
+        "the entry was added a second time: a search which could not run was read as an "
+            + "Add which was not replayed here yet");
+    assertTrue(entryExists(baseDN.child(renamedRDN)), "the renamed entry is gone");
+    assertTrue(domain.getServerState().cover(csn),
+        "a change which is in the data must be recorded as replayed");
+  }
+
+  /**
+   * Test case for [Issue 956]: the search which checks that the parent of a replayed
+   * Add is still the one the change was made under fails, and the one before it - the
+   * check that the Add was not replayed here already - ran.
+   * <p>
+   * A parent that search did not report is not a parent which was deleted: the Add is
+   * attempted again once the storage serves the search, and no naming conflict is
+   * counted for a search which read nothing. Reading it as a parent which is gone hands
+   * the Add to conflict resolution as the naming conflict it is not - and renames the
+   * entry under the base DN as a conflicting entry, a divergence which is left for an
+   * administrator to repair by hand, when the search conflict resolution makes fails as
+   * well.
+   */
+  @Test
+  public void addIsRetriedWhileTheParentEntryUUIDSearchCanNotRun() throws Exception
+  {
+    final Entry parent = addParentEntry("addWhoseParentSearchCanNotRun");
+    final String parentUUID = getEntryUUID(parent.getName());
+    final Entry child = makeChildEntry("addedWhileTheParentSearchFailed", parent.getName());
+    final CSN csn = gen.newCSN();
+    final long resolvedConflicts = getMonitorAttrValue(baseDN, RESOLVED_NAMING_CONFLICTS);
+    final long unresolvedConflicts = getMonitorAttrValue(baseDN, UNRESOLVED_NAMING_CONFLICTS);
+
+    /*
+     * The first search of the first attempt - the check for an Add replayed already - is
+     * let through, the parent check right after it fails, and every search after that
+     * one is served. A parent search read as a parent which is gone hands the Add to
+     * conflict resolution, whose own search finds the parent where it was and rewrites
+     * the message to the DN the Add already carries: the entry lands where it should
+     * either way, and what tells the two apart is the naming conflict counted for a
+     * search which read nothing.
+     */
+    ShortCircuitPlugin.registerShortCircuit(
+        OperationType.SEARCH, "PreParse", ResultCode.UNAVAILABLE.intValue(), 1, 1);
+    try
+    {
+      replayMsg(addMsg(child, csn, parentUUID, "1c3c2c4d-2b5e-4b9f-8a7c-3d5e6f7a8b9c"));
+      assertShortCircuitSpentBy(2);
+    }
+    finally
+    {
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.SEARCH, "PreParse");
+    }
+
+    assertTrue(entryExists(child.getName()),
+        "the entry was not added under its parent: a parent search which could not run "
+            + "was read as a parent which is gone");
+    assertTrue(domain.getServerState().cover(csn),
+        "a change which was applied must be recorded as replayed");
+    assertEquals(getMonitorAttrValue(baseDN, RESOLVED_NAMING_CONFLICTS), resolvedConflicts,
+        "a search which did not run is not a naming conflict which was resolved");
+    assertEquals(getMonitorAttrValue(baseDN, UNRESOLVED_NAMING_CONFLICTS), unresolvedConflicts,
+        "a search which did not run is not a naming conflict which could not be resolved");
+  }
+
+  /**
+   * Test case for [Issue 956]: the search conflict resolution reads the data with once a
+   * replayed Add failed on a genuine conflict fails, and the checks before the Add ran.
+   * <p>
+   * The parent of the entry was renamed here, so the Add carries a DN which is not
+   * where the parent is anymore: a conflict which is solved by adding the entry under
+   * the parent's current DN, once the search which finds that DN runs. A search which
+   * did not run is not a parent which is gone, and the conflict is counted once, when
+   * it is solved - not for the search which read nothing.
+   */
+  @Test
+  public void addIsRetriedWhileTheConflictResolutionSearchCanNotRun() throws Exception
+  {
+    final Entry parent = addParentEntry("addWhoseConflictSearchCanNotRun");
+    final String parentUUID = getEntryUUID(parent.getName());
+    final Entry child = makeChildEntry("addedWhileTheConflictSearchFailed", parent.getName());
+    final String entryUUID = "2d4d3d5e-3c6f-4ca0-9b8d-4e6f7a8b9cad";
+    final CSN csn = gen.newCSN();
+
+    final RDN renamedParentRDN = RDN.valueOf("ou=renamedBeforeTheAdd");
+    final ModifyDNOperation renameParent =
+        getRootConnection().processModifyDN(parent.getName(), renamedParentRDN, true);
+    assertEquals(renameParent.getResultCode(), ResultCode.SUCCESS);
+    final DN expectedDN = baseDN.child(renamedParentRDN).child(child.getName().rdn());
+    final long resolvedConflicts = getMonitorAttrValue(baseDN, RESOLVED_NAMING_CONFLICTS);
+    final long unresolvedConflicts = getMonitorAttrValue(baseDN, UNRESOLVED_NAMING_CONFLICTS);
+
+    /*
+     * The two searches which check the Add before it runs are let through - they find
+     * the parent under its new DN, which is what fails the Add on a conflict - and the
+     * search conflict resolution then reads the data with is the one which fails. The
+     * next attempt has every search served.
+     */
+    ShortCircuitPlugin.registerShortCircuit(
+        OperationType.SEARCH, "PreParse", ResultCode.UNAVAILABLE.intValue(), 2, 1);
+    try
+    {
+      replayMsg(addMsg(child, csn, parentUUID, entryUUID));
+      assertShortCircuitSpentBy(3);
+    }
+    finally
+    {
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.SEARCH, "PreParse");
+    }
+
+    assertTrue(entryExists(expectedDN),
+        "the entry was not added under the current DN of its parent: a search which could "
+            + "not run was read as a parent which is gone");
+    // A parent read as gone puts the entry under the base DN as a conflicting entry, with
+    // its entryUUID added to its RDN.
+    assertFalse(entryExists(DN.valueOf(
+            "entryuuid=" + entryUUID + "+" + child.getName().rdn() + "," + TEST_ROOT_DN_STRING)),
+        "the entry was renamed under the base DN as a conflicting entry");
+    assertTrue(domain.getServerState().cover(csn),
+        "a change which was applied must be recorded as replayed");
+    assertEquals(getMonitorAttrValue(baseDN, RESOLVED_NAMING_CONFLICTS), resolvedConflicts + 1,
+        "the renamed parent is one naming conflict, solved once the search ran");
+    assertEquals(getMonitorAttrValue(baseDN, UNRESOLVED_NAMING_CONFLICTS), unresolvedConflicts,
+        "a search which did not run is not a naming conflict which could not be resolved");
+  }
+
+  /**
+   * Test case for [Issue 956]: a replayed Delete reads the data with the same search
+   * once it failed on a conflict, and rides on the same retry.
+   * <p>
+   * The entry was renamed here, so the Delete carries a DN which is not the entry's
+   * anymore, and only the entryUUID search finds it. Reading the search's failure as an
+   * entry which was deleted already answers NOTHING_TO_DO: the entry stays, and the
+   * change is recorded as replayed.
+   */
+  @Test
+  public void deleteIsRetriedWhileTheEntryUUIDSearchCanNotRun() throws Exception
+  {
+    final Entry entry = createAndAddEntry("deleteWhoseSearchCanNotRun");
+    final String entryUUID = getEntryUUID(entry.getName());
+    final DN staleDN = DN.valueOf("cn=movedAway," + TEST_ROOT_DN_STRING);
+    final CSN csn = gen.newCSN();
+
+    ShortCircuitPlugin.registerShortCircuit(
+        OperationType.SEARCH, "PreParse", ResultCode.UNAVAILABLE.intValue(), 2);
+    try
+    {
+      replayMsg(new DeleteMsg(staleDN, csn, entryUUID));
+      assertShortCircuitSpentBy(2);
+    }
+    finally
+    {
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.SEARCH, "PreParse");
+    }
+
+    assertFalse(entryExists(entry.getName()),
+        "the entry was not deleted: a search which could not run was read as an entry "
+            + "which was deleted already");
+    assertTrue(domain.getServerState().cover(csn),
+        "a change which was applied must be recorded as replayed");
+  }
+
+  /**
+   * Test case for [Issue 956]: a replayed Modify DN reads the data with the same search
+   * once it failed on a conflict, and rides on the same retry.
+   * <p>
+   * {@code solveNamingConflict(ModifyDNOperation)} declares {@code throws Exception}
+   * rather than the search failure alone, so this is the one path where the failure
+   * reaches the replay loop through a declaration which does not name it.
+   */
+  @Test
+  public void modifyDnIsRetriedWhileTheEntryUUIDSearchCanNotRun() throws Exception
+  {
+    final Entry entry = createAndAddEntry("modifyDnWhoseSearchCanNotRun");
+    final String entryUUID = getEntryUUID(entry.getName());
+    final DN staleDN = DN.valueOf("cn=movedAway," + TEST_ROOT_DN_STRING);
+    final RDN newRDN = RDN.valueOf("cn=renamedWhileTheSearchFailed");
+    final CSN csn = gen.newCSN();
+
+    ShortCircuitPlugin.registerShortCircuit(
+        OperationType.SEARCH, "PreParse", ResultCode.UNAVAILABLE.intValue(), 2);
+    try
+    {
+      replayMsg(new ModifyDNMsg(staleDN, csn, entryUUID, null, false, null, newRDN.toString()));
+      assertShortCircuitSpentBy(2);
+    }
+    finally
+    {
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.SEARCH, "PreParse");
+    }
+
+    assertTrue(entryExists(baseDN.child(newRDN)),
+        "the entry was not renamed: a search which could not run was read as an entry "
+            + "which is not in the data anymore");
+    assertFalse(entryExists(entry.getName()), "the entry kept its former DN");
+    assertTrue(domain.getServerState().cover(csn),
+        "a change which was applied must be recorded as replayed");
+  }
+
+  /**
+   * Test case for [Issue 956], the half which closes [Issue 889] for this path: a
+   * change whose entryUUID search never runs is left out of the ServerState once the
+   * attempts in place are spent, so that the replication server sends it again.
+   * <p>
+   * The result code of every attempt is the conflict the operation failed on, which the
+   * exhaustion exit does not read as a failure of the server: without the attempt itself
+   * telling that its search did not run, the exit reads the attempts as conflict
+   * resolution rewriting an operation which keeps failing, and skips the change - the
+   * CSN is committed, and a change which is not in the data is never asked for again.
+   */
+  @Test
+  public void modifyIsLeftOutOfTheServerStateWhenTheEntryUUIDSearchNeverRuns() throws Exception
+  {
+    final Entry entry = createAndAddEntry("modifyWhoseSearchNeverRuns");
+    final String entryUUID = getEntryUUID(entry.getName());
+    final DN staleDN = DN.valueOf("cn=movedAway," + TEST_ROOT_DN_STRING);
+    final CSN csn = gen.newCSN();
+
+    // No number of times: every attempt in place fails its search.
+    ShortCircuitPlugin.registerShortCircuit(
+        OperationType.SEARCH, "PreParse", ResultCode.UNAVAILABLE.intValue());
+    try
+    {
+      replayMsg(new ModifyMsg(csn, staleDN, generatemods("telephonenumber", "01 02 45"), entryUUID));
+      assertTrue(ShortCircuitPlugin.getShortCircuitCount(OperationType.SEARCH, "PreParse")
+              >= LDAPReplicationDomain.IN_PLACE_REPLAY_ATTEMPTS,
+          "every attempt in place must have made its search");
+    }
+    finally
+    {
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.SEARCH, "PreParse");
+    }
+
+    assertFalse(domain.getServerState().cover(csn),
+        "a change whose search never ran is not in the data and must not advance the ServerState");
+    assertThat(DirectoryServer.getEntry(entry.getName()).getAllAttributes("telephonenumber"))
+        .as("the change was applied to the entry the searches never found").isEmpty();
+    /*
+     * The result code of the last attempt is the conflict the operation failed on, which
+     * says nothing of the search: the line which reports the change must carry the search
+     * which did not run, which is the one thing that names the entryUUID it was made for.
+     */
+    final List<String> reports = exhaustionExitRecordsOf(csn);
+    assertThat(reports).as("the change was not reported once the attempts in place were spent")
+        .isNotEmpty();
+    assertThat(reports)
+        .as("the exhaustion exit reports the error of the operation, not the search which did not run")
+        .allMatch(record -> record.contains(entryUUID));
+  }
+
+  /**
+   * Test case for [Issue 956]: the exhaustion exit reports the attempt which spent the
+   * last of the attempts in place, not an earlier one which ended on a search conflict
+   * resolution could not run.
+   * <p>
+   * The first attempt reaches the data, fails on the conflict, and its search does not
+   * run; the server then refuses every attempt after it before the data is reached. Each
+   * of these is a failure of the server, and the change is left out of the ServerState
+   * either way - what the line which reports it carries is the question. Its result
+   * code is the last attempt's, and so must be the error next to it: a line which reads
+   * the server refusing the operation next to a search which did not run names two
+   * causes, and the operator chases the wrong one.
+   */
+  @Test
+  public void theExhaustionExitReportsTheAttemptWhichSpentTheLastOfThem() throws Exception
+  {
+    final Entry entry = createAndAddEntry("modifyWhoseLastAttemptIsRefused");
+    final String entryUUID = getEntryUUID(entry.getName());
+    final DN staleDN = DN.valueOf("cn=movedAway," + TEST_ROOT_DN_STRING);
+    final CSN csn = gen.newCSN();
+
+    /*
+     * The first attempt is let through to the data and fails on the conflict of the
+     * stale DN; its search is the one the short circuit stops. The attempts after it are
+     * refused before they reach the data, the way a backend which went offline after the
+     * first attempt refuses them: no search is made on any of them.
+     */
+    ShortCircuitPlugin.registerShortCircuit(
+        OperationType.SEARCH, "PreParse", ResultCode.UNAVAILABLE.intValue(), 1);
+    // The replayed operation only, named by its CSN: see the flush below.
+    ShortCircuitPlugin.registerShortCircuit(OperationType.MODIFY, "PreParse",
+        ResultCode.UNAVAILABLE.intValue(), 1, LDAPReplicationDomain.IN_PLACE_REPLAY_ATTEMPTS - 1,
+        op -> csn.equals(OperationContext.getCSN(op)));
+    try
+    {
+      /*
+       * The ServerState flush thread saves the state with a Modify of the base entry on
+       * its tick, which the add above made dirty: a tick which lands among the attempts in
+       * place is a Modify the short circuit meets like any other. Made here rather than
+       * left to the tick, so that the case says what it does about it every time instead
+       * of once in a while: that Modify is not the replayed operation, and the short
+       * circuit must neither let it through in place of the first attempt nor refuse it
+       * in place of a later one.
+       */
+      flushLikeTheStateFlushThread();
+      assertEquals(ShortCircuitPlugin.getShortCircuitCount(OperationType.MODIFY, "PreParse"), 0,
+          "the Modify of the state flush thread was counted against the short circuit");
+
+      replayMsg(new ModifyMsg(csn, staleDN, generatemods("telephonenumber", "01 02 45"), entryUUID));
+      assertTrue(ShortCircuitPlugin.getShortCircuitCount(OperationType.SEARCH, "PreParse") >= 1,
+          "the first attempt must have made its search");
+      assertTrue(ShortCircuitPlugin.getShortCircuitCount(OperationType.MODIFY, "PreParse")
+              >= LDAPReplicationDomain.IN_PLACE_REPLAY_ATTEMPTS,
+          "every attempt in place must have been made");
+    }
+    finally
+    {
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.MODIFY, "PreParse");
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.SEARCH, "PreParse");
+    }
+
+    assertFalse(domain.getServerState().cover(csn),
+        "a change the server kept refusing is not in the data and must not advance the ServerState");
+    final List<String> reports = exhaustionExitRecordsOf(csn);
+    assertThat(reports).as("the change was not reported once the attempts in place were spent")
+        .isNotEmpty();
+    // The last attempt was refused before it reached the data and made no search: a line
+    // which names the entryUUID reports the search of an earlier attempt next to its result.
+    assertThat(reports).as("the exhaustion exit reports an attempt other than the last one")
+        .allMatch(record -> !record.contains(entryUUID));
+  }
+
+  /**
+   * Test case for [Issue 956]: the base entry of the domain replayed into a replica
+   * which has none.
+   * <p>
+   * Two empty replicas share the generation ID of an empty backend, so no initialization
+   * is needed and the first change replayed is the base entry itself. The searches which
+   * check that Add for a conflict run under the base DN, which the backend serves and
+   * has no entry for: they answer NO_SUCH_OBJECT, which is the answer of a backend which
+   * is offline as well. Here the search ran and nothing is below a base entry which is
+   * not there, so the Add must go through rather than be retried until the give-up
+   * budget skips it as a change this replica can not apply.
+   */
+  @Test
+  public void baseEntryIsAddedToAnEmptyReplica() throws Exception
+  {
+    // The backend, without its base entry.
+    TestCaseUtils.initializeTestBackend(false);
+    final Entry base = TestCaseUtils.makeEntry(
+        "dn: " + TEST_ROOT_DN_STRING,
+        "objectClass: top",
+        "objectClass: organization",
+        "o: test");
+    final CSN csn = gen.newCSN();
+
+    replayMsg(addMsg(base, csn, null, "7c1a0d2e-4b6f-4c8a-9e1d-3f5b7a9c1e2d"));
+
+    assertTrue(entryExists(base.getName()),
+        "the base entry of an empty replica must land: its searches found nothing, they did not fail");
+    assertTrue(domain.getServerState().cover(csn),
+        "a change which was applied must be recorded as replayed");
+  }
+
+  /**
+   * Test case for [Issue 956]: the entryUUID a change carries is looked up as a value,
+   * not read as a filter.
+   * <p>
+   * The entryUUID comes off the wire and nothing validates it as one. Built into a
+   * filter string, a value which does not parse as a filter is a search which never
+   * runs - a permanent condition retried as a transient one, for as long as the change
+   * is asked for, until the give-up budget skips it and raises an alert. Looked up as a
+   * value, such an entryUUID names no entry, which is what a search which ran and found
+   * nothing says: the change is resolved as one on an entry which is not in the data.
+   */
+  @Test
+  public void anEntryUUIDWhichIsNotOneNamesNoEntry() throws Exception
+  {
+    final Entry entry = createAndAddEntry("modifyWhoseEntryUUIDIsNotOne");
+    // A value no filter string parses: the backslash escapes nothing.
+    final String entryUUID = getEntryUUID(entry.getName()) + "\\";
+    final DN staleDN = DN.valueOf("cn=movedAway," + TEST_ROOT_DN_STRING);
+    final CSN csn = gen.newCSN();
+
+    replayMsg(new ModifyMsg(csn, staleDN, generatemods("telephonenumber", "01 02 45"), entryUUID));
+
+    assertTrue(domain.getServerState().cover(csn),
+        "a change on an entry which is not in the data is a conflict which is resolved, and recorded");
+    assertThat(DirectoryServer.getEntry(entry.getName()).getAllAttributes("telephonenumber"))
+        .as("a change on an entryUUID which is not one was applied to an entry").isEmpty();
+  }
+
+  /**
+   * The records of the error log which report the provided change once its attempts in
+   * place were spent. The record the error logger writes carries the id of the message
+   * rather than its text.
+   */
+  private static List<String> exhaustionExitRecordsOf(CSN csn)
+  {
+    final String exhaustionExit = "msgID=" + ERR_ERROR_REPLAYING_OPERATION.ordinal();
+    final List<String> reports = new ArrayList<>();
+    for (String record : TestCaseUtils.ERROR_TEXT_WRITER.getMessages())
+    {
+      if (record.contains(exhaustionExit) && record.contains(csn.toString()))
+      {
+        reports.add(record);
+      }
+    }
+    return reports;
+  }
+
+  /**
+   * Asserts that the searches a short circuit was registered over were made - the ones
+   * let through before it and the ones it applied to - and that the search after them
+   * was made as well.
+   * <p>
+   * The count includes the searches let through once the short circuit was spent, so a
+   * count past what it was registered over says that the budget was used and that the
+   * search after it ran. Read before the short circuit is deregistered, which drops the
+   * count with it.
+   *
+   * @param searchesRegisteredOver the searches let through before the short circuit plus
+   *                               the ones it applied to
+   */
+  private void assertShortCircuitSpentBy(int searchesRegisteredOver)
+  {
+    assertTrue(
+        ShortCircuitPlugin.getShortCircuitCount(OperationType.SEARCH, "PreParse") > searchesRegisteredOver,
+        "the short circuit must have been spent by the attempts in place");
+  }
+
+  private Entry addParentEntry(String ou) throws Exception
+  {
+    return TestCaseUtils.addEntry(
+        "dn: ou=" + ou + "," + TEST_ROOT_DN_STRING,
+        "objectClass: top",
+        "objectClass: organizationalUnit",
+        "ou: " + ou);
+  }
+
+  private Entry makeChildEntry(String cn, DN parentDN) throws Exception
+  {
+    return TestCaseUtils.makeEntry(
+        "dn: cn=" + cn + "," + parentDN,
+        "objectClass: top",
+        "objectClass: person",
+        "cn: " + cn,
+        "sn: Amar");
+  }
+
+  /**
    * Test that when a previous conflict is resolved because
    * a delete operation has removed one of the conflicting entries
    * the other conflicting entry is correctly renamed to its original name.
@@ -317,6 +854,24 @@
     assertThat(resultEntry.getAllAttributes(LDAPReplicationDomain.DS_SYNC_CONFLICT)).isEmpty();
   }
 
+  /**
+   * Makes the Modify the ServerState flush thread makes on its tick: an internal
+   * synchronization Modify of the base entry, which is not synchronized itself. The
+   * attribute is a harmless one rather than ds-sync-state, which is the flush thread's to
+   * write.
+   */
+  private void flushLikeTheStateFlushThread()
+  {
+    final ModifyOperationBasis op = new ModifyOperationBasis(getRootConnection(),
+        nextOperationID(), nextMessageID(), null,
+        baseDN, generatemods("description", "written on the tick of the flush thread"));
+    op.setInternalOperation(true);
+    op.setSynchronizationOperation(true);
+    op.setDontSynchronize(true);
+    op.run();
+    assertEquals(op.getResultCode(), ResultCode.SUCCESS, op.getErrorMessage().toString());
+  }
+
   private Entry createAndAddEntry(String commonName) throws Exception
   {
     // @formatter:off
diff --git a/opendj-server-legacy/src/test/java/org/opends/server/replication/plugin/ReplayDuringImportTest.java b/opendj-server-legacy/src/test/java/org/opends/server/replication/plugin/ReplayDuringImportTest.java
new file mode 100644
index 0000000..3bedecb
--- /dev/null
+++ b/opendj-server-legacy/src/test/java/org/opends/server/replication/plugin/ReplayDuringImportTest.java
@@ -0,0 +1,385 @@
+/*
+ * The contents of this file are subject to the terms of the Common Development and
+ * Distribution License (the License). You may not use this file except in compliance with the
+ * License.
+ *
+ * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
+ * specific language governing permission and limitations under the License.
+ *
+ * When distributing Covered Software, include this CDDL Header Notice in each file and include
+ * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
+ * Header, with the fields enclosed by brackets [] replaced by your own identifying
+ * information: "Portions copyright [year] [name of copyright owner]".
+ *
+ * Copyright 2026 3A Systems, LLC.
+ */
+package org.opends.server.replication.plugin;
+
+import static java.nio.charset.StandardCharsets.*;
+import static org.assertj.core.api.Assertions.*;
+import static org.opends.messages.ReplicationMessages.*;
+import static org.opends.server.TestCaseUtils.*;
+import static org.opends.server.core.DirectoryServer.*;
+import static org.testng.Assert.*;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.SortedSet;
+import java.util.TreeSet;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.forgerock.opendj.ldap.DN;
+import org.forgerock.opendj.ldap.ResultCode;
+import org.forgerock.opendj.server.config.meta.ReplicationDomainCfgDefn.IsolationPolicy;
+import org.opends.server.TestCaseUtils;
+import org.opends.server.core.DirectoryServer;
+import org.opends.server.plugins.ShortCircuitPlugin;
+import org.opends.server.replication.ReplicationTestCase;
+import org.opends.server.replication.common.CSN;
+import org.opends.server.replication.common.CSNGenerator;
+import org.opends.server.replication.protocol.DoneMsg;
+import org.opends.server.replication.protocol.EntryMsg;
+import org.opends.server.replication.protocol.InitializeRequestMsg;
+import org.opends.server.replication.protocol.InitializeTargetMsg;
+import org.opends.server.replication.protocol.LDAPUpdateMsg;
+import org.opends.server.replication.protocol.ModifyMsg;
+import org.opends.server.replication.protocol.UpdateMsg;
+import org.opends.server.replication.server.ReplServerFakeConfiguration;
+import org.opends.server.replication.server.ReplicationServer;
+import org.opends.server.replication.service.ReplicationBroker;
+import org.opends.server.types.Entry;
+import org.opends.server.types.OperationType;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+/**
+ * Tests the replay of a change while this replica is the target of a total update.
+ * <p>
+ * The import of a total update streams over the session of the domain, on its listener
+ * thread, and the backend it replaces is deregistered for the length of it. A change which
+ * was queued for replay before the {@code InitializeTargetMsg} arrived is replayed into no
+ * backend: whatever such a replay decides is about to be overwritten by the import, and the
+ * one thing it must not do is stop the session the import is reading (issue #956). The same
+ * holds from the moment the total update is asked for: the answer to the request arrives
+ * over that session, so a replay which fails while it is on its way must not restart it.
+ * <p>
+ * The exporter is a broker of this test, so that the test says when the entries arrive: the
+ * change is replayed while the import is waiting for them - or, for the request, while the
+ * exporter is holding the answer.
+ */
+@SuppressWarnings("javadoc")
+public class ReplayDuringImportTest extends ReplicationTestCase
+{
+  /**
+   * The memory backend of {@code o=test} loses its data when it is disabled and enabled
+   * back, which is what an import does to the backend it replaces: a total update needs a
+   * backend which keeps what was imported into it.
+   */
+  private static final String EXAMPLE_DN = "dc=example,dc=com";
+  private static final int RS_ID = 611;
+  private static final int DS_ID = 1;
+  private static final int EXPORTER_ID = 2;
+  private static final int INIT_WINDOW = 100;
+  private static final AtomicBoolean SHUTDOWN = new AtomicBoolean(false);
+  /** An entry of the exporter's data, and its entryUUID. */
+  private static final String IMPORTED_ENTRY_DN = "cn=imported,ou=People," + EXAMPLE_DN;
+  private static final String IMPORTED_ENTRY_UUID = "21111111-1111-1111-1111-111111111113";
+
+  private DN baseDN;
+  private ReplicationServer replicationServer;
+  private LDAPReplicationDomain domain;
+  private TestSynchronousReplayQueue queue;
+  private ReplicationBroker exporter;
+  private CSNGenerator gen;
+
+  @BeforeMethod
+  public void setUpLocal() throws Exception
+  {
+    baseDN = DN.valueOf(EXAMPLE_DN);
+    TestCaseUtils.clearBackend("userRoot", EXAMPLE_DN);
+
+    final int rsPort = TestCaseUtils.findFreePort();
+    replicationServer = new ReplicationServer(new ReplServerFakeConfiguration(
+        rsPort, "replayDuringImportTestDb", 0, RS_ID, 0, 100, new TreeSet<String>()));
+
+    final SortedSet<String> replServers = new TreeSet<>();
+    replServers.add("localhost:" + rsPort);
+    final DomainFakeCfg conf = new DomainFakeCfg(baseDN, DS_ID, replServers);
+    conf.setIsolationPolicy(IsolationPolicy.ACCEPT_ALL_UPDATES);
+    queue = new TestSynchronousReplayQueue();
+    domain = MultimasterReplication.createNewDomain(conf, queue);
+    domain.start();
+    assertTrue(domain.isConnected(), "the domain did not connect to the replication server");
+
+    exporter = openReplicationSession(baseDN, EXPORTER_ID, 100, rsPort, 10000);
+    gen = new CSNGenerator(201, 0);
+  }
+
+  @AfterMethod
+  public void tearDown() throws Exception
+  {
+    try
+    {
+      stop(exporter);
+      MultimasterReplication.deleteDomain(baseDN);
+    }
+    finally
+    {
+      remove(replicationServer);
+    }
+  }
+
+  /**
+   * A change replayed while the import streams must leave the session to the import.
+   * <p>
+   * The change is given back at the top of its first attempt: the data it would be applied
+   * to is being replaced, so nothing is attempted into the backend the import took away,
+   * nothing is reported, and the session is left to the import - which streams every entry
+   * to its end. Without the hold-off the operation is refused with NO_SUCH_OBJECT - nothing
+   * serves the base DN - and the entryUUID search conflict resolution reads the data with
+   * can not run either: the attempts in place are spent into no backend and the exit
+   * reports the change; without the owner the total update is, the session is then
+   * restarted for the change to be delivered again, which stops the broker the import is
+   * reading, and the import ends on the entries which had arrived with nothing to say it.
+   */
+  @Test(timeOut = 120_000)
+  public void aReplayDuringTheImportLeavesTheSessionToTheImport() throws Exception
+  {
+    final Entry entry = TestCaseUtils.addEntry(
+        "dn: cn=renamedSince," + EXAMPLE_DN,
+        "objectClass: top",
+        "objectClass: person",
+        "cn: renamedSince",
+        "sn: renamedSince");
+    final String entryUUID = getEntryUUID(entry.getName());
+    final String[] exported = exportedEntries();
+    startImportInto(exported.length);
+
+    // Queued before the InitializeTargetMsg arrived, replayed into no backend.
+    final CSN csn = gen.newCSN();
+    replayMsg(new ModifyMsg(csn, DN.valueOf("cn=movedAway," + EXAMPLE_DN),
+        generatemods("description", "replayed during the import"), entryUUID));
+
+    finishImport(exported);
+
+    for (String ldif : exported)
+    {
+      final DN dn = dnOf(ldif);
+      assertTrue(entryExists(dn), "the import ended before " + dn
+          + " arrived: the session it streams over was stopped from under it");
+    }
+    /*
+     * The two roads which leave the session to the import are told apart here: the
+     * hold-off gives the change back before an attempt is made, the guard on the restart
+     * after the attempts are spent. The exhaustion exit is the one thing the first road
+     * leaves no record of.
+     */
+    assertThat(errorLogRecordsOf(ERR_ERROR_REPLAYING_OPERATION.ordinal(), csn))
+        .as("the change was attempted into no backend instead of being given back at once")
+        .isEmpty();
+    assertThat(errorLogRecordsOf(WARN_REPLAY_RETRYING_CHANGE.ordinal(), csn))
+        .as("the change was asked for again, which restarts the session the import streams over")
+        .isEmpty();
+  }
+
+  /**
+   * A change given back while the import ran must not hold the ServerState back once the
+   * import has replaced the data.
+   * <p>
+   * A change which is given back stays listed as pending and uncommitted - that is what
+   * has the replication server send it again - and a commit advances the ServerState no
+   * further than the oldest uncommitted change. The state the import loads is the
+   * exporter's, which covers the change already, so nothing sends it again: left listed,
+   * it would stop the ServerState of this replica for good.
+   */
+  @Test(timeOut = 120_000)
+  public void aChangeGivenBackDuringTheImportDoesNotHoldTheServerStateBack() throws Exception
+  {
+    final Entry entry = TestCaseUtils.addEntry(
+        "dn: cn=renamedSince," + EXAMPLE_DN,
+        "objectClass: top",
+        "objectClass: person",
+        "cn: renamedSince",
+        "sn: renamedSince");
+    final String entryUUID = getEntryUUID(entry.getName());
+    final String[] exported = exportedEntries();
+    startImportInto(exported.length);
+    replayMsg(new ModifyMsg(gen.newCSN(), DN.valueOf("cn=movedAway," + EXAMPLE_DN),
+        generatemods("description", "replayed during the import"), entryUUID));
+    finishImport(exported);
+
+    // A change on an entry the import brought, replayed once the import is over.
+    final DN importedDN = DN.valueOf(IMPORTED_ENTRY_DN);
+    final CSN csn = gen.newCSN();
+    replayMsg(new ModifyMsg(csn, importedDN,
+        generatemods("description", "replayed after the import"), IMPORTED_ENTRY_UUID));
+
+    assertThat(DirectoryServer.getEntry(importedDN).getAllAttributes("description"))
+        .as("a change replayed after the import was not applied").isNotEmpty();
+    assertTrue(domain.getServerState().cover(csn), "a change applied after the import was not"
+        + " recorded: the change given back during the import is still listed and holds the"
+        + " ServerState back");
+  }
+
+  /**
+   * A total update this replica asked for owns the session from the request, not from the
+   * first entry: the {@code InitializeTargetMsg} which answers the request arrives over
+   * that session, and a restart made while the answer is on its way loses it.
+   * <p>
+   * The backend is live for the length of the request - nothing has been taken away yet -
+   * so the change is attempted, every attempt ends on an entryUUID search which does not
+   * run, and the exhaustion exit reports it: what is refused is the restart which would
+   * have followed, and the retry warning which goes with it. The exporter then answers the
+   * request, and its entries stream to their end over the session which was left alone.
+   */
+  @Test(timeOut = 120_000)
+  public void aRequestOnItsWayOwnsTheSessionTheAnswerArrivesOver() throws Exception
+  {
+    final Entry entry = TestCaseUtils.addEntry(
+        "dn: cn=renamedSince," + EXAMPLE_DN,
+        "objectClass: top",
+        "objectClass: person",
+        "cn: renamedSince",
+        "sn: renamedSince");
+    final String entryUUID = getEntryUUID(entry.getName());
+    final String[] exported = exportedEntries();
+
+    // The request is out, and the exporter holds it until the change below has been replayed.
+    domain.initializeFromRemote(EXPORTER_ID, null);
+    assertNotNull(waitForSpecificMsg(exporter, InitializeRequestMsg.class));
+
+    final CSN csn = gen.newCSN();
+    ShortCircuitPlugin.registerShortCircuit(
+        OperationType.SEARCH, "PreParse", ResultCode.UNAVAILABLE.intValue());
+    try
+    {
+      replayMsg(new ModifyMsg(csn, DN.valueOf("cn=movedAway," + EXAMPLE_DN),
+          generatemods("description", "replayed while the request was on its way"), entryUUID));
+      assertTrue(ShortCircuitPlugin.getShortCircuitCount(OperationType.SEARCH, "PreParse")
+              >= LDAPReplicationDomain.IN_PLACE_REPLAY_ATTEMPTS,
+          "every attempt in place must have made its search: the backend is live while the"
+              + " request is on its way, so nothing holds the replay off");
+    }
+    finally
+    {
+      ShortCircuitPlugin.deregisterShortCircuit(OperationType.SEARCH, "PreParse");
+    }
+
+    assertThat(errorLogRecordsOf(ERR_ERROR_REPLAYING_OPERATION.ordinal(), csn))
+        .as("the attempts in place were spent, which the exhaustion exit reports").isNotEmpty();
+    assertThat(errorLogRecordsOf(WARN_REPLAY_RETRYING_CHANGE.ordinal(), csn))
+        .as("the change was asked for again, which restarts the session the answer to the"
+            + " request arrives over")
+        .isEmpty();
+    assertTrue(domain.isConnected(), "the session the request was made over was stopped");
+
+    answerImportRequest(exported.length);
+    finishImport(exported);
+    for (String ldif : exported)
+    {
+      final DN dn = dnOf(ldif);
+      assertTrue(entryExists(dn), "the import ended before " + dn
+          + " arrived: the answer to the request was lost with the session it was made over");
+    }
+  }
+
+  /**
+   * Has the exporter start a total update into this replica, and returns once the backend
+   * of the domain is deregistered for it: from then on the import is reading the session,
+   * and a change replayed here is replayed into no backend.
+   */
+  private void startImportInto(int entryCount) throws Exception
+  {
+    exporter.publish(new InitializeTargetMsg(
+        baseDN, EXPORTER_ID, DS_ID, EXPORTER_ID, entryCount, INIT_WINDOW));
+    final long deadline = System.currentTimeMillis() + 30_000;
+    while (getServerContext().getBackendConfigManager().findLocalBackendForEntry(baseDN) != null)
+    {
+      assertTrue(System.currentTimeMillis() < deadline,
+          "the import did not deregister the backend of the domain");
+      Thread.sleep(20);
+    }
+  }
+
+  /**
+   * Has the exporter answer the total update this replica asked for: the requestor of the
+   * {@code InitializeTargetMsg} is this replica, so the import runs in the context the
+   * request acquired.
+   */
+  private void answerImportRequest(int entryCount) throws Exception
+  {
+    exporter.publish(new InitializeTargetMsg(
+        baseDN, EXPORTER_ID, DS_ID, DS_ID, entryCount, INIT_WINDOW));
+  }
+
+  /** Has the exporter send the entries of the total update, and waits for the import to end. */
+  private void finishImport(String... ldifEntries) throws Exception
+  {
+    int msgId = 0;
+    for (String ldif : ldifEntries)
+    {
+      exporter.publish(new EntryMsg(EXPORTER_ID, DS_ID, ldif.getBytes(UTF_8), ++msgId));
+    }
+    exporter.publish(new DoneMsg(EXPORTER_ID, DS_ID));
+    final long deadline = System.currentTimeMillis() + 60_000;
+    while (domain.ieRunning())
+    {
+      assertTrue(System.currentTimeMillis() < deadline, "the import did not end");
+      Thread.sleep(50);
+    }
+  }
+
+  /** The data of the exporter: the base entry and two entries below it. */
+  private static String[] exportedEntries()
+  {
+    return new String[] {
+      "dn: " + EXAMPLE_DN + "\n"
+          + "objectClass: top\n"
+          + "objectClass: domain\n"
+          + "dc: example\n"
+          + "entryUUID: 21111111-1111-1111-1111-111111111111\n"
+          + "\n",
+      "dn: ou=People," + EXAMPLE_DN + "\n"
+          + "objectClass: top\n"
+          + "objectClass: organizationalUnit\n"
+          + "ou: People\n"
+          + "entryUUID: 21111111-1111-1111-1111-111111111112\n"
+          + "\n",
+      "dn: " + IMPORTED_ENTRY_DN + "\n"
+          + "objectClass: top\n"
+          + "objectClass: person\n"
+          + "cn: imported\n"
+          + "sn: imported\n"
+          + "entryUUID: " + IMPORTED_ENTRY_UUID + "\n"
+          + "\n",
+    };
+  }
+
+  private static DN dnOf(String ldif)
+  {
+    return DN.valueOf(ldif.substring("dn: ".length(), ldif.indexOf('\n')));
+  }
+
+  /** The records of the error log which carry the provided message id and the provided CSN. */
+  private static List<String> errorLogRecordsOf(int msgId, CSN csn)
+  {
+    final List<String> records = new ArrayList<>();
+    for (String record : TestCaseUtils.ERROR_TEXT_WRITER.getMessages())
+    {
+      if (record.contains("msgID=" + msgId) && record.contains(csn.toString()))
+      {
+        records.add(record);
+      }
+    }
+    return records;
+  }
+
+  private void replayMsg(UpdateMsg updateMsg) throws InterruptedException
+  {
+    domain.processUpdate(updateMsg);
+    final LDAPUpdateMsg ldapUpdate = queue.take().getUpdateMessage();
+    domain.markInProgress(ldapUpdate);
+    domain.replay(ldapUpdate, SHUTDOWN);
+  }
+}

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