From 32a3660838f983699af8ff548507288cc9a1bc07 Mon Sep 17 00:00:00 2001
From: Maxim Thomas <maxim.thomas@gmail.com>
Date: Wed, 09 Sep 2026 07:20:47 +0000
Subject: [PATCH] [#921] Bound the transaction replay of PDBStorage.write() (#937)
---
opendj-server-legacy/src/main/java/org/opends/server/backends/pdb/PDBStorage.java | 160 +++++++++++++++++
opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/spi/Storage.java | 17 +
opendj-server-legacy/src/test/java/org/opends/server/backends/pdb/PDBStorageTest.java | 328 ++++++++++++++++++++++++++++++++++++
3 files changed, 496 insertions(+), 9 deletions(-)
diff --git a/opendj-server-legacy/src/main/java/org/opends/server/backends/pdb/PDBStorage.java b/opendj-server-legacy/src/main/java/org/opends/server/backends/pdb/PDBStorage.java
index e99db98..7ad8cc7 100644
--- a/opendj-server-legacy/src/main/java/org/opends/server/backends/pdb/PDBStorage.java
+++ b/opendj-server-legacy/src/main/java/org/opends/server/backends/pdb/PDBStorage.java
@@ -42,6 +42,7 @@
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Set;
+import java.util.concurrent.TimeUnit;
import org.forgerock.i18n.LocalizableMessage;
import org.forgerock.i18n.slf4j.LocalizedLogger;
@@ -101,7 +102,37 @@
{
private static final int IMPORT_DB_CACHE_SIZE = 32 * MB;
- private static final double MAX_SLEEP_ON_RETRY_MS = 50.0;
+ /**
+ * Number of attempts a {@link WriteableStorageImpl#write} makes before it propagates the conflict to the caller.
+ * <p>
+ * It is a budget of attempts and not of time, so it is only ever reached by the conflicts that report quickly.
+ * PersistIt reports a write-write conflict only once it has waited on it, up to
+ * {@code SharedResource.DEFAULT_MAX_WAIT_TIME} - a minute, which this backend never lowers - so a conflict slower
+ * to report than {@link #MAX_RETRY_WINDOW_NANOS} spends the whole window inside its first attempt, is granted the
+ * single replay that window's exemption guarantees, and gives up on the window after two attempts rather than
+ * after this many.
+ */
+ static final int MAX_RETRIES = 10;
+
+ /**
+ * Wall-clock budget the replays of a {@link WriteableStorageImpl#write} may spend, in nanoseconds. It is checked
+ * between attempts, so an attempt already running is never interrupted, and never before one replay has been
+ * made: the loop returns after at most this window plus two attempts. It bounds the conflicts that are slow to
+ * report, which {@link #MAX_RETRIES} alone does not - an operation whose own work takes seconds would otherwise
+ * multiply that wait by the attempt count.
+ */
+ static final long MAX_RETRY_WINDOW_NANOS = 10L * 1000L * 1000L * 1000L; //10 s
+
+ /**
+ * Upper bound of the random delay before the second attempt, in milliseconds; it doubles with every attempt. This
+ * is the bound of the flat sleep this loop took before it was bounded, so the first replay is delayed exactly as
+ * it was and only the later ones back off.
+ */
+ private static final double BASE_SLEEP_ON_RETRY_MS = 50.0;
+
+ /** Upper bound the doubled delay is capped at, in milliseconds. */
+ private static final double MAX_SLEEP_ON_RETRY_MS = 1000.0;
+
private static final String VOLUME_NAME = "dj";
private static final String JOURNAL_NAME = VOLUME_NAME + "_journal";
/** The buffer / page size used by the PersistIt storage. */
@@ -635,8 +666,11 @@
public void write(WriteOperation operation) throws Exception
{
final Transaction txn = db.getTransaction();
- for (;;)
+ final long startedAt = System.nanoTime();
+ final long giveUpAt = startedAt + retryWindowNanos;
+ for (int attempt = 1;; attempt++)
{
+ final RollbackException conflict;
txn.begin();
try
{
@@ -653,8 +687,7 @@
}
catch (final RollbackException e)
{
- // retry after random sleep (reduces transactions collision. Drawback: increased latency)
- Thread.sleep((long) (Math.random() * MAX_SLEEP_ON_RETRY_MS));
+ conflict = e;
}
catch (final Exception e)
{
@@ -665,6 +698,68 @@
{
txn.end();
}
+ // decided and slept for outside the try statement: the sleep used to run before the finally ended the
+ // rolled back transaction, holding it open for the whole backoff and lengthening the window every other
+ // writer collides with
+ //System.nanoTime() - giveUpAt is the overflow safe form of the comparison, and attempt > 1 keeps the
+ //window from ending the loop before a single replay: persistit reports a write-write conflict only once
+ //it has waited on it, up to SharedResource.DEFAULT_MAX_WAIT_TIME - a minute, which this backend never
+ //lowers - so one attempt can outlast the window on its own, and it is the attempt after that one which
+ //is likeliest to succeed, the transaction that blocked it having just finished
+ //one clock sample for both, so that the elapsed time reported is the one the give up was decided on
+ final long now = System.nanoTime();
+ final boolean capSpent = attempt >= maxRetries;
+ if (capSpent || (attempt > 1 && now - giveUpAt >= 0))
+ {
+ final long elapsedMs = TimeUnit.NANOSECONDS.toMillis(now - startedAt);
+ //which of the two bounds was spent, so that the config change paths - which report this as a bare stack
+ //trace with no message id - say whether raising the attempts or the window is what would have helped
+ final String boundSpent = capSpent ? "attempt cap" : "retry window";
+ final StorageRuntimeException spent = new StorageRuntimeException(
+ "pdb: backend '" + config.getBackendId() + "' did not apply the transaction after " + attempt
+ + " attempts in " + elapsedMs + " ms, the " + boundSpent + " being spent; the last conflict was "
+ + conflict);
+ // the conflict is suppressed rather than made the cause, because a cause is what every caller strips
+ // this message off with: write(WriteOperation) below unwraps a StorageRuntimeException that carries one
+ // and throws the cause in its place, and EntryContainer.throwAllowedExceptionTypes:1121 rethrows a
+ // StorageRuntimeException unchanged only while getCause() is null, wrapping it a second time otherwise.
+ // Either way the caller would be left holding a bare RollbackException, whose StorageRuntimeException
+ // message is only its class name - which is all ERR_OPEN_ENV_FAIL would then print at startup
+ spent.addSuppressed(conflict);
+ //warned once, at exhaustion only, unlike JDBCStorage which warns on every replay: a conflict is routine
+ //on the ordinary add and modify path of this engine and a line per replay would flood the log. It names
+ //the bound that was spent for the same reason the exception does, and it is the only rendering that can
+ //carry the stack of the conflict: stackTraceToSingleLineString, the form the config change paths report
+ //this exception with, walks the causes and never prints a suppressed exception
+ logger.warn(LocalizableMessage.raw("pdb: giving up on the transaction of backend '%s' after %d attempts"
+ + " in %d ms, the %s being spent: %s", config.getBackendId(), attempt, elapsedMs, boundSpent,
+ stackTraceToSingleLineString(conflict)));
+ throw spent;
+ }
+ if (logger.isTraceEnabled())
+ {
+ logger.trace("pdb: replaying the transaction after %s, attempt %d of %d", conflict, attempt, maxRetries);
+ }
+ try
+ {
+ // retry after random sleep (reduces transactions collision. Drawback: increased latency), growing with
+ // every attempt so that a contention the first delays did not outlast still has a chance to clear
+ Thread.sleep(retryDelayMillis(attempt));
+ }
+ catch (final InterruptedException e)
+ {
+ //sleep cleared the interrupt flag: restore it, and report the conflict being replayed rather than the
+ //interrupt, which would hide from the caller what actually went wrong. Wrapped the way the exhausted
+ //loop above wraps it, and for the same reason: a RollbackException carries no message of its own, so
+ //every caller that wraps one reports nothing but its class name
+ Thread.currentThread().interrupt();
+ final StorageRuntimeException interrupted = new StorageRuntimeException(
+ "pdb: backend '" + config.getBackendId() + "' was interrupted while replaying the transaction after "
+ + attempt + " attempts; the last conflict was " + conflict);
+ interrupted.addSuppressed(conflict);
+ interrupted.addSuppressed(e);
+ throw interrupted;
+ }
}
}
}
@@ -915,6 +1010,10 @@
private PDBMonitor monitor;
private MemoryQuota memQuota;
private StorageStatus storageStatus = StorageStatus.working();
+ /** Attempt bound of a {@link WriteableStorageImpl#write}, {@link #MAX_RETRIES} outside the tests. */
+ private final int maxRetries;
+ /** Wall-clock bound of a {@link WriteableStorageImpl#write}, {@link #MAX_RETRY_WINDOW_NANOS} outside the tests. */
+ private final long retryWindowNanos;
/**
* Creates a new persistit storage with the provided configuration.
@@ -928,7 +1027,34 @@
// FIXME: should be package private once importer is decoupled.
public PDBStorage(final PDBBackendCfg cfg, ServerContext serverContext) throws ConfigException
{
+ this(cfg, serverContext, MAX_RETRIES, MAX_RETRY_WINDOW_NANOS);
+ }
+
+ /**
+ * Creates a new persistit storage whose replay bounds are the given ones rather than {@link #MAX_RETRIES} and
+ * {@link #MAX_RETRY_WINDOW_NANOS}.
+ * <p>
+ * Only a test builds one of these, and it does so to stop the two bounds racing each other: with the shipped
+ * values a run of replays spends a random share of the window on backoff alone, so a test of the attempt cap
+ * can be ended by the window on a loaded machine, and a test of the window has to spend seconds of build time
+ * to reach it.
+ *
+ * @param cfg
+ * The configuration.
+ * @param serverContext
+ * This server instance context
+ * @param maxRetries
+ * Number of attempts a write makes before it propagates the conflict to the caller.
+ * @param retryWindowNanos
+ * Wall-clock budget the replays of a write may spend, in nanoseconds.
+ * @throws ConfigException if memory cannot be reserved
+ */
+ PDBStorage(final PDBBackendCfg cfg, ServerContext serverContext, int maxRetries, long retryWindowNanos)
+ throws ConfigException
+ {
this.serverContext = serverContext;
+ this.maxRetries = maxRetries;
+ this.retryWindowNanos = retryWindowNanos;
backendDirectory = getBackendDirectory(cfg);
config = cfg;
cfg.addPDBChangeListener(this);
@@ -1095,6 +1221,24 @@
return new ImporterImpl();
}
+ /**
+ * {@inheritDoc}
+ * <p>
+ * A transaction the engine rolled back is replayed, bounded twice: by {@link #MAX_RETRIES} attempts and by the
+ * {@link #MAX_RETRY_WINDOW_NANOS} wall-clock window, whichever is spent first - except that the window alone
+ * never ends the replays before one has been made. It is bounded because the
+ * configuration change paths of the pluggable backend hold an entry container's exclusive lock across this
+ * method, and every reader of that suffix then waits - untimed and uninterruptibly - until it returns, so a
+ * conflict that never clears would park every worker thread of that suffix rather than fail one operation.
+ * <p>
+ * Once the bound is spent the conflict is reported as a {@link StorageRuntimeException} naming the backend, the
+ * attempts spent, the time they took and which of the two bounds ran out. It carries the conflict as a
+ * suppressed exception rather than as its cause: a cause is unwrapped below and thrown in its place, and
+ * {@code EntryContainer.throwAllowedExceptionTypes} likewise passes a {@link StorageRuntimeException} through
+ * untouched only while it has no cause. Given a cause, both hand the caller a bare RollbackException instead,
+ * and the message of a {@link StorageRuntimeException} wrapping one is just its class name - which is all
+ * {@code ERR_OPEN_ENV_FAIL} would report when this happens as a backend starts.
+ */
@Override
public void write(final WriteOperation operation) throws Exception
{
@@ -1108,6 +1252,14 @@
}
}
+ /** Returns the randomized delay before the given attempt is replayed, doubling with each attempt up to a cap. */
+ //package private like the JDBCStorage copy it is taken from, so that a test can pin the growth and the cap
+ static long retryDelayMillis(int attempt)
+ {
+ final double bound = Math.min(MAX_SLEEP_ON_RETRY_MS, BASE_SLEEP_ON_RETRY_MS * (1 << Math.min(attempt - 1, 5)));
+ return (long) (Math.random() * bound);
+ }
+
private Exception unwrap(StorageRuntimeException e) throws Exception
{
if (e.getCause() != null)
diff --git a/opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/spi/Storage.java b/opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/spi/Storage.java
index cf04069..2164d2e 100644
--- a/opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/spi/Storage.java
+++ b/opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/spi/Storage.java
@@ -73,13 +73,24 @@
<T> T read(ReadOperation<T> readOperation) throws Exception;
/**
- * Executes a write operation. In case of a write operation rollback, implementations must ensure
- * the write operation is retried until it succeeds.
+ * Executes a write operation. In case of a write operation rollback, implementations may replay the write
+ * operation rather than propagate the failure: a {@link WriteOperation} is required to be idempotent for
+ * exactly that reason. A replay must be bounded - by a number of attempts, by a window of time, or by both -
+ * so that a conflict which does not clear reaches the caller instead of being retried forever. The pluggable
+ * backend holds locks across this method, up to the exclusive lock of an entry container, and every thread
+ * waiting on one of those locks waits for as long as this method does.
+ * <p>
+ * A caller that mutates state around this method must handle that bound being spent. Removing an entry from an
+ * in-memory map before the write so that a replay still finds the work to do, or reading configuration back out
+ * of the operation once it returns, both assume the write is applied; when it is not, this method throws with
+ * that state already changed and the transaction not applied, and the caller is the only place that can reconcile
+ * the two.
*
* @param writeOperation
* the write operation to execute
* @throws Exception
- * if a problem occurs with the underlying storage engine
+ * if a problem occurs with the underlying storage engine, including a conflict that outlasted the
+ * replays the implementation makes
*/
void write(WriteOperation writeOperation) throws Exception;
diff --git a/opendj-server-legacy/src/test/java/org/opends/server/backends/pdb/PDBStorageTest.java b/opendj-server-legacy/src/test/java/org/opends/server/backends/pdb/PDBStorageTest.java
index 7ea514d..f633849 100644
--- a/opendj-server-legacy/src/test/java/org/opends/server/backends/pdb/PDBStorageTest.java
+++ b/opendj-server-legacy/src/test/java/org/opends/server/backends/pdb/PDBStorageTest.java
@@ -12,6 +12,7 @@
* information: "Portions Copyright [year] [name of copyright owner]".
*
* Copyright 2016 ForgeRock AS.
+ * Portions Copyright 2026 3A Systems, LLC.
*/
package org.opends.server.backends.pdb;
@@ -21,11 +22,17 @@
import static org.opends.server.util.StaticUtils.*;
import static org.forgerock.opendj.ldap.ByteString.*;
+import java.util.concurrent.atomic.AtomicInteger;
+
import org.forgerock.opendj.config.server.ConfigException;
+import org.forgerock.opendj.ldap.ByteString;
import org.opends.server.DirectoryServerTestCase;
import org.opends.server.TestCaseUtils;
import org.forgerock.opendj.server.config.server.PDBBackendCfg;
import org.opends.server.backends.pluggable.spi.AccessMode;
+import org.opends.server.backends.pluggable.spi.ReadOperation;
+import org.opends.server.backends.pluggable.spi.ReadableTransaction;
+import org.opends.server.backends.pluggable.spi.StorageRuntimeException;
import org.opends.server.backends.pluggable.spi.TreeName;
import org.opends.server.backends.pluggable.spi.WriteOperation;
import org.opends.server.backends.pluggable.spi.WriteableTransaction;
@@ -38,10 +45,19 @@
import org.testng.annotations.Test;
import com.persistit.Exchange;
+import com.persistit.exception.RollbackException;
public class PDBStorageTest extends DirectoryServerTestCase
{
+ /** A window no run of replays can spend, so that a test of the attempt cap is only ever ended by the cap. */
+ private static final long UNREACHABLE_RETRY_WINDOW_NANOS = 300L * 1000L * 1000L * 1000L; //5 min
+ /** A window a single attempt outlasts, so that a test of the window reaches it without seconds of build time. */
+ private static final long SHORT_RETRY_WINDOW_NANOS = 200L * 1000L * 1000L; //200 ms
+ /** An attempt long enough to outlast {@link #SHORT_RETRY_WINDOW_NANOS} on its own, in milliseconds. */
+ private static final long ATTEMPT_LONGER_THAN_SHORT_WINDOW_MS = 300;
+
private final TreeName treeName = new TreeName("dc=test", "test");
+ private ServerContext serverContext;
private PDBStorage storage;
@BeforeClass
@@ -53,18 +69,72 @@
@BeforeMethod
public void setUp() throws ConfigException
{
- ServerContext serverContext = mock(ServerContext.class);
+ serverContext = mock(ServerContext.class);
when(serverContext.getMemoryQuota()).thenReturn(new MemoryQuota());
when(serverContext.getDiskSpaceMonitor()).thenReturn(mock(DiskSpaceMonitor.class));
storage = new PDBStorage(createBackendCfg(), serverContext);
+ // the volume is removed on the way in as well as on the way out: a build whose JVM died never ran tearDown(),
+ // and this class shares a fixed db-directory across methods and across builds, so what that run left behind
+ // would still be here to answer this method's reads
+ storage.removeStorageFiles();
storage.open(AccessMode.READ_WRITE);
}
@AfterMethod
public void tearDown()
{
- storage.close();
+ closeAndRemove(storage);
+ }
+
+ /**
+ * Closes the storage and removes its volume, keeping whichever of the two failed first. Removing it from a
+ * finally would let a removal failure replace the close() failure (JLS 14.20.2) - and a close() that throws is
+ * exactly the case the removal is here for.
+ */
+ private static void closeAndRemove(PDBStorage storage)
+ {
+ RuntimeException failure = null;
+ try
+ {
+ storage.close();
+ }
+ catch (RuntimeException e)
+ {
+ failure = e;
+ }
+ try
+ {
+ storage.removeStorageFiles();
+ }
+ catch (RuntimeException e)
+ {
+ if (failure == null)
+ {
+ failure = e;
+ }
+ else
+ {
+ failure.addSuppressed(e);
+ }
+ }
+ if (failure != null)
+ {
+ throw failure;
+ }
+ }
+
+ /**
+ * Replaces the storage under test with one bounded by the given values, so that the bound a test is about is
+ * the one that ends its replays. With the shipped values the two race: the nine backoffs of a full ladder draw
+ * from 50+100+200+400+800+1000x4, so an attempt cap test can be ended by the ten second window instead, and a
+ * window test has to make every attempt outlast seconds of that window to reach it.
+ */
+ private void reopenWithReplayBounds(int maxRetries, long retryWindowNanos) throws Exception
+ {
+ closeAndRemove(storage);
+ storage = new PDBStorage(createBackendCfg(), serverContext, maxRetries, retryWindowNanos);
+ storage.open(AccessMode.READ_WRITE);
}
@Test
@@ -122,6 +192,260 @@
assertThat(storage.getNewExchange(treeName, true)).isNotSameAs(initial);
}
+ @Test
+ public void testWriteGivesUpAfterTheAttemptCap() throws Exception
+ {
+ // the shipped cap, against a window the ladder of backoffs cannot reach: on the shipped window those nine
+ // backoffs draw from up to 5550 ms, so a loaded machine ends this loop on the window and the cap goes untested
+ reopenWithReplayBounds(PDBStorage.MAX_RETRIES, UNREACHABLE_RETRY_WINDOW_NANOS);
+ createTree();
+
+ final RollbackException conflict = new RollbackException();
+ final AtomicInteger attempts = new AtomicInteger();
+ try
+ {
+ storage.write(new WriteOperation()
+ {
+ @Override
+ public void run(WriteableTransaction txn) throws Exception
+ {
+ attempts.incrementAndGet();
+ txn.put(treeName, valueOfUtf8("abandoned"), valueOfUtf8("value"));
+ throw conflict;
+ }
+ });
+ failBecauseExceptionWasNotThrown(StorageRuntimeException.class);
+ }
+ catch (StorageRuntimeException e)
+ {
+ assertThat(e.getSuppressed()).contains(conflict);
+ }
+ assertThat(attempts.get()).isEqualTo(PDBStorage.MAX_RETRIES);
+ assertThat(read("abandoned")).isNull();
+ }
+
+ @Test
+ public void testWriteIsReplayedUntilTheConflictClears() throws Exception
+ {
+ createTree();
+
+ final AtomicInteger attempts = new AtomicInteger();
+ storage.write(new WriteOperation()
+ {
+ @Override
+ public void run(WriteableTransaction txn) throws Exception
+ {
+ if (attempts.incrementAndGet() <= 3)
+ {
+ throw new RollbackException();
+ }
+ txn.put(treeName, valueOfUtf8("applied"), valueOfUtf8("value"));
+ }
+ });
+
+ assertThat(attempts.get()).isEqualTo(4);
+ assertThat(read("applied")).isEqualTo(valueOfUtf8("value"));
+ }
+
+ /**
+ * PersistIt reports a write-write conflict only once it has waited on it - up to
+ * {@code SharedResource.DEFAULT_MAX_WAIT_TIME}, a minute, which this backend never lowers - so a single attempt
+ * can outlast the whole window. Giving up on the window alone would then replay nothing, in the very case where
+ * the replay is likeliest to succeed: the transaction that was blocking this one has just finished.
+ */
+ @Test
+ public void testWriteIsReplayedOnceWhenTheFirstAttemptOutlastsTheWindow() throws Exception
+ {
+ reopenWithReplayBounds(PDBStorage.MAX_RETRIES, SHORT_RETRY_WINDOW_NANOS);
+ createTree();
+
+ final AtomicInteger attempts = new AtomicInteger();
+ storage.write(new WriteOperation()
+ {
+ @Override
+ public void run(WriteableTransaction txn) throws Exception
+ {
+ if (attempts.incrementAndGet() == 1)
+ {
+ Thread.sleep(ATTEMPT_LONGER_THAN_SHORT_WINDOW_MS);
+ throw new RollbackException();
+ }
+ txn.put(treeName, valueOfUtf8("outlasted"), valueOfUtf8("written"));
+ }
+ });
+
+ assertThat(attempts.get()).isEqualTo(2);
+ assertThat(read("outlasted")).isEqualTo(valueOfUtf8("written"));
+ }
+
+ @Test
+ public void testExhaustedWriteNamesTheAttemptsItSpent() throws Exception
+ {
+ // the message is the same at any cap, so this one is spent in two backoffs rather than in the shipped ladder
+ final int maxRetries = 3;
+ reopenWithReplayBounds(maxRetries, UNREACHABLE_RETRY_WINDOW_NANOS);
+ createTree();
+
+ try
+ {
+ storage.write(new WriteOperation()
+ {
+ @Override
+ public void run(WriteableTransaction txn) throws Exception
+ {
+ throw new RollbackException();
+ }
+ });
+ failBecauseExceptionWasNotThrown(StorageRuntimeException.class);
+ }
+ catch (StorageRuntimeException e)
+ {
+ assertThat(e.getMessage()).contains("PDBStorageTest").contains(maxRetries + " attempts");
+ // and which of the two bounds ran out, since the attempt count alone does not say
+ assertThat(e.getMessage()).contains("attempt cap");
+ // write() unwraps a StorageRuntimeException that carries a cause, which would replace this message with
+ // the bare RollbackException, and it is the message the config change paths report
+ assertThat(e.getCause()).isNull();
+ }
+ }
+
+ @Test
+ public void testWriteGivesUpOnTheWindowWhenAttemptsAreSlow() throws Exception
+ {
+ reopenWithReplayBounds(PDBStorage.MAX_RETRIES, SHORT_RETRY_WINDOW_NANOS);
+ createTree();
+
+ final AtomicInteger attempts = new AtomicInteger();
+ try
+ {
+ storage.write(new WriteOperation()
+ {
+ @Override
+ public void run(WriteableTransaction txn) throws Exception
+ {
+ attempts.incrementAndGet();
+ // a conflict this slow to report spends the wall clock window long before the attempt cap
+ Thread.sleep(ATTEMPT_LONGER_THAN_SHORT_WINDOW_MS);
+ throw new RollbackException();
+ }
+ });
+ failBecauseExceptionWasNotThrown(StorageRuntimeException.class);
+ }
+ catch (StorageRuntimeException e)
+ {
+ // the window is what ended it, and it says so: an assertion on the attempt count alone would also pass for
+ // a give up on attempt 1, which is the regression the attempt > 1 exemption exists to prevent
+ assertThat(e.getMessage()).contains("retry window");
+ }
+ // one attempt beyond the first: the first spends the window, the exemption grants the replay, and the check
+ // after that replay is the one that gives up
+ assertThat(attempts.get()).isEqualTo(2);
+ }
+
+ @Test
+ public void testInterruptedWriteReportsTheConflictItWasReplaying() throws Exception
+ {
+ createTree();
+
+ final RollbackException conflict = new RollbackException();
+ final AtomicInteger attempts = new AtomicInteger();
+ final boolean interruptedAfterwards;
+ try
+ {
+ storage.write(new WriteOperation()
+ {
+ @Override
+ public void run(WriteableTransaction txn) throws Exception
+ {
+ attempts.incrementAndGet();
+ // interrupted here rather than before the write, where the transaction this attempt begins would
+ // report the interrupt itself and the loop would never reach the backoff being tested
+ Thread.currentThread().interrupt();
+ throw conflict;
+ }
+ });
+ failBecauseExceptionWasNotThrown(StorageRuntimeException.class);
+ return;
+ }
+ catch (StorageRuntimeException e)
+ {
+ interruptedAfterwards = Thread.interrupted();
+ // the conflict, not the interrupt, is what the caller is told about - but through the same shape the
+ // exhausted loop uses, since a bare RollbackException reaches every caller as its own class name
+ assertThat(e.getMessage()).contains("PDBStorageTest").contains("interrupted");
+ assertThat(e.getSuppressed()).contains(conflict).hasAtLeastOneElementOfType(InterruptedException.class);
+ assertThat(e.getCause()).isNull();
+ }
+ finally
+ {
+ Thread.interrupted();
+ }
+ // sleep() cleared the flag, so the caller only learns of the interrupt if the loop restores it
+ assertThat(interruptedAfterwards).isTrue();
+ // one attempt even though the first backoff is a random 0-49 ms and so is sometimes 0: Thread.sleep() checks
+ // the interrupt flag before it checks for a zero duration, so the replay is never reached
+ assertThat(attempts.get()).isEqualTo(1);
+ }
+
+ /**
+ * The delay grows with the attempt and stays under the cap, so that a contention the first delays did not
+ * outlast still has a chance to clear without the replays overrunning the window on sleep alone.
+ */
+ @Test
+ public void testRetryDelayGrowsAndStaysBounded()
+ {
+ long previousBound = 0;
+ for (int attempt = 1; attempt <= PDBStorage.MAX_RETRIES; attempt++)
+ {
+ long bound = 0;
+ for (int i = 0; i < 100; i++)
+ {
+ final long delay = PDBStorage.retryDelayMillis(attempt);
+ assertThat(delay).as("attempt %d", attempt).isGreaterThanOrEqualTo(0).isLessThan(1000);
+ bound = Math.max(bound, delay);
+ }
+ if (attempt == 1)
+ {
+ // the flat sleep this loop took before it was bounded, unchanged: only the later attempts back off
+ assertThat(bound).as("attempt 1 delays past the sleep this loop always took").isLessThan(50);
+ }
+ assertThat(bound).as("attempt %d did not grow past attempt %d", attempt, attempt - 1)
+ .isGreaterThanOrEqualTo(previousBound / 2);
+ previousBound = bound;
+ }
+ // and the growth is real rather than a delay that never leaves the first tier
+ long grown = 0;
+ for (int i = 0; i < 100; i++)
+ {
+ grown = Math.max(grown, PDBStorage.retryDelayMillis(PDBStorage.MAX_RETRIES));
+ }
+ assertThat(grown).as("the last attempts still sleep within the first attempt's bound").isGreaterThan(500);
+ }
+
+ private void createTree() throws Exception
+ {
+ storage.write(new WriteOperation()
+ {
+ @Override
+ public void run(WriteableTransaction txn) throws Exception
+ {
+ txn.openTree(treeName, true);
+ }
+ });
+ }
+
+ private ByteString read(final String key) throws Exception
+ {
+ return storage.read(new ReadOperation<ByteString>()
+ {
+ @Override
+ public ByteString run(ReadableTransaction txn) throws Exception
+ {
+ return txn.read(treeName, valueOfUtf8(key));
+ }
+ });
+ }
+
protected PDBBackendCfg createBackendCfg()
{
PDBBackendCfg backendCfg = mockCfg(PDBBackendCfg.class);
--
Gitblit v1.10.0