/*
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* The contents of this file are subject to the terms of the Common Development and
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* Distribution License (the License). You may not use this file except in compliance with the
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* License.
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*
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* You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
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* specific language governing permission and limitations under the License.
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*
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* When distributing Covered Software, include this CDDL Header Notice in each file and include
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* the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
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* Header, with the fields enclosed by brackets [] replaced by your own identifying
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* information: "Portions Copyright [year] [name of copyright owner]".
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*
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* Copyright 2014-2016 ForgeRock AS.
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* Portions Copyright 2026 3A Systems, LLC.
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*/
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package org.opends.server.replication.service;
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import static java.util.concurrent.TimeUnit.MILLISECONDS;
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import static java.util.concurrent.TimeUnit.NANOSECONDS;
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import java.util.Collection;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentMap;
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import org.forgerock.opendj.ldap.DN;
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import org.opends.server.replication.common.CSN;
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/**
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* Class useful for the case where DS/RS instances are collocated inside the
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* same JVM. It synchronizes the shutdown of the DS and RS sides.
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* <p>
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* More specifically, it ensures a ReplicaOfflineMsg sent by the DS is
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* relayed/forwarded by the collocated RS to the other RSs in the topology
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* before the whole process shuts down.
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* <p>
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* The state is kept per domain and per instance: the collocated DS and RS
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* sides coordinate through the single instance MultimasterReplication hands
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* to both of them.
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*
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* @since OPENDJ-1453
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*/
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public class DSRSShutdownSync
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{
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/**
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* How long a ReplicaOfflineMsg may hold back the shutdown of the collocated
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* RS, in milliseconds, counted from the moment the message was sent.
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*/
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public static final long REPLICA_OFFLINE_GRACE_PERIOD = 5000;
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private final long gracePeriod;
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/**
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* The ReplicaOfflineMsg which has not been forwarded yet, per domain and per
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* replica of that domain.
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* <p>
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* It is kept per domain because a domain sends this message whenever its
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* replication service is disabled - an online import, a restore, a
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* configuration change - and not only when the process shuts down. A single
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* entry for the whole process would be the one of the first such message and
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* would leave no grace period at all to the shutdown this class exists for.
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* <p>
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* It is kept per replica because the collocated RS relays the message of
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* every replica connected to it, and the forward of another replica's
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* message says nothing about this one.
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*/
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private final ConcurrentMap<DN, ConcurrentMap<Integer, PendingOfflineMsg>> replicaOfflineMsgs =
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new ConcurrentHashMap<>();
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/** Monitor notified whenever a ReplicaOfflineMsg has been forwarded. */
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private final Object forwardedMonitor = new Object();
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/** Creates a synchronization object using the default grace period. */
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public DSRSShutdownSync()
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{
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this(REPLICA_OFFLINE_GRACE_PERIOD);
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}
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/**
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* Creates a synchronization object using the provided grace period.
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*
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* @param gracePeriod
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* how long a ReplicaOfflineMsg may hold back the shutdown, in milliseconds
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*/
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DSRSShutdownSync(long gracePeriod)
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{
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this.gracePeriod = gracePeriod;
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}
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/**
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* Message has been sent.
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*
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* @param baseDN
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* the domain for which the message has been sent
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* @param offlineCSN
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* the CSN of the message, which identifies both the replica which announced itself
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* offline and the announcement being waited for
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*/
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public void replicaOfflineMsgSent(DN baseDN, CSN offlineCSN)
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{
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replicaOfflineMsgs
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.computeIfAbsent(baseDN, dn -> new ConcurrentHashMap<Integer, PendingOfflineMsg>())
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.put(offlineCSN.getServerId(), new PendingOfflineMsg(offlineCSN, System.nanoTime()));
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}
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/**
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* Message has been forwarded.
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*
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* @param baseDN
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* the domain for which the message has been sent
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* @param forwardedCSN
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* the CSN of the forwarded message
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*/
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public void replicaOfflineMsgForwarded(DN baseDN, CSN forwardedCSN)
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{
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final ConcurrentMap<Integer, PendingOfflineMsg> msgs = replicaOfflineMsgs.get(baseDN);
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if (msgs != null)
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{
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final int serverId = forwardedCSN.getServerId();
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final PendingOfflineMsg pending = msgs.get(serverId);
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/*
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* A replica announces itself offline on every disableService(), so the message which is
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* forwarded now may be an older one - queued behind a backlog since an earlier import, or
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* synthesized from the offline CSN of the changelog for a server which is catching up.
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* Such a forward says nothing about the announcement the shutdown is waiting for, and must
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* not consume its grace period.
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*/
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if (pending != null && pending.csn.isOlderThanOrEqualTo(forwardedCSN))
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{
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msgs.remove(serverId, pending);
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}
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}
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synchronized (forwardedMonitor)
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{
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forwardedMonitor.notifyAll();
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}
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}
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/**
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* Whether the shutdown of a domain can proceed, i.e. its ReplicaOfflineMsg
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* has been forwarded or its grace period has expired.
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* <p>
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* The shutdown itself blocks on {@link #awaitReplicaOfflineMsgsForwarded(Collection, long)}
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* rather than polling this; it is the same state, observable without waiting for it.
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*
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* @param baseDN
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* the baseDN of the domain being shut down
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* @return true if the shutdown of this domain need not wait any longer, i.e. its message was
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* forwarded or its grace period has expired, false otherwise
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*/
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public boolean canShutdown(DN baseDN)
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{
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return remainingGracePeriod(baseDN) <= 0;
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}
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/**
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* Returns the time by which every wait of one shutdown must be over.
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* <p>
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* A process shuts its domains down one after the other and each of them may have a message
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* pending, so a deadline computed once and shared by all of them keeps the whole shutdown
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* bounded by one grace period instead of one per domain.
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*
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* @return the point in time, on the {@link System#nanoTime()} clock, by which the waits must
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* be over
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*/
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public long newShutdownDeadline()
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{
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return System.nanoTime() + MILLISECONDS.toNanos(gracePeriod);
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}
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/**
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* Waits for the ReplicaOfflineMsg of every provided domain to be forwarded, or for their grace
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* periods or the provided deadline to expire.
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* <p>
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* This must be called before the server handlers of those domains are stopped: stopping them
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* deactivates their consumer, clears their message queue and closes their session, after which
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* the message can no longer be forwarded.
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* <p>
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* All the domains of one shutdown wait together rather than one after the other, so that the
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* shutdown is bounded by one grace period without the wait of one domain spending the grace
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* period of the next.
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*
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* @param baseDNs
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* the baseDNs of the domains whose messages must be forwarded
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* @param deadline
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* the point in time, on the {@link System#nanoTime()} clock, by which this wait must
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* be over whatever the domains announce in the meantime - see
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* {@link #newShutdownDeadline()}. A deadline which is not in the future returns
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* without waiting at all, for a caller which has nothing to wait for.
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*/
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public void awaitReplicaOfflineMsgsForwarded(Collection<DN> baseDNs, long deadline)
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{
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if (deadline - System.nanoTime() <= 0)
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{
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return;
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}
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synchronized (forwardedMonitor)
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{
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while (true)
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{
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final long timeout = Math.min(remainingGracePeriod(baseDNs),
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NANOSECONDS.toMillis(deadline - System.nanoTime()));
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if (timeout <= 0)
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{
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return;
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}
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try
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{
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forwardedMonitor.wait(timeout);
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}
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catch (InterruptedException e)
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{
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/*
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* Give up waiting. The interrupt is deliberately not restored: what follows this call is
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* the rest of the shutdown - joining the reader and writer thread of every handler, then
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* closing the changelog DB - and an interrupt flag would make all of it give up too.
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*/
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return;
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}
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}
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}
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}
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/**
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* Returns the time left, in milliseconds, to forward the ReplicaOfflineMsg of the replica of
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* the provided domains which has the longest to wait, zero or less if none of them has a
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* message pending.
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*/
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private long remainingGracePeriod(Collection<DN> baseDNs)
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{
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long remaining = 0;
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for (DN baseDN : baseDNs)
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{
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remaining = Math.max(remaining, remainingGracePeriod(baseDN));
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}
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return remaining;
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}
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/**
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* Returns the time left, in milliseconds, to forward the ReplicaOfflineMsg of the replica of
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* this domain which has the longest to wait, zero or less if no message of this domain is
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* pending.
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*/
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private long remainingGracePeriod(DN baseDN)
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{
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final ConcurrentMap<Integer, PendingOfflineMsg> msgs = replicaOfflineMsgs.get(baseDN);
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if (msgs == null)
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{
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return 0;
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}
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final long now = System.nanoTime();
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long remaining = 0;
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for (PendingOfflineMsg pending : msgs.values())
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{
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remaining = Math.max(remaining, gracePeriod - NANOSECONDS.toMillis(now - pending.sentTime));
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}
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return remaining;
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}
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/**
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* A ReplicaOfflineMsg a replica announced and which has not been forwarded yet.
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* <p>
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* This deliberately does not override {@code equals}: the two-argument
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* {@link ConcurrentMap#remove(Object, Object)} of the forward guard must match the very
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* announcement it read, not another one which happens to carry the same values.
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*/
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private static final class PendingOfflineMsg
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{
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/** The CSN of the message, so that the forward of an older one is not taken for this one. */
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private final CSN csn;
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/** When the message was announced, on the {@link System#nanoTime()} clock. */
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private final long sentTime;
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private PendingOfflineMsg(CSN csn, long sentTime)
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{
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this.csn = csn;
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this.sentTime = sentTime;
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}
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@Override
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public String toString()
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{
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return "PendingOfflineMsg(" + csn + ")";
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}
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}
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}
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