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Efficient reliable UDP unicast, UDP multicast, and IPC transport protocol.
/*
* Copyright 2014-2024 Real Logic Limited.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.aeron.cluster.service;
import io.aeron.ExclusivePublication;
import io.aeron.Publication;
import io.aeron.cluster.client.ClusterException;
import io.aeron.cluster.codecs.MessageHeaderEncoder;
import io.aeron.cluster.codecs.SnapshotMark;
import io.aeron.cluster.codecs.SnapshotMarkerEncoder;
import io.aeron.logbuffer.BufferClaim;
import org.agrona.DirectBuffer;
import org.agrona.concurrent.AgentInvoker;
import org.agrona.concurrent.AgentTerminationException;
import org.agrona.concurrent.IdleStrategy;
import java.util.concurrent.TimeUnit;
/**
* Base class of common functions required to take a snapshot of cluster state.
*/
public class SnapshotTaker
{
/**
* Reusable {@link BufferClaim} to avoid allocation.
*/
protected final BufferClaim bufferClaim = new BufferClaim();
/**
* Reusable {@link MessageHeaderEncoder} to avoid allocation.
*/
protected final MessageHeaderEncoder messageHeaderEncoder = new MessageHeaderEncoder();
/**
* {@link Publication} to which the snapshot will be written.
*/
protected final ExclusivePublication publication;
/**
* {@link IdleStrategy} to be called when back pressure is propagated from the {@link #publication}.
*/
protected final IdleStrategy idleStrategy;
private static final int ENCODED_MARKER_LENGTH =
MessageHeaderEncoder.ENCODED_LENGTH + SnapshotMarkerEncoder.BLOCK_LENGTH;
private final AgentInvoker aeronAgentInvoker;
private final SnapshotMarkerEncoder snapshotMarkerEncoder = new SnapshotMarkerEncoder();
/**
* Construct a {@link SnapshotTaker} which will encode the snapshot to a publication.
*
* @param publication into which the snapshot will be encoded.
* @param idleStrategy to call when the publication is back pressured.
* @param aeronAgentInvoker to call when idling so it stays active.
*/
public SnapshotTaker(
final ExclusivePublication publication, final IdleStrategy idleStrategy, final AgentInvoker aeronAgentInvoker)
{
this.publication = publication;
this.idleStrategy = idleStrategy;
this.aeronAgentInvoker = aeronAgentInvoker;
}
/**
* Mark the beginning of the encoded snapshot.
*
* @param snapshotTypeId type to identify snapshot within a cluster.
* @param logPosition at which the snapshot was taken.
* @param leadershipTermId at which the snapshot was taken.
* @param snapshotIndex so the snapshot can be sectioned.
* @param timeUnit of the cluster timestamps stored in the snapshot.
* @param appVersion associated with the snapshot from {@link ClusteredServiceContainer.Context#appVersion()}.
*/
public void markBegin(
final long snapshotTypeId,
final long logPosition,
final long leadershipTermId,
final int snapshotIndex,
final TimeUnit timeUnit,
final int appVersion)
{
markSnapshot(
snapshotTypeId, logPosition, leadershipTermId, snapshotIndex, SnapshotMark.BEGIN, timeUnit, appVersion);
}
/**
* Mark the end of the encoded snapshot.
*
* @param snapshotTypeId type to identify snapshot within a cluster.
* @param logPosition at which the snapshot was taken.
* @param leadershipTermId at which the snapshot was taken.
* @param snapshotIndex so the snapshot can be sectioned.
* @param timeUnit of the cluster timestamps stored in the snapshot.
* @param appVersion associated with the snapshot from {@link ClusteredServiceContainer.Context#appVersion()}.
*/
public void markEnd(
final long snapshotTypeId,
final long logPosition,
final long leadershipTermId,
final int snapshotIndex,
final TimeUnit timeUnit,
final int appVersion)
{
markSnapshot(
snapshotTypeId, logPosition, leadershipTermId, snapshotIndex, SnapshotMark.END, timeUnit, appVersion);
}
/**
* Generically {@link SnapshotMark} a snapshot.
*
* @param snapshotTypeId type to identify snapshot within a cluster.
* @param logPosition at which the snapshot was taken.
* @param leadershipTermId at which the snapshot was taken.
* @param snapshotIndex so the snapshot can be sectioned.
* @param snapshotMark which specifies the type of snapshot mark.
* @param timeUnit of the cluster timestamps stored in the snapshot.
* @param appVersion associated with the snapshot from {@link ClusteredServiceContainer.Context#appVersion()}.
*/
public void markSnapshot(
final long snapshotTypeId,
final long logPosition,
final long leadershipTermId,
final int snapshotIndex,
final SnapshotMark snapshotMark,
final TimeUnit timeUnit,
final int appVersion)
{
idleStrategy.reset();
while (true)
{
final long result = publication.tryClaim(ENCODED_MARKER_LENGTH, bufferClaim);
if (result > 0)
{
snapshotMarkerEncoder
.wrapAndApplyHeader(bufferClaim.buffer(), bufferClaim.offset(), messageHeaderEncoder)
.typeId(snapshotTypeId)
.logPosition(logPosition)
.leadershipTermId(leadershipTermId)
.index(snapshotIndex)
.mark(snapshotMark)
.timeUnit(ClusterClock.map(timeUnit))
.appVersion(appVersion);
bufferClaim.commit();
break;
}
checkResultAndIdle(result);
}
}
/**
* Check for thread interrupt and throw an {@link AgentTerminationException} if interrupted.
*/
protected static void checkInterruptStatus()
{
if (Thread.currentThread().isInterrupted())
{
throw new AgentTerminationException("interrupted");
}
}
/**
* Check the result of offering to a publication when writing a snapshot.
*
* @param position of an offer or try claim to a publication.
* @param publication on which the offer or try claim was attempted.
*/
protected static void checkResult(final long position, final Publication publication)
{
if (Publication.NOT_CONNECTED == position)
{
throw new ClusterException("publication is not connected");
}
if (Publication.CLOSED == position)
{
throw new ClusterException("publication is closed");
}
if (Publication.MAX_POSITION_EXCEEDED == position)
{
throw new ClusterException("publication at max position: term-length=" + publication.termBufferLength());
}
}
/**
* Check the result of offering to a publication when writing a snapshot and then idle after invoking the client
* agent if necessary.
*
* @param position of an offer or try claim to a publication.
*/
protected void checkResultAndIdle(final long position)
{
checkResult(position, publication);
checkInterruptStatus();
invokeAgentClient();
idleStrategy.idle();
}
/**
* Invoke the Aeron client agent if necessary.
*/
protected void invokeAgentClient()
{
if (null != aeronAgentInvoker)
{
aeronAgentInvoker.invoke();
}
}
/**
* Helper method to offer a message into the snapshot publication.
*
* @param buffer containing the message.
* @param offset at which the message begins.
* @param length of the message.
*/
protected final void offer(final DirectBuffer buffer, final int offset, final int length)
{
idleStrategy.reset();
while (true)
{
final long result = publication.offer(buffer, offset, length);
if (result > 0)
{
break;
}
checkResultAndIdle(result);
}
}
}
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