com.nfsdb.journal.net.bridge.JournalEventBridge Maven / Gradle / Ivy
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/*
* Copyright (c) 2014-2015. Vlad Ilyushchenko
*
* 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
*
* http://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 com.nfsdb.journal.net.bridge;
import com.lmax.disruptor.*;
import com.nfsdb.journal.concurrent.NamedDaemonThreadFactory;
import com.nfsdb.journal.tx.TxFuture;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import static java.util.Arrays.copyOf;
/**
*
* +---------+
* +---> | AGENT 1 |----+ +--------------+
* +----------+ | +---------+ | +--> | writer 1 ack |
* | writer 1 +----+ | | | +--------------+
* +----------+ | +-------+ +--------+ | +---------+ | |
* +----> | IN_RB +------> | OUT RB +----+---> | AGENT 2 |----+-----+
* | +-------+ +--------+ | +---------+ | |
* +----------+ | | | | +--------------+
* | writer 2 +----+ | +---------+ | +--> | writer 2 ack |
* +----------+ +---> | AGENT 3 |----+ +--------------+
* +---------+
*
*/
public class JournalEventBridge {
private static final AtomicReferenceFieldUpdater AGENT_SEQUENCES_UPDATER =
AtomicReferenceFieldUpdater.newUpdater(JournalEventBridge.class, AgentBarrierHolder.class, "agentBarrierHolder");
private final ExecutorService executor = Executors.newFixedThreadPool(1, new NamedDaemonThreadFactory("jj-event-bridge", false));
private final RingBuffer inRingBuffer;
private final BatchEventProcessor batchEventProcessor;
private final RingBuffer outRingBuffer;
private final SequenceBarrier outBarrier;
private volatile AgentBarrierHolder agentBarrierHolder = new AgentBarrierHolder();
/**
* Many-to-many bridge between multiple journals publishing their commits and multiple subscribers consuming them.
* These subscribers are typically {@link com.nfsdb.journal.net.JournalServerAgent} instances.
* Disruptor library doesn't provide many-to-many ring buffer out-of-box, so this implementation employs
* two many-to-one ring buffers, in and out. Single thread is the sole consumer on the in buffer and
* sole publisher on the out ring buffer.
* Out ring buffer has timeout blocking wait strategy to enable {@link com.nfsdb.journal.net.JournalServerAgent} to send
* heartbeat message to client. Value of {@code timeout} is heartbeat frequency between server agent and client.
*
* @param timeout for out buffer wait.
* @param unit time unit for timeout value
* @param eventBufferSize size of ring buffer
*/
public JournalEventBridge(long timeout, TimeUnit unit, int eventBufferSize) {
this.inRingBuffer = RingBuffer.createMultiProducer(JournalEvent.EVENT_FACTORY, eventBufferSize, new BlockingWaitStrategy());
this.outRingBuffer = RingBuffer.createSingleProducer(JournalEvent.EVENT_FACTORY, eventBufferSize, new TimeoutBlockingWaitStrategy(timeout, unit));
this.outBarrier = outRingBuffer.newBarrier();
this.batchEventProcessor = new BatchEventProcessor<>(inRingBuffer, inRingBuffer.newBarrier(), new EventHandler() {
@Override
public void onEvent(JournalEvent event, long sequence, boolean endOfBatch) throws Exception {
long outSeq = outRingBuffer.next();
JournalEvent outEvent = outRingBuffer.get(outSeq);
outEvent.setIndex(event.getIndex());
outEvent.setTimestamp(event.getTimestamp());
outRingBuffer.publish(outSeq);
}
});
inRingBuffer.addGatingSequences(batchEventProcessor.getSequence());
}
public void start() {
executor.submit(batchEventProcessor);
}
public void halt() {
executor.shutdown();
while (batchEventProcessor.isRunning()) {
batchEventProcessor.halt();
}
}
public void publish(final int journalIndex, final long timestamp) {
long sequence = inRingBuffer.next();
JournalEvent event = inRingBuffer.get(sequence);
event.setIndex(journalIndex);
event.setTimestamp(timestamp);
inRingBuffer.publish(sequence);
}
public RingBuffer getOutRingBuffer() {
return outRingBuffer;
}
public SequenceBarrier getOutBarrier() {
return outBarrier;
}
public Sequence createAgentSequence() {
Sequence sequence = new Sequence(outBarrier.getCursor());
outRingBuffer.addGatingSequences(sequence);
AgentBarrierHolder currentHolder;
AgentBarrierHolder updatedHolder = new AgentBarrierHolder();
do {
currentHolder = AGENT_SEQUENCES_UPDATER.get(this);
updatedHolder.agentSequences = copyOf(currentHolder.agentSequences, currentHolder.agentSequences.length + 1);
updatedHolder.agentSequences[currentHolder.agentSequences.length] = sequence;
updatedHolder.barrier = outRingBuffer.newBarrier(updatedHolder.agentSequences);
}
while (!AGENT_SEQUENCES_UPDATER.compareAndSet(this, currentHolder, updatedHolder));
return sequence;
}
public void removeAgentSequence(Sequence sequence) {
AgentBarrierHolder currentHolder;
AgentBarrierHolder updatedHolder = new AgentBarrierHolder();
do {
currentHolder = AGENT_SEQUENCES_UPDATER.get(this);
int toRemove = 0;
for (int i1 = 0; i1 < currentHolder.agentSequences.length; i1++) {
if (currentHolder.agentSequences[i1] == sequence) // Specifically uses identity
{
toRemove++;
}
}
if (toRemove == 0) {
break;
}
final int oldSize = currentHolder.agentSequences.length;
updatedHolder.agentSequences = new Sequence[oldSize - toRemove];
for (int i = 0, pos = 0; i < oldSize; i++) {
final Sequence testSequence = currentHolder.agentSequences[i];
if (sequence != testSequence) {
updatedHolder.agentSequences[pos++] = testSequence;
}
}
if (updatedHolder.agentSequences.length > 0) {
updatedHolder.barrier = outRingBuffer.newBarrier(updatedHolder.agentSequences);
}
}
while (!AGENT_SEQUENCES_UPDATER.compareAndSet(this, currentHolder, updatedHolder));
outRingBuffer.removeGatingSequence(sequence);
}
public TxFuture createRemoteCommitFuture(int journalIndex, long timestamp) {
return new RemoteCommitFuture(outRingBuffer, agentBarrierHolder.barrier, journalIndex, timestamp);
}
}