/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
package org.mozilla.gecko.sync.synchronizer;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.atomic.AtomicInteger;
import org.mozilla.gecko.sync.Logger;
import org.mozilla.gecko.sync.ThreadPool;
import org.mozilla.gecko.sync.repositories.InvalidSessionTransitionException;
import org.mozilla.gecko.sync.repositories.NoStoreDelegateException;
import org.mozilla.gecko.sync.repositories.RepositorySession;
import org.mozilla.gecko.sync.repositories.delegates.DeferredRepositorySessionBeginDelegate;
import org.mozilla.gecko.sync.repositories.delegates.DeferredRepositorySessionStoreDelegate;
import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionBeginDelegate;
import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionFetchRecordsDelegate;
import org.mozilla.gecko.sync.repositories.delegates.RepositorySessionStoreDelegate;
import org.mozilla.gecko.sync.repositories.domain.Record;
/**
* Pulls records from `source`, applying them to `sink`.
* Notifies its delegate of errors and completion.
*
* All stores (initiated by a fetch) must have been completed before storeDone
* is invoked on the sink. This is to avoid the existing stored items being
* considered as the total set, with onStoreCompleted being called when they're
* done:
*
* store(A) store(B)
* store(C) storeDone()
* store(A) finishes. Store job begins.
* store(C) finishes. Store job begins.
* storeDone() finishes.
* Storing of A complete.
* Storing of C complete.
* We're done! Call onStoreCompleted.
* store(B) finishes... uh oh.
*
* In other words, storeDone must be gated on the synchronous invocation of every store.
*
* Similarly, we require that every store callback have returned before onStoreCompleted is invoked.
*
* This whole set of guarantees should be achievable thusly:
*
* * The fetch process must run in a single thread, and invoke store()
* synchronously. After processing every incoming record, storeDone is called,
* setting a flag.
* If the fetch cannot be implicitly queued, it must be explicitly queued.
* In this implementation, we assume that fetch callbacks are strictly ordered in this way.
*
* * The store process must be (implicitly or explicitly) queued. When the
* queue empties, the consumer checks the storeDone flag. If it's set, and the
* queue is exhausted, invoke onStoreCompleted.
*
* RecordsChannel exists to enforce this ordering of operations.
*
* @author rnewman
*
*/
public class RecordsChannel implements
RepositorySessionFetchRecordsDelegate,
RepositorySessionStoreDelegate,
RecordsConsumerDelegate,
RepositorySessionBeginDelegate {
private static final String LOG_TAG = "RecordsChannel";
public RepositorySession source;
public RepositorySession sink;
private RecordsChannelDelegate delegate;
private long timestamp;
private long fetchEnd = -1;
protected final AtomicInteger numFetched = new AtomicInteger();
protected final AtomicInteger numFetchFailed = new AtomicInteger();
protected final AtomicInteger numStored = new AtomicInteger();
protected final AtomicInteger numStoreFailed = new AtomicInteger();
public RecordsChannel(RepositorySession source, RepositorySession sink, RecordsChannelDelegate delegate) {
this.source = source;
this.sink = sink;
this.delegate = delegate;
this.timestamp = source.lastSyncTimestamp;
}
/*
* We push fetched records into a queue.
* A separate thread is waiting for us to notify it of work to do.
* When we tell it to stop, it'll stop. We do that when the fetch
* is completed.
* When it stops, we tell the sink that there are no more records,
* and wait for the sink to tell us that storing is done.
* Then we notify our delegate of completion.
*/
private RecordConsumer consumer;
private boolean waitingForQueueDone = false;
private ConcurrentLinkedQueue<Record> toProcess = new ConcurrentLinkedQueue<Record>();
@Override
public ConcurrentLinkedQueue<Record> getQueue() {
return toProcess;
}
protected boolean isReady() {
return source.isActive() && sink.isActive();
}
/**
* Get the number of records fetched so far.
*
* @return number of fetches.
*/
public int getFetchCount() {
return numFetched.get();
}
/**
* Get the number of fetch failures recorded so far.
*
* @return number of fetch failures.
*/
public int getFetchFailureCount() {
return numFetchFailed.get();
}
/**
* Get the number of store attempts (successful or not) so far.
*
* @return number of stores attempted.
*/
public int getStoreCount() {
return numStored.get();
}
/**
* Get the number of store failures recorded so far.
*
* @return number of store failures.
*/
public int getStoreFailureCount() {
return numStoreFailed.get();
}
/**
* Start records flowing through the channel.
*/
public void flow() {
if (!isReady()) {
RepositorySession failed = source;
if (source.isActive()) {
failed = sink;
}
this.delegate.onFlowBeginFailed(this, new SessionNotBegunException(failed));
return;
}
sink.setStoreDelegate(this);
numFetched.set(0);
numFetchFailed.set(0);
numStored.set(0);
numStoreFailed.set(0);
// Start a consumer thread.
this.consumer = new ConcurrentRecordConsumer(this);
ThreadPool.run(this.consumer);
waitingForQueueDone = true;
source.fetchSince(timestamp, this);
}
/**
* Begin both sessions, invoking flow() when done.
* @throws InvalidSessionTransitionException
*/
public void beginAndFlow() throws InvalidSessionTransitionException {
Logger.trace(LOG_TAG, "Beginning source.");
source.begin(this);
}
@Override
public void store(Record record) {
numStored.incrementAndGet();
try {
sink.store(record);
} catch (NoStoreDelegateException e) {
Logger.error(LOG_TAG, "Got NoStoreDelegateException in RecordsChannel.store(). This should not occur. Aborting.", e);
delegate.onFlowStoreFailed(this, e, record.guid);
}
}
@Override
public void onFetchFailed(Exception ex, Record record) {
Logger.warn(LOG_TAG, "onFetchFailed. Calling for immediate stop.", ex);
numFetchFailed.incrementAndGet();
this.consumer.halt();
delegate.onFlowFetchFailed(this, ex);
}
@Override
public void onFetchedRecord(Record record) {
numFetched.incrementAndGet();
this.toProcess.add(record);
this.consumer.doNotify();
}
@Override
public void onFetchCompleted(final long fetchEnd) {
Logger.trace(LOG_TAG, "onFetchCompleted. Stopping consumer once stores are done.");
Logger.trace(LOG_TAG, "Fetch timestamp is " + fetchEnd);
this.fetchEnd = fetchEnd;
this.consumer.queueFilled();
}
@Override
public void onRecordStoreFailed(Exception ex, String recordGuid) {
Logger.trace(LOG_TAG, "Failed to store record with guid " + recordGuid);
numStoreFailed.incrementAndGet();
this.consumer.stored();
delegate.onFlowStoreFailed(this, ex, recordGuid);
// TODO: abort?
}
@Override
public void onRecordStoreSucceeded(String guid) {
Logger.trace(LOG_TAG, "Stored record with guid " + guid);
this.consumer.stored();
}
@Override
public void consumerIsDone(boolean allRecordsQueued) {
Logger.trace(LOG_TAG, "Consumer is done. Are we waiting for it? " + waitingForQueueDone);
if (waitingForQueueDone) {
waitingForQueueDone = false;
this.sink.storeDone(); // Now we'll be waiting for onStoreCompleted.
}
}
@Override
public void onStoreCompleted(long storeEnd) {
Logger.trace(LOG_TAG, "onStoreCompleted. Notifying delegate of onFlowCompleted. " +
"Fetch end is " + fetchEnd + ", store end is " + storeEnd);
// TODO: synchronize on consumer callback?
delegate.onFlowCompleted(this, fetchEnd, storeEnd);
}
@Override
public void onBeginFailed(Exception ex) {
delegate.onFlowBeginFailed(this, ex);
}
@Override
public void onBeginSucceeded(RepositorySession session) {
if (session == source) {
Logger.trace(LOG_TAG, "Source session began. Beginning sink session.");
try {
sink.begin(this);
} catch (InvalidSessionTransitionException e) {
onBeginFailed(e);
return;
}
}
if (session == sink) {
Logger.trace(LOG_TAG, "Sink session began. Beginning flow.");
this.flow();
return;
}
// TODO: error!
}
@Override
public RepositorySessionStoreDelegate deferredStoreDelegate(final ExecutorService executor) {
return new DeferredRepositorySessionStoreDelegate(this, executor);
}
@Override
public RepositorySessionBeginDelegate deferredBeginDelegate(final ExecutorService executor) {
return new DeferredRepositorySessionBeginDelegate(this, executor);
}
@Override
public RepositorySessionFetchRecordsDelegate deferredFetchDelegate(ExecutorService executor) {
// Lie outright. We know that all of our fetch methods are safe.
return this;
}
}