/**
* Copyright 2008 Google Inc.
*
* 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 org.waveprotocol.wave.concurrencycontrol.client;
import org.waveprotocol.wave.common.logging.LoggerBundle;
import org.waveprotocol.wave.concurrencycontrol.common.ChannelException;
import org.waveprotocol.wave.concurrencycontrol.common.DeltaPair;
import org.waveprotocol.wave.concurrencycontrol.common.Recoverable;
import org.waveprotocol.wave.concurrencycontrol.common.UnsavedDataListener;
import org.waveprotocol.wave.model.operation.OperationException;
import org.waveprotocol.wave.model.operation.TransformException;
import org.waveprotocol.wave.model.operation.wave.TransformedWaveletDelta;
import org.waveprotocol.wave.model.operation.wave.WaveletDelta;
import org.waveprotocol.wave.model.operation.wave.WaveletOperation;
import org.waveprotocol.wave.model.util.CollectionUtils;
import org.waveprotocol.wave.model.util.Preconditions;
import org.waveprotocol.wave.model.version.HashedVersion;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
public class ConcurrencyControl implements ServerConnectionListener {
/**
* The size and result version of an acknowledged delta.
*/
private static final class AckInfo {
/** Number of ops acknowledged. */
final int numOps;
/** Version of the wavelet after the acknowledged ops. */
final HashedVersion ackedVersion;
AckInfo(int numOps, HashedVersion ackedVersion) {
this.numOps = numOps;
this.ackedVersion = ackedVersion;
}
}
/**
* A client delta with the server acknowledgement.
*/
private static final class AckedDelta {
/** The delta sent to the server. */
final WaveletDelta delta;
/** The server's acknowledgement. */
final AckInfo ack;
AckedDelta(WaveletDelta delta, AckInfo ack) {
this.delta = delta;
this.ack = ack;
}
}
/**
* A listener for server operations.
*/
public interface ConnectionListener {
/** Called when a server operation is received. */
void onOperationReceived();
}
private final UnsavedDataListener.UnsavedDataInfo unsavedDataInfo =
new UnsavedDataListener.UnsavedDataInfo() {
@Override
public int inFlightSize() {
return (unacknowledged != null) ? unacknowledged.size() : 0;
}
@Override
public int estimateUnacknowledgedSize() {
return clientOperationQueue.estimateSize() + inFlightSize();
}
@Override
public int estimateUncommittedSize() {
int ackedButUncommitted = 0;
for (AckInfo ack : acks) {
ackedButUncommitted += ack.numOps;
}
return ackedButUncommitted + estimateUnacknowledgedSize();
}
@Override
public long laskAckVersion() {
if (!acks.isEmpty()) {
return acks.getLast().ackedVersion.getVersion();
}
return lastCommitVersion();
}
@Override
public long lastCommitVersion() {
return lastCommitVersion;
}
@Override
public String getInfo() {
return serverConnection.debugGetProfilingInfo() + "\n ====== CC Info ====== \n"
+ ConcurrencyControl.this;
}
};
private final LoggerBundle logger;
/**
* The hash from the server before any the inferredServerPath.
*/
private HashedVersion startSignature;
/**
* This marks the end of the intial sequence of deltas the server sends to
* the client when we open a connection to the server.
*/
private HashedVersion endOfStartingDelta;
/**
* This is the server's path inferred by the client. It contains deltas that
* was sent by the client and acked by server. The list is cleared when any
* server delta is received since we can't currently recover past a server
* delta.
*/
private final LinkedList<AckedDelta> inferredServerPath = CollectionUtils.newLinkedList();
/**
* Acknowledgments received for deltas not yet committed, in contiguous
* version order. Unlike {@link #inferredServerPath} items are not cleared
* when server deltas are received, but when commits are received.
*/
private final LinkedList<AckInfo> acks = CollectionUtils.newLinkedList();
/**
* Latest committed version.
*/
private long lastCommitVersion = 0;
/**
* This is the delta in the inferredServerPath that is not yet acked by the
* server. Any new operations coming from the client will be queued in other
* deltas after this delta in the inferredServerPath.
*
* If null, nothing is in flight to the server.
*/
private WaveletDelta unacknowledged;
/** Queue of operations from the client not yet sent to the server. */
private final OperationQueue clientOperationQueue = new OperationQueue();
/**
* The operations that have been received from the server and have been transformed
* against any relevant client operations but have not yet been received by the wave
* client. This is needed to allow the wave client to grab operations from
* CC when ever it's ready.
*/
private List<WaveletOperation> serverOperations = CollectionUtils.newLinkedList();
/**
* A listener for this class to broadcast its transformed server ops.
*/
private ConnectionListener clientListener = null;
/**
* The connection to the server where we can send client operations.
*/
private ServerConnection serverConnection;
/**
* For pause sending to the server. This is needed when we tell the client to
* flush its operations and we want to send to the server when all the
* operations are flushed.
*/
private boolean pauseSendForFlush = false;
/**
* Listener for unsaved data info.
*/
private UnsavedDataListener unsavedDataListener;
/**
* Constructs a client side concurrency control module. The class must be
* {@link #initialise(ServerConnection, ConnectionListener) initialised}
* before use.
* @param logger a Logger to use for trace output
* @param startSignature the version/hash at which to begin connecting
*/
public ConcurrencyControl(LoggerBundle logger, HashedVersion startSignature) {
Preconditions.checkNotNull(startSignature, "startSignature cannot be null");
this.logger = logger;
this.startSignature = startSignature;
}
/**
* Initialises the server connection and client listener for this connection. This
* method must be invoked exactly once.
*
* @param serverConnection connection to which to send deltas
* @param clientListener listener for inbound deltas
*/
public void initialise(ServerConnection serverConnection, ConnectionListener clientListener) {
Preconditions.checkNotNull(clientListener, "CC initialised with null connection listener");
Preconditions.checkNotNull(serverConnection, "CC initialised with null server connection");
this.clientListener = clientListener;
this.serverConnection = serverConnection;
}
/**
* Sets the listener for unsaved data info.
*/
public void setUnsavedDataListener(UnsavedDataListener udl) {
unsavedDataListener = udl;
}
/**
* Closes this concurrency control.
*/
public void close() {
if (unsavedDataListener != null) {
unsavedDataListener.onClose(everythingIsCommitted());
}
if (!clientOperationQueue.isEmpty()) {
logger.error().log("Concurrency control closed with pending operations. Data has been lost");
}
}
@Override
public void onOpen(HashedVersion connectVersion, HashedVersion currentVersion)
throws ChannelException {
if ((connectVersion == null) || (currentVersion == null) || (connectVersion.getVersion() < 0)
|| (currentVersion.getVersion() < connectVersion.getVersion())) {
throw new ChannelException("ConcurrencyControl onOpen received invalid versions, "
+ "connect version: " + connectVersion + ", current version: " + currentVersion,
Recoverable.NOT_RECOVERABLE);
}
// Try to recover from where we were.
// Find the point in the inferred server path to start resending pending
// deltas to the server.
int startResend = -1;
if (startSignature.equals(connectVersion)) {
startResend = 0;
} else {
int i = 0;
Iterator<AckedDelta> iter = inferredServerPath.iterator();
while (iter.hasNext()) {
if (connectVersion.equals(iter.next().ack.ackedVersion)) {
startResend = i + 1;
break;
}
i++;
}
}
if (startResend < 0) {
// No matching signatures.
throw new ChannelException(
"Failed to recover from reconnection to server. No matching signatures. "
+ "[Received startSignature:" + connectVersion + " endSignature:" + currentVersion
+ "] " + this, Recoverable.NOT_RECOVERABLE);
} else if (startResend < inferredServerPath.size()) {
// Found a matching signature.
mergeToClientQueue(startResend);
} else if (startResend == inferredServerPath.size() && connectVersion.equals(currentVersion)) {
// Matched all signatures and we are also the end of the server operations.
// We are short circuiting, because we know that the server definitely have not got
// our unacknowledged delta since we are at the end of its signatures.
mergeToClientQueue(startResend);
} else {
// All the signatures matched, that means we need to compare server operations when
// we get them.
logger.trace().log("All signatures in CC queue matched on reconnection to server.");
}
forgetAcksAfter(startSignature.getVersion());
this.endOfStartingDelta = currentVersion;
sendDelta();
}
/**
* Push all deltas at startResend and after back into clientOperationQueue,
* discarding their ack info.
*
* @param startMerge The starting index to the delta in the
* {@link #inferredServerPath} to start to merge into clientOperationQueue.
*/
private void mergeToClientQueue(int startMerge) {
List<WaveletDelta> deltas = CollectionUtils.newArrayList();
// Use the version at the resend
if (startMerge < inferredServerPath.size()) {
Iterator<AckedDelta> iter = inferredServerPath.listIterator(startMerge);
while (iter.hasNext()) {
deltas.add(iter.next().delta);
iter.remove();
}
}
if (unacknowledged != null) {
deltas.add(unacknowledged);
unacknowledged = null;
}
Collections.reverse(deltas);
for (WaveletDelta delta : deltas) {
clientOperationQueue.insertHead(delta);
}
}
/**
* Forgets about any acknowledgments after some version.
*/
private void forgetAcksAfter(long version) {
Iterator<AckInfo> ackItr = acks.iterator();
while (ackItr.hasNext()) {
if (ackItr.next().ackedVersion.getVersion() > version) {
ackItr.remove();
}
}
}
/**
* Packages up transformed client operations as a delta, and sends it to the
* server. A send does not occur if there are unacknowledged deltas.
*/
private void sendDelta() {
if (!isReadyToSend()) {
return;
}
if (unacknowledged != null) {
logger.trace().log("Unacknowledged delta, expected to be applied at version ",
unacknowledged.getTargetVersion().getVersion());
return;
}
if (clientOperationQueue.isEmpty()) {
logger.trace().log("Nothing to send");
// Since the outgoing queue might have been transformed away, we need to reset
// the estimated queue.
triggerUnsavedDataListener();
return;
}
// If we are sending something then we have inferred our location on the server path
endOfStartingDelta = null;
List<WaveletOperation> ops = clientOperationQueue.take();
unacknowledged = new WaveletDelta(ops.get(0).getContext().getCreator(),
getLastSignature(), ops);
if (logger.isModuleEnabled() && logger.trace().shouldLog()) {
logger.trace().log("Sending delta to server with last known server version " +
unacknowledged.getTargetVersion(), unacknowledged);
}
serverConnection.send(unacknowledged);
triggerUnsavedDataListener();
}
/**
* Transform all the operation in the incoming server delta against all the
* operation in {@link #unacknowledged} and {@link #clientOperationQueue}
* before notifying the client.
*
* Also keep track of the transformed client operation so that we can infer
* the server's OT path.
*
* Assumption:
* <ul>
* <li>serverDelta.getVersion() == unacknowledged.getVersion()</li>
* <li>clientOps will never skip a version</li>
* <li>serverDelta.getSignature() is never null</li>
* </ul>
*
* @throws TransformException
* @throws OperationException
*/
private void transformOperationsAndNotify(TransformedWaveletDelta serverDelta) throws
TransformException, OperationException {
// Sanity check
long latestVersion = inferredServerPath.size() > 0 ?
inferredServerPath.getLast().ack.ackedVersion.getVersion() :
startSignature.getVersion();
if (serverDelta.getAppliedAtVersion() < latestVersion) {
throw new OperationException("Server sent a delta containing a version that is older than " +
"the version at end of inferred server path. [Received serverDelta" + serverDelta +
"] " + this);
}
if (detectEchoBack(serverDelta)) {
return;
}
// Clear inferred server path as we can not recover past a server Delta.
inferredServerPath.clear();
startSignature = serverDelta.getResultingVersion();
// Transform against any unacknowledged ops.
List<WaveletOperation> transformedServerDelta = serverDelta;
if (unacknowledged != null) {
if (serverDelta.getAppliedAtVersion() != unacknowledged.getTargetVersion().getVersion()) {
throw new TransformException(
"Cannot accept server version newer than unacknowledged. server version:"
+ serverDelta.getAppliedAtVersion() + " unacknowledged version:"
+ unacknowledged.getTargetVersion() + ". [Received serverDelta:" + serverDelta
+ "] " + this);
}
DeltaPair transformedPair = (new DeltaPair(unacknowledged, serverDelta)).transform();
// The ops of the server delta are transformed, all metadata remains.
transformedServerDelta = transformedPair.getServer();
// The unacknowledged delta must have applied after the server delta.
unacknowledged = new WaveletDelta(unacknowledged.getAuthor(),
serverDelta.getResultingVersion(), transformedPair.getClient());
}
// Transform against any queued ops
transformedServerDelta = clientOperationQueue.transform(transformedServerDelta);
// Notify server-operation listeners.
for (WaveletOperation serverOp : transformedServerDelta) {
serverOperations.add(serverOp);
}
}
/**
* Detect if the whole delta is an echo back. If it is then take it as if it was an ack.
* Echo back is a result of reconnection/recovery.
* @return If the delta is a echo back.
* @throws TransformException
*/
private boolean detectEchoBack(TransformedWaveletDelta serverDelta) throws TransformException {
// We have got all the initial list of operations. So do nothing.
if (endOfStartingDelta == null
|| endOfStartingDelta.getVersion() <= serverDelta.getAppliedAtVersion()) {
return false;
}
// Check to see if we are getting a delta that was sent by us, in case the
// server echos back our own delta from a recovery scenario.
if (unacknowledged != null && DeltaPair.areSame(serverDelta, unacknowledged)) {
// If we completely match then take it as an ack.
onSuccess(serverDelta.size(), serverDelta.getResultingVersion());
return true;
}
// We've just got to the end of the initial list of operations
// and there is no match. That means we need to merge the unacknowledged
// ops and resend again.
if (endOfStartingDelta.equals(serverDelta.getResultingVersion())) {
mergeToClientQueue(inferredServerPath.size());
}
return false;
}
@Override
public void onSuccess(int opsApplied, HashedVersion signature) throws TransformException {
if (unacknowledged == null) {
// Note: An ACK will only occur before echoBack delta.
throw new TransformException("Got ACK from server, but we had not sent anything. " + this);
}
if (unacknowledged.getResultingVersion() != signature.getVersion()) {
throw new TransformException("Got ACK from server, but we don't have the same version. " +
"Client expects new version " + unacknowledged.getResultingVersion() +
" and " + unacknowledged.size() + " acked ops, " +
" Server acked " + opsApplied + ", new version " + signature.getVersion() + ". " +
"[Received signature:" + signature + "] [Received opsApplied:" + opsApplied + "] " +
this);
}
if (opsApplied != unacknowledged.size()) {
throw new TransformException("Unable to accept ACK of different number of operations than "
+ "client issued. Client sent = " + unacknowledged.size() + " Server acked = "
+ opsApplied + ". " + this);
}
if (!acks.isEmpty()) {
Preconditions.checkState(
signature.getVersion() > acks.getLast().ackedVersion.getVersion(),
"Unexpected ack for version " + signature.getVersion() + " less than last acked version "
+ acks.getLast().ackedVersion);
}
// We know the server has done this now.
if (unacknowledged.getTargetVersion().getVersion() < startSignature.getVersion()) {
logger.error().log(
"unexpected ack for version " + unacknowledged.getTargetVersion()
+ " before start version " + startSignature.getVersion() + ". [Received signature:"
+ signature + "] [Received opsApplied:" + opsApplied + "] " + this);
}
// Remember delta as received by the server (unless it transformed away).
AckInfo ack = new AckInfo(opsApplied, signature);
if (unacknowledged.size() > 0) {
inferredServerPath.add(new AckedDelta(unacknowledged, ack));
}
acks.add(ack);
// We now need to tell the client model about how the server applied the operation by
// faking a server operation which contains the version number.
makeFakeServerOpsFromAckAndNotify(signature);
// Mark nothing in flight.
unacknowledged = null;
triggerUnsavedDataListener();
// Send any pending client operations as a new delta.
sendDelta();
}
/**
* We have just been acked, let's make a fake noop operation to tell the client about the
* server version and last modified time.
*
* Assumption:
* Server applied the ops starting at unacknowledged.getVersion()
* @throws TransformException
*/
private void makeFakeServerOpsFromAckAndNotify(HashedVersion ackedSignature)
throws TransformException {
List<WaveletOperation> versionOps = CollectionUtils.newArrayList();
// All unacknowledged ops are assumed to be acked now. Ops in unacknowledged
// are transformed against any server ops received prior to the ack. We now
// create a version update op for each unacknowledged op. The last one also
// includes the acked signature.
Iterator<WaveletOperation> opItr = unacknowledged.iterator();
while (opItr.hasNext()) {
WaveletOperation op = opItr.next();
HashedVersion signedVersion = opItr.hasNext() ? null : ackedSignature;
versionOps.add(op.createVersionUpdateOp(1, signedVersion));
}
// Transform against any queued ops. Note server ops even when they are nullified will
// leave behind a version updating op. i.e. the total number of server ops will never change.
clientOperationQueue.transform(versionOps);
// Notify server-operation listeners.
for (WaveletOperation serverOp : versionOps) {
serverOperations.add(serverOp);
logger.trace().log("Fake version update op ", serverOp);
}
if (!serverOperations.isEmpty()) {
onOperationReceived();
}
}
// TODO(zdwang): Remove one of onServerDelta() to have a single interface.
@Override
public void onServerDelta(TransformedWaveletDelta delta) throws TransformException,
OperationException {
onServerDeltas(Collections.singletonList(delta));
}
@Override
public void onServerDeltas(List<TransformedWaveletDelta> deltas) throws TransformException,
OperationException {
if (deltas.isEmpty()) {
logger.error().log("Unexpected empty deltas.");
return;
}
logger.trace().log("Server deltas received: ");
logger.trace().log(deltas.toArray());
for (TransformedWaveletDelta delta : deltas) {
transformOperationsAndNotify(delta);
}
if (!serverOperations.isEmpty()) {
onOperationReceived();
}
// Re-send any pending client operations.
sendDelta();
}
/**
* Returns a list of signature information providing versions on the inferred
* server path, suitable for reconnection.
*
* The start signature is always a reconnection version, even if it's zero and
* we never even sent an op to the server so that the server sends us ops
* rather than a clobbering snapshot.
*/
public List<HashedVersion> getReconnectionVersions() {
ArrayList<HashedVersion> signatures = CollectionUtils.newArrayList();
signatures.add(startSignature);
for (AckedDelta d : inferredServerPath) {
signatures.add(d.ack.ackedVersion);
}
return signatures;
}
/**
* Tests whether or not a delta can be sent.
*
* @return {@code true} if and only if the buffered client operations can and
* should be sent to the server as a delta.
*/
private boolean isReadyToSend() {
boolean ready = !pauseSendForFlush && serverConnection.isOpen();
if (!ready) {
logger.trace().log("Not ready to send, pauseSendForFlush is ", pauseSendForFlush,
" server connection ", serverConnection.isOpen() ? "IS" : "is NOT", " open");
}
return ready;
}
/**
* Queues the client operations, and sends them to the server as a delta at
* the first opportunity. Will call any registered UnsavedDataListeners before
* returning.
*
* @param operations the operations to send, all of which must specify a creator
*/
public void onClientOperations(WaveletOperation operations[]) throws TransformException {
DeltaPair transformedPair =
(new DeltaPair(Arrays.asList(operations), serverOperations)).transform();
serverOperations = transformedPair.getServer();
for (WaveletOperation o : transformedPair.getClient()) {
clientOperationQueue.add(o);
}
triggerUnsavedDataListener();
sendDelta();
}
@Override
public void onCommit(long committedVersion) {
// Remove old cache.
while (!inferredServerPath.isEmpty()) {
AckedDelta d = inferredServerPath.getFirst();
if (d.delta.getResultingVersion() <= committedVersion) {
startSignature = d.ack.ackedVersion;
inferredServerPath.removeFirst();
} else {
break;
}
}
// Remove from acked-but-uncommitted.
while (!acks.isEmpty() && acks.getFirst().ackedVersion.getVersion() <= committedVersion) {
acks.remove();
}
lastCommitVersion = committedVersion;
logger.trace().log("onCommit: version =", committedVersion, " serverpathsize =",
inferredServerPath.size(), " any unacknowledged ? ", (unacknowledged == null));
triggerUnsavedDataListener();
}
private void onOperationReceived() {
boolean oldPauseValue = pauseSendForFlush;
// Pause sending first as we want to gather all the client ops in case
// the client does multiple operations.
pauseSendForFlush = true;
if (clientListener != null) {
clientListener.onOperationReceived();
}
pauseSendForFlush = oldPauseValue;
}
/**
* Receive (transformed) server operation from the wave server, if any is available.
*
* @return the next server operation, if any is received from the server (and makes it
* through transformation), null otherwise
*/
public WaveletOperation receive() {
if (serverOperations.isEmpty()) {
return null;
} else {
WaveletOperation op = serverOperations.remove(0);
logger.trace().log("Processing server op ", op);
return op;
}
}
/**
* Peek at the next (transformed) server operation from the wave server, if any is available.
*
* @return the next server operation, if any is received from the server (and makes it
* through transformation), null otherwise
*/
public WaveletOperation peek() {
return serverOperations.isEmpty() ? null : serverOperations.get(0);
}
/**
* @return last received signature.
*/
private HashedVersion getLastSignature() {
return inferredServerPath.size() == 0 ? startSignature
: inferredServerPath.getLast().ack.ackedVersion;
}
/** True if nothing is queued or in flight or uncommitted. */
private boolean everythingIsCommitted() {
return acks.isEmpty() && (unacknowledged == null);
}
private void triggerUnsavedDataListener() {
if (unsavedDataListener != null) {
unsavedDataListener.onUpdate(unsavedDataInfo);
}
}
@Override
public String toString() {
// Space before \n in case some logger swallows the newline.
return "Client CC State = " +
"[startSignature:" + startSignature + "] \n" +
"[endOfStartingDelta:" + endOfStartingDelta + "] \n" +
"[lastCommittedVersion: " + lastCommitVersion + "] \n" +
"[inferredServerPath:" + inferredServerPath + "] \n" +
"[unacknowledged:" + unacknowledged + "] \n" +
"[clientOperationQueue:" + clientOperationQueue + "] \n" +
"[serverOperations:" + serverOperations + "] \n";
}
}