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/*
* Copyright 2017 The gRPC Authors
*
* 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 io.grpc.internal;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Objects;
import io.grpc.Attributes;
import io.grpc.ClientStreamTracer;
import io.grpc.Compressor;
import io.grpc.Deadline;
import io.grpc.DecompressorRegistry;
import io.grpc.Metadata;
import io.grpc.MethodDescriptor;
import io.grpc.Status;
import io.grpc.SynchronizationContext;
import io.grpc.internal.ClientStreamListener.RpcProgress;
import java.io.InputStream;
import java.lang.Thread.UncaughtExceptionHandler;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import java.util.concurrent.Executor;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import javax.annotation.CheckForNull;
import javax.annotation.CheckReturnValue;
import javax.annotation.Nullable;
import javax.annotation.concurrent.GuardedBy;
/** A logical {@link ClientStream} that is retriable. */
abstract class RetriableStream implements ClientStream {
@VisibleForTesting
static final Metadata.Key GRPC_PREVIOUS_RPC_ATTEMPTS =
Metadata.Key.of("grpc-previous-rpc-attempts", Metadata.ASCII_STRING_MARSHALLER);
@VisibleForTesting
static final Metadata.Key GRPC_RETRY_PUSHBACK_MS =
Metadata.Key.of("grpc-retry-pushback-ms", Metadata.ASCII_STRING_MARSHALLER);
private static final Status CANCELLED_BECAUSE_COMMITTED =
Status.CANCELLED.withDescription("Stream thrown away because RetriableStream committed");
private final MethodDescriptor method;
private final Executor callExecutor;
private final Executor listenerSerializeExecutor = new SynchronizationContext(
new UncaughtExceptionHandler() {
@Override
public void uncaughtException(Thread t, Throwable e) {
throw Status.fromThrowable(e)
.withDescription("Uncaught exception in the SynchronizationContext. Re-thrown.")
.asRuntimeException();
}
}
);
private final ScheduledExecutorService scheduledExecutorService;
// Must not modify it.
private final Metadata headers;
@Nullable
private final RetryPolicy retryPolicy;
@Nullable
private final HedgingPolicy hedgingPolicy;
private final boolean isHedging;
/** Must be held when updating state, accessing state.buffer, or certain substream attributes. */
private final Object lock = new Object();
private final ChannelBufferMeter channelBufferUsed;
private final long perRpcBufferLimit;
private final long channelBufferLimit;
@Nullable
private final Throttle throttle;
@GuardedBy("lock")
private final InsightBuilder closedSubstreamsInsight = new InsightBuilder();
private volatile State state = new State(
new ArrayList(8), Collections.emptyList(), null, null, false, false,
false, 0);
/**
* Either transparent retry happened or reached server's application logic.
*/
private final AtomicBoolean noMoreTransparentRetry = new AtomicBoolean();
// Used for recording the share of buffer used for the current call out of the channel buffer.
// This field would not be necessary if there is no channel buffer limit.
@GuardedBy("lock")
private long perRpcBufferUsed;
private ClientStreamListener masterListener;
@GuardedBy("lock")
private FutureCanceller scheduledRetry;
@GuardedBy("lock")
private FutureCanceller scheduledHedging;
private long nextBackoffIntervalNanos;
private Status cancellationStatus;
private boolean isClosed;
RetriableStream(
MethodDescriptor method, Metadata headers,
ChannelBufferMeter channelBufferUsed, long perRpcBufferLimit, long channelBufferLimit,
Executor callExecutor, ScheduledExecutorService scheduledExecutorService,
@Nullable RetryPolicy retryPolicy, @Nullable HedgingPolicy hedgingPolicy,
@Nullable Throttle throttle) {
this.method = method;
this.channelBufferUsed = channelBufferUsed;
this.perRpcBufferLimit = perRpcBufferLimit;
this.channelBufferLimit = channelBufferLimit;
this.callExecutor = callExecutor;
this.scheduledExecutorService = scheduledExecutorService;
this.headers = headers;
this.retryPolicy = retryPolicy;
if (retryPolicy != null) {
this.nextBackoffIntervalNanos = retryPolicy.initialBackoffNanos;
}
this.hedgingPolicy = hedgingPolicy;
checkArgument(
retryPolicy == null || hedgingPolicy == null,
"Should not provide both retryPolicy and hedgingPolicy");
this.isHedging = hedgingPolicy != null;
this.throttle = throttle;
}
@SuppressWarnings("GuardedBy")
@Nullable // null if already committed
@CheckReturnValue
private Runnable commit(final Substream winningSubstream) {
synchronized (lock) {
if (state.winningSubstream != null) {
return null;
}
final Collection savedDrainedSubstreams = state.drainedSubstreams;
state = state.committed(winningSubstream);
// subtract the share of this RPC from channelBufferUsed.
channelBufferUsed.addAndGet(-perRpcBufferUsed);
final Future retryFuture;
if (scheduledRetry != null) {
// TODO(b/145386688): This access should be guarded by 'this.scheduledRetry.lock'; instead
// found: 'this.lock'
retryFuture = scheduledRetry.markCancelled();
scheduledRetry = null;
} else {
retryFuture = null;
}
// cancel the scheduled hedging if it is scheduled prior to the commitment
final Future hedgingFuture;
if (scheduledHedging != null) {
// TODO(b/145386688): This access should be guarded by 'this.scheduledHedging.lock'; instead
// found: 'this.lock'
hedgingFuture = scheduledHedging.markCancelled();
scheduledHedging = null;
} else {
hedgingFuture = null;
}
class CommitTask implements Runnable {
@Override
public void run() {
// For hedging only, not needed for normal retry
for (Substream substream : savedDrainedSubstreams) {
if (substream != winningSubstream) {
substream.stream.cancel(CANCELLED_BECAUSE_COMMITTED);
}
}
if (retryFuture != null) {
retryFuture.cancel(false);
}
if (hedgingFuture != null) {
hedgingFuture.cancel(false);
}
postCommit();
}
}
return new CommitTask();
}
}
abstract void postCommit();
/**
* Calls commit() and if successful runs the post commit task.
*/
private void commitAndRun(Substream winningSubstream) {
Runnable postCommitTask = commit(winningSubstream);
if (postCommitTask != null) {
postCommitTask.run();
}
}
private Substream createSubstream(int previousAttemptCount, boolean isTransparentRetry) {
Substream sub = new Substream(previousAttemptCount);
// one tracer per substream
final ClientStreamTracer bufferSizeTracer = new BufferSizeTracer(sub);
ClientStreamTracer.Factory tracerFactory = new ClientStreamTracer.InternalLimitedInfoFactory() {
@Override
public ClientStreamTracer newClientStreamTracer(
ClientStreamTracer.StreamInfo info, Metadata headers) {
return bufferSizeTracer;
}
};
Metadata newHeaders = updateHeaders(headers, previousAttemptCount);
// NOTICE: This set _must_ be done before stream.start() and it actually is.
sub.stream = newSubstream(newHeaders, tracerFactory, previousAttemptCount, isTransparentRetry);
return sub;
}
/**
* Creates a new physical ClientStream that represents a retry/hedging attempt. The returned
* Client stream is not yet started.
*/
abstract ClientStream newSubstream(
Metadata headers, ClientStreamTracer.Factory tracerFactory, int previousAttempts,
boolean isTransparentRetry);
/** Adds grpc-previous-rpc-attempts in the headers of a retry/hedging RPC. */
@VisibleForTesting
final Metadata updateHeaders(
Metadata originalHeaders, int previousAttemptCount) {
Metadata newHeaders = new Metadata();
newHeaders.merge(originalHeaders);
if (previousAttemptCount > 0) {
newHeaders.put(GRPC_PREVIOUS_RPC_ATTEMPTS, String.valueOf(previousAttemptCount));
}
return newHeaders;
}
private void drain(Substream substream) {
int index = 0;
int chunk = 0x80;
List list = null;
boolean streamStarted = false;
Runnable onReadyRunnable = null;
while (true) {
State savedState;
synchronized (lock) {
savedState = state;
if (streamStarted) {
if (savedState.winningSubstream != null && savedState.winningSubstream != substream) {
// committed but not me, to be cancelled
break;
}
if (savedState.cancelled) {
break;
}
}
if (index == savedState.buffer.size()) { // I'm drained
state = savedState.substreamDrained(substream);
if (!isReady()) {
return;
}
onReadyRunnable = new Runnable() {
@Override
public void run() {
if (!isClosed) {
masterListener.onReady();
}
}
};
break;
}
if (substream.closed) {
return;
}
int stop = Math.min(index + chunk, savedState.buffer.size());
if (list == null) {
list = new ArrayList<>(savedState.buffer.subList(index, stop));
} else {
list.clear();
list.addAll(savedState.buffer.subList(index, stop));
}
index = stop;
}
for (BufferEntry bufferEntry : list) {
bufferEntry.runWith(substream);
if (bufferEntry instanceof RetriableStream.StartEntry) {
streamStarted = true;
}
if (streamStarted) {
savedState = state;
if (savedState.winningSubstream != null && savedState.winningSubstream != substream) {
// committed but not me, to be cancelled
break;
}
if (savedState.cancelled) {
break;
}
}
}
}
if (onReadyRunnable != null) {
listenerSerializeExecutor.execute(onReadyRunnable);
return;
}
substream.stream.cancel(
state.winningSubstream == substream ? cancellationStatus : CANCELLED_BECAUSE_COMMITTED);
}
/**
* Runs pre-start tasks. Returns the Status of shutdown if the channel is shutdown.
*/
@CheckReturnValue
@Nullable
abstract Status prestart();
class StartEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.start(new Sublistener(substream));
}
}
/** Starts the first PRC attempt. */
@Override
public final void start(ClientStreamListener listener) {
masterListener = listener;
Status shutdownStatus = prestart();
if (shutdownStatus != null) {
cancel(shutdownStatus);
return;
}
synchronized (lock) {
state.buffer.add(new StartEntry());
}
Substream substream = createSubstream(0, false);
if (isHedging) {
FutureCanceller scheduledHedgingRef = null;
synchronized (lock) {
state = state.addActiveHedge(substream);
if (hasPotentialHedging(state)
&& (throttle == null || throttle.isAboveThreshold())) {
scheduledHedging = scheduledHedgingRef = new FutureCanceller(lock);
}
}
if (scheduledHedgingRef != null) {
scheduledHedgingRef.setFuture(
scheduledExecutorService.schedule(
new HedgingRunnable(scheduledHedgingRef),
hedgingPolicy.hedgingDelayNanos,
TimeUnit.NANOSECONDS));
}
}
drain(substream);
}
@SuppressWarnings("GuardedBy")
private void pushbackHedging(@Nullable Integer delayMillis) {
if (delayMillis == null) {
return;
}
if (delayMillis < 0) {
freezeHedging();
return;
}
// Cancels the current scheduledHedging and reschedules a new one.
FutureCanceller future;
Future futureToBeCancelled;
synchronized (lock) {
if (scheduledHedging == null) {
return;
}
// TODO(b/145386688): This access should be guarded by 'this.scheduledHedging.lock'; instead
// found: 'this.lock'
futureToBeCancelled = scheduledHedging.markCancelled();
scheduledHedging = future = new FutureCanceller(lock);
}
if (futureToBeCancelled != null) {
futureToBeCancelled.cancel(false);
}
future.setFuture(scheduledExecutorService.schedule(
new HedgingRunnable(future), delayMillis, TimeUnit.MILLISECONDS));
}
private final class HedgingRunnable implements Runnable {
// Need to hold a ref to the FutureCanceller in case RetriableStrea.scheduledHedging is renewed
// by a positive push-back just after newSubstream is instantiated, so that we can double check.
final FutureCanceller scheduledHedgingRef;
HedgingRunnable(FutureCanceller scheduledHedging) {
scheduledHedgingRef = scheduledHedging;
}
@Override
public void run() {
callExecutor.execute(
new Runnable() {
@SuppressWarnings("GuardedBy")
@Override
public void run() {
// It's safe to read state.hedgingAttemptCount here.
// If this run is not cancelled, the value of state.hedgingAttemptCount won't change
// until state.addActiveHedge() is called subsequently, even the state could possibly
// change.
Substream newSubstream = createSubstream(state.hedgingAttemptCount, false);
boolean cancelled = false;
FutureCanceller future = null;
synchronized (lock) {
// TODO(b/145386688): This access should be guarded by
// 'HedgingRunnable.this.scheduledHedgingRef.lock'; instead found:
// 'RetriableStream.this.lock'
if (scheduledHedgingRef.isCancelled()) {
cancelled = true;
} else {
state = state.addActiveHedge(newSubstream);
if (hasPotentialHedging(state)
&& (throttle == null || throttle.isAboveThreshold())) {
scheduledHedging = future = new FutureCanceller(lock);
} else {
state = state.freezeHedging();
scheduledHedging = null;
}
}
}
if (cancelled) {
newSubstream.stream.cancel(Status.CANCELLED.withDescription("Unneeded hedging"));
return;
}
if (future != null) {
future.setFuture(
scheduledExecutorService.schedule(
new HedgingRunnable(future),
hedgingPolicy.hedgingDelayNanos,
TimeUnit.NANOSECONDS));
}
drain(newSubstream);
}
});
}
}
@Override
public final void cancel(final Status reason) {
Substream noopSubstream = new Substream(0 /* previousAttempts doesn't matter here */);
noopSubstream.stream = new NoopClientStream();
Runnable runnable = commit(noopSubstream);
if (runnable != null) {
runnable.run();
listenerSerializeExecutor.execute(
new Runnable() {
@Override
public void run() {
isClosed = true;
masterListener.closed(reason, RpcProgress.PROCESSED, new Metadata());
}
});
return;
}
Substream winningSubstreamToCancel = null;
synchronized (lock) {
if (state.drainedSubstreams.contains(state.winningSubstream)) {
winningSubstreamToCancel = state.winningSubstream;
} else { // the winningSubstream will be cancelled while draining
cancellationStatus = reason;
}
state = state.cancelled();
}
if (winningSubstreamToCancel != null) {
winningSubstreamToCancel.stream.cancel(reason);
}
}
private void delayOrExecute(BufferEntry bufferEntry) {
Collection savedDrainedSubstreams;
synchronized (lock) {
if (!state.passThrough) {
state.buffer.add(bufferEntry);
}
savedDrainedSubstreams = state.drainedSubstreams;
}
for (Substream substream : savedDrainedSubstreams) {
bufferEntry.runWith(substream);
}
}
/**
* Do not use it directly. Use {@link #sendMessage(Object)} instead because we don't use
* InputStream for buffering.
*/
@Override
public final void writeMessage(InputStream message) {
throw new IllegalStateException("RetriableStream.writeMessage() should not be called directly");
}
final void sendMessage(final ReqT message) {
State savedState = state;
if (savedState.passThrough) {
savedState.winningSubstream.stream.writeMessage(method.streamRequest(message));
return;
}
class SendMessageEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.writeMessage(method.streamRequest(message));
}
}
delayOrExecute(new SendMessageEntry());
}
@Override
public final void request(final int numMessages) {
State savedState = state;
if (savedState.passThrough) {
savedState.winningSubstream.stream.request(numMessages);
return;
}
class RequestEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.request(numMessages);
}
}
delayOrExecute(new RequestEntry());
}
@Override
public final void flush() {
State savedState = state;
if (savedState.passThrough) {
savedState.winningSubstream.stream.flush();
return;
}
class FlushEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.flush();
}
}
delayOrExecute(new FlushEntry());
}
@Override
public final boolean isReady() {
for (Substream substream : state.drainedSubstreams) {
if (substream.stream.isReady()) {
return true;
}
}
return false;
}
@Override
public void optimizeForDirectExecutor() {
class OptimizeDirectEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.optimizeForDirectExecutor();
}
}
delayOrExecute(new OptimizeDirectEntry());
}
@Override
public final void setCompressor(final Compressor compressor) {
class CompressorEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.setCompressor(compressor);
}
}
delayOrExecute(new CompressorEntry());
}
@Override
public final void setFullStreamDecompression(final boolean fullStreamDecompression) {
class FullStreamDecompressionEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.setFullStreamDecompression(fullStreamDecompression);
}
}
delayOrExecute(new FullStreamDecompressionEntry());
}
@Override
public final void setMessageCompression(final boolean enable) {
class MessageCompressionEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.setMessageCompression(enable);
}
}
delayOrExecute(new MessageCompressionEntry());
}
@Override
public final void halfClose() {
class HalfCloseEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.halfClose();
}
}
delayOrExecute(new HalfCloseEntry());
}
@Override
public final void setAuthority(final String authority) {
class AuthorityEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.setAuthority(authority);
}
}
delayOrExecute(new AuthorityEntry());
}
@Override
public final void setDecompressorRegistry(final DecompressorRegistry decompressorRegistry) {
class DecompressorRegistryEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.setDecompressorRegistry(decompressorRegistry);
}
}
delayOrExecute(new DecompressorRegistryEntry());
}
@Override
public final void setMaxInboundMessageSize(final int maxSize) {
class MaxInboundMessageSizeEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.setMaxInboundMessageSize(maxSize);
}
}
delayOrExecute(new MaxInboundMessageSizeEntry());
}
@Override
public final void setMaxOutboundMessageSize(final int maxSize) {
class MaxOutboundMessageSizeEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.setMaxOutboundMessageSize(maxSize);
}
}
delayOrExecute(new MaxOutboundMessageSizeEntry());
}
@Override
public final void setDeadline(final Deadline deadline) {
class DeadlineEntry implements BufferEntry {
@Override
public void runWith(Substream substream) {
substream.stream.setDeadline(deadline);
}
}
delayOrExecute(new DeadlineEntry());
}
@Override
public final Attributes getAttributes() {
if (state.winningSubstream != null) {
return state.winningSubstream.stream.getAttributes();
}
return Attributes.EMPTY;
}
@Override
public void appendTimeoutInsight(InsightBuilder insight) {
State currentState;
synchronized (lock) {
insight.appendKeyValue("closed", closedSubstreamsInsight);
currentState = state;
}
if (currentState.winningSubstream != null) {
// TODO(zhangkun83): in this case while other drained substreams have been cancelled in favor
// of the winning substream, they may not have received closed() notifications yet, thus they
// may be missing from closedSubstreamsInsight. This may be a little confusing to the user.
// We need to figure out how to include them.
InsightBuilder substreamInsight = new InsightBuilder();
currentState.winningSubstream.stream.appendTimeoutInsight(substreamInsight);
insight.appendKeyValue("committed", substreamInsight);
} else {
InsightBuilder openSubstreamsInsight = new InsightBuilder();
// drainedSubstreams doesn't include all open substreams. Those which have just been created
// and are still catching up with buffered requests (in other words, still draining) will not
// show up. We think this is benign, because the draining should be typically fast, and it'd
// be indistinguishable from the case where those streams are to be created a little late due
// to delays in the timer.
for (Substream sub : currentState.drainedSubstreams) {
InsightBuilder substreamInsight = new InsightBuilder();
sub.stream.appendTimeoutInsight(substreamInsight);
openSubstreamsInsight.append(substreamInsight);
}
insight.appendKeyValue("open", openSubstreamsInsight);
}
}
private static Random random = new Random();
@VisibleForTesting
static void setRandom(Random random) {
RetriableStream.random = random;
}
/**
* Whether there is any potential hedge at the moment. A false return value implies there is
* absolutely no potential hedge. At least one of the hedges will observe a false return value
* when calling this method, unless otherwise the rpc is committed.
*/
// only called when isHedging is true
@GuardedBy("lock")
private boolean hasPotentialHedging(State state) {
return state.winningSubstream == null
&& state.hedgingAttemptCount < hedgingPolicy.maxAttempts
&& !state.hedgingFrozen;
}
@SuppressWarnings("GuardedBy")
private void freezeHedging() {
Future futureToBeCancelled = null;
synchronized (lock) {
if (scheduledHedging != null) {
// TODO(b/145386688): This access should be guarded by 'this.scheduledHedging.lock'; instead
// found: 'this.lock'
futureToBeCancelled = scheduledHedging.markCancelled();
scheduledHedging = null;
}
state = state.freezeHedging();
}
if (futureToBeCancelled != null) {
futureToBeCancelled.cancel(false);
}
}
private interface BufferEntry {
/** Replays the buffer entry with the given stream. */
void runWith(Substream substream);
}
private final class Sublistener implements ClientStreamListener {
final Substream substream;
Sublistener(Substream substream) {
this.substream = substream;
}
@Override
public void headersRead(final Metadata headers) {
commitAndRun(substream);
if (state.winningSubstream == substream) {
if (throttle != null) {
throttle.onSuccess();
}
listenerSerializeExecutor.execute(
new Runnable() {
@Override
public void run() {
masterListener.headersRead(headers);
}
});
}
}
@Override
public void closed(
final Status status, final RpcProgress rpcProgress, final Metadata trailers) {
synchronized (lock) {
state = state.substreamClosed(substream);
closedSubstreamsInsight.append(status.getCode());
}
// handle a race between buffer limit exceeded and closed, when setting
// substream.bufferLimitExceeded = true happens before state.substreamClosed(substream).
if (substream.bufferLimitExceeded) {
commitAndRun(substream);
if (state.winningSubstream == substream) {
listenerSerializeExecutor.execute(
new Runnable() {
@Override
public void run() {
isClosed = true;
masterListener.closed(status, rpcProgress, trailers);
}
});
}
return;
}
if (state.winningSubstream == null) {
if (rpcProgress == RpcProgress.REFUSED
&& noMoreTransparentRetry.compareAndSet(false, true)) {
// transparent retry
final Substream newSubstream = createSubstream(substream.previousAttemptCount, true);
if (isHedging) {
boolean commit = false;
synchronized (lock) {
// Although this operation is not done atomically with
// noMoreTransparentRetry.compareAndSet(false, true), it does not change the size() of
// activeHedges, so neither does it affect the commitment decision of other threads,
// nor do the commitment decision making threads affect itself.
state = state.replaceActiveHedge(substream, newSubstream);
// optimization for early commit
if (!hasPotentialHedging(state)
&& state.activeHedges.size() == 1) {
commit = true;
}
}
if (commit) {
commitAndRun(newSubstream);
}
} else {
if (retryPolicy == null || retryPolicy.maxAttempts == 1) {
// optimization for early commit
commitAndRun(newSubstream);
}
}
callExecutor.execute(new Runnable() {
@Override
public void run() {
drain(newSubstream);
}
});
return;
} else if (rpcProgress == RpcProgress.DROPPED) {
// For normal retry, nothing need be done here, will just commit.
// For hedging, cancel scheduled hedge that is scheduled prior to the drop
if (isHedging) {
freezeHedging();
}
} else {
noMoreTransparentRetry.set(true);
if (isHedging) {
HedgingPlan hedgingPlan = makeHedgingDecision(status, trailers);
if (hedgingPlan.isHedgeable) {
pushbackHedging(hedgingPlan.hedgingPushbackMillis);
}
synchronized (lock) {
state = state.removeActiveHedge(substream);
// The invariant is whether or not #(Potential Hedge + active hedges) > 0.
// Once hasPotentialHedging(state) is false, it will always be false, and then
// #(state.activeHedges) will be decreasing. This guarantees that even there may be
// multiple concurrent hedges, one of the hedges will end up committed.
if (hedgingPlan.isHedgeable) {
if (hasPotentialHedging(state) || !state.activeHedges.isEmpty()) {
return;
}
// else, no activeHedges, no new hedges possible, try to commit
} // else, isHedgeable is false, try to commit
}
} else {
RetryPlan retryPlan = makeRetryDecision(status, trailers);
if (retryPlan.shouldRetry) {
// The check state.winningSubstream == null, checking if is not already committed, is
// racy, but is still safe b/c the retry will also handle committed/cancellation
FutureCanceller scheduledRetryCopy;
synchronized (lock) {
scheduledRetry = scheduledRetryCopy = new FutureCanceller(lock);
}
class RetryBackoffRunnable implements Runnable {
@Override
public void run() {
callExecutor.execute(
new Runnable() {
@Override
public void run() {
// retry
Substream newSubstream = createSubstream(
substream.previousAttemptCount + 1,
false);
drain(newSubstream);
}
});
}
}
scheduledRetryCopy.setFuture(
scheduledExecutorService.schedule(
new RetryBackoffRunnable(),
retryPlan.backoffNanos,
TimeUnit.NANOSECONDS));
return;
}
}
}
}
commitAndRun(substream);
if (state.winningSubstream == substream) {
listenerSerializeExecutor.execute(
new Runnable() {
@Override
public void run() {
isClosed = true;
masterListener.closed(status, rpcProgress, trailers);
}
});
}
}
/**
* Decides in current situation whether or not the RPC should retry and if it should retry how
* long the backoff should be. The decision does not take the commitment status into account, so
* caller should check it separately. It also updates the throttle. It does not change state.
*/
private RetryPlan makeRetryDecision(Status status, Metadata trailer) {
if (retryPolicy == null) {
return new RetryPlan(false, 0);
}
boolean shouldRetry = false;
long backoffNanos = 0L;
boolean isRetryableStatusCode = retryPolicy.retryableStatusCodes.contains(status.getCode());
Integer pushbackMillis = getPushbackMills(trailer);
boolean isThrottled = false;
if (throttle != null) {
if (isRetryableStatusCode || (pushbackMillis != null && pushbackMillis < 0)) {
isThrottled = !throttle.onQualifiedFailureThenCheckIsAboveThreshold();
}
}
if (retryPolicy.maxAttempts > substream.previousAttemptCount + 1 && !isThrottled) {
if (pushbackMillis == null) {
if (isRetryableStatusCode) {
shouldRetry = true;
backoffNanos = (long) (nextBackoffIntervalNanos * random.nextDouble());
nextBackoffIntervalNanos = Math.min(
(long) (nextBackoffIntervalNanos * retryPolicy.backoffMultiplier),
retryPolicy.maxBackoffNanos);
} // else no retry
} else if (pushbackMillis >= 0) {
shouldRetry = true;
backoffNanos = TimeUnit.MILLISECONDS.toNanos(pushbackMillis);
nextBackoffIntervalNanos = retryPolicy.initialBackoffNanos;
} // else no retry
} // else no retry
return new RetryPlan(shouldRetry, backoffNanos);
}
private HedgingPlan makeHedgingDecision(Status status, Metadata trailer) {
Integer pushbackMillis = getPushbackMills(trailer);
boolean isFatal = !hedgingPolicy.nonFatalStatusCodes.contains(status.getCode());
boolean isThrottled = false;
if (throttle != null) {
if (!isFatal || (pushbackMillis != null && pushbackMillis < 0)) {
isThrottled = !throttle.onQualifiedFailureThenCheckIsAboveThreshold();
}
}
return new HedgingPlan(!isFatal && !isThrottled, pushbackMillis);
}
@Nullable
private Integer getPushbackMills(Metadata trailer) {
String pushbackStr = trailer.get(GRPC_RETRY_PUSHBACK_MS);
Integer pushbackMillis = null;
if (pushbackStr != null) {
try {
pushbackMillis = Integer.valueOf(pushbackStr);
} catch (NumberFormatException e) {
pushbackMillis = -1;
}
}
return pushbackMillis;
}
@Override
public void messagesAvailable(final MessageProducer producer) {
State savedState = state;
checkState(
savedState.winningSubstream != null, "Headers should be received prior to messages.");
if (savedState.winningSubstream != substream) {
return;
}
listenerSerializeExecutor.execute(
new Runnable() {
@Override
public void run() {
masterListener.messagesAvailable(producer);
}
});
}
@Override
public void onReady() {
// FIXME(#7089): hedging case is broken.
if (!isReady()) {
return;
}
listenerSerializeExecutor.execute(
new Runnable() {
@Override
public void run() {
if (!isClosed) {
masterListener.onReady();
}
}
});
}
}
private static final class State {
/** Committed and the winning substream drained. */
final boolean passThrough;
/** A list of buffered ClientStream runnables. Set to Null once passThrough. */
@Nullable final List buffer;
/**
* Unmodifiable collection of all the open substreams that are drained. Singleton once
* passThrough; Empty if committed but not passTrough.
*/
final Collection drainedSubstreams;
/**
* Unmodifiable collection of all the active hedging substreams.
*
* A substream even with the attribute substream.closed being true may be considered still
* "active" at the moment as long as it is in this collection.
*/
final Collection activeHedges; // not null once isHedging = true
final int hedgingAttemptCount;
/** Null until committed. */
@Nullable final Substream winningSubstream;
/** Not required to set to true when cancelled, but can short-circuit the draining process. */
final boolean cancelled;
/** No more hedging due to events like drop or pushback. */
final boolean hedgingFrozen;
State(
@Nullable List buffer,
Collection drainedSubstreams,
Collection activeHedges,
@Nullable Substream winningSubstream,
boolean cancelled,
boolean passThrough,
boolean hedgingFrozen,
int hedgingAttemptCount) {
this.buffer = buffer;
this.drainedSubstreams =
checkNotNull(drainedSubstreams, "drainedSubstreams");
this.winningSubstream = winningSubstream;
this.activeHedges = activeHedges;
this.cancelled = cancelled;
this.passThrough = passThrough;
this.hedgingFrozen = hedgingFrozen;
this.hedgingAttemptCount = hedgingAttemptCount;
checkState(!passThrough || buffer == null, "passThrough should imply buffer is null");
checkState(
!passThrough || winningSubstream != null,
"passThrough should imply winningSubstream != null");
checkState(
!passThrough
|| (drainedSubstreams.size() == 1 && drainedSubstreams.contains(winningSubstream))
|| (drainedSubstreams.size() == 0 && winningSubstream.closed),
"passThrough should imply winningSubstream is drained");
checkState(!cancelled || winningSubstream != null, "cancelled should imply committed");
}
@CheckReturnValue
// GuardedBy RetriableStream.lock
State cancelled() {
return new State(
buffer, drainedSubstreams, activeHedges, winningSubstream, true, passThrough,
hedgingFrozen, hedgingAttemptCount);
}
/** The given substream is drained. */
@CheckReturnValue
// GuardedBy RetriableStream.lock
State substreamDrained(Substream substream) {
checkState(!passThrough, "Already passThrough");
Collection drainedSubstreams;
if (substream.closed) {
drainedSubstreams = this.drainedSubstreams;
} else if (this.drainedSubstreams.isEmpty()) {
// optimize for 0-retry, which is most of the cases.
drainedSubstreams = Collections.singletonList(substream);
} else {
drainedSubstreams = new ArrayList<>(this.drainedSubstreams);
drainedSubstreams.add(substream);
drainedSubstreams = Collections.unmodifiableCollection(drainedSubstreams);
}
boolean passThrough = winningSubstream != null;
List buffer = this.buffer;
if (passThrough) {
checkState(
winningSubstream == substream, "Another RPC attempt has already committed");
buffer = null;
}
return new State(
buffer, drainedSubstreams, activeHedges, winningSubstream, cancelled, passThrough,
hedgingFrozen, hedgingAttemptCount);
}
/** The given substream is closed. */
@CheckReturnValue
// GuardedBy RetriableStream.lock
State substreamClosed(Substream substream) {
substream.closed = true;
if (this.drainedSubstreams.contains(substream)) {
Collection drainedSubstreams = new ArrayList<>(this.drainedSubstreams);
drainedSubstreams.remove(substream);
drainedSubstreams = Collections.unmodifiableCollection(drainedSubstreams);
return new State(
buffer, drainedSubstreams, activeHedges, winningSubstream, cancelled, passThrough,
hedgingFrozen, hedgingAttemptCount);
} else {
return this;
}
}
@CheckReturnValue
// GuardedBy RetriableStream.lock
State committed(Substream winningSubstream) {
checkState(this.winningSubstream == null, "Already committed");
boolean passThrough = false;
List buffer = this.buffer;
Collection drainedSubstreams;
if (this.drainedSubstreams.contains(winningSubstream)) {
passThrough = true;
buffer = null;
drainedSubstreams = Collections.singleton(winningSubstream);
} else {
drainedSubstreams = Collections.emptyList();
}
return new State(
buffer, drainedSubstreams, activeHedges, winningSubstream, cancelled, passThrough,
hedgingFrozen, hedgingAttemptCount);
}
@CheckReturnValue
// GuardedBy RetriableStream.lock
State freezeHedging() {
if (hedgingFrozen) {
return this;
}
return new State(
buffer, drainedSubstreams, activeHedges, winningSubstream, cancelled, passThrough,
true, hedgingAttemptCount);
}
@CheckReturnValue
// GuardedBy RetriableStream.lock
// state.hedgingAttemptCount is modified only here.
// The method is only called in RetriableStream.start() and HedgingRunnable.run()
State addActiveHedge(Substream substream) {
// hasPotentialHedging must be true
checkState(!hedgingFrozen, "hedging frozen");
checkState(winningSubstream == null, "already committed");
Collection activeHedges;
if (this.activeHedges == null) {
activeHedges = Collections.singleton(substream);
} else {
activeHedges = new ArrayList<>(this.activeHedges);
activeHedges.add(substream);
activeHedges = Collections.unmodifiableCollection(activeHedges);
}
int hedgingAttemptCount = this.hedgingAttemptCount + 1;
return new State(
buffer, drainedSubstreams, activeHedges, winningSubstream, cancelled, passThrough,
hedgingFrozen, hedgingAttemptCount);
}
@CheckReturnValue
// GuardedBy RetriableStream.lock
// The method is only called in Sublistener.closed()
State removeActiveHedge(Substream substream) {
Collection activeHedges = new ArrayList<>(this.activeHedges);
activeHedges.remove(substream);
activeHedges = Collections.unmodifiableCollection(activeHedges);
return new State(
buffer, drainedSubstreams, activeHedges, winningSubstream, cancelled, passThrough,
hedgingFrozen, hedgingAttemptCount);
}
@CheckReturnValue
// GuardedBy RetriableStream.lock
// The method is only called for transparent retry.
State replaceActiveHedge(Substream oldOne, Substream newOne) {
Collection activeHedges = new ArrayList<>(this.activeHedges);
activeHedges.remove(oldOne);
activeHedges.add(newOne);
activeHedges = Collections.unmodifiableCollection(activeHedges);
return new State(
buffer, drainedSubstreams, activeHedges, winningSubstream, cancelled, passThrough,
hedgingFrozen, hedgingAttemptCount);
}
}
/**
* A wrapper of a physical stream of a retry/hedging attempt, that comes with some useful
* attributes.
*/
private static final class Substream {
ClientStream stream;
// GuardedBy RetriableStream.lock
boolean closed;
// setting to true must be GuardedBy RetriableStream.lock
boolean bufferLimitExceeded;
final int previousAttemptCount;
Substream(int previousAttemptCount) {
this.previousAttemptCount = previousAttemptCount;
}
}
/**
* Traces the buffer used by a substream.
*/
class BufferSizeTracer extends ClientStreamTracer {
// Each buffer size tracer is dedicated to one specific substream.
private final Substream substream;
@GuardedBy("lock")
long bufferNeeded;
BufferSizeTracer(Substream substream) {
this.substream = substream;
}
/**
* A message is sent to the wire, so its reference would be released if no retry or
* hedging were involved. So at this point we have to hold the reference of the message longer
* for retry, and we need to increment {@code substream.bufferNeeded}.
*/
@Override
public void outboundWireSize(long bytes) {
if (state.winningSubstream != null) {
return;
}
Runnable postCommitTask = null;
// TODO(zdapeng): avoid using the same lock for both in-bound and out-bound.
synchronized (lock) {
if (state.winningSubstream != null || substream.closed) {
return;
}
bufferNeeded += bytes;
if (bufferNeeded <= perRpcBufferUsed) {
return;
}
if (bufferNeeded > perRpcBufferLimit) {
substream.bufferLimitExceeded = true;
} else {
// Only update channelBufferUsed when perRpcBufferUsed is not exceeding perRpcBufferLimit.
long savedChannelBufferUsed =
channelBufferUsed.addAndGet(bufferNeeded - perRpcBufferUsed);
perRpcBufferUsed = bufferNeeded;
if (savedChannelBufferUsed > channelBufferLimit) {
substream.bufferLimitExceeded = true;
}
}
if (substream.bufferLimitExceeded) {
postCommitTask = commit(substream);
}
}
if (postCommitTask != null) {
postCommitTask.run();
}
}
}
/**
* Used to keep track of the total amount of memory used to buffer retryable or hedged RPCs for
* the Channel. There should be a single instance of it for each channel.
*/
static final class ChannelBufferMeter {
private final AtomicLong bufferUsed = new AtomicLong();
@VisibleForTesting
long addAndGet(long newBytesUsed) {
return bufferUsed.addAndGet(newBytesUsed);
}
}
/**
* Used for retry throttling.
*/
static final class Throttle {
private static final int THREE_DECIMAL_PLACES_SCALE_UP = 1000;
/**
* 1000 times the maxTokens field of the retryThrottling policy in service config.
* The number of tokens starts at maxTokens. The token_count will always be between 0 and
* maxTokens.
*/
final int maxTokens;
/**
* Half of {@code maxTokens}.
*/
final int threshold;
/**
* 1000 times the tokenRatio field of the retryThrottling policy in service config.
*/
final int tokenRatio;
final AtomicInteger tokenCount = new AtomicInteger();
Throttle(float maxTokens, float tokenRatio) {
// tokenRatio is up to 3 decimal places
this.tokenRatio = (int) (tokenRatio * THREE_DECIMAL_PLACES_SCALE_UP);
this.maxTokens = (int) (maxTokens * THREE_DECIMAL_PLACES_SCALE_UP);
this.threshold = this.maxTokens / 2;
tokenCount.set(this.maxTokens);
}
@VisibleForTesting
boolean isAboveThreshold() {
return tokenCount.get() > threshold;
}
/**
* Counts down the token on qualified failure and checks if it is above the threshold
* atomically. Qualified failure is a failure with a retryable or non-fatal status code or with
* a not-to-retry pushback.
*/
@VisibleForTesting
boolean onQualifiedFailureThenCheckIsAboveThreshold() {
while (true) {
int currentCount = tokenCount.get();
if (currentCount == 0) {
return false;
}
int decremented = currentCount - (1 * THREE_DECIMAL_PLACES_SCALE_UP);
boolean updated = tokenCount.compareAndSet(currentCount, Math.max(decremented, 0));
if (updated) {
return decremented > threshold;
}
}
}
@VisibleForTesting
void onSuccess() {
while (true) {
int currentCount = tokenCount.get();
if (currentCount == maxTokens) {
break;
}
int incremented = currentCount + tokenRatio;
boolean updated = tokenCount.compareAndSet(currentCount, Math.min(incremented, maxTokens));
if (updated) {
break;
}
}
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (!(o instanceof Throttle)) {
return false;
}
Throttle that = (Throttle) o;
return maxTokens == that.maxTokens && tokenRatio == that.tokenRatio;
}
@Override
public int hashCode() {
return Objects.hashCode(maxTokens, tokenRatio);
}
}
private static final class RetryPlan {
final boolean shouldRetry;
final long backoffNanos;
RetryPlan(boolean shouldRetry, long backoffNanos) {
this.shouldRetry = shouldRetry;
this.backoffNanos = backoffNanos;
}
}
private static final class HedgingPlan {
final boolean isHedgeable;
@Nullable
final Integer hedgingPushbackMillis;
public HedgingPlan(
boolean isHedgeable, @Nullable Integer hedgingPushbackMillis) {
this.isHedgeable = isHedgeable;
this.hedgingPushbackMillis = hedgingPushbackMillis;
}
}
/** Allows cancelling a Future without racing with setting the future. */
private static final class FutureCanceller {
final Object lock;
@GuardedBy("lock")
Future future;
@GuardedBy("lock")
boolean cancelled;
FutureCanceller(Object lock) {
this.lock = lock;
}
void setFuture(Future future) {
synchronized (lock) {
if (!cancelled) {
this.future = future;
}
}
}
@GuardedBy("lock")
@CheckForNull // Must cancel the returned future if not null.
Future markCancelled() {
cancelled = true;
return future;
}
@GuardedBy("lock")
boolean isCancelled() {
return cancelled;
}
}
}