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Make DEADLINE_EXCEEDED more reliable 

The client can race with the server in cancelling due to deadline. If
server cancels we don't get DEADLINE_EXCEEDED, so double-check on
client-side to reduce the chances of losing the race.

Generally we expect the client to lose the race because of coarse timer
granularity for timer expirary. This change does little to help if the
server's clock runs noticably "fast" relative to the client.
This commit is contained in:
Eric Anderson 2015-07-18 00:06:42 -07:00
parent f48bc3b3eb
commit 0eae0d9264
1 changed files with 20 additions and 5 deletions
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25
core/src/main/java/io/grpc/ChannelImpl.java
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@ -326,7 +326,8 @@ public final class ChannelImpl extends Channel {
@Override
public void start(Listener<RespT> observer, Metadata.Headers headers) {
Preconditions.checkState(stream == null, "Already started");
ClientStreamListener listener = new ClientStreamListenerImpl(observer);
Long deadlineNanoTime = callOptions.getDeadlineNanoTime();
ClientStreamListener listener = new ClientStreamListenerImpl(observer, deadlineNanoTime);
ClientTransport transport;
try {
transport = obtainActiveTransport();
@ -343,7 +344,6 @@ public final class ChannelImpl extends Channel {
headers.removeAll(TIMEOUT_KEY);
// Convert the deadline to timeout. Timeout is more favorable than deadline on the wire
// because timeout tolerates the clock difference between machines.
Long deadlineNanoTime = callOptions.getDeadlineNanoTime();
long timeoutMicros = 0;
if (deadlineNanoTime != null) {
timeoutMicros = TimeUnit.NANOSECONDS.toMicros(deadlineNanoTime - System.nanoTime());
@ -441,11 +441,13 @@ public final class ChannelImpl extends Channel {
private class ClientStreamListenerImpl implements ClientStreamListener {
private final Listener<RespT> observer;
private final Long deadlineNanoTime;
private boolean closed;
public ClientStreamListenerImpl(Listener<RespT> observer) {
public ClientStreamListenerImpl(Listener<RespT> observer, Long deadlineNanoTime) {
Preconditions.checkNotNull(observer);
this.observer = observer;
this.deadlineNanoTime = deadlineNanoTime;
}
@Override
@ -491,7 +493,20 @@ public final class ChannelImpl extends Channel {
}
@Override
public void closed(final Status status, final Metadata.Trailers trailers) {
public void closed(Status status, Metadata.Trailers trailers) {
if (status.getCode() == Status.Code.CANCELLED && deadlineNanoTime != null) {
// When the server's deadline expires, it can only reset the stream with CANCEL and no
// description. Since our timer may be delayed in firing, we double-check the deadline and
// turn the failure into the likely more helpful DEADLINE_EXCEEDED status. This is always
// safe, but we avoid wasting resources getting the nanoTime() when unnecessary.
if (deadlineNanoTime <= System.nanoTime()) {
status = Status.DEADLINE_EXCEEDED;
// Replace trailers to prevent mixing sources of status and trailers.
trailers = new Metadata.Trailers();
}
}
final Status savedStatus = status;
final Metadata.Trailers savedTrailers = trailers;
callExecutor.execute(new Runnable() {
@Override
public void run() {
@ -501,7 +516,7 @@ public final class ChannelImpl extends Channel {
if (future != null) {
future.cancel(false);
}
observer.onClose(status, trailers);
observer.onClose(savedStatus, savedTrailers);
}
});
}