io.grpc.internal.MetadataApplierImpl Maven / Gradle / Ivy
/*
* Copyright 2016 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 io.grpc.CallCredentials.MetadataApplier;
import io.grpc.CallOptions;
import io.grpc.Context;
import io.grpc.Metadata;
import io.grpc.MethodDescriptor;
import io.grpc.Status;
import javax.annotation.Nullable;
import javax.annotation.concurrent.GuardedBy;
final class MetadataApplierImpl extends MetadataApplier {
private final ClientTransport transport;
private final MethodDescriptor method;
private final Metadata origHeaders;
private final CallOptions callOptions;
private final Context ctx;
private final Object lock = new Object();
// null if neither apply() or returnStream() are called.
// Needs this lock because apply() and returnStream() may race
@GuardedBy("lock")
@Nullable
private ClientStream returnedStream;
boolean finalized;
// not null if returnStream() was called before apply()
DelayedStream delayedStream;
MetadataApplierImpl(
ClientTransport transport, MethodDescriptor method, Metadata origHeaders,
CallOptions callOptions) {
this.transport = transport;
this.method = method;
this.origHeaders = origHeaders;
this.callOptions = callOptions;
this.ctx = Context.current();
}
@Override
public void apply(Metadata headers) {
checkState(!finalized, "apply() or fail() already called");
checkNotNull(headers, "headers");
origHeaders.merge(headers);
ClientStream realStream;
Context origCtx = ctx.attach();
try {
realStream = transport.newStream(method, origHeaders, callOptions);
} finally {
ctx.detach(origCtx);
}
finalizeWith(realStream);
}
@Override
public void fail(Status status) {
checkArgument(!status.isOk(), "Cannot fail with OK status");
checkState(!finalized, "apply() or fail() already called");
finalizeWith(new FailingClientStream(status));
}
private void finalizeWith(ClientStream stream) {
checkState(!finalized, "already finalized");
finalized = true;
synchronized (lock) {
if (returnedStream == null) {
// Fast path: returnStream() hasn't been called, the call will use the
// real stream directly.
returnedStream = stream;
return;
}
}
// returnStream() has been called before me, thus delayedStream must have been
// created.
checkState(delayedStream != null, "delayedStream is null");
delayedStream.setStream(stream);
}
/**
* Return a stream on which the RPC will run on.
*/
ClientStream returnStream() {
synchronized (lock) {
if (returnedStream == null) {
// apply() has not been called, needs to buffer the requests.
delayedStream = new DelayedStream();
return returnedStream = delayedStream;
} else {
return returnedStream;
}
}
}
}