io.grpc.internal.Http2Ping Maven / Gradle / Ivy
/*
* Copyright 2015, gRPC Authors All rights reserved.
*
* 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 com.google.common.base.Stopwatch;
import io.grpc.internal.ClientTransport.PingCallback;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.concurrent.GuardedBy;
/**
* Represents an outstanding PING operation on an HTTP/2 channel. This can be used by HTTP/2-based
* transports to implement {@link ClientTransport#ping}.
*
* A typical transport need only support one outstanding ping at a time. So, if a ping is
* requested while an operation is already in progress, the given callback is notified when the
* existing operation completes.
*/
public class Http2Ping {
private static final Logger log = Logger.getLogger(Http2Ping.class.getName());
/**
* The PING frame includes 8 octets of payload data, e.g. 64 bits.
*/
private final long data;
/**
* Used to measure elapsed time.
*/
private final Stopwatch stopwatch;
/**
* The registered callbacks and the executor used to invoke them.
*/
@GuardedBy("this") private Map callbacks
= new LinkedHashMap();
/**
* False until the operation completes, either successfully (other side sent acknowledgement) or
* unsuccessfully.
*/
@GuardedBy("this") private boolean completed;
/**
* If non-null, indicates the ping failed.
*/
@GuardedBy("this") private Throwable failureCause;
/**
* The round-trip time for the ping, in nanoseconds. This value is only meaningful when
* {@link #completed} is true and {@link #failureCause} is null.
*/
@GuardedBy("this") private long roundTripTimeNanos;
/**
* Creates a new ping operation. The caller is responsible for sending a ping on an HTTP/2 channel
* using the given payload. The caller is also responsible for starting the stopwatch when the
* PING frame is sent.
*
* @param data the ping payload
* @param stopwatch a stopwatch for measuring round-trip time
*/
public Http2Ping(long data, Stopwatch stopwatch) {
this.data = data;
this.stopwatch = stopwatch;
}
/**
* Registers a callback that is invoked when the ping operation completes. If this ping operation
* is already completed, the callback is invoked immediately.
*
* @param callback the callback to invoke
* @param executor the executor to use
*/
public void addCallback(final ClientTransport.PingCallback callback, Executor executor) {
Runnable runnable;
synchronized (this) {
if (!completed) {
callbacks.put(callback, executor);
return;
}
// otherwise, invoke callback immediately (but not while holding lock)
runnable = this.failureCause != null ? asRunnable(callback, failureCause)
: asRunnable(callback, roundTripTimeNanos);
}
doExecute(executor, runnable);
}
/**
* Returns the expected ping payload for this outstanding operation.
*
* @return the expected payload for this outstanding ping
*/
public long payload() {
return data;
}
/**
* Completes this operation successfully. The stopwatch given during construction is used to
* measure the elapsed time. Registered callbacks are invoked and provided the measured elapsed
* time.
*
* @return true if the operation is marked as complete; false if it was already complete
*/
public boolean complete() {
Map callbacks;
long roundTripTimeNanos;
synchronized (this) {
if (completed) {
return false;
}
completed = true;
roundTripTimeNanos = this.roundTripTimeNanos = stopwatch.elapsed(TimeUnit.NANOSECONDS);
callbacks = this.callbacks;
this.callbacks = null;
}
for (Map.Entry entry : callbacks.entrySet()) {
doExecute(entry.getValue(), asRunnable(entry.getKey(), roundTripTimeNanos));
}
return true;
}
/**
* Completes this operation exceptionally. Registered callbacks are invoked and provided the
* given throwable as the cause of failure.
*
* @param failureCause the cause of failure
*/
public void failed(Throwable failureCause) {
Map callbacks;
synchronized (this) {
if (completed) {
return;
}
completed = true;
this.failureCause = failureCause;
callbacks = this.callbacks;
this.callbacks = null;
}
for (Map.Entry entry : callbacks.entrySet()) {
notifyFailed(entry.getKey(), entry.getValue(), failureCause);
}
}
/**
* Notifies the given callback that the ping operation failed.
*
* @param callback the callback
* @param executor the executor used to invoke the callback
* @param cause the cause of failure
*/
public static void notifyFailed(PingCallback callback, Executor executor, Throwable cause) {
doExecute(executor, asRunnable(callback, cause));
}
/**
* Executes the given runnable. This prevents exceptions from propagating so that an exception
* thrown by one callback won't prevent subsequent callbacks from being executed.
*/
private static void doExecute(Executor executor, Runnable runnable) {
try {
executor.execute(runnable);
} catch (Throwable th) {
log.log(Level.SEVERE, "Failed to execute PingCallback", th);
}
}
/**
* Returns a runnable that, when run, invokes the given callback, providing the given round-trip
* duration.
*/
private static Runnable asRunnable(final ClientTransport.PingCallback callback,
final long roundTripTimeNanos) {
return new Runnable() {
@Override
public void run() {
callback.onSuccess(roundTripTimeNanos);
}
};
}
/**
* Returns a runnable that, when run, invokes the given callback, providing the given cause of
* failure.
*/
private static Runnable asRunnable(final ClientTransport.PingCallback callback,
final Throwable failureCause) {
return new Runnable() {
@Override
public void run() {
callback.onFailure(failureCause);
}
};
}
}