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/*
* 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.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.util.concurrent.MoreExecutors;
import io.grpc.Status;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import javax.annotation.concurrent.GuardedBy;
/**
* Manages keepalive pings.
*/
public class KeepAliveManager {
private static final SystemTicker SYSTEM_TICKER = new SystemTicker();
private static final long MIN_KEEPALIVE_TIME_NANOS = TimeUnit.SECONDS.toNanos(10);
private static final long MIN_KEEPALIVE_TIMEOUT_NANOS = TimeUnit.MILLISECONDS.toNanos(10L);
private final ScheduledExecutorService scheduler;
private final Ticker ticker;
private final KeepAlivePinger keepAlivePinger;
private final boolean keepAliveDuringTransportIdle;
@GuardedBy("this")
private State state = State.IDLE;
@GuardedBy("this")
private long nextKeepaliveTime;
@GuardedBy("this")
private ScheduledFuture shutdownFuture;
@GuardedBy("this")
private ScheduledFuture pingFuture;
private final Runnable shutdown = new LogExceptionRunnable(new Runnable() {
@Override
public void run() {
boolean shouldShutdown = false;
synchronized (KeepAliveManager.this) {
if (state != State.DISCONNECTED) {
// We haven't received a ping response within the timeout. The connection is likely gone
// already. Shutdown the transport and fail all existing rpcs.
state = State.DISCONNECTED;
shouldShutdown = true;
}
}
if (shouldShutdown) {
keepAlivePinger.onPingTimeout();
}
}
});
private final Runnable sendPing = new LogExceptionRunnable(new Runnable() {
@Override
public void run() {
boolean shouldSendPing = false;
synchronized (KeepAliveManager.this) {
pingFuture = null;
if (state == State.PING_SCHEDULED) {
shouldSendPing = true;
state = State.PING_SENT;
// Schedule a shutdown. It fires if we don't receive the ping response within the timeout.
shutdownFuture = scheduler.schedule(shutdown, keepAliveTimeoutInNanos,
TimeUnit.NANOSECONDS);
} else if (state == State.PING_DELAYED) {
// We have received some data. Reschedule the ping with the new time.
pingFuture = scheduler.schedule(
sendPing,
nextKeepaliveTime - ticker.read(),
TimeUnit.NANOSECONDS);
state = State.PING_SCHEDULED;
}
}
if (shouldSendPing) {
// Send the ping.
keepAlivePinger.ping();
}
}
});
private final long keepAliveTimeInNanos;
private final long keepAliveTimeoutInNanos;
private enum State {
/*
* We don't need to do any keepalives. This means the transport has no active rpcs and
* keepAliveDuringTransportIdle == false.
*/
IDLE,
/*
* We have scheduled a ping to be sent in the future. We may decide to delay it if we receive
* some data.
*/
PING_SCHEDULED,
/*
* We need to delay the scheduled keepalive ping.
*/
PING_DELAYED,
/*
* The ping has been sent out. Waiting for a ping response.
*/
PING_SENT,
/*
* Transport goes idle after ping has been sent.
*/
IDLE_AND_PING_SENT,
/*
* The transport has been disconnected. We won't do keepalives any more.
*/
DISCONNECTED,
}
/**
* Creates a KeepAliverManager.
*/
public KeepAliveManager(KeepAlivePinger keepAlivePinger, ScheduledExecutorService scheduler,
long keepAliveTimeInNanos, long keepAliveTimeoutInNanos,
boolean keepAliveDuringTransportIdle) {
this(keepAlivePinger, scheduler, SYSTEM_TICKER, keepAliveTimeInNanos, keepAliveTimeoutInNanos,
keepAliveDuringTransportIdle);
}
@VisibleForTesting
KeepAliveManager(KeepAlivePinger keepAlivePinger, ScheduledExecutorService scheduler,
Ticker ticker, long keepAliveTimeInNanos, long keepAliveTimeoutInNanos,
boolean keepAliveDuringTransportIdle) {
this.keepAlivePinger = checkNotNull(keepAlivePinger, "keepAlivePinger");
this.scheduler = checkNotNull(scheduler, "scheduler");
this.ticker = checkNotNull(ticker, "ticker");
this.keepAliveTimeInNanos = keepAliveTimeInNanos;
this.keepAliveTimeoutInNanos = keepAliveTimeoutInNanos;
this.keepAliveDuringTransportIdle = keepAliveDuringTransportIdle;
nextKeepaliveTime = ticker.read() + keepAliveTimeInNanos;
}
/** Start keepalive monitoring. */
public synchronized void onTransportStarted() {
if (keepAliveDuringTransportIdle) {
onTransportActive();
}
}
/**
* Transport has received some data so that we can delay sending keepalives.
*/
public synchronized void onDataReceived() {
nextKeepaliveTime = ticker.read() + keepAliveTimeInNanos;
// We do not cancel the ping future here. This avoids constantly scheduling and cancellation in
// a busy transport. Instead, we update the status here and reschedule later. So we actually
// keep one sendPing task always in flight when there're active rpcs.
if (state == State.PING_SCHEDULED) {
state = State.PING_DELAYED;
} else if (state == State.PING_SENT || state == State.IDLE_AND_PING_SENT) {
// Ping acked or effectively ping acked. Cancel shutdown, and then if not idle,
// schedule a new keep-alive ping.
if (shutdownFuture != null) {
shutdownFuture.cancel(false);
}
if (state == State.IDLE_AND_PING_SENT) {
// not to schedule new pings until onTransportActive
state = State.IDLE;
return;
}
// schedule a new ping
state = State.PING_SCHEDULED;
checkState(pingFuture == null, "There should be no outstanding pingFuture");
pingFuture = scheduler.schedule(sendPing, keepAliveTimeInNanos, TimeUnit.NANOSECONDS);
}
}
/**
* Transport has active streams. Start sending keepalives if necessary.
*/
public synchronized void onTransportActive() {
if (state == State.IDLE) {
// When the transport goes active, we do not reset the nextKeepaliveTime. This allows us to
// quickly check whether the connection is still working.
state = State.PING_SCHEDULED;
if (pingFuture == null) {
pingFuture = scheduler.schedule(
sendPing,
nextKeepaliveTime - ticker.read(),
TimeUnit.NANOSECONDS);
}
} else if (state == State.IDLE_AND_PING_SENT) {
state = State.PING_SENT;
} // Other states are possible when keepAliveDuringTransportIdle == true
}
/**
* Transport has finished all streams.
*/
public synchronized void onTransportIdle() {
if (keepAliveDuringTransportIdle) {
return;
}
if (state == State.PING_SCHEDULED || state == State.PING_DELAYED) {
state = State.IDLE;
}
if (state == State.PING_SENT) {
state = State.IDLE_AND_PING_SENT;
}
}
/**
* Transport is being terminated. We no longer need to do keepalives.
*/
public synchronized void onTransportTermination() {
if (state != State.DISCONNECTED) {
state = State.DISCONNECTED;
if (shutdownFuture != null) {
shutdownFuture.cancel(false);
}
if (pingFuture != null) {
pingFuture.cancel(false);
pingFuture = null;
}
}
}
/**
* Bumps keepalive time to 10 seconds if the specified value was smaller than that.
*/
public static long clampKeepAliveTimeInNanos(long keepAliveTimeInNanos) {
return Math.max(keepAliveTimeInNanos, MIN_KEEPALIVE_TIME_NANOS);
}
/**
* Bumps keepalive timeout to 10 milliseconds if the specified value was smaller than that.
*/
public static long clampKeepAliveTimeoutInNanos(long keepAliveTimeoutInNanos) {
return Math.max(keepAliveTimeoutInNanos, MIN_KEEPALIVE_TIMEOUT_NANOS);
}
public interface KeepAlivePinger {
/**
* Sends out a keep-alive ping.
*/
void ping();
/**
* Callback when Ping Ack was not received in KEEPALIVE_TIMEOUT. Should shutdown the transport.
*/
void onPingTimeout();
}
/**
* Default client side {@link KeepAlivePinger}.
*/
public static final class ClientKeepAlivePinger implements KeepAlivePinger {
private final ConnectionClientTransport transport;
public ClientKeepAlivePinger(ConnectionClientTransport transport) {
this.transport = transport;
}
@Override
public void ping() {
transport.ping(new ClientTransport.PingCallback() {
@Override
public void onSuccess(long roundTripTimeNanos) {}
@Override
public void onFailure(Throwable cause) {
transport.shutdownNow(Status.UNAVAILABLE.withDescription(
"Keepalive failed. The connection is likely gone"));
}
}, MoreExecutors.directExecutor());
}
@Override
public void onPingTimeout() {
transport.shutdownNow(Status.UNAVAILABLE.withDescription(
"Keepalive failed. The connection is likely gone"));
}
}
// TODO(zsurocking): Classes below are copied from Deadline.java. We should consider share the
// code.
/** Time source representing nanoseconds since fixed but arbitrary point in time. */
abstract static class Ticker {
/** Returns the number of nanoseconds since this source's epoch. */
public abstract long read();
}
private static class SystemTicker extends Ticker {
@Override
public long read() {
return System.nanoTime();
}
}
}
