/*
* Copyright 2015 The Netty Project
*
* The Netty Project licenses this file to you 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.netty.channel.pool;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoop;
import io.netty.util.AttributeKey;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.FutureListener;
import io.netty.util.concurrent.Promise;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.ThrowableUtil;
import java.util.Deque;
import static io.netty.util.internal.ObjectUtil.*;
/**
* Simple {@link ChannelPool} implementation which will create new {@link Channel}s if someone tries to acquire
* a {@link Channel} but none is in the pool atm. No limit on the maximal concurrent {@link Channel}s is enforced.
*
* This implementation uses LIFO order for {@link Channel}s in the {@link ChannelPool}.
*
*/
public class SimpleChannelPool implements ChannelPool {
private static final AttributeKey<SimpleChannelPool> POOL_KEY = AttributeKey.newInstance("channelPool");
private static final IllegalStateException FULL_EXCEPTION = ThrowableUtil.unknownStackTrace(
new IllegalStateException("ChannelPool full"), SimpleChannelPool.class, "releaseAndOffer(...)");
private static final IllegalStateException UNHEALTHY_NON_OFFERED_TO_POOL = ThrowableUtil.unknownStackTrace(
new IllegalStateException("Channel is unhealthy not offering it back to pool"),
SimpleChannelPool.class, "releaseAndOffer(...)");
private final Deque<Channel> deque = PlatformDependent.newConcurrentDeque();
private final ChannelPoolHandler handler;
private final ChannelHealthChecker healthCheck;
private final Bootstrap bootstrap;
private final boolean releaseHealthCheck;
/**
* Creates a new instance using the {@link ChannelHealthChecker#ACTIVE}.
*
* @param bootstrap the {@link Bootstrap} that is used for connections
* @param handler the {@link ChannelPoolHandler} that will be notified for the different pool actions
*/
public SimpleChannelPool(Bootstrap bootstrap, final ChannelPoolHandler handler) {
this(bootstrap, handler, ChannelHealthChecker.ACTIVE);
}
/**
* Creates a new instance.
*
* @param bootstrap the {@link Bootstrap} that is used for connections
* @param handler the {@link ChannelPoolHandler} that will be notified for the different pool actions
* @param healthCheck the {@link ChannelHealthChecker} that will be used to check if a {@link Channel} is
* still healthy when obtain from the {@link ChannelPool}
*/
public SimpleChannelPool(Bootstrap bootstrap, final ChannelPoolHandler handler, ChannelHealthChecker healthCheck) {
this(bootstrap, handler, healthCheck, true);
}
/**
* Creates a new instance.
*
* @param bootstrap the {@link Bootstrap} that is used for connections
* @param handler the {@link ChannelPoolHandler} that will be notified for the different pool actions
* @param healthCheck the {@link ChannelHealthChecker} that will be used to check if a {@link Channel} is
* still healthy when obtain from the {@link ChannelPool}
* @param releaseHealthCheck will check channel health before offering back if this parameter set to {@code true};
* otherwise, channel health is only checked at acquisition time
*/
public SimpleChannelPool(Bootstrap bootstrap, final ChannelPoolHandler handler, ChannelHealthChecker healthCheck,
boolean releaseHealthCheck) {
this.handler = checkNotNull(handler, "handler");
this.healthCheck = checkNotNull(healthCheck, "healthCheck");
this.releaseHealthCheck = releaseHealthCheck;
// Clone the original Bootstrap as we want to set our own handler
this.bootstrap = checkNotNull(bootstrap, "bootstrap").clone();
this.bootstrap.handler(new ChannelInitializer<Channel>() {
@Override
protected void initChannel(Channel ch) throws Exception {
assert ch.eventLoop().inEventLoop();
handler.channelCreated(ch);
}
});
}
/**
* Returns the {@link Bootstrap} this pool will use to open new connections.
*
* @return the {@link Bootstrap} this pool will use to open new connections
*/
protected Bootstrap bootstrap() {
return bootstrap;
}
/**
* Returns the {@link ChannelPoolHandler} that will be notified for the different pool actions.
*
* @return the {@link ChannelPoolHandler} that will be notified for the different pool actions
*/
protected ChannelPoolHandler handler() {
return handler;
}
/**
* Returns the {@link ChannelHealthChecker} that will be used to check if a {@link Channel} is healthy.
*
* @return the {@link ChannelHealthChecker} that will be used to check if a {@link Channel} is healthy
*/
protected ChannelHealthChecker healthChecker() {
return healthCheck;
}
/**
* Indicates whether this pool will check the health of channels before offering them back into the pool.
*
* @return {@code true} if this pool will check the health of channels before offering them back into the pool, or
* {@code false} if channel health is only checked at acquisition time
*/
protected boolean releaseHealthCheck() {
return releaseHealthCheck;
}
@Override
public final Future<Channel> acquire() {
return acquire(bootstrap.config().group().next().<Channel>newPromise());
}
@Override
public Future<Channel> acquire(final Promise<Channel> promise) {
checkNotNull(promise, "promise");
return acquireHealthyFromPoolOrNew(promise);
}
/**
* Tries to retrieve healthy channel from the pool if any or creates a new channel otherwise.
* @param promise the promise to provide acquire result.
* @return future for acquiring a channel.
*/
private Future<Channel> acquireHealthyFromPoolOrNew(final Promise<Channel> promise) {
try {
final Channel ch = pollChannel();
if (ch == null) {
// No Channel left in the pool bootstrap a new Channel
Bootstrap bs = bootstrap.clone();
bs.attr(POOL_KEY, this);
ChannelFuture f = connectChannel(bs);
if (f.isDone()) {
notifyConnect(f, promise);
} else {
f.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
notifyConnect(future, promise);
}
});
}
return promise;
}
EventLoop loop = ch.eventLoop();
if (loop.inEventLoop()) {
doHealthCheck(ch, promise);
} else {
loop.execute(new Runnable() {
@Override
public void run() {
doHealthCheck(ch, promise);
}
});
}
} catch (Throwable cause) {
promise.tryFailure(cause);
}
return promise;
}
private void notifyConnect(ChannelFuture future, Promise<Channel> promise) {
if (future.isSuccess()) {
Channel channel = future.channel();
if (!promise.trySuccess(channel)) {
// Promise was completed in the meantime (like cancelled), just release the channel again
release(channel);
}
} else {
promise.tryFailure(future.cause());
}
}
private void doHealthCheck(final Channel ch, final Promise<Channel> promise) {
assert ch.eventLoop().inEventLoop();
Future<Boolean> f = healthCheck.isHealthy(ch);
if (f.isDone()) {
notifyHealthCheck(f, ch, promise);
} else {
f.addListener(new FutureListener<Boolean>() {
@Override
public void operationComplete(Future<Boolean> future) throws Exception {
notifyHealthCheck(future, ch, promise);
}
});
}
}
private void notifyHealthCheck(Future<Boolean> future, Channel ch, Promise<Channel> promise) {
assert ch.eventLoop().inEventLoop();
if (future.isSuccess()) {
if (future.getNow()) {
try {
ch.attr(POOL_KEY).set(this);
handler.channelAcquired(ch);
promise.setSuccess(ch);
} catch (Throwable cause) {
closeAndFail(ch, cause, promise);
}
} else {
closeChannel(ch);
acquireHealthyFromPoolOrNew(promise);
}
} else {
closeChannel(ch);
acquireHealthyFromPoolOrNew(promise);
}
}
/**
* Bootstrap a new {@link Channel}. The default implementation uses {@link Bootstrap#connect()}, sub-classes may
* override this.
* <p>
* The {@link Bootstrap} that is passed in here is cloned via {@link Bootstrap#clone()}, so it is safe to modify.
*/
protected ChannelFuture connectChannel(Bootstrap bs) {
return bs.connect();
}
@Override
public final Future<Void> release(Channel channel) {
return release(channel, channel.eventLoop().<Void>newPromise());
}
@Override
public Future<Void> release(final Channel channel, final Promise<Void> promise) {
checkNotNull(channel, "channel");
checkNotNull(promise, "promise");
try {
EventLoop loop = channel.eventLoop();
if (loop.inEventLoop()) {
doReleaseChannel(channel, promise);
} else {
loop.execute(new Runnable() {
@Override
public void run() {
doReleaseChannel(channel, promise);
}
});
}
} catch (Throwable cause) {
closeAndFail(channel, cause, promise);
}
return promise;
}
private void doReleaseChannel(Channel channel, Promise<Void> promise) {
assert channel.eventLoop().inEventLoop();
// Remove the POOL_KEY attribute from the Channel and check if it was acquired from this pool, if not fail.
if (channel.attr(POOL_KEY).getAndSet(null) != this) {
closeAndFail(channel,
// Better include a stacktrace here as this is an user error.
new IllegalArgumentException(
"Channel " + channel + " was not acquired from this ChannelPool"),
promise);
} else {
try {
if (releaseHealthCheck) {
doHealthCheckOnRelease(channel, promise);
} else {
releaseAndOffer(channel, promise);
}
} catch (Throwable cause) {
closeAndFail(channel, cause, promise);
}
}
}
private void doHealthCheckOnRelease(final Channel channel, final Promise<Void> promise) throws Exception {
final Future<Boolean> f = healthCheck.isHealthy(channel);
if (f.isDone()) {
releaseAndOfferIfHealthy(channel, promise, f);
} else {
f.addListener(new FutureListener<Boolean>() {
@Override
public void operationComplete(Future<Boolean> future) throws Exception {
releaseAndOfferIfHealthy(channel, promise, f);
}
});
}
}
/**
* Adds the channel back to the pool only if the channel is healthy.
* @param channel the channel to put back to the pool
* @param promise offer operation promise.
* @param future the future that contains information fif channel is healthy or not.
* @throws Exception in case when failed to notify handler about release operation.
*/
private void releaseAndOfferIfHealthy(Channel channel, Promise<Void> promise, Future<Boolean> future)
throws Exception {
if (future.getNow()) { //channel turns out to be healthy, offering and releasing it.
releaseAndOffer(channel, promise);
} else { //channel ont healthy, just releasing it.
handler.channelReleased(channel);
closeAndFail(channel, UNHEALTHY_NON_OFFERED_TO_POOL, promise);
}
}
private void releaseAndOffer(Channel channel, Promise<Void> promise) throws Exception {
if (offerChannel(channel)) {
handler.channelReleased(channel);
promise.setSuccess(null);
} else {
closeAndFail(channel, FULL_EXCEPTION, promise);
}
}
private static void closeChannel(Channel channel) {
channel.attr(POOL_KEY).getAndSet(null);
channel.close();
}
private static void closeAndFail(Channel channel, Throwable cause, Promise<?> promise) {
closeChannel(channel);
promise.tryFailure(cause);
}
/**
* Poll a {@link Channel} out of the internal storage to reuse it. This will return {@code null} if no
* {@link Channel} is ready to be reused.
*
* Sub-classes may override {@link #pollChannel()} and {@link #offerChannel(Channel)}. Be aware that
* implementations of these methods needs to be thread-safe!
*/
protected Channel pollChannel() {
return deque.pollLast();
}
/**
* Offer a {@link Channel} back to the internal storage. This will return {@code true} if the {@link Channel}
* could be added, {@code false} otherwise.
*
* Sub-classes may override {@link #pollChannel()} and {@link #offerChannel(Channel)}. Be aware that
* implementations of these methods needs to be thread-safe!
*/
protected boolean offerChannel(Channel channel) {
return deque.offer(channel);
}
@Override
public void close() {
for (;;) {
Channel channel = pollChannel();
if (channel == null) {
break;
}
channel.close();
}
}
}