/*
* Copyright 2002-2016 the original author or 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 org.springframework.web.socket.handler;
import java.io.IOException;
import java.util.Queue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.web.socket.CloseStatus;
import org.springframework.web.socket.WebSocketMessage;
import org.springframework.web.socket.WebSocketSession;
/**
* Wrap a {@link org.springframework.web.socket.WebSocketSession WebSocketSession}
* to guarantee only one thread can send messages at a time.
*
* <p>If a send is slow, subsequent attempts to send more messages from other
* threads will not be able to acquire the flush lock and messages will be
* buffered instead -- at that time, the specified buffer-size limit and
* send-time limit will be checked and the session closed if the limits are
* exceeded.
*
* @author Rossen Stoyanchev
* @since 4.0.3
*/
public class ConcurrentWebSocketSessionDecorator extends WebSocketSessionDecorator {
private static final Log logger = LogFactory.getLog(ConcurrentWebSocketSessionDecorator.class);
private final int sendTimeLimit;
private final int bufferSizeLimit;
private final Queue<WebSocketMessage<?>> buffer = new LinkedBlockingQueue<>();
private final AtomicInteger bufferSize = new AtomicInteger();
private volatile long sendStartTime;
private volatile boolean limitExceeded;
private volatile boolean closeInProgress;
private final Lock flushLock = new ReentrantLock();
private final Lock closeLock = new ReentrantLock();
/**
* Create a new {@code ConcurrentWebSocketSessionDecorator}.
* @param delegate the {@code WebSocketSession} to delegate to
* @param sendTimeLimit the send-time limit (milliseconds)
* @param bufferSizeLimit the buffer-size limit (number of bytes)
*/
public ConcurrentWebSocketSessionDecorator(WebSocketSession delegate, int sendTimeLimit, int bufferSizeLimit) {
super(delegate);
this.sendTimeLimit = sendTimeLimit;
this.bufferSizeLimit = bufferSizeLimit;
}
public int getBufferSize() {
return this.bufferSize.get();
}
public long getTimeSinceSendStarted() {
long start = this.sendStartTime;
return (start > 0 ? (System.currentTimeMillis() - start) : 0);
}
public void sendMessage(WebSocketMessage<?> message) throws IOException {
if (shouldNotSend()) {
return;
}
this.buffer.add(message);
this.bufferSize.addAndGet(message.getPayloadLength());
do {
if (!tryFlushMessageBuffer()) {
if (logger.isTraceEnabled()) {
String text = String.format("Another send already in progress: " +
"session id '%s':, \"in-progress\" send time %d (ms), buffer size %d bytes",
getId(), getTimeSinceSendStarted(), this.bufferSize.get());
logger.trace(text);
}
checkSessionLimits();
break;
}
}
while (!this.buffer.isEmpty() && !shouldNotSend());
}
private boolean shouldNotSend() {
return (this.limitExceeded || this.closeInProgress);
}
private boolean tryFlushMessageBuffer() throws IOException {
if (this.flushLock.tryLock()) {
try {
while (true) {
WebSocketMessage<?> message = this.buffer.poll();
if (message == null || shouldNotSend()) {
break;
}
this.bufferSize.addAndGet(message.getPayloadLength() * -1);
this.sendStartTime = System.currentTimeMillis();
getDelegate().sendMessage(message);
this.sendStartTime = 0;
}
}
finally {
this.sendStartTime = 0;
flushLock.unlock();
}
return true;
}
return false;
}
private void checkSessionLimits() throws IOException {
if (!shouldNotSend() && this.closeLock.tryLock()) {
try {
if (getTimeSinceSendStarted() > this.sendTimeLimit) {
String format = "Message send time %d (ms) for session '%s' exceeded the allowed limit %d";
String reason = String.format(format, getTimeSinceSendStarted(), getId(), this.sendTimeLimit);
setLimitExceeded(reason);
}
else if (this.bufferSize.get() > this.bufferSizeLimit) {
String format = "The send buffer size %d bytes for session '%s' exceeded the allowed limit %d";
String reason = String.format(format, this.bufferSize.get(), getId(), this.bufferSizeLimit);
setLimitExceeded(reason);
}
}
finally {
this.closeLock.unlock();
}
}
}
private void setLimitExceeded(String reason) {
this.limitExceeded = true;
throw new SessionLimitExceededException(reason, CloseStatus.SESSION_NOT_RELIABLE);
}
@Override
public void close(CloseStatus status) throws IOException {
this.closeLock.lock();
try {
if (this.closeInProgress) {
return;
}
if (!CloseStatus.SESSION_NOT_RELIABLE.equals(status)) {
try {
checkSessionLimits();
}
catch (SessionLimitExceededException ex) {
// Ignore
}
if (this.limitExceeded) {
if (logger.isDebugEnabled()) {
logger.debug("Changing close status " + status + " to SESSION_NOT_RELIABLE.");
}
status = CloseStatus.SESSION_NOT_RELIABLE;
}
}
this.closeInProgress = true;
super.close(status);
}
finally {
this.closeLock.unlock();
}
}
@Override
public String toString() {
return getDelegate().toString();
}
}