序
本文主要研究一下redisson的DelayedQueue
maven
<dependency>
<groupId>org.redisson</groupId>
<artifactId>redisson</artifactId>
<version>3.8.1</version>
</dependency>实例
@Test
public void testDelayedQueue() throws InterruptedException {
Config config = new Config();
config.useSingleServer()
.setAddress("redis://192.168.99.100:6379");
RedissonClient redisson = Redisson.create(config);
RBlockingQueue<String> blockingQueue = redisson.getBlockingQueue("dest_queue1");
RDelayedQueue<String> delayedQueue = redisson.getDelayedQueue(blockingQueue);
delayedQueue.offer("demo", 10, TimeUnit.SECONDS);
Assert.assertFalse(blockingQueue.contains("demo"));
TimeUnit.SECONDS.sleep(15);
Assert.assertTrue(blockingQueue.contains("demo"));
}- 这里使用了两个queue，对delayedQueue的offer操作是直接进入delayedQueue，但是delay是作用在目标队列上，这里就是RBlockingQueue
源码解析
RDelayedQueue.offer
redisson-3.8.1-sources.jar!/org/redisson/RedissonDelayedQueue.java
public class RedissonDelayedQueue<V> extends RedissonExpirable implements RDelayedQueue<V> {
private final QueueTransferService queueTransferService;
private final String channelName;
private final String queueName;
private final String timeoutSetName;
protected RedissonDelayedQueue(QueueTransferService queueTransferService, Codec codec, final CommandAsyncExecutor commandExecutor, String name) {
super(codec, commandExecutor, name);
channelName = prefixName("redisson_delay_queue_channel", getName());
queueName = prefixName("redisson_delay_queue", getName());
timeoutSetName = prefixName("redisson_delay_queue_timeout", getName());
//QueueTransferTask task = ......
queueTransferService.schedule(queueName, task);
this.queueTransferService = queueTransferService;
}
public void offer(V e, long delay, TimeUnit timeUnit) {
get(offerAsync(e, delay, timeUnit));
}
public RFuture<Void> offerAsync(V e, long delay, TimeUnit timeUnit) {
long delayInMs = timeUnit.toMillis(delay);
long timeout = System.currentTimeMillis() + delayInMs;
long randomId = PlatformDependent.threadLocalRandom().nextLong();
return commandExecutor.evalWriteAsync(getName(), codec, RedisCommands.EVAL_VOID,
"local value = struct.pack('dLc0', tonumber(ARGV[2]), string.len(ARGV[3]), ARGV[3]);"
+ "redis.call('zadd', KEYS[2], ARGV[1], value);"
+ "redis.call('rpush', KEYS[3], value);"
// if new object added to queue head when publish its startTime
// to all scheduler workers
+ "local v = redis.call('zrange', KEYS[2], 0, 0); "
+ "if v[1] == value then "
+ "redis.call('publish', KEYS[4], ARGV[1]); "
+ "end;"
,
Arrays.<Object>asList(getName(), timeoutSetName, queueName, channelName),
timeout, randomId, encode(e));
}
public ByteBuf encode(Object value) {
if (commandExecutor.isRedissonReferenceSupportEnabled()) {
RedissonReference reference = RedissonObjectFactory.toReference(commandExecutor.getConnectionManager().getCfg(), value);
if (reference != null) {
value = reference;
}
}
try {
return codec.getValueEncoder().encode(value);
} catch (IOException e) {
throw new IllegalArgumentException(e);
}
}
public static String prefixName(String prefix, String name) {
if (name.contains("{")) {
return prefix + ":" + name;
}
return prefix + ":{" + name + "}";
}
//......
}- 这里使用的是一段lua脚本，其中keys参数数组有四个值，KEYS[1]为getName(), KEYS[2]为timeoutSetName, KEYS[3]为queueName, KEYS[4]为channelName
- 变量有三个，ARGV[1]为timeout，ARGV[2]为randomId，ARGV[3]为encode(e)
- 这段lua脚本对timeoutSetName的zset添加一个结构体，其score为timeout值；对queueName的list的表尾添加结构体；然后判断timeoutSetName的zset的第一个元素是否是当前的结构体，如果是则对channel发布timeout消息
queueTransferService.schedule
redisson-3.8.1-sources.jar!/org/redisson/RedissonDelayedQueue.java
QueueTransferTask task = new QueueTransferTask(commandExecutor.getConnectionManager()) {
@Override
protected RFuture<Long> pushTaskAsync() {
return commandExecutor.evalWriteAsync(getName(), LongCodec.INSTANCE, RedisCommands.EVAL_LONG,
"local expiredValues = redis.call('zrangebyscore', KEYS[2], 0, ARGV[1], 'limit', 0, ARGV[2]); "
+ "if #expiredValues > 0 then "
+ "for i, v in ipairs(expiredValues) do "
+ "local randomId, value = struct.unpack('dLc0', v);"
+ "redis.call('rpush', KEYS[1], value);"
+ "redis.call('lrem', KEYS[3], 1, v);"
+ "end; "
+ "redis.call('zrem', KEYS[2], unpack(expiredValues));"
+ "end; "
// get startTime from scheduler queue head task
+ "local v = redis.call('zrange', KEYS[2], 0, 0, 'WITHSCORES'); "
+ "if v[1] ~= nil then "
+ "return v[2]; "
+ "end "
+ "return nil;",
Arrays.<Object>asList(getName(), timeoutSetName, queueName),
System.currentTimeMillis(), 100);
}
@Override
protected RTopic<Long> getTopic() {
return new RedissonTopic<Long>(LongCodec.INSTANCE, commandExecutor, channelName);
}
};
queueTransferService.schedule(queueName, task);- RedissonDelayedQueue构造器里头对QueueTransferTask进行调度
- 调度执行的是pushTaskAsync方法，主要就是将到期的元素从元素队列移到目标队列
- 这里使用一段lua脚本，KEYS[1]为getName()，KEYS[2]为timeoutSetName，KEYS[3]为queueName；ARGV[1]为当前时间戳，ARGV[2]为100
- 这里调用zrangebyscore，对timeoutSetName的zset使用timeout参数进行排序，取得分介于0和当前时间戳的元素，取前200条
- 如果有值表示该元素需要移交到目标队列，然后调用rpush移交到目标队列，再调用lrem从元素队列移除，最后在从timeoutSetName的zset中删除掉已经处理的这些元素
- 处理完过元素转移之后，再取timeoutSetName的zset的第一个元素的得分返回，如果没有返回nil
QueueTransferService.schedule
redisson-3.8.1-sources.jar!/org/redisson/QueueTransferService.java
public class QueueTransferService {
private final ConcurrentMap<String, QueueTransferTask> tasks = PlatformDependent.newConcurrentHashMap();
public synchronized void schedule(String name, QueueTransferTask task) {
QueueTransferTask oldTask = tasks.putIfAbsent(name, task);
if (oldTask == null) {
task.start();
} else {
oldTask.incUsage();
}
}
public synchronized void remove(String name) {
QueueTransferTask task = tasks.get(name);
if (task != null) {
if (task.decUsage() == 0) {
tasks.remove(name, task);
task.stop();
}
}
}
}- 这里的schedule方法首先添加到ConcurrentMap中，如果该任务已经存在，则调用oldTask.incUsage()，不存在则启动该任务
QueueTransferTask.start
redisson-3.8.1-sources.jar!/org/redisson/QueueTransferTask.java
public void start() {
RTopic<Long> schedulerTopic = getTopic();
statusListenerId = schedulerTopic.addListener(new BaseStatusListener() {
@Override
public void onSubscribe(String channel) {
pushTask();
}
});
messageListenerId = schedulerTopic.addListener(new MessageListener<Long>() {
@Override
public void onMessage(CharSequence channel, Long startTime) {
scheduleTask(startTime);
}
});
}
private void scheduleTask(final Long startTime) {
TimeoutTask oldTimeout = lastTimeout.get();
if (startTime == null) {
return;
}
if (oldTimeout != null) {
oldTimeout.getTask().cancel();
}
long delay = startTime - System.currentTimeMillis();
if (delay > 10) {
Timeout timeout = connectionManager.newTimeout(new TimerTask() {
@Override
public void run(Timeout timeout) throws Exception {
pushTask();
TimeoutTask currentTimeout = lastTimeout.get();
if (currentTimeout.getTask() == timeout) {
lastTimeout.compareAndSet(currentTimeout, null);
}
}
}, delay, TimeUnit.MILLISECONDS);
if (!lastTimeout.compareAndSet(oldTimeout, new TimeoutTask(startTime, timeout))) {
timeout.cancel();
}
} else {
pushTask();
}
}
private void pushTask() {
RFuture<Long> startTimeFuture = pushTaskAsync();
startTimeFuture.addListener(new FutureListener<Long>() {
@Override
public void operationComplete(io.netty.util.concurrent.Future<Long> future) throws Exception {
if (!future.isSuccess()) {
if (future.cause() instanceof RedissonShutdownException) {
return;
}
log.error(future.cause().getMessage(), future.cause());
scheduleTask(System.currentTimeMillis() + 5 * 1000L);
return;
}
if (future.getNow() != null) {
scheduleTask(future.getNow());
}
}
});
}- 这里用到了RTopic，添加了StatusListener以及MessageListener
- StatusListener在订阅的时候触发pushTask，MessageListener主要是调用scheduleTask
- pushTaskAsync在RedissonDelayedQueue的实现就是上面讲的实现元素在原始队列及目标队列的转移
- scheduleTask方法会重新计算delay，对于大于10的延时触发pushTask，小于等于10的则立刻触发pushTask
- pushTask会对pushTaskAsync操作进行回调，如果执行不成功则重新触发scheduleTask，如果执行成功但是返回值(
timeoutSetName的zset的第一个元素的得分)不为null的话，则以该值触发scheduleTask
小结
- redisson的DelayedQueue使用上是将元素及延时信息入队，之后定时任务将到期的元素转移到目标队列
- 这里使用了三个结构来存储，一个是目标队列list；一个是原生队列list，添加的是带有延时信息的结构体；一个是timeoutSetName的zset，元素是结构体，其score为timeout值
- redisson使用了很多异步回调来操作，整体代码阅读上会相对费劲些
