Redisson学习

顺便学习一下原理

1. 启动，看从上到下的调用和回调关系；

注册topic的元素数量和状态的变更通知，元素放入在被通知后不断加入，zrangebyscore 拿出0 ~ expiretime中的limit多少元素，然后rpush从右边放入target链表，lrem从左侧删除元素，zrem再删除有序集合元素，zrange取出有序集的第一个元素和他的timeout时间

        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 getTopic() {
                return new RedissonTopic(LongCodec.INSTANCE, commandExecutor, channelName);
            }
        };
        
        queueTransferService.schedule(queueName, task);

2. 定时任务调度

    public synchronized void schedule(String name, QueueTransferTask task) {
        QueueTransferTask oldTask = tasks.putIfAbsent(name, task);
        if (oldTask == null) {
            task.start();
        } else {
            oldTask.incUsage();
        }
    }

3. 任务启动注册

    public void start() {
        RTopic schedulerTopic = getTopic();
        statusListenerId = schedulerTopic.addListener(new BaseStatusListener() {
            @Override
            public void onSubscribe(String channel) {
                pushTask();
            }
        });
        
        messageListenerId = schedulerTopic.addListener(Long.class, new MessageListener<Long>() {
            @Override
            public void onMessage(CharSequence channel, Long startTime) {
                scheduleTask(startTime);
            }
        });
    }

4. 循环调度

    private void pushTask() {
        RFuture<Long> startTimeFuture = pushTaskAsync();
        startTimeFuture.onComplete((res, e) -> {
            if (e != null) {
                if (e instanceof RedissonShutdownException) {
                    return;
                }
                log.error(e.getMessage(), e);
                scheduleTask(System.currentTimeMillis() + 5 * 1000L);
                return;
            }
            
            if (res != null) {
                scheduleTask(res);
            }
        });
    }

 定时任务用的Netty的HashedWheelTimer

    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();
        }
    }

5. 加入： zadd 为按照到期时间有序的集合，加入； rpush 添加元素到一个list

                zrange  0 0 取有序集合中第一个元素，如果有，则publish发一个通知到chennel，内容为到期时间

    @Override
    public RFuture<Void> offerAsync(V e, long delay, TimeUnit timeUnit) {
        if (delay < 0) {
            throw new IllegalArgumentException("Delay can't be negative");
        }
        
        long delayInMs = timeUnit.toMillis(delay);
        long timeout = System.currentTimeMillis() + delayInMs;
     
        long randomId = ThreadLocalRandom.current().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));
    }