聊聊redisson的RRateLimiter

序

本文主要研究一下redisson的RRateLimiter

RRateLimiter

redisson/src/main/java/org/redisson/api/RRateLimiter.java

public interface RRateLimiter extends RRateLimiterAsync, RExpirable {

    /**
     * Initializes RateLimiter's state and stores config to Redis server.
     * 
     * @param mode - rate mode
     * @param rate - rate
     * @param rateInterval - rate time interval
     * @param rateIntervalUnit - rate time interval unit
     * @return {@code true} if rate was set and {@code false}
     *         otherwise
     */
    boolean trySetRate(RateType mode, long rate, long rateInterval, RateIntervalUnit rateIntervalUnit);

    /**
     * Updates RateLimiter's state and stores config to Redis server.
     *
     * @param mode - rate mode
     * @param rate - rate
     * @param rateInterval - rate time interval
     * @param rateIntervalUnit - rate time interval unit
     */
    void setRate(RateType mode, long rate, long rateInterval, RateIntervalUnit rateIntervalUnit);
    
    /**
     * Acquires a permit only if one is available at the
     * time of invocation.
     *
     * <p>Acquires a permit, if one is available and returns immediately,
     * with the value {@code true},
     * reducing the number of available permits by one.
     *
     * <p>If no permit is available then this method will return
     * immediately with the value {@code false}.
     *
     * @return {@code true} if a permit was acquired and {@code false}
     *         otherwise
     */
    boolean tryAcquire();
    
    /**
     * Acquires the given number of <code>permits</code> only if all are available at the
     * time of invocation.
     *
     * <p>Acquires a permits, if all are available and returns immediately,
     * with the value {@code true},
     * reducing the number of available permits by given number of permits.
     *
     * <p>If no permits are available then this method will return
     * immediately with the value {@code false}.
     *
     * @param permits the number of permits to acquire
     * @return {@code true} if a permit was acquired and {@code false}
     *         otherwise
     */
    boolean tryAcquire(long permits);
    
    /**
     * Acquires a permit from this RateLimiter, blocking until one is available.
     *
     * <p>Acquires a permit, if one is available and returns immediately,
     * reducing the number of available permits by one.
     * 
     */
    void acquire();

    /**
     * Acquires a specified <code>permits</code> from this RateLimiter, 
     * blocking until one is available.
     *
     * <p>Acquires the given number of permits, if they are available 
     * and returns immediately, reducing the number of available permits 
     * by the given amount.
     * 
     * @param permits the number of permits to acquire
     */
    void acquire(long permits);
    
    /**
     * Acquires a permit from this RateLimiter, if one becomes available
     * within the given waiting time.
     *
     * <p>Acquires a permit, if one is available and returns immediately,
     * with the value {@code true},
     * reducing the number of available permits by one.
     *
     * <p>If no permit is available then the current thread becomes
     * disabled for thread scheduling purposes and lies dormant until
     * specified waiting time elapses.
     *
     * <p>If a permit is acquired then the value {@code true} is returned.
     *
     * <p>If the specified waiting time elapses then the value {@code false}
     * is returned.  If the time is less than or equal to zero, the method
     * will not wait at all.
     *
     * @param timeout the maximum time to wait for a permit
     * @param unit the time unit of the {@code timeout} argument
     * @return {@code true} if a permit was acquired and {@code false}
     *         if the waiting time elapsed before a permit was acquired
     */
    boolean tryAcquire(long timeout, TimeUnit unit);
    
    /**
     * Acquires the given number of <code>permits</code> only if all are available
     * within the given waiting time.
     *
     * <p>Acquires the given number of permits, if all are available and returns immediately,
     * with the value {@code true}, reducing the number of available permits by one.
     *
     * <p>If no permit is available then the current thread becomes
     * disabled for thread scheduling purposes and lies dormant until
     * the specified waiting time elapses.
     *
     * <p>If a permits is acquired then the value {@code true} is returned.
     *
     * <p>If the specified waiting time elapses then the value {@code false}
     * is returned.  If the time is less than or equal to zero, the method
     * will not wait at all.
     *
     * @param permits amount
     * @param timeout the maximum time to wait for a permit
     * @param unit the time unit of the {@code timeout} argument
     * @return {@code true} if a permit was acquired and {@code false}
     *         if the waiting time elapsed before a permit was acquired
     */
    boolean tryAcquire(long permits, long timeout, TimeUnit unit);

    /**
     * Returns current configuration of this RateLimiter object.
     * 
     * @return config object
     */
    RateLimiterConfig getConfig();

    /**
     * Returns amount of available permits.
     *
     * @return number of permits
     */
    long availablePermits();

}

RRateLimiter继承了RRateLimiterAsync、RExpirable接口，它主要定义了trySetRate、setRate、tryAcquire、acquire、getConfig、availablePermits方法

RRateLimiterAsync

redisson/src/main/java/org/redisson/api/RRateLimiterAsync.java

public interface RRateLimiterAsync extends RExpirableAsync {

    /**
     * Initializes RateLimiter's state and stores config to Redis server.
     * 
     * @param mode - rate mode
     * @param rate - rate
     * @param rateInterval - rate time interval
     * @param rateIntervalUnit - rate time interval unit
     * @return {@code true} if rate was set and {@code false}
     *         otherwise
     */
    RFuture<Boolean> trySetRateAsync(RateType mode, long rate, long rateInterval, RateIntervalUnit rateIntervalUnit);

    /**
     * Acquires a permit only if one is available at the
     * time of invocation.
     *
     * <p>Acquires a permit, if one is available and returns immediately,
     * with the value {@code true},
     * reducing the number of available permits by one.
     *
     * <p>If no permit is available then this method will return
     * immediately with the value {@code false}.
     *
     * @return {@code true} if a permit was acquired and {@code false}
     *         otherwise
     */
    RFuture<Boolean> tryAcquireAsync();
    
    /**
     * Acquires the given number of <code>permits</code> only if all are available at the
     * time of invocation.
     *
     * <p>Acquires a permits, if all are available and returns immediately,
     * with the value {@code true},
     * reducing the number of available permits by given number of permits.
     *
     * <p>If no permits are available then this method will return
     * immediately with the value {@code false}.
     *
     * @param permits the number of permits to acquire
     * @return {@code true} if a permit was acquired and {@code false}
     *         otherwise
     */
    RFuture<Boolean> tryAcquireAsync(long permits);
    
    /**
     * Acquires a permit from this RateLimiter, blocking until one is available.
     *
     * <p>Acquires a permit, if one is available and returns immediately,
     * reducing the number of available permits by one.
     * 
     * @return void
     */
    RFuture<Void> acquireAsync();
    
    /**
     * Acquires a specified <code>permits</code> from this RateLimiter, 
     * blocking until one is available.
     *
     * <p>Acquires the given number of permits, if they are available 
     * and returns immediately, reducing the number of available permits 
     * by the given amount.
     * 
     * @param permits the number of permits to acquire
     * @return void
     */
    RFuture<Void> acquireAsync(long permits);
    
    /**
     * Acquires a permit from this RateLimiter, if one becomes available
     * within the given waiting time.
     *
     * <p>Acquires a permit, if one is available and returns immediately,
     * with the value {@code true},
     * reducing the number of available permits by one.
     *
     * <p>If no permit is available then the current thread becomes
     * disabled for thread scheduling purposes and lies dormant until
     * specified waiting time elapses.
     *
     * <p>If a permit is acquired then the value {@code true} is returned.
     *
     * <p>If the specified waiting time elapses then the value {@code false}
     * is returned.  If the time is less than or equal to zero, the method
     * will not wait at all.
     *
     * @param timeout the maximum time to wait for a permit
     * @param unit the time unit of the {@code timeout} argument
     * @return {@code true} if a permit was acquired and {@code false}
     *         if the waiting time elapsed before a permit was acquired
     */
    RFuture<Boolean> tryAcquireAsync(long timeout, TimeUnit unit);
    
    /**
     * Acquires the given number of <code>permits</code> only if all are available
     * within the given waiting time.
     *
     * <p>Acquires the given number of permits, if all are available and returns immediately,
     * with the value {@code true}, reducing the number of available permits by one.
     *
     * <p>If no permit is available then the current thread becomes
     * disabled for thread scheduling purposes and lies dormant until
     * the specified waiting time elapses.
     *
     * <p>If a permits is acquired then the value {@code true} is returned.
     *
     * <p>If the specified waiting time elapses then the value {@code false}
     * is returned.  If the time is less than or equal to zero, the method
     * will not wait at all.
     *
     * @param permits amount
     * @param timeout the maximum time to wait for a permit
     * @param unit the time unit of the {@code timeout} argument
     * @return {@code true} if a permit was acquired and {@code false}
     *         if the waiting time elapsed before a permit was acquired
     */
    RFuture<Boolean> tryAcquireAsync(long permits, long timeout, TimeUnit unit);


    /**
     * Updates RateLimiter's state and stores config to Redis server.
     *
     *
     * @param mode - rate mode
     * @param rate - rate
     * @param rateInterval - rate time interval
     * @param rateIntervalUnit - rate time interval unit
     * @return {@code true} if rate was set and {@code false}
     *         otherwise
     */
    RFuture<Void> setRateAsync(RateType mode, long rate, long rateInterval, RateIntervalUnit rateIntervalUnit);

    /**
     * Returns current configuration of this RateLimiter object.
     * 
     * @return config object
     */
    RFuture<RateLimiterConfig> getConfigAsync();

    /**
     * Returns amount of available permits.
     *
     * @return number of permits
     */
    RFuture<Long> availablePermitsAsync();

}

RRateLimiterAsync继承了RExpirableAsync，它是async版本的RRateLimiter，它主要定义了trySetRateAsync、setRateAsync、tryAcquireAsync、acquireAsync、getConfigAsync、availablePermitsAsync方法

RedissonRateLimiter

redisson/src/main/java/org/redisson/RedissonRateLimiter.java

public class RedissonRateLimiter extends RedissonExpirable implements RRateLimiter {

    //......

    @Override
    public boolean tryAcquire() {
        return tryAcquire(1);
    }
    
    @Override
    public RFuture<Boolean> tryAcquireAsync() {
        return tryAcquireAsync(1L);
    }
    
    @Override
    public boolean tryAcquire(long permits) {
        return get(tryAcquireAsync(RedisCommands.EVAL_NULL_BOOLEAN, permits));
    }
    
    @Override
    public RFuture<Boolean> tryAcquireAsync(long permits) {
        return tryAcquireAsync(RedisCommands.EVAL_NULL_BOOLEAN, permits);
    }

    @Override
    public void acquire() {
        get(acquireAsync());
    }
    
    @Override
    public RFuture<Void> acquireAsync() {
        return acquireAsync(1);
    }

    @Override
    public void acquire(long permits) {
        get(acquireAsync(permits));
    }

    @Override
    public RFuture<Void> acquireAsync(long permits) {
        CompletionStage<Void> f = tryAcquireAsync(permits, -1, null).thenApply(res -> null);
        return new CompletableFutureWrapper<>(f);
    }

    @Override
    public boolean tryAcquire(long timeout, TimeUnit unit) {
        return get(tryAcquireAsync(timeout, unit));
    }

    @Override
    public RFuture<Boolean> tryAcquireAsync(long timeout, TimeUnit unit) {
        return tryAcquireAsync(1, timeout, unit);
    }
    
    @Override
    public boolean tryAcquire(long permits, long timeout, TimeUnit unit) {
        return get(tryAcquireAsync(permits, timeout, unit));
    }
}

RedissonRateLimiter继承了RedissonExpirable，实现了RRateLimiter接口

trySetRate

    public boolean trySetRate(RateType type, long rate, long rateInterval, RateIntervalUnit unit) {
        return get(trySetRateAsync(type, rate, rateInterval, unit));
    }

    public RFuture<Boolean> trySetRateAsync(RateType type, long rate, long rateInterval, RateIntervalUnit unit) {
        return commandExecutor.evalWriteNoRetryAsync(getRawName(), LongCodec.INSTANCE, RedisCommands.EVAL_BOOLEAN,
                "redis.call('hsetnx', KEYS[1], 'rate', ARGV[1]);"
              + "redis.call('hsetnx', KEYS[1], 'interval', ARGV[2]);"
              + "return redis.call('hsetnx', KEYS[1], 'type', ARGV[3]);",
                Collections.singletonList(getRawName()), rate, unit.toMillis(rateInterval), type.ordinal());
    }  

trySetRate委托给了trySetRateAsync，这里主要是使用hsetnx来设置rate、interval、type三个值

setRate

    public void setRate(RateType type, long rate, long rateInterval, RateIntervalUnit unit) {
        get(setRateAsync(type, rate, rateInterval, unit));
    }

    public RFuture<Void> setRateAsync(RateType type, long rate, long rateInterval, RateIntervalUnit unit) {
        return commandExecutor.evalWriteAsync(getRawName(), LongCodec.INSTANCE, RedisCommands.EVAL_BOOLEAN,
                "local valueName = KEYS[2];"
                    + "local permitsName = KEYS[4];"
                    + "if ARGV[3] == '1' then "
                    + "    valueName = KEYS[3];"
                    + "    permitsName = KEYS[5];"
                    + "end "
                    +"redis.call('hset', KEYS[1], 'rate', ARGV[1]);"
                        + "redis.call('hset', KEYS[1], 'interval', ARGV[2]);"
                        + "redis.call('hset', KEYS[1], 'type', ARGV[3]);"
                        + "redis.call('del', valueName, permitsName);",
                Arrays.asList(getRawName(), getValueName(), getClientValueName(), getPermitsName(), getClientPermitsName()), rate, unit.toMillis(rateInterval), type.ordinal());
    }  

setRate委托给了setRateAsync，这里使用hset来写入rate、interval、type三个值，如果存在则覆盖；另外这里删除了valueName、permitsName这两个key

tryAcquire

    public boolean tryAcquire(long permits) {
        return get(tryAcquireAsync(RedisCommands.EVAL_NULL_BOOLEAN, permits));
    }

    private <T> RFuture<T> tryAcquireAsync(RedisCommand<T> command, Long value) {
        byte[] random = getServiceManager().generateIdArray();

        return commandExecutor.evalWriteAsync(getRawName(), LongCodec.INSTANCE, command,
                "local rate = redis.call('hget', KEYS[1], 'rate');"
              + "local interval = redis.call('hget', KEYS[1], 'interval');"
              + "local type = redis.call('hget', KEYS[1], 'type');"
              + "assert(rate ~= false and interval ~= false and type ~= false, 'RateLimiter is not initialized')"
              
              + "local valueName = KEYS[2];"
              + "local permitsName = KEYS[4];"
              + "if type == '1' then "
                  + "valueName = KEYS[3];"
                  + "permitsName = KEYS[5];"
              + "end;"

              + "assert(tonumber(rate) >= tonumber(ARGV[1]), 'Requested permits amount could not exceed defined rate'); "

              + "local currentValue = redis.call('get', valueName); "
              + "local res;"
              + "if currentValue ~= false then "
                     + "local expiredValues = redis.call('zrangebyscore', permitsName, 0, tonumber(ARGV[2]) - interval); "
                     + "local released = 0; "
                     + "for i, v in ipairs(expiredValues) do "
                          + "local random, permits = struct.unpack('Bc0I', v);"
                          + "released = released + permits;"
                     + "end; "

                     + "if released > 0 then "
                          + "redis.call('zremrangebyscore', permitsName, 0, tonumber(ARGV[2]) - interval); "
                          + "if tonumber(currentValue) + released > tonumber(rate) then "
                               + "currentValue = tonumber(rate) - redis.call('zcard', permitsName); "
                          + "else "
                               + "currentValue = tonumber(currentValue) + released; "
                          + "end; "
                          + "redis.call('set', valueName, currentValue);"
                     + "end;"

                     + "if tonumber(currentValue) < tonumber(ARGV[1]) then "
                         + "local firstValue = redis.call('zrange', permitsName, 0, 0, 'withscores'); "
                         + "res = 3 + interval - (tonumber(ARGV[2]) - tonumber(firstValue[2]));"
                     + "else "
                         + "redis.call('zadd', permitsName, ARGV[2], struct.pack('Bc0I', string.len(ARGV[3]), ARGV[3], ARGV[1])); "
                         + "redis.call('decrby', valueName, ARGV[1]); "
                         + "res = nil; "
                     + "end; "
              + "else "
                     + "redis.call('set', valueName, rate); "
                     + "redis.call('zadd', permitsName, ARGV[2], struct.pack('Bc0I', string.len(ARGV[3]), ARGV[3], ARGV[1])); "
                     + "redis.call('decrby', valueName, ARGV[1]); "
                     + "res = nil; "
              + "end;"

              + "local ttl = redis.call('pttl', KEYS[1]); "
              + "if ttl > 0 then "
                  + "redis.call('pexpire', valueName, ttl); "
                  + "redis.call('pexpire', permitsName, ttl); "
              + "end; "
              + "return res;",
                Arrays.asList(getRawName(), getValueName(), getClientValueName(), getPermitsName(), getClientPermitsName()),
                value, System.currentTimeMillis(), random);
    }    

tryAcquire委托给了tryAcquireAsync，它通过一个lua脚本来执行，首先通过hget获取rate、interval、type的值，然后根据type来确定valueName、permitsName，如果type为0则valueName是getValueName()，permitsName是getPermitsName()，如果type=1则valueName是getClientValueName()，permitsName是getClientPermitsName()；之后获取valueName的值，若为false则直接用设置rate、permits，并递减valueName；若为true则获取expiredValues计算released值，再计算出currentValue，若不够扣则计算返回值，若够扣则通过zadd添加当前permit(System.currentTimeMillis())，然后递减valueName

acquire

    public void acquire() {
        get(acquireAsync());
    }

    public RFuture<Void> acquireAsync() {
        return acquireAsync(1);
    }

    public RFuture<Void> acquireAsync(long permits) {
        CompletionStage<Void> f = tryAcquireAsync(permits, -1, null).thenApply(res -> null);
        return new CompletableFutureWrapper<>(f);
    }

    public RFuture<Boolean> tryAcquireAsync(long permits, long timeout, TimeUnit unit) {
        long timeoutInMillis = -1;
        if (timeout >= 0) {
            timeoutInMillis = unit.toMillis(timeout);
        }
        CompletableFuture<Boolean> f = tryAcquireAsync(permits, timeoutInMillis);
        return new CompletableFutureWrapper<>(f);
    }

    private CompletableFuture<Boolean> tryAcquireAsync(long permits, long timeoutInMillis) {
        long s = System.currentTimeMillis();
        RFuture<Long> future = tryAcquireAsync(RedisCommands.EVAL_LONG, permits);
        return future.thenCompose(delay -> {
            if (delay == null) {
                return CompletableFuture.completedFuture(true);
            }
            
            if (timeoutInMillis == -1) {
                CompletableFuture<Boolean> f = new CompletableFuture<>();
                getServiceManager().getGroup().schedule(() -> {
                    CompletableFuture<Boolean> r = tryAcquireAsync(permits, timeoutInMillis);
                    commandExecutor.transfer(r, f);
                }, delay, TimeUnit.MILLISECONDS);
                return f;
            }
            
            long el = System.currentTimeMillis() - s;
            long remains = timeoutInMillis - el;
            if (remains <= 0) {
                return CompletableFuture.completedFuture(false);
            }

            CompletableFuture<Boolean> f = new CompletableFuture<>();
            if (remains < delay) {
                getServiceManager().getGroup().schedule(() -> {
                    f.complete(false);
                }, remains, TimeUnit.MILLISECONDS);
            } else {
                long start = System.currentTimeMillis();
                getServiceManager().getGroup().schedule(() -> {
                    long elapsed = System.currentTimeMillis() - start;
                    if (remains <= elapsed) {
                        f.complete(false);
                        return;
                    }

                    CompletableFuture<Boolean> r = tryAcquireAsync(permits, remains - elapsed);
                    commandExecutor.transfer(r, f);
                }, delay, TimeUnit.MILLISECONDS);
            }
            return f;
        }).toCompletableFuture();
    }                

acquire也是复用了tryAcquireAsync方法，只获取不到时会根据返回的delay进行重新调度，若timeoutInMillis不为-1则会根据超时时间进行计算和重新调度

availablePermits

    public long availablePermits() {
        return get(availablePermitsAsync());
    }

    public RFuture<Long> availablePermitsAsync() {
        return commandExecutor.evalWriteAsync(getRawName(), LongCodec.INSTANCE, RedisCommands.EVAL_LONG,
                "local rate = redis.call('hget', KEYS[1], 'rate');"
              + "local interval = redis.call('hget', KEYS[1], 'interval');"
              + "local type = redis.call('hget', KEYS[1], 'type');"
              + "assert(rate ~= false and interval ~= false and type ~= false, 'RateLimiter is not initialized')"

              + "local valueName = KEYS[2];"
              + "local permitsName = KEYS[4];"
              + "if type == '1' then "
                  + "valueName = KEYS[3];"
                  + "permitsName = KEYS[5];"
              + "end;"

              + "local currentValue = redis.call('get', valueName); "
              + "if currentValue == false then "
                     + "redis.call('set', valueName, rate); "
                     + "return rate; "
              + "else "
                     + "local expiredValues = redis.call('zrangebyscore', permitsName, 0, tonumber(ARGV[1]) - interval); "
                     + "local released = 0; "
                     + "for i, v in ipairs(expiredValues) do "
                          + "local random, permits = struct.unpack('Bc0I', v);"
                          + "released = released + permits;"
                     + "end; "

                     + "if released > 0 then "
                          + "redis.call('zremrangebyscore', permitsName, 0, tonumber(ARGV[1]) - interval); "
                          + "currentValue = tonumber(currentValue) + released; "
                          + "redis.call('set', valueName, currentValue);"
                     + "end;"

                     + "return currentValue; "
              + "end;",
                Arrays.asList(getRawName(), getValueName(), getClientValueName(), getPermitsName(), getClientPermitsName()),
                System.currentTimeMillis());
    }

availablePermits委托给了availablePermitsAsync，它执行lua脚本，先通过hget获取rate、interval、type的值，然后根据type来确定valueName、permitsName，如果type为0则valueName是getValueName()，permitsName是getPermitsName()，如果type=1则valueName是getClientValueName()，permitsName是getClientPermitsName()；之后获取valueName对应的值currentValue，若值为false则重新设置rate，否则通过expiredValues重新计算released，若released大于0则更新到currentValue，最后返回currentValue

小结

redisson的RRateLimiter提供了trySetRate、setRate、tryAcquire、acquire、getConfig、availablePermits方法

• 其RateType有OVERALL(值为0)、PER_CLIENT(值为1)两个类型，如果type为0则valueName是getValueName()，permitsName是getPermitsName()，如果type=1则valueName是getClientValueName()，permitsName是getClientPermitsName()
• 它主要定义了几个key，一个是getRawName，类型为hash，其key有rate、interval、type；一个是key为valueName，存储了当前的permits；一个是key为permitsName，类型是sorted set，其score为System.currentTimeMillis()，value通过struct.pack了随机数长度、随机数、此次permit的value
• trySetRate委托给了trySetRateAsync，这里主要是使用hsetnx来设置rate、interval、type三个值；setRate委托给了setRateAsync，这里使用hset来写入rate、interval、type三个值，如果存在则覆盖；另外这里删除了valueName、permitsName这两个key
• tryAcquire委托给了tryAcquireAsync，它通过一个lua脚本来执行，首先通过hget获取rate、interval、type的值，之后获取valueName的值，若为false则直接用设置rate、permits，并递减valueName；若为true则获取expiredValues计算released值，再计算出currentValue，若不够扣则计算返回值(告诉调用方可以延时多长时间再重试)，若够扣则通过zadd添加当前permit(System.currentTimeMillis())，然后递减valueName
• acquire是也是复用了tryAcquireAsync方法，只获取不到时会根据返回的delay进行重新调度，若timeoutInMillis不为-1则会根据超时时间进行计算和重新调度