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本文主要研究一下redisson的RRateLimiter
RRateLimiter
redisson/src/main/java/org/redisson/api/RRateLimiter.java
代码语言：javascript复制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
代码语言：javascript复制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
代码语言：javascript复制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
代码语言：javascript复制 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
代码语言：javascript复制 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
代码语言：javascript复制 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
代码语言：javascript复制 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
代码语言：javascript复制 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
