/*
- Copyright 2014 Netflix, Inc.
* - 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/license...
* - 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.
*/
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
/**
- Rate limiter implementation is based on token bucket algorithm. There are two parameters:
- burst size - maximum number of requests allowed into the system as a burst
- average rate - expected number of requests per second (RateLimiters using MINUTES is also supported)
*
*/
private final long rateToMsConversion;
private final AtomicInteger consumedTokens = new AtomicInteger();
private final AtomicLong lastRefillTime = new AtomicLong(0);
@Deprecated
public RateLimiter() {
this(TimeUnit.SECONDS);
}public RateLimiter(TimeUnit averageRateUnit) {
switch (averageRateUnit) {
case SECONDS:
rateToMsConversion = 1000;
break;
case MINUTES:
rateToMsConversion = 60 * 1000;
break;
default:
throw new IllegalArgumentException("TimeUnit of " + averageRateUnit + " is not supported");
}
}public boolean acquire(int burstSize, long averageRate) {
return acquire(burstSize, averageRate, System.currentTimeMillis());
}public boolean acquire(int burstSize, long averageRate, long currentTimeMillis) {
if (burstSize <= 0 || averageRate <= 0) { // Instead of throwing exception, we just let all the traffic go
return true;
}refillToken(burstSize, averageRate, currentTimeMillis);
return consumeToken(burstSize);
}private void refillToken(int burstSize, long averageRate, long currentTimeMillis) {
long refillTime = lastRefillTime.get();
long timeDelta = currentTimeMillis - refillTime;
long newTokens = timeDelta * averageRate / rateToMsConversion;
if (newTokens > 0) {
long newRefillTime = refillTime == 0
? currentTimeMillis
: refillTime + newTokens * rateToMsConversion / averageRate;
if (lastRefillTime.compareAndSet(refillTime, newRefillTime)) {
while (true) {
int currentLevel = consumedTokens.get();
int adjustedLevel = Math.min(currentLevel, burstSize);
// In case burstSize decreased
int newLevel = (int) Math.max(0, adjustedLevel - newTokens);
if (consumedTokens.compareAndSet(currentLevel, newLevel)) {
return;
}
}
}
}
}private boolean consumeToken(int burstSize) {
while (true) {
int currentLevel = consumedTokens.get();
if (currentLevel >= burstSize) {
return false;
}
if (consumedTokens.compareAndSet(currentLevel, currentLevel + 1)) {
return true;
}
}
}public void reset() {
consumedTokens.set(0);
lastRefillTime.set(0);
}【限流实现-Eureka-client 的RateLimiter】}
