com.google.common.flogger.CountingRateLimiter Maven / Gradle / Ivy
/*
* Copyright (C) 2014 The Flogger Authors.
*
* 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/licenses/LICENSE-2.0
*
* 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.
*/
package com.google.common.flogger;
import static com.google.common.flogger.LogContext.Key.LOG_EVERY_N;
import static com.google.common.flogger.RateLimitStatus.DISALLOW;
import com.google.common.flogger.backend.Metadata;
import java.util.concurrent.atomic.AtomicLong;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;
/**
* Rate limiter to support {@code every(N)} functionality.
*
* Instances of this class are created for each unique {@link LogSiteKey} for which rate limiting
* via the {@code LOG_EVERY_N} metadata key is required. This class implements {@code
* RateLimitStatus} as a mechanism for resetting the rate limiter state.
*
*
Instances of this class are thread safe.
*/
final class CountingRateLimiter extends RateLimitStatus {
private static final LogSiteMap map =
new LogSiteMap() {
@Override
protected CountingRateLimiter initialValue() {
return new CountingRateLimiter();
}
};
/**
* Returns the status of the rate limiter, or {@code null} if the {@code LOG_EVERY_N} metadata was
* not present.
*
* The rate limiter status is {@code DISALLOW} until the log count exceeds the specified limit,
* and then the limiter switches to its pending state and returns an allow status until it is
* reset.
*/
@NullableDecl
static RateLimitStatus check(Metadata metadata, LogSiteKey logSiteKey) {
Integer rateLimitCount = metadata.findValue(LOG_EVERY_N);
if (rateLimitCount == null) {
// Without rate limiter specific metadata, this limiter has no effect.
return null;
}
return map.get(logSiteKey, metadata).incrementAndCheckLogCount(rateLimitCount);
}
// By setting the initial value as Integer#MAX_VALUE we ensure that the first time rate limiting
// is checked, the rate limit count (which is only an Integer) must be reached, placing the
// limiter into its pending state immediately. If this is the only limiter used, this corresponds
// to the first log statement always being emitted.
private final AtomicLong invocationCount = new AtomicLong(Integer.MAX_VALUE);
// Visible for testing.
CountingRateLimiter() {}
/**
* Increments the invocation count and returns true if it reached the specified rate limit count.
* This is invoked during post-processing if a rate limiting count was set via {@link
* LoggingApi#every(int)}.
*/
// Visible for testing.
RateLimitStatus incrementAndCheckLogCount(int rateLimitCount) {
return invocationCount.incrementAndGet() >= rateLimitCount ? this : DISALLOW;
}
// Reset function called to move the limiter out of the "pending" state after a log occurs.
@Override
public void reset() {
invocationCount.set(0);
}
}