io.grpc.internal.AtomicBackoff Maven / Gradle / Ivy
/*
* Copyright 2017 The gRPC 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 io.grpc.internal;
import com.google.common.base.Preconditions;
import java.util.concurrent.atomic.AtomicLong;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.concurrent.ThreadSafe;
/**
* A {@code long} atomically updated due to errors caused by the value being too small.
*/
@ThreadSafe
public final class AtomicBackoff {
private static final Logger log = Logger.getLogger(AtomicBackoff.class.getName());
private final String name;
private final AtomicLong value = new AtomicLong();
/** Construct an atomic with initial value {@code value}. {@code name} is used for logging. */
public AtomicBackoff(String name, long value) {
Preconditions.checkArgument(value > 0, "value must be positive");
this.name = name;
this.value.set(value);
}
/** Returns the current state. The state instance's value does not change of time. */
public State getState() {
return new State(value.get());
}
@ThreadSafe
public final class State {
private final long savedValue;
private State(long value) {
this.savedValue = value;
}
public long get() {
return savedValue;
}
/**
* Causes future invocations of {@link AtomicBackoff#getState} to have a value at least double
* this state's value. Subsequent calls to this method will not increase the value further.
*/
public void backoff() {
// Use max to handle overflow
long newValue = Math.max(savedValue * 2, savedValue);
boolean swapped = value.compareAndSet(savedValue, newValue);
// Even if swapped is false, the current value should be at least as large as newValue
assert value.get() >= newValue;
if (swapped) {
log.log(Level.WARNING, "Increased {0} to {1}", new Object[] {name, newValue});
}
}
}
}