/*
* Copyright 2014 Effektif GmbH.
*
* 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.effektif.workflow.impl;
/** Implement retry with incremental backoff on operations that can fail. */
public abstract class Retry<T> {
long wait = 50l;
long attempts = 0;
long maxAttempts = 4;
long backoffFactor = 5;
public Retry() {
}
public Retry(long wait, long attempts, long maxAttempts, long backoffFactor) {
this.wait = wait;
this.attempts = attempts;
this.maxAttempts = maxAttempts;
this.backoffFactor = backoffFactor;
}
/** invokes {@link #tryOnce()} till it produces a result or till the max attempts did not deliver a result.
* Blocks the current thread in case retries have to be performed. */
public T tryManyTimes() {
T returnValue = tryOnce();
while ( returnValue==null
&& attempts <= maxAttempts ) {
try {
failedWaitingForRetry();
Thread.sleep(wait);
} catch (InterruptedException e) {
interrupted();
}
wait = wait * backoffFactor;
attempts++;
returnValue = tryOnce();
}
if (returnValue==null) {
failedPermanent();
}
return returnValue;
}
/** returns null if the command failed, or not null if the command succeeded */
public abstract T tryOnce();
protected void failedWaitingForRetry() {
}
protected void interrupted() {
}
protected void failedPermanent() {
}
}