RetryPolicies.java
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上传日期:2018-01-08
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- /*
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements. See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership. The ASF licenses this file
- * to you 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 org.apache.hadoop.io.retry;
- import java.util.HashMap;
- import java.util.Map;
- import java.util.Random;
- import java.util.Set;
- import java.util.Map.Entry;
- import java.util.concurrent.TimeUnit;
- import org.apache.hadoop.ipc.RemoteException;
- /**
- * <p>
- * A collection of useful implementations of {@link RetryPolicy}.
- * </p>
- */
- public class RetryPolicies {
-
- /**
- * <p>
- * Try once, and fail by re-throwing the exception.
- * This corresponds to having no retry mechanism in place.
- * </p>
- */
- public static final RetryPolicy TRY_ONCE_THEN_FAIL = new TryOnceThenFail();
-
- /**
- * <p>
- * Try once, and fail silently for <code>void</code> methods, or by
- * re-throwing the exception for non-<code>void</code> methods.
- * </p>
- */
- public static final RetryPolicy TRY_ONCE_DONT_FAIL = new TryOnceDontFail();
-
- /**
- * <p>
- * Keep trying forever.
- * </p>
- */
- public static final RetryPolicy RETRY_FOREVER = new RetryForever();
-
- /**
- * <p>
- * Keep trying a limited number of times, waiting a fixed time between attempts,
- * and then fail by re-throwing the exception.
- * </p>
- */
- public static final RetryPolicy retryUpToMaximumCountWithFixedSleep(int maxRetries, long sleepTime, TimeUnit timeUnit) {
- return new RetryUpToMaximumCountWithFixedSleep(maxRetries, sleepTime, timeUnit);
- }
-
- /**
- * <p>
- * Keep trying for a maximum time, waiting a fixed time between attempts,
- * and then fail by re-throwing the exception.
- * </p>
- */
- public static final RetryPolicy retryUpToMaximumTimeWithFixedSleep(long maxTime, long sleepTime, TimeUnit timeUnit) {
- return new RetryUpToMaximumTimeWithFixedSleep(maxTime, sleepTime, timeUnit);
- }
-
- /**
- * <p>
- * Keep trying a limited number of times, waiting a growing amount of time between attempts,
- * and then fail by re-throwing the exception.
- * The time between attempts is <code>sleepTime</code> mutliplied by the number of tries so far.
- * </p>
- */
- public static final RetryPolicy retryUpToMaximumCountWithProportionalSleep(int maxRetries, long sleepTime, TimeUnit timeUnit) {
- return new RetryUpToMaximumCountWithProportionalSleep(maxRetries, sleepTime, timeUnit);
- }
-
- /**
- * <p>
- * Keep trying a limited number of times, waiting a growing amount of time between attempts,
- * and then fail by re-throwing the exception.
- * The time between attempts is <code>sleepTime</code> mutliplied by a random
- * number in the range of [0, 2 to the number of retries)
- * </p>
- */
- public static final RetryPolicy exponentialBackoffRetry(
- int maxRetries, long sleepTime, TimeUnit timeUnit) {
- return new ExponentialBackoffRetry(maxRetries, sleepTime, timeUnit);
- }
-
- /**
- * <p>
- * Set a default policy with some explicit handlers for specific exceptions.
- * </p>
- */
- public static final RetryPolicy retryByException(RetryPolicy defaultPolicy,
- Map<Class<? extends Exception>, RetryPolicy> exceptionToPolicyMap) {
- return new ExceptionDependentRetry(defaultPolicy, exceptionToPolicyMap);
- }
-
- /**
- * <p>
- * A retry policy for RemoteException
- * Set a default policy with some explicit handlers for specific exceptions.
- * </p>
- */
- public static final RetryPolicy retryByRemoteException(
- RetryPolicy defaultPolicy,
- Map<Class<? extends Exception>, RetryPolicy> exceptionToPolicyMap) {
- return new RemoteExceptionDependentRetry(defaultPolicy, exceptionToPolicyMap);
- }
-
- static class TryOnceThenFail implements RetryPolicy {
- public boolean shouldRetry(Exception e, int retries) throws Exception {
- throw e;
- }
- }
- static class TryOnceDontFail implements RetryPolicy {
- public boolean shouldRetry(Exception e, int retries) throws Exception {
- return false;
- }
- }
-
- static class RetryForever implements RetryPolicy {
- public boolean shouldRetry(Exception e, int retries) throws Exception {
- return true;
- }
- }
-
- static abstract class RetryLimited implements RetryPolicy {
- int maxRetries;
- long sleepTime;
- TimeUnit timeUnit;
-
- public RetryLimited(int maxRetries, long sleepTime, TimeUnit timeUnit) {
- this.maxRetries = maxRetries;
- this.sleepTime = sleepTime;
- this.timeUnit = timeUnit;
- }
- public boolean shouldRetry(Exception e, int retries) throws Exception {
- if (retries >= maxRetries) {
- throw e;
- }
- try {
- timeUnit.sleep(calculateSleepTime(retries));
- } catch (InterruptedException ie) {
- // retry
- }
- return true;
- }
-
- protected abstract long calculateSleepTime(int retries);
- }
-
- static class RetryUpToMaximumCountWithFixedSleep extends RetryLimited {
- public RetryUpToMaximumCountWithFixedSleep(int maxRetries, long sleepTime, TimeUnit timeUnit) {
- super(maxRetries, sleepTime, timeUnit);
- }
-
- @Override
- protected long calculateSleepTime(int retries) {
- return sleepTime;
- }
- }
-
- static class RetryUpToMaximumTimeWithFixedSleep extends RetryUpToMaximumCountWithFixedSleep {
- public RetryUpToMaximumTimeWithFixedSleep(long maxTime, long sleepTime, TimeUnit timeUnit) {
- super((int) (maxTime / sleepTime), sleepTime, timeUnit);
- }
- }
-
- static class RetryUpToMaximumCountWithProportionalSleep extends RetryLimited {
- public RetryUpToMaximumCountWithProportionalSleep(int maxRetries, long sleepTime, TimeUnit timeUnit) {
- super(maxRetries, sleepTime, timeUnit);
- }
-
- @Override
- protected long calculateSleepTime(int retries) {
- return sleepTime * (retries + 1);
- }
- }
-
- static class ExceptionDependentRetry implements RetryPolicy {
- RetryPolicy defaultPolicy;
- Map<Class<? extends Exception>, RetryPolicy> exceptionToPolicyMap;
-
- public ExceptionDependentRetry(RetryPolicy defaultPolicy,
- Map<Class<? extends Exception>, RetryPolicy> exceptionToPolicyMap) {
- this.defaultPolicy = defaultPolicy;
- this.exceptionToPolicyMap = exceptionToPolicyMap;
- }
- public boolean shouldRetry(Exception e, int retries) throws Exception {
- RetryPolicy policy = exceptionToPolicyMap.get(e.getClass());
- if (policy == null) {
- policy = defaultPolicy;
- }
- return policy.shouldRetry(e, retries);
- }
-
- }
-
- static class RemoteExceptionDependentRetry implements RetryPolicy {
- RetryPolicy defaultPolicy;
- Map<String, RetryPolicy> exceptionNameToPolicyMap;
-
- public RemoteExceptionDependentRetry(RetryPolicy defaultPolicy,
- Map<Class<? extends Exception>,
- RetryPolicy> exceptionToPolicyMap) {
- this.defaultPolicy = defaultPolicy;
- this.exceptionNameToPolicyMap = new HashMap<String, RetryPolicy>();
- for (Entry<Class<? extends Exception>, RetryPolicy> e :
- exceptionToPolicyMap.entrySet()) {
- exceptionNameToPolicyMap.put(e.getKey().getName(), e.getValue());
- }
- }
- public boolean shouldRetry(Exception e, int retries) throws Exception {
- RetryPolicy policy = null;
- if (e instanceof RemoteException) {
- policy = exceptionNameToPolicyMap.get(
- ((RemoteException) e).getClassName());
- }
- if (policy == null) {
- policy = defaultPolicy;
- }
- return policy.shouldRetry(e, retries);
- }
- }
-
- static class ExponentialBackoffRetry extends RetryLimited {
- private Random r = new Random();
- public ExponentialBackoffRetry(
- int maxRetries, long sleepTime, TimeUnit timeUnit) {
- super(maxRetries, sleepTime, timeUnit);
- }
-
- @Override
- protected long calculateSleepTime(int retries) {
- return sleepTime*r.nextInt(1<<(retries+1));
- }
- }
- }