/*
* Copyright 2010-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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.amazonaws.retry;
import com.amazonaws.AmazonClientException;
import com.amazonaws.AmazonServiceException;
import com.amazonaws.AmazonWebServiceRequest;
import com.amazonaws.ClientConfiguration;
import org.apache.http.HttpStatus;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.util.Random;
/**
* This class includes a set of pre-defined retry policies, including default
* policies used by SDK.
*/
public class PredefinedRetryPolicies {
/* SDK default */
/** Base sleep time (milliseconds) for throttling exceptions. **/
private static final int BASE_DELAY_IN_MILLISECONDS = 100;
/** Maximum exponential back-off time before retrying a request */
private static final int MAX_BACKOFF_IN_MILLISECONDS = 20 * 1000;
/** SDK default max retry count **/
public static final int DEFAULT_MAX_ERROR_RETRY = 3;
/** SDK default retry policy **/
public static final RetryPolicy DEFAULT;
/* Default for DynamoDB client */
/** Default max retry count for DynamoDB client **/
public static final int DYNAMODB_DEFAULT_MAX_ERROR_RETRY = 10;
/** Default policy for DynamoDB client **/
public static final RetryPolicy DYNAMODB_DEFAULT;
/* Reusable retry policy components */
/**
* The SDK default retry condition, which checks for various conditions in
* the following order:
* <ul>
* <li>Never retry on requests with non-repeatable content;
* <li>Retry on client exceptions caused by IOException;
* <li>Retry on service exceptions that are either 500 internal server
* errors, 503 service unavailable errors, service throttling errors or
* clock skew errors.
* </ul>
*/
public static final RetryPolicy.RetryCondition DEFAULT_RETRY_CONDITION = new SDKDefaultRetryCondition();
/**
* The SDK default back-off strategy, which increases exponentially up to a
* max amount of delay. It also applies a larger scale factor upon service
* throttling exception.
*/
public static final RetryPolicy.BackoffStrategy DEFAULT_BACKOFF_STRATEGY = new SDKDefaultBackoffStrategy(
BASE_DELAY_IN_MILLISECONDS, MAX_BACKOFF_IN_MILLISECONDS);
static {
DEFAULT = getDefaultRetryPolicy();
DYNAMODB_DEFAULT = getDynamoDBDefaultRetryPolicy();
}
/**
* Returns the SDK default retry policy. This policy will honor the
* maxErrorRetry set in ClientConfiguration.
*
* @see ClientConfiguration#setMaxErrorRetry(int)
*/
public static RetryPolicy getDefaultRetryPolicy() {
return new RetryPolicy(DEFAULT_RETRY_CONDITION,
DEFAULT_BACKOFF_STRATEGY,
DEFAULT_MAX_ERROR_RETRY,
true);
}
/**
* Returns the default retry policy for DynamoDB client. This policy will
* honor the maxErrorRetry set in ClientConfiguration.
*
* @see ClientConfiguration#setMaxErrorRetry(int)
*/
public static RetryPolicy getDynamoDBDefaultRetryPolicy() {
return new RetryPolicy(DEFAULT_RETRY_CONDITION,
DEFAULT_BACKOFF_STRATEGY,
DYNAMODB_DEFAULT_MAX_ERROR_RETRY,
true);
}
/**
* Returns the SDK default retry policy with the specified max retry count.
*/
public static RetryPolicy getDefaultRetryPolicyWithCustomMaxRetries(int maxErrorRetry) {
return new RetryPolicy(DEFAULT_RETRY_CONDITION,
DEFAULT_BACKOFF_STRATEGY,
maxErrorRetry,
false);
}
/**
* Returns the default retry policy for DynamoDB client with the specified
* max retry count.
*/
public static RetryPolicy getDynamoDBDefaultRetryPolicyWithCustomMaxRetries(int maxErrorRetry) {
return new RetryPolicy(DEFAULT_RETRY_CONDITION,
DEFAULT_BACKOFF_STRATEGY,
maxErrorRetry,
false);
}
/**
* The default implementation of RetryCondition used by the SDK. User could
* extend this class to provide additional custom conditions. The default
* implementation checks for various conditions in the following order:
* <ul>
* <li>Retry on client exceptions caused by IOException;
* <li>Retry on service exceptions that are either 500 internal server
* errors, 503 service unavailable errors, service throttling errors or
* clock skew errors.
* </ul>
*/
public static class SDKDefaultRetryCondition implements RetryPolicy.RetryCondition {
@Override
public boolean shouldRetry(AmazonWebServiceRequest originalRequest,
AmazonClientException exception,
int retriesAttempted) {
// Always retry on client exceptions caused by IOException, unless
// it's caused by a thread interruption
if ((exception.getCause() instanceof IOException)
&& !(exception.getCause() instanceof InterruptedIOException))
return true;
// Only retry on a subset of service exceptions
if (exception instanceof AmazonServiceException) {
AmazonServiceException ase = (AmazonServiceException) exception;
/*
* For 500 internal server errors and 503 service unavailable
* errors, we want to retry, but we need to use an exponential
* back-off strategy so that we don't overload a server with a
* flood of retries.
*/
int statusCode = ase.getStatusCode();
if (statusCode == HttpStatus.SC_INTERNAL_SERVER_ERROR
|| statusCode == HttpStatus.SC_SERVICE_UNAVAILABLE
|| statusCode == HttpStatus.SC_BAD_GATEWAY
|| statusCode == HttpStatus.SC_GATEWAY_TIMEOUT) {
return true;
}
/*
* Throttling is reported as a 400 error from newer services. To
* try and smooth out an occasional throttling error, we'll
* pause and retry, hoping that the pause is long enough for the
* request to get through the next time.
*/
if (RetryUtils.isThrottlingException(ase))
return true;
/*
* Clock skew exception. If it is then we will get the time
* offset between the device time and the server time to set the
* clock skew and then retry the request.
*/
if (RetryUtils.isClockSkewError(ase))
return true;
}
return false;
}
}
/** A private class that implements the default back-off strategy. **/
private static class SDKDefaultBackoffStrategy implements RetryPolicy.BackoffStrategy {
/** For generating a random scale factor **/
private final Random random = new Random();
private final int baseDelayMs;
private final int maxDelayMs;
private SDKDefaultBackoffStrategy(int baseDelayMs, int maxDelayMs) {
this.baseDelayMs = baseDelayMs;
this.maxDelayMs = maxDelayMs;
}
/** {@inheritDoc} */
@Override
public final long delayBeforeNextRetry(AmazonWebServiceRequest originalRequest,
AmazonClientException exception,
int retries) {
if (retries <= 0)
return 0;
// Full jitter
// https://www.awsarchitectureblog.com/2015/03/backoff.html
return random.nextInt(Math.min(maxDelayMs, (1 << retries) * baseDelayMs));
}
}
}