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SDK for Microsoft Azure Storage Clients
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/**
 * Copyright Microsoft Corporation
 * 
 * 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.microsoft.azure.storage;

import java.net.HttpURLConnection;

/**
 * Represents a retry policy that performs a specified number of retries, using a specified fixed time interval between
 * retries.
 * 
 * This class extends the {@link RetryPolicy} class and implements the {@link RetryPolicyFactory} interface.
 */
public final class RetryLinearRetry extends RetryPolicy implements RetryPolicyFactory {

    /**
     * Creates an instance of the RetryLinearRetry class.
     */
    public RetryLinearRetry() {
        this(RetryPolicy.DEFAULT_CLIENT_BACKOFF, RetryPolicy.DEFAULT_CLIENT_RETRY_COUNT);
    }

    /**
     * Creates an instance of the RetryLinearRetry class using the specified delta backoff and maximum
     * retry attempts.
     * 
     * @param deltaBackoff
     *            The backoff interval, in milliseconds, between retries.
     * @param maxAttempts
     *            The maximum number of retry attempts.
     */
    public RetryLinearRetry(final int deltaBackoff, final int maxAttempts) {
        super(deltaBackoff, maxAttempts);
    }

    /**
     * Generates a new retry policy for the current request attempt.
     * 
     * @param opContext
     *            An {@link OperationContext} object that represents the context for the current operation. This object
     *            is used to track requests to the storage service, and to provide additional runtime information about
     *            the operation.
     * 
     * @return A {@link RetryPolicy} object that represents the retry policy for the current request attempt.
     */
    @Override
    public RetryPolicy createInstance(final OperationContext opContext) {
        return new RetryLinearRetry(this.deltaBackoffIntervalInMs, this.maximumAttempts);
    }

    /**
     * Determines whether the operation should be retried and specifies the interval until the next retry.
     * 
     * @param retryContext
     *            A {@link RetryContext} object that indicates the number of retries, last request's results, whether
     *            the next retry should happen in the primary or secondary location, and specifies the location mode.
     * @param operationContext
     *            An {@link OperationContext} object for tracking the current operation.
     * @return
     *         A {@link RetryInfo} object that indicates whether the next retry will happen in the primary or secondary
     *         location, and specifies the location mode. If null, the operation will not be retried.
     */
    @Override
    public RetryInfo evaluate(RetryContext retryContext, OperationContext operationContext) {

        boolean secondaryNotFound = this.evaluateLastAttemptAndSecondaryNotFound(retryContext);

        if (retryContext.getCurrentRetryCount() < this.maximumAttempts) {
            int statusCode = retryContext.getLastRequestResult().getStatusCode();
            if ((!secondaryNotFound && statusCode >= 400 && statusCode < 500)
                    || statusCode == HttpURLConnection.HTTP_NOT_IMPLEMENTED
                    || statusCode == HttpURLConnection.HTTP_VERSION
                    || statusCode == Constants.HeaderConstants.HTTP_UNUSED_306) {
                return null;
            }

            final long retryInterval = Math.max(
                    Math.min(this.deltaBackoffIntervalInMs, RetryPolicy.DEFAULT_MAX_BACKOFF),
                    RetryPolicy.DEFAULT_MIN_BACKOFF);

            return this.evaluateRetryInfo(retryContext, secondaryNotFound, retryInterval);
        }

        return null;
    }
}