org.apache.hadoop.io.retry.RetryInvocationHandler.java Source code

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Here is the source code for org.apache.hadoop.io.retry.RetryInvocationHandler.java

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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.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.util.StringUtils;

class RetryInvocationHandler implements InvocationHandler {
    public static final Log LOG = LogFactory.getLog(RetryInvocationHandler.class);
    private Object implementation;

    private RetryPolicy defaultPolicy;
    private Map<String, RetryPolicy> methodNameToPolicyMap;

    public RetryInvocationHandler(Object implementation, RetryPolicy retryPolicy) {
        this.implementation = implementation;
        this.defaultPolicy = retryPolicy;
        this.methodNameToPolicyMap = Collections.emptyMap();
    }

    public RetryInvocationHandler(Object implementation, Map<String, RetryPolicy> methodNameToPolicyMap) {
        this.implementation = implementation;
        this.defaultPolicy = RetryPolicies.TRY_ONCE_THEN_FAIL;
        this.methodNameToPolicyMap = methodNameToPolicyMap;
    }

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        RetryPolicy policy = methodNameToPolicyMap.get(method.getName());
        if (policy == null) {
            policy = defaultPolicy;
        }

        int retries = 0;
        while (true) {
            try {
                return invokeMethod(method, args);
            } catch (Exception e) {
                if (!policy.shouldRetry(e, retries++)) {
                    LOG.info("Exception while invoking " + method.getName() + " of " + implementation.getClass()
                            + ". Not retrying." + StringUtils.stringifyException(e));
                    if (!method.getReturnType().equals(Void.TYPE)) {
                        throw e; // non-void methods can't fail without an exception
                    }
                    return null;
                }
                LOG.debug("Exception while invoking " + method.getName() + " of " + implementation.getClass()
                        + ". Retrying." + StringUtils.stringifyException(e));
            }
        }
    }

    private Object invokeMethod(Method method, Object[] args) throws Throwable {
        try {
            if (!method.isAccessible()) {
                method.setAccessible(true);
            }
            return method.invoke(implementation, args);
        } catch (InvocationTargetException e) {
            throw e.getCause();
        }
    }

}