org.apache.lens.server.api.retry.ChainedRetryPolicyDecider.java Source code

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Here is the source code for org.apache.lens.server.api.retry.ChainedRetryPolicyDecider.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.lens.server.api.retry;

import java.util.List;

import org.apache.lens.server.api.error.LensException;

import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;

import com.google.common.collect.Lists;
import lombok.Data;

@Data
public class ChainedRetryPolicyDecider<FC extends FailureContext> implements RetryPolicyDecider<FC> {
    private final Iterable<RetryPolicyDecider<FC>> policyDeciders;

    @Override
    public BackOffRetryHandler<FC> decidePolicy(String errorMessage) {
        for (RetryPolicyDecider<FC> policyDecider : policyDeciders) {
            BackOffRetryHandler<FC> policy = policyDecider.decidePolicy(errorMessage);
            if (policy != null) {
                return policy;
            }
        }
        return new NoRetryHandler<>();
    }

    public static <FC extends FailureContext> ChainedRetryPolicyDecider<FC> from(Configuration conf, String key)
            throws LensException {
        String[] classNames = conf.getStrings(key);
        List<RetryPolicyDecider<FC>> retryPolicyDeciders = Lists.newArrayList();
        if (classNames != null) {
            for (String className : classNames) {
                Class<? extends RetryPolicyDecider<FC>> clazz;
                try {
                    clazz = (Class<? extends RetryPolicyDecider<FC>>) conf.getClassByName(className)
                            .asSubclass(RetryPolicyDecider.class);
                } catch (ClassNotFoundException e) {
                    throw new LensException("Couldn't load class " + className, e);
                }
                RetryPolicyDecider<FC> instance;
                try {
                    instance = clazz.newInstance();
                } catch (InstantiationException | IllegalAccessException e) {
                    throw new LensException("Couldn't create instance of class " + clazz.getName(), e);
                }
                if (instance instanceof Configurable) {
                    ((Configurable) instance).setConf(conf);
                }
                retryPolicyDeciders.add(instance);
            }
        }
        return new ChainedRetryPolicyDecider<>(retryPolicyDeciders);
    }
}