org.apache.hadoop.hdfs.client.HdfsUtils.java Source code

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Here is the source code for org.apache.hadoop.hdfs.client.HdfsUtils.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.hdfs.client;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.hdfs.DistributedFileSystem;
import org.apache.hadoop.hdfs.protocol.HdfsConstants;
import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
import org.apache.hadoop.io.IOUtils;

import java.io.IOException;
import java.net.URI;
import java.util.concurrent.ThreadLocalRandom;
import org.apache.hadoop.hdfs.DFSConfigKeys;

/**
 * The public utility API for HDFS.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class HdfsUtils {
    private static final Log LOG = LogFactory.getLog(HdfsUtils.class);

    /**
     * Is the HDFS healthy?
     * HDFS is considered as healthy if it is up and not in safemode.
     *
     * @param uri
     *     the HDFS URI.  Note that the URI path is ignored.
     * @return true if HDFS is healthy; false, otherwise.
     */
    public static boolean isHealthy(URI uri) {
        //check scheme
        final String scheme = uri.getScheme();
        if (!HdfsConstants.HDFS_URI_SCHEME.equalsIgnoreCase(scheme)) {
            throw new IllegalArgumentException(
                    "The scheme is not " + HdfsConstants.HDFS_URI_SCHEME + ", uri=" + uri);
        }

        final Configuration conf = new Configuration();
        //disable FileSystem cache
        conf.setBoolean(String.format("fs.%s.impl.disable.cache", scheme), true);
        //disable client retry for rpc connection and rpc calls
        conf.setBoolean(HdfsClientConfigKeys.Retry.POLICY_ENABLED_KEY, false);
        conf.setInt(CommonConfigurationKeysPublic.IPC_CLIENT_CONNECT_MAX_RETRIES_KEY, 0);
        conf.setInt(DFSConfigKeys.DFS_CLIENT_FAILOVER_MAX_ATTEMPTS_KEY, /*default 15*/ 1);

        DistributedFileSystem fs = null;
        try {
            fs = (DistributedFileSystem) FileSystem.get(uri, conf);
            final boolean safemode = fs.setSafeMode(SafeModeAction.SAFEMODE_GET);
            if (LOG.isDebugEnabled()) {
                LOG.debug("Is namenode in safemode? " + safemode + "; uri=" + uri);
            }

            fs.close();
            fs = null;
            return !safemode;
        } catch (IOException e) {
            if (LOG.isDebugEnabled()) {
                LOG.debug("Got an exception for uri=" + uri, e);
            }
            return false;
        } finally {
            IOUtils.cleanup(LOG, fs);
        }
    }

    public static long calculateExponentialTime(long time, int retries, long cap) {
        long baseTime = Math.min(time * (1L << retries), cap);
        return (long) (baseTime * (ThreadLocalRandom.current().nextDouble() + 0.5));
    }
}