org.apache.hadoop.hbase.trace.SpanReceiverHost.java Source code

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Here is the source code for org.apache.hadoop.hbase.trace.SpanReceiverHost.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.hbase.trace;

import java.io.IOException;
import java.util.Collection;
import java.util.HashSet;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.htrace.SpanReceiver;
import org.htrace.Trace;

/**
 * This class provides functions for reading the names of SpanReceivers from
 * hbase-site.xml, adding those SpanReceivers to the Tracer, and closing those
 * SpanReceivers when appropriate.
 */
public class SpanReceiverHost {
    public static final String SPAN_RECEIVERS_CONF_KEY = "hbase.trace.spanreceiver.classes";
    private static final Log LOG = LogFactory.getLog(SpanReceiverHost.class);
    private Collection<SpanReceiver> receivers;
    private Configuration conf;
    private boolean closed = false;

    private static enum SingletonHolder {
        INSTANCE;
        Object lock = new Object();
        SpanReceiverHost host = null;
    }

    public static SpanReceiverHost getInstance(Configuration conf) {
        if (SingletonHolder.INSTANCE.host != null) {
            return SingletonHolder.INSTANCE.host;
        }
        synchronized (SingletonHolder.INSTANCE.lock) {
            if (SingletonHolder.INSTANCE.host != null) {
                return SingletonHolder.INSTANCE.host;
            }

            SpanReceiverHost host = new SpanReceiverHost(conf);
            host.loadSpanReceivers();
            SingletonHolder.INSTANCE.host = host;
            return SingletonHolder.INSTANCE.host;
        }

    }

    SpanReceiverHost(Configuration conf) {
        receivers = new HashSet<SpanReceiver>();
        this.conf = conf;
    }

    /**
     * Reads the names of classes specified in the
     * "hbase.trace.spanreceiver.classes" property and instantiates and registers
     * them with the Tracer as SpanReceiver's.
     *
     */
    public void loadSpanReceivers() {
        Class<?> implClass = null;
        String[] receiverNames = conf.getStrings(SPAN_RECEIVERS_CONF_KEY);
        if (receiverNames == null || receiverNames.length == 0) {
            return;
        }
        for (String className : receiverNames) {
            className = className.trim();

            try {
                implClass = Class.forName(className);
                SpanReceiver receiver = loadInstance(implClass);
                if (receiver != null) {
                    receivers.add(receiver);
                    LOG.info("SpanReceiver " + className + " was loaded successfully.");
                }

            } catch (ClassNotFoundException e) {
                LOG.warn("Class " + className + " cannot be found. " + e.getMessage());
            } catch (IOException e) {
                LOG.warn("Load SpanReceiver " + className + " failed. " + e.getMessage());
            }
        }
        for (SpanReceiver rcvr : receivers) {
            Trace.addReceiver(rcvr);
        }
    }

    private SpanReceiver loadInstance(Class<?> implClass) throws IOException {
        SpanReceiver impl = null;
        try {
            Object o = implClass.newInstance();
            impl = (SpanReceiver) o;
            impl.configure(new HBaseHTraceConfiguration(this.conf));
        } catch (SecurityException e) {
            throw new IOException(e);
        } catch (IllegalArgumentException e) {
            throw new IOException(e);
        } catch (RuntimeException e) {
            throw new IOException(e);
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }

        return impl;
    }

    /**
     * Calls close() on all SpanReceivers created by this SpanReceiverHost.
     */
    public synchronized void closeReceivers() {
        if (closed)
            return;
        closed = true;
        for (SpanReceiver rcvr : receivers) {
            try {
                rcvr.close();
            } catch (IOException e) {
                LOG.warn("Unable to close SpanReceiver correctly: " + e.getMessage(), e);
            }
        }
    }
}