org.apache.accumulo.tracer.ZooTraceClient.java Source code

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Here is the source code for org.apache.accumulo.tracer.ZooTraceClient.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.accumulo.tracer;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import org.apache.accumulo.core.Constants;
import org.apache.accumulo.core.trace.DistributedTrace;
import org.apache.accumulo.fate.zookeeper.ZooReader;
import org.apache.htrace.HTraceConfiguration;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.util.concurrent.ThreadFactoryBuilder;

/**
 * Find a Span collector via zookeeper and push spans there via Thrift RPC
 */
public class ZooTraceClient extends SendSpansViaThrift implements Watcher {
    private static final Logger log = LoggerFactory.getLogger(ZooTraceClient.class);

    private static final int DEFAULT_TIMEOUT = 30 * 1000;

    ZooReader zoo = null;
    String path;
    boolean pathExists = false;
    final Random random = new Random();
    final List<String> hosts = new ArrayList<>();
    long retryPause = 5000l;

    // Visible for testing
    ZooTraceClient() {
    }

    public ZooTraceClient(HTraceConfiguration conf) {
        super(conf);

        String keepers = conf.get(DistributedTrace.TRACER_ZK_HOST);
        if (keepers == null)
            throw new IllegalArgumentException("Must configure " + DistributedTrace.TRACER_ZK_HOST);
        int timeout = conf.getInt(DistributedTrace.TRACER_ZK_TIMEOUT, DEFAULT_TIMEOUT);
        zoo = new ZooReader(keepers, timeout);
        path = conf.get(DistributedTrace.TRACER_ZK_PATH, Constants.ZTRACERS);
        setInitialTraceHosts();
    }

    @VisibleForTesting
    protected void setRetryPause(long pause) {
        retryPause = pause;
    }

    @Override
    synchronized protected String getSpanKey(Map<String, String> data) {
        if (hosts.size() > 0) {
            String host = hosts.get(random.nextInt(hosts.size()));
            return host;
        }
        return null;
    }

    @Override
    public void process(WatchedEvent event) {
        log.debug("Processing event for trace server zk watch");
        try {
            updateHostsFromZooKeeper();
        } catch (Exception ex) {
            log.error("unable to get destination hosts in zookeeper", ex);
        }
    }

    protected void setInitialTraceHosts() {
        // Make a single thread pool with a daemon thread
        final ScheduledExecutorService svc = Executors.newScheduledThreadPool(1,
                new ThreadFactoryBuilder().setDaemon(true).build());
        final Runnable task = new Runnable() {
            @Override
            public void run() {
                try {
                    updateHostsFromZooKeeper();
                    log.debug("Successfully initialized tracer hosts from ZooKeeper");
                    // Once this passes, we can issue a shutdown of the pool
                    svc.shutdown();
                } catch (Exception e) {
                    log.error("Unabled to get destination tracer hosts in ZooKeeper, will retry in " + retryPause
                            + " milliseconds", e);
                    // We failed to connect to ZK, try again in `retryPause` milliseconds
                    svc.schedule(this, retryPause, TimeUnit.MILLISECONDS);
                }
            }
        };

        // Start things off
        task.run();
    }

    protected void updateHostsFromZooKeeper() throws KeeperException, InterruptedException {
        if (pathExists || zoo.exists(path)) {
            pathExists = true;
            updateHosts(path, zoo.getChildren(path, this));
        } else {
            zoo.exists(path, this);
        }
    }

    @Override
    protected void sendSpans() {
        if (hosts.isEmpty()) {
            if (!sendQueue.isEmpty()) {
                log.error("No hosts to send data to, dropping queued spans");
                synchronized (sendQueue) {
                    sendQueue.clear();
                    sendQueue.notifyAll();
                    sendQueueSize.set(0);
                }
            }
        } else {
            super.sendSpans();
        }
    }

    synchronized private void updateHosts(String path, List<String> children) {
        log.debug("Scanning trace hosts in zookeeper: " + path);
        try {
            List<String> hosts = new ArrayList<>();
            for (String child : children) {
                byte[] data = zoo.getData(path + "/" + child, null);
                hosts.add(new String(data, UTF_8));
            }
            this.hosts.clear();
            this.hosts.addAll(hosts);
            log.debug("Trace hosts: " + this.hosts);
        } catch (Exception ex) {
            log.error("unable to get destination hosts in zookeeper", ex);
        }
    }
}