com.netflix.curator.framework.recipes.locks.ChildReaper.java Source code

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Here is the source code for com.netflix.curator.framework.recipes.locks.ChildReaper.java

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/*
 * Copyright 2012 Netflix, Inc.
 *
 *    Licensed 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 com.netflix.curator.framework.recipes.locks;

import java.io.Closeable;
import java.io.IOException;
import java.util.List;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.commons.io.IOUtils;
import org.apache.zookeeper.data.Stat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Preconditions;
import com.netflix.curator.framework.CuratorFramework;
import com.netflix.curator.utils.ThreadUtils;
import com.netflix.curator.utils.ZKPaths;

/**
 * Utility to reap empty child nodes of a parent node. Periodically calls getChildren on
 * the node and adds empty nodes to an internally managed {@link Reaper}
 */
public class ChildReaper implements Closeable {
    private final Logger log = LoggerFactory.getLogger(getClass());
    private final Reaper reaper;
    private final AtomicReference<State> state = new AtomicReference<State>(State.LATENT);
    private final CuratorFramework client;
    private final String path;
    private final Reaper.Mode mode;
    private final ScheduledExecutorService executor;
    private final int reapingThresholdMs;

    private volatile ScheduledFuture<?> task;

    private enum State {
        LATENT, STARTED, CLOSED
    }

    /**
     * @param client the client
     * @param path path to reap children from
     * @param mode reaping mode
     */
    public ChildReaper(CuratorFramework client, String path, Reaper.Mode mode) {
        this(client, path, mode, newExecutorService(), Reaper.DEFAULT_REAPING_THRESHOLD_MS);
    }

    /**
     * @param client the client
     * @param path path to reap children from
     * @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
     * @param mode reaping mode
     */
    public ChildReaper(CuratorFramework client, String path, Reaper.Mode mode, int reapingThresholdMs) {
        this(client, path, mode, newExecutorService(), reapingThresholdMs);
    }

    /**
     * @param client the client
     * @param path path to reap children from
     * @param executor executor to use for background tasks
     * @param reapingThresholdMs threshold in milliseconds that determines that a path can be deleted
     * @param mode reaping mode
     */
    public ChildReaper(CuratorFramework client, String path, Reaper.Mode mode, ScheduledExecutorService executor,
            int reapingThresholdMs) {
        this.client = client;
        this.path = path;
        this.mode = mode;
        this.executor = executor;
        this.reapingThresholdMs = reapingThresholdMs;
        this.reaper = new Reaper(client, executor, reapingThresholdMs);
    }

    /**
     * The reaper must be started
     *
     * @throws Exception errors
     */
    public void start() throws Exception {
        Preconditions.checkState(state.compareAndSet(State.LATENT, State.STARTED),
                "Cannot be started more than once");

        task = executor.scheduleWithFixedDelay(new Runnable() {
            @Override
            public void run() {
                doWork();
            }
        }, reapingThresholdMs, reapingThresholdMs, TimeUnit.MILLISECONDS);

        reaper.start();
    }

    @Override
    public void close() throws IOException {
        if (state.compareAndSet(State.STARTED, State.CLOSED)) {
            IOUtils.closeQuietly(reaper);
            task.cancel(true);
        }
    }

    private static ScheduledExecutorService newExecutorService() {
        return ThreadUtils.newFixedThreadScheduledPool(2, "ChildReaper");
    }

    private void doWork() {
        try {
            List<String> children = client.getChildren().forPath(path);
            for (String name : children) {
                String thisPath = ZKPaths.makePath(path, name);
                Stat stat = client.checkExists().forPath(thisPath);
                if ((stat != null) && (stat.getNumChildren() == 0)) {
                    reaper.addPath(thisPath, mode);
                }
            }
        } catch (Exception e) {
            log.error("Could not get children for path: " + path, e);
        }
    }
}