net.oneandone.stool.locking.LockManager Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of main Show documentation
Stool's main component. Java Library, cli, setup code.
There is a newer version: 4.0.3
/**
 * Copyright 1&1 Internet AG, https://github.com/1and1/
 *
 * 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 net.oneandone.stool.locking;

import net.oneandone.inline.Console;
import net.oneandone.stool.util.Processes;
import net.oneandone.sushi.fs.file.FileNode;
import net.oneandone.sushi.util.Pid;

import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileLock;
import java.util.ArrayList;
import java.util.List;

/**
 * High-level management for the locks file. Factory for locks.
 * Thread-save and save against concurrent processes.
 */
public class LockManager extends Thread implements AutoCloseable {
    public static LockManager create(FileNode file, String comment, int timeout) {
        return new LockManager(file, new Process(Pid.pid(), comment), timeout);
    }

    private final List active;
    private final FileNode file;
    private final Process self;
    /** seconds */
    private final int timeout;

    public LockManager(FileNode file, Process self, int timeout) {
        super("LockManager Shutdown Hook");
        this.active = new ArrayList<>();
        this.file = file;
        this.self = self;
        this.timeout = timeout;
        Runtime.getRuntime().addShutdownHook(this);
    }

    public synchronized Lock acquire(String name, Console console, Mode mode) throws IOException {
        Lock result;

        awaitLock(name, mode, console);
        result = new Lock(this, name, mode);
        active.add(result);
        return result;
    }

    /** for testing */
    public synchronized Lock acquireOpt(String name, Console console, Mode mode) throws IOException {
        try {
            return acquire(name, console, mode);
        } catch (LockException e) {
            return null;
        }
    }


    private void awaitLock(String name, Mode mode, Console console) throws IOException {
        Queue problem;
        int seconds;

        seconds = 0;
        while (true) {
            try {
                problem = tryLock(name, mode);
            } catch (IOException e) {
                throw new IOException("cannot acquire lock '" + name + "': " + e.getMessage(), e);
            }
            if (problem == null) {
                return;
            }
            if (seconds > timeout) {
                throw new LockException(name, problem);
            }
            if (seconds % 10 == 0) {
                console.info.println("trying to acquire lock '" + name + "'");
            }
            seconds++;
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                // continue
            }
        }
    }

    /** @return null or problematic queue otherwise */
    private Queue tryLock(String name, Mode mode) throws IOException {
        Store lf;
        Queue problem;

        try (RandomAccessFile raf = new RandomAccessFile(file.toPath().toFile(), "rw"); FileLock lock = raf.getChannel().lock()) {
            lf = Store.load(raf);
            problem = lf.tryLock(name, mode, self);
            if (problem != null) {
                return problem;
            }
            lf.save(raf);
            return null;
        }

    }

    public synchronized void release(Lock lock) throws IOException {
        Store lf;

        active.remove(lock);
        try (RandomAccessFile raf = new RandomAccessFile(file.toPath().toFile(), "rw"); FileLock l = raf.getChannel().lock()) {
            lf = Store.load(raf);
            lf.release(lock.name, lock.mode, self);
            lf.save(raf);
        }
    }

    /** @return list of stale processes */
    public synchronized List validate(Processes running, boolean repair) throws IOException {
        Store lf;
        List stale;

        stale = new ArrayList<>();
        try (RandomAccessFile raf = new RandomAccessFile(file.toPath().toFile(), "rw"); FileLock lock = raf.getChannel().lock()) {
            lf = Store.load(raf);
            for (Process process : lf.processes()) {
                if (!running.hasPid(process.id)) {
                    stale.add(process.id);
                    if (repair) {
                        lf.releaseAll(process);
                    }
                }
            }
            if (repair) {
                lf.save(raf);
            }
        }
        return stale;
    }

    public synchronized boolean empty() throws IOException {
        Store lf;

        try (RandomAccessFile raf = new RandomAccessFile(file.toPath().toFile(), "rw");
             FileLock lock = raf.getChannel().lock()) {
            lf = Store.load(raf);
            return lf.isEmpty();
        }
    }

    public synchronized boolean hasExclusiveLocks(String ... locks) throws IOException {
        Store lf;
        Queue queue;

        try (RandomAccessFile raf = new RandomAccessFile(file.toPath().toFile(), "rw");
             FileLock l = raf.getChannel().lock()) {
            lf = Store.load(raf);
            for (String lock : locks) {
                queue = lf.lookup(lock);
                if (queue != null) {
                    if (queue.exclusiveCount > 0) {
                        return true;
                    }
                }
            }
            return false;
        }
    }

    /** close explicitly on LockManager object */
    public void close() {
        Runtime.getRuntime().removeShutdownHook(this);
        removeActive();
    }

    /** close implicitly during shutdown hook */
    @Override
    public void run() {
        removeActive();
    }

    private synchronized void removeActive() {
        Lock lock;

        while (!active.isEmpty()) {
            // caution: do no invoke active.remove(0) - lock.close() will remove it from the list
            lock = active.get(0);
            System.err.println("shutdown: unlocking " + lock.name);
            try {
                lock.close(); // does not need sushi
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}