alluxio.master.journal.AbstractJournalSystem.java Source code

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Here is the source code for alluxio.master.journal.AbstractJournalSystem.java

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/*
 * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
 * (the "License"). You may not use this work except in compliance with the License, which is
 * available at www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied, as more fully set forth in the License.
 *
 * See the NOTICE file distributed with this work for information regarding copyright ownership.
 */

package alluxio.master.journal;

import com.google.common.base.Preconditions;

import java.io.IOException;
import java.util.concurrent.atomic.AtomicBoolean;

import javax.annotation.concurrent.ThreadSafe;

/**
 * Base implementation for journal systems.
 */
@ThreadSafe
public abstract class AbstractJournalSystem implements JournalSystem {
    private Mode mMode = Mode.SECONDARY;
    private boolean mRunning = false;

    public static final AtomicBoolean ALLOW_JOURNAL_MODIFY = new AtomicBoolean(true);

    @Override
    public synchronized void start() throws InterruptedException, IOException {
        Preconditions.checkState(!mRunning, "Journal is already running");
        startInternal();
        mRunning = true;
    }

    @Override
    public synchronized void stop() throws InterruptedException, IOException {
        Preconditions.checkState(mRunning, "Journal is not running");
        mRunning = false;
        stopInternal();
    }

    @Override
    public synchronized void setMode(Mode mode) {
        Preconditions.checkState(mRunning, "Cannot change journal system mode while it is not running");
        if (mMode.equals(mode)) {
            return;
        }
        switch (mode) {
        case PRIMARY:
            gainPrimacy();
            break;
        case SECONDARY:
            losePrimacy();
            break;
        default:
            throw new IllegalStateException("Unrecognized mode: " + mode);
        }
        mMode = mode;
    }

    /**
     * Starts the journal system.
     */
    protected abstract void startInternal() throws InterruptedException, IOException;

    /**
     * Stops the journal system.
     */
    protected abstract void stopInternal() throws InterruptedException, IOException;

    /**
     * Transition the journal from secondary to primary mode.
     */
    protected abstract void gainPrimacy();

    /**
     * Transition the journal from primary to secondary mode.
     */
    protected abstract void losePrimacy();
}