com.yahoo.gondola.Command Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of core Show documentation
Java implementation of Raft
The newest version!
package com.yahoo.gondola;

import com.yahoo.gondola.core.CoreCmd;
import com.yahoo.gondola.core.CoreMember;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.UnsupportedEncodingException;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * This object is used to commit entries into the Raft log.
 * Usage:
 * Command c = cluster.checkoutCommand();
 * c.commit(buffer, 0, len);
 * c.release();
 * 
 * This object is generally not thread-safe; that is, an object of this class should not be called by multiple client
 * threads simultaneously.
 */
public class Command {
    final static Logger logger = LoggerFactory.getLogger(Command.class);

    public final static int STATUS_NONE = -1;
    public final static int STATUS_OK = 0;
    public final static int STATUS_NOT_LEADER = 1;
    public final static int STATUS_INTERRUPTED = 2; // Not used
    public final static int STATUS_ERROR = 3;       // Storage or system error
    public final static int STATUS_TIMEOUT = 4;

    final Cluster cluster;
    final CoreCmd ccmd;

    Command(Gondola gondola, Cluster cluster, CoreMember cmember) {
        this.cluster = cluster;
        ccmd = new CoreCmd(gondola, cluster, cmember);
    }

    /**
     * Returns the maximum number of bytes that can be committed.
     */
    public int getCapacity() {
        return ccmd.buffer.length;
    }

    /**
     * Returns the byte buffer holding the command.
     */
    public byte[] getBuffer() {
        return ccmd.buffer;
    }

    /**
     * Returns the size of the command in bytes.
     */
    public int getSize() {
        return ccmd.size;
    }

    /**
     * Returns the index assigned to this command after a commit() or after a Cluster.getCommittedIndex() call.
     */
    public int getIndex() {
        return ccmd.index;
    }

    /**
     * Returns the commitIndex at the time this command is returned to the client. Applies only for commit.
     *
     * @return -1 if the command was not committed.
     */
    public int getCommitIndex() {
        return ccmd.commitIndex;
    }

    public int getStatus() {
        return ccmd.status;
    }

    /**
     * Returns the contents of this command in string form. Assumes UTF-8 encoding.
     */
    public String getString() {
        try {
            return new String(ccmd.buffer, 0, ccmd.size, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            logger.error(e.getMessage(), e);
            throw new IllegalStateException(e);
        }
    }

    /**
     * Equivalent to commit(buf, buffOffset, bufLen, -1);
     *
     * @return 0 if successful.
     * @throws NotLeaderException if the member is not currently the leader.
     */
    public void commit(byte[] buf, int bufOffset, int bufLen)
            throws InterruptedException, NotLeaderException {
        try {
            ccmd.commit(buf, bufOffset, bufLen, -1);
        } catch (TimeoutException e) {
            throw new IllegalStateException(e); // Can't happen
        }
    }

    /**
     * Blocks until the command in buffer has been committed or the timeout has expired.
     * After this call, this command object can be used again.
     *
     * @param timeout If -1, timeout is disabled.
     * @return 0 if successful.
     * @throws NotLeaderException if the member is not currently the leader.
     */
    public void commit(byte[] buf, int bufOffset, int bufLen, int timeout)
            throws InterruptedException, NotLeaderException, TimeoutException {
        ccmd.commit(buf, bufOffset, bufLen, timeout);
    }

    /**
     * Returns this command object back to the pool.
     */
    public void release() {
        cluster.checkinCommand(this);
    }
}