Example usage for org.apache.hadoop.hdfs.shortcircuit ShortCircuitReplica ShortCircuitReplica

Introduction

In this page you can find the example usage for org.apache.hadoop.hdfs.shortcircuit ShortCircuitReplica ShortCircuitReplica.

Prototype

public ShortCircuitReplica(ExtendedBlockId key, FileInputStream dataStream, FileInputStream metaStream,
            ShortCircuitCache cache, long creationTimeMs, Slot slot) throws IOException 

Source Link

Usage

From source file:BlockReaderFactory.java

License:Apache License

/**
 * Request file descriptors from a DomainPeer.
 *
 * @param peer   The peer to use for communication.
 * @param slot   If non-null, the shared memory slot to associate with the 
 *               new ShortCircuitReplica.
 * // ww w.j a va 2  s  .  co  m
 * @return  A ShortCircuitReplica object if we could communicate with the
 *          datanode; null, otherwise. 
 * @throws  IOException If we encountered an I/O exception while communicating
 *          with the datanode.
 */
private ShortCircuitReplicaInfo requestFileDescriptors(DomainPeer peer, Slot slot) throws IOException {
    ShortCircuitCache cache = clientContext.getShortCircuitCache();
    final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(peer.getOutputStream()));
    SlotId slotId = slot == null ? null : slot.getSlotId();
    new Sender(out).requestShortCircuitFds(block, token, slotId, 1);
    DataInputStream in = new DataInputStream(peer.getInputStream());
    BlockOpResponseProto resp = BlockOpResponseProto.parseFrom(PBHelper.vintPrefixed(in));
    DomainSocket sock = peer.getDomainSocket();
    switch (resp.getStatus()) {
    case SUCCESS:
        byte buf[] = new byte[1];
        FileInputStream fis[] = new FileInputStream[2];
        sock.recvFileInputStreams(fis, buf, 0, buf.length);
        ShortCircuitReplica replica = null;
        try {
            ExtendedBlockId key = new ExtendedBlockId(block.getBlockId(), block.getBlockPoolId());
            replica = new ShortCircuitReplica(key, fis[0], fis[1], cache, Time.monotonicNow(), slot);
        } catch (IOException e) {
            // This indicates an error reading from disk, or a format error.  Since
            // it's not a socket communication problem, we return null rather than
            // throwing an exception.
            LOG.warn(this + ": error creating ShortCircuitReplica.", e);
            return null;
        } finally {
            if (replica == null) {
                IOUtils.cleanup(DFSClient.LOG, fis[0], fis[1]);
            }
        }
        return new ShortCircuitReplicaInfo(replica);
    case ERROR_UNSUPPORTED:
        if (!resp.hasShortCircuitAccessVersion()) {
            LOG.warn("short-circuit read access is disabled for " + "DataNode " + datanode + ".  reason: "
                    + resp.getMessage());
            clientContext.getDomainSocketFactory().disableShortCircuitForPath(pathInfo.getPath());
        } else {
            LOG.warn("short-circuit read access for the file " + fileName + " is disabled for DataNode "
                    + datanode + ".  reason: " + resp.getMessage());
        }
        return null;
    case ERROR_ACCESS_TOKEN:
        String msg = "access control error while " + "attempting to set up short-circuit access to " + fileName
                + resp.getMessage();
        if (LOG.isDebugEnabled()) {
            LOG.debug(this + ":" + msg);
        }
        return new ShortCircuitReplicaInfo(new InvalidToken(msg));
    default:
        LOG.warn(this + ": unknown response code " + resp.getStatus()
                + " while attempting to set up short-circuit access. " + resp.getMessage());
        clientContext.getDomainSocketFactory().disableShortCircuitForPath(pathInfo.getPath());
        return null;
    }
}

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