How to use

org.apache.hadoop.hdfs.server.namenode.EditsDoubleBuffer

constructor

public QuorumOutputStream(AsyncLoggerSet loggers,
  long txId, int outputBufferCapacity,
  int writeTimeoutMs, boolean updateCommittedTxId) throws IOException {
 super();
 this.buf = new EditsDoubleBuffer(outputBufferCapacity);
 this.loggers = loggers;
 this.segmentTxId = txId;
 this.writeTimeoutMs = writeTimeoutMs;
 this.updateCommittedTxId = updateCommittedTxId;
}

/**
 * There is no persistent storage. Just clear the buffers.
 */
@Override // EditLogOutputStream
public void create(int layoutVersion) throws IOException {
 assert doubleBuf.isFlushed() : "previous data is not flushed yet";
 this.doubleBuf = new EditsDoubleBuffer(DEFAULT_BUFFER_SIZE);
}

/**
 * Creates output buffers and file object.
 * 
 * @param conf
 *          Configuration object
 * @param name
 *          File name to store edit log
 * @param size
 *          Size of flush buffer
 * @throws IOException
 */
public EditLogFileOutputStream(Configuration conf, File name, int size)
  throws IOException {
 super();
 shouldSyncWritesAndSkipFsync = conf.getBoolean(
     DFSConfigKeys.DFS_NAMENODE_EDITS_NOEDITLOGCHANNELFLUSH,
     DFSConfigKeys.DFS_NAMENODE_EDITS_NOEDITLOGCHANNELFLUSH_DEFAULT);
 file = name;
 doubleBuf = new EditsDoubleBuffer(size);
 RandomAccessFile rp;
 if (shouldSyncWritesAndSkipFsync) {
  rp = new RandomAccessFile(name, "rws");
 } else {
  rp = new RandomAccessFile(name, "rw");
 }
 fp = new FileOutputStream(rp.getFD()); // open for append
 fc = rp.getChannel();
 fc.position(fc.size());
}

EditLogBackupOutputStream(NamenodeRegistration bnReg, // backup node
             JournalInfo journalInfo) // active name-node
throws IOException {
 super();
 this.bnRegistration = bnReg;
 this.journalInfo = journalInfo;
 InetSocketAddress bnAddress =
  NetUtils.createSocketAddr(bnRegistration.getAddress());
 try {
  this.backupNode = NameNodeProxies.createNonHAProxy(new HdfsConfiguration(),
    bnAddress, JournalProtocol.class, UserGroupInformation.getCurrentUser(),
    true).getProxy();
 } catch(IOException e) {
  Storage.LOG.error("Error connecting to: " + bnAddress, e);
  throw e;
 }
 this.doubleBuf = new EditsDoubleBuffer(DEFAULT_BUFFER_SIZE);
 this.out = new DataOutputBuffer(DEFAULT_BUFFER_SIZE);
}

public QuorumOutputStream(AsyncLoggerSet loggers,
  long txId, int outputBufferCapacity,
  int writeTimeoutMs) throws IOException {
 super();
 this.buf = new EditsDoubleBuffer(outputBufferCapacity);
 this.loggers = loggers;
 this.segmentTxId = txId;
 this.writeTimeoutMs = writeTimeoutMs;
}

public QuorumOutputStream(AsyncLoggerSet loggers,
  long txId, int outputBufferCapacity,
  int writeTimeoutMs) throws IOException {
 super();
 this.buf = new EditsDoubleBuffer(outputBufferCapacity);
 this.loggers = loggers;
 this.segmentTxId = txId;
 this.writeTimeoutMs = writeTimeoutMs;
}

/**
 * There is no persistent storage. Just clear the buffers.
 */
@Override // EditLogOutputStream
public void create(int layoutVersion) throws IOException {
 assert doubleBuf.isFlushed() : "previous data is not flushed yet";
 this.doubleBuf = new EditsDoubleBuffer(DEFAULT_BUFFER_SIZE);
}

/**
 * There is no persistent storage. Just clear the buffers.
 */
@Override // EditLogOutputStream
public void create(int layoutVersion) throws IOException {
 assert doubleBuf.isFlushed() : "previous data is not flushed yet";
 this.doubleBuf = new EditsDoubleBuffer(DEFAULT_BUFFER_SIZE);
}

/**
 * Creates output buffers and file object.
 * 
 * @param conf
 *          Configuration object
 * @param name
 *          File name to store edit log
 * @param size
 *          Size of flush buffer
 * @throws IOException
 */
public EditLogFileOutputStream(Configuration conf, File name, int size)
  throws IOException {
 super();
 shouldSyncWritesAndSkipFsync = conf.getBoolean(
     DFSConfigKeys.DFS_NAMENODE_EDITS_NOEDITLOGCHANNELFLUSH,
     DFSConfigKeys.DFS_NAMENODE_EDITS_NOEDITLOGCHANNELFLUSH_DEFAULT);
 file = name;
 doubleBuf = new EditsDoubleBuffer(size);
 RandomAccessFile rp;
 if (shouldSyncWritesAndSkipFsync) {
  rp = new RandomAccessFile(name, "rws");
 } else {
  rp = new RandomAccessFile(name, "rw");
 }
 fp = new FileOutputStream(rp.getFD()); // open for append
 fc = rp.getChannel();
 fc.position(fc.size());
}

/**
 * Creates output buffers and file object.
 * 
 * @param conf
 *          Configuration object
 * @param name
 *          File name to store edit log
 * @param size
 *          Size of flush buffer
 * @throws IOException
 */
public EditLogFileOutputStream(Configuration conf, File name, int size)
  throws IOException {
 super();
 shouldSyncWritesAndSkipFsync = conf.getBoolean(
     DFSConfigKeys.DFS_NAMENODE_EDITS_NOEDITLOGCHANNELFLUSH,
     DFSConfigKeys.DFS_NAMENODE_EDITS_NOEDITLOGCHANNELFLUSH_DEFAULT);
 file = name;
 doubleBuf = new EditsDoubleBuffer(size);
 RandomAccessFile rp;
 if (shouldSyncWritesAndSkipFsync) {
  rp = new RandomAccessFile(name, "rws");
 } else {
  rp = new RandomAccessFile(name, "rw");
 }
 fp = new FileOutputStream(rp.getFD()); // open for append
 fc = rp.getChannel();
 fc.position(fc.size());
}

           FSEditLog.maxBufferedTransactions);
file = name;
doubleBuf = new EditsDoubleBuffer(FSEditLog.sizeFlushBuffer);
RandomAccessFile rp = new RandomAccessFile(name, "rw");
fp = new FileOutputStream(rp.getFD()); // open for append

EditLogBackupOutputStream(NamenodeRegistration bnReg, // backup node
             JournalInfo journalInfo) // active name-node
throws IOException {
 super();
 this.bnRegistration = bnReg;
 this.journalInfo = journalInfo;
 InetSocketAddress bnAddress =
  NetUtils.createSocketAddr(bnRegistration.getAddress());
 try {
  this.backupNode = NameNodeProxies.createNonHAProxy(new HdfsConfiguration(),
    bnAddress, JournalProtocol.class, UserGroupInformation.getCurrentUser(),
    true).getProxy();
 } catch(IOException e) {
  Storage.LOG.error("Error connecting to: " + bnAddress, e);
  throw e;
 }
 this.doubleBuf = new EditsDoubleBuffer(DEFAULT_BUFFER_SIZE);
 this.out = new DataOutputBuffer(DEFAULT_BUFFER_SIZE);
}

EditLogBackupOutputStream(NamenodeRegistration bnReg, // backup node
             JournalInfo journalInfo) // active name-node
throws IOException {
 super();
 this.bnRegistration = bnReg;
 this.journalInfo = journalInfo;
 InetSocketAddress bnAddress =
  NetUtils.createSocketAddr(bnRegistration.getAddress());
 try {
  this.backupNode = NameNodeProxies.createNonHAProxy(new HdfsConfiguration(),
    bnAddress, JournalProtocol.class, UserGroupInformation.getCurrentUser(),
    true).getProxy();
 } catch(IOException e) {
  Storage.LOG.error("Error connecting to: " + bnAddress, e);
  throw e;
 }
 this.doubleBuf = new EditsDoubleBuffer(DEFAULT_BUFFER_SIZE);
 this.out = new DataOutputBuffer(DEFAULT_BUFFER_SIZE);
}

 @Test
 public void shouldFailToCloseWhenUnflushed() throws IOException {
  EditsDoubleBuffer buf = new EditsDoubleBuffer(1024);
  buf.writeRaw(new byte[1], 0, 1);
  try {
   buf.close();
   fail("Did not fail to close with unflushed data");
  } catch (IOException ioe) {
   if (!ioe.toString().contains("still to be flushed")) {
    throw ioe;
   }
  }
 }
}

@Test
public void testDoubleBuffer() throws IOException {
 EditsDoubleBuffer buf = new EditsDoubleBuffer(1024);