How to use

flushTo

method

in

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

/**
 * Flush ready buffer to persistent store. currentBuffer is not flushed as it
 * accumulates new log records while readyBuffer will be flushed and synced.
 */
@Override
public void flushAndSync(boolean durable) throws IOException {
 if (fp == null) {
  throw new IOException("Trying to use aborted output stream");
 }
 if (doubleBuf.isFlushed()) {
  LOG.info("Nothing to flush");
  return;
 }
 preallocate(); // preallocate file if necessary
 doubleBuf.flushTo(fp);
 if (durable && !shouldSkipFsyncForTests && !shouldSyncWritesAndSkipFsync) {
  fc.force(false); // metadata updates not needed
 }
}

@Override // EditLogOutputStream
protected void flushAndSync(boolean durable) throws IOException {
 assert out.getLength() == 0 : "Output buffer is not empty";
 
 if (doubleBuf.isFlushed()) {
  LOG.info("Nothing to flush");
  return;
 }
 int numReadyTxns = doubleBuf.countReadyTxns();
 long firstTxToFlush = doubleBuf.getFirstReadyTxId();
 
 doubleBuf.flushTo(out);
 if (out.getLength() > 0) {
  assert numReadyTxns > 0;
  
  byte[] data = Arrays.copyOf(out.getData(), out.getLength());
  out.reset();
  assert out.getLength() == 0 : "Output buffer is not empty";
  backupNode.journal(journalInfo, 0, firstTxToFlush, numReadyTxns, data);
 }
}

buf.flushTo(bufToSend);
assert bufToSend.getLength() == numReadyBytes;
byte[] data = bufToSend.getData();

/**
 * Flush ready buffer to persistent store. currentBuffer is not flushed as it
 * accumulates new log records while readyBuffer will be flushed and synced.
 */
@Override
protected void flushAndSync() throws IOException {
 if (fp == null) {
  throw new IOException("Trying to use aborted output stream");
 }
 preallocate(); // preallocate file if necessary
 if (doubleBuf.isFlushed()) {
  return;
 }
 doubleBuf.flushTo(fp);
 fc.force(false); // metadata updates not needed
 fc.position(fc.position() - 1); // skip back the end-of-file marker         
}

/**
 * Flush ready buffer to persistent store. currentBuffer is not flushed as it
 * accumulates new log records while readyBuffer will be flushed and synced.
 */
@Override
public void flushAndSync(boolean durable) throws IOException {
 if (fp == null) {
  throw new IOException("Trying to use aborted output stream");
 }
 if (doubleBuf.isFlushed()) {
  LOG.info("Nothing to flush");
  return;
 }
 preallocate(); // preallocate file if necessary
 doubleBuf.flushTo(fp);
 if (durable && !shouldSkipFsyncForTests && !shouldSyncWritesAndSkipFsync) {
  fc.force(false); // metadata updates not needed
 }
}

/**
 * Flush ready buffer to persistent store. currentBuffer is not flushed as it
 * accumulates new log records while readyBuffer will be flushed and synced.
 */
@Override
public void flushAndSync(boolean durable) throws IOException {
 if (fp == null) {
  throw new IOException("Trying to use aborted output stream");
 }
 if (doubleBuf.isFlushed()) {
  LOG.info("Nothing to flush");
  return;
 }
 preallocate(); // preallocate file if necessary
 doubleBuf.flushTo(fp);
 if (durable && !shouldSkipFsyncForTests && !shouldSyncWritesAndSkipFsync) {
  fc.force(false); // metadata updates not needed
 }
}

@Override // EditLogOutputStream
protected void flushAndSync(boolean durable) throws IOException {
 assert out.getLength() == 0 : "Output buffer is not empty";
 
 if (doubleBuf.isFlushed()) {
  LOG.info("Nothing to flush");
  return;
 }
 int numReadyTxns = doubleBuf.countReadyTxns();
 long firstTxToFlush = doubleBuf.getFirstReadyTxId();
 
 doubleBuf.flushTo(out);
 if (out.getLength() > 0) {
  assert numReadyTxns > 0;
  
  byte[] data = Arrays.copyOf(out.getData(), out.getLength());
  out.reset();
  assert out.getLength() == 0 : "Output buffer is not empty";
  backupNode.journal(journalInfo, 0, firstTxToFlush, numReadyTxns, data);
 }
}

@Override // EditLogOutputStream
protected void flushAndSync(boolean durable) throws IOException {
 assert out.getLength() == 0 : "Output buffer is not empty";
 
 if (doubleBuf.isFlushed()) {
  LOG.info("Nothing to flush");
  return;
 }
 int numReadyTxns = doubleBuf.countReadyTxns();
 long firstTxToFlush = doubleBuf.getFirstReadyTxId();
 
 doubleBuf.flushTo(out);
 if (out.getLength() > 0) {
  assert numReadyTxns > 0;
  
  byte[] data = Arrays.copyOf(out.getData(), out.getLength());
  out.reset();
  assert out.getLength() == 0 : "Output buffer is not empty";
  backupNode.journal(journalInfo, 0, firstTxToFlush, numReadyTxns, data);
 }
}

@Override
protected void flushAndSync(boolean durable) throws IOException {
 int numReadyBytes = buf.countReadyBytes();
 if (numReadyBytes > 0) {
  int numReadyTxns = buf.countReadyTxns();
  long firstTxToFlush = buf.getFirstReadyTxId();
  assert numReadyTxns > 0;
  // Copy from our double-buffer into a new byte array. This is for
  // two reasons:
  // 1) The IPC code has no way of specifying to send only a slice of
  //    a larger array.
  // 2) because the calls to the underlying nodes are asynchronous, we
  //    need a defensive copy to avoid accidentally mutating the buffer
  //    before it is sent.
  DataOutputBuffer bufToSend = new DataOutputBuffer(numReadyBytes);
  buf.flushTo(bufToSend);
  assert bufToSend.getLength() == numReadyBytes;
  byte[] data = bufToSend.getData();
  assert data.length == bufToSend.getLength();
  QuorumCall<AsyncLogger, Void> qcall = loggers.sendEdits(
    segmentTxId, firstTxToFlush,
    numReadyTxns, data);
  loggers.waitForWriteQuorum(qcall, writeTimeoutMs, "sendEdits");
  
  // Since we successfully wrote this batch, let the loggers know. Any future
  // RPCs will thus let the loggers know of the most recent transaction, even
  // if a logger has fallen behind.
  loggers.setCommittedTxId(firstTxToFlush + numReadyTxns - 1);
 }
}

@Override
protected void flushAndSync(boolean durable) throws IOException {
 int numReadyBytes = buf.countReadyBytes();
 if (numReadyBytes > 0) {
  int numReadyTxns = buf.countReadyTxns();
  long firstTxToFlush = buf.getFirstReadyTxId();
  assert numReadyTxns > 0;
  // Copy from our double-buffer into a new byte array. This is for
  // two reasons:
  // 1) The IPC code has no way of specifying to send only a slice of
  //    a larger array.
  // 2) because the calls to the underlying nodes are asynchronous, we
  //    need a defensive copy to avoid accidentally mutating the buffer
  //    before it is sent.
  DataOutputBuffer bufToSend = new DataOutputBuffer(numReadyBytes);
  buf.flushTo(bufToSend);
  assert bufToSend.getLength() == numReadyBytes;
  byte[] data = bufToSend.getData();
  assert data.length == bufToSend.getLength();
  QuorumCall<AsyncLogger, Void> qcall = loggers.sendEdits(
    segmentTxId, firstTxToFlush,
    numReadyTxns, data);
  loggers.waitForWriteQuorum(qcall, writeTimeoutMs, "sendEdits");
  
  // Since we successfully wrote this batch, let the loggers know. Any future
  // RPCs will thus let the loggers know of the most recent transaction, even
  // if a logger has fallen behind.
  loggers.setCommittedTxId(firstTxToFlush + numReadyTxns - 1);
 }
}

buf.flushTo(outBuf);
assertEquals(data.length, outBuf.getLength());
assertTrue(buf.isFlushed());
  data.length, buf.countBufferedBytes());
buf.setReadyToFlush();
buf.flushTo(outBuf);