/// <summary>
/// Write out a header to the given stream that indicates the chosen
/// compression codec, and return the same stream wrapped with that codec.
/// </summary>
/// <remarks>
/// Write out a header to the given stream that indicates the chosen
/// compression codec, and return the same stream wrapped with that codec.
/// If no codec is specified, simply adds buffering to the stream, so that
/// the returned stream is always buffered.
/// </remarks>
/// <param name="os">
/// The stream to write header to and wrap. This stream should
/// be unbuffered.
/// </param>
/// <returns>
/// A stream wrapped with the specified compressor, or buffering
/// if compression is not enabled.
/// </returns>
/// <exception cref="System.IO.IOException">
/// if an IO error occurs or the compressor cannot be
/// instantiated
/// </exception>
internal virtual DataOutputStream WriteHeaderAndWrapStream(OutputStream os)
{
DataOutputStream dos = new DataOutputStream(os);
dos.WriteBoolean(imageCodec != null);
if (imageCodec != null)
{
string codecClassName = imageCodec.GetType().GetCanonicalName();
Text.WriteString(dos, codecClassName);
return(new DataOutputStream(imageCodec.CreateOutputStream(os)));
}
else
{
// use a buffered output stream
return(new DataOutputStream(new BufferedOutputStream(os)));
}
}
/// <exception cref="System.IO.IOException"/>
private void SaveInternal(FileOutputStream fout, FSImageCompression compression,
string filePath)
{
StartupProgress prog = NameNode.GetStartupProgress();
MessageDigest digester = MD5Hash.GetDigester();
underlyingOutputStream = new DigestOutputStream(new BufferedOutputStream(fout), digester
);
underlyingOutputStream.Write(FSImageUtil.MagicHeader);
fileChannel = fout.GetChannel();
FsImageProto.FileSummary.Builder b = FsImageProto.FileSummary.NewBuilder().SetOndiskVersion
(FSImageUtil.FileVersion).SetLayoutVersion(NameNodeLayoutVersion.CurrentLayoutVersion
);
codec = compression.GetImageCodec();
if (codec != null)
{
b.SetCodec(codec.GetType().GetCanonicalName());
sectionOutputStream = codec.CreateOutputStream(underlyingOutputStream);
}
else
{
sectionOutputStream = underlyingOutputStream;
}
SaveNameSystemSection(b);
// Check for cancellation right after serializing the name system section.
// Some unit tests, such as TestSaveNamespace#testCancelSaveNameSpace
// depends on this behavior.
context.CheckCancelled();
Step step = new Step(StepType.Inodes, filePath);
prog.BeginStep(Phase.SavingCheckpoint, step);
SaveInodes(b);
SaveSnapshots(b);
prog.EndStep(Phase.SavingCheckpoint, step);
step = new Step(StepType.DelegationTokens, filePath);
prog.BeginStep(Phase.SavingCheckpoint, step);
SaveSecretManagerSection(b);
prog.EndStep(Phase.SavingCheckpoint, step);
step = new Step(StepType.CachePools, filePath);
prog.BeginStep(Phase.SavingCheckpoint, step);
SaveCacheManagerSection(b);
prog.EndStep(Phase.SavingCheckpoint, step);
SaveStringTableSection(b);
// We use the underlyingOutputStream to write the header. Therefore flush
// the buffered stream (which is potentially compressed) first.
FlushSectionOutputStream();
FsImageProto.FileSummary summary = ((FsImageProto.FileSummary)b.Build());
SaveFileSummary(underlyingOutputStream, summary);
underlyingOutputStream.Close();
savedDigest = new MD5Hash(digester.Digest());
}
