internal RedundantEditLogInputStream(ICollection <EditLogInputStream> streams, long
startTxId)
{
this.curIdx = 0;
this.prevTxId = (startTxId == HdfsConstants.InvalidTxid) ? HdfsConstants.InvalidTxid
: (startTxId - 1);
this.state = (streams.IsEmpty()) ? RedundantEditLogInputStream.State.Eof : RedundantEditLogInputStream.State
.SkipUntil;
this.prevException = null;
// EditLogInputStreams in a RedundantEditLogInputStream must be finalized,
// and can't be pre-transactional.
EditLogInputStream first = null;
foreach (EditLogInputStream s in streams)
{
Preconditions.CheckArgument(s.GetFirstTxId() != HdfsConstants.InvalidTxid, "invalid first txid in stream: %s"
, s);
Preconditions.CheckArgument(s.GetLastTxId() != HdfsConstants.InvalidTxid, "invalid last txid in stream: %s"
, s);
if (first == null)
{
first = s;
}
else
{
Preconditions.CheckArgument(s.GetFirstTxId() == first.GetFirstTxId(), "All streams in the RedundantEditLogInputStream must have the same "
+ "start transaction ID! " + first + " had start txId " + first.GetFirstTxId()
+ ", but " + s + " had start txId " + s.GetFirstTxId());
}
}
this.streams = Sharpen.Collections.ToArray(streams, new EditLogInputStream[0]);
// We sort the streams here so that the streams that end later come first.
Arrays.Sort(this.streams, new _IComparer_117());
}
protected internal override FSEditLogOp NextValidOp()
{
try
{
if (state == RedundantEditLogInputStream.State.StreamFailed)
{
state = RedundantEditLogInputStream.State.StreamFailedResync;
}
return(NextOp());
}
catch (IOException)
{
return(null);
}
}
/// <exception cref="System.IO.IOException"/>
protected internal override FSEditLogOp NextOp()
{
while (true)
{
switch (state)
{
case RedundantEditLogInputStream.State.SkipUntil:
{
try
{
if (prevTxId != HdfsConstants.InvalidTxid)
{
Log.Info("Fast-forwarding stream '" + streams[curIdx].GetName() + "' to transaction ID "
+ (prevTxId + 1));
streams[curIdx].SkipUntil(prevTxId + 1);
}
}
catch (IOException e)
{
prevException = e;
state = RedundantEditLogInputStream.State.StreamFailed;
}
state = RedundantEditLogInputStream.State.Ok;
break;
}
case RedundantEditLogInputStream.State.Ok:
{
try
{
FSEditLogOp op = streams[curIdx].ReadOp();
if (op == null)
{
state = RedundantEditLogInputStream.State.Eof;
if (streams[curIdx].GetLastTxId() == prevTxId)
{
return(null);
}
else
{
throw new RedundantEditLogInputStream.PrematureEOFException("got premature end-of-file "
+ "at txid " + prevTxId + "; expected file to go up to " + streams[curIdx].GetLastTxId
());
}
}
prevTxId = op.GetTransactionId();
return(op);
}
catch (IOException e)
{
prevException = e;
state = RedundantEditLogInputStream.State.StreamFailed;
}
break;
}
case RedundantEditLogInputStream.State.StreamFailed:
{
if (curIdx + 1 == streams.Length)
{
throw prevException;
}
long oldLast = streams[curIdx].GetLastTxId();
long newLast = streams[curIdx + 1].GetLastTxId();
if (newLast < oldLast)
{
throw new IOException("We encountered an error reading " + streams[curIdx].GetName
() + ". During automatic edit log " + "failover, we noticed that all of the remaining edit log "
+ "streams are shorter than the current one! The best " + "remaining edit log ends at transaction "
+ newLast + ", but we thought we could read up to transaction " + oldLast + ". If you continue, metadata will be lost forever!"
);
}
Log.Error("Got error reading edit log input stream " + streams[curIdx].GetName()
+ "; failing over to edit log " + streams[curIdx + 1].GetName(), prevException);
curIdx++;
state = RedundantEditLogInputStream.State.SkipUntil;
break;
}
case RedundantEditLogInputStream.State.StreamFailedResync:
{
if (curIdx + 1 == streams.Length)
{
if (prevException is RedundantEditLogInputStream.PrematureEOFException)
{
// bypass early EOF check
state = RedundantEditLogInputStream.State.Eof;
}
else
{
streams[curIdx].Resync();
state = RedundantEditLogInputStream.State.SkipUntil;
}
}
else
{
Log.Error("failing over to edit log " + streams[curIdx + 1].GetName());
curIdx++;
state = RedundantEditLogInputStream.State.SkipUntil;
}
break;
}
case RedundantEditLogInputStream.State.Eof:
{
return(null);
}
}
}
}
