Josh Elser created HBASE-21544:
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Summary: WAL writer for recovered.edits file in WalSplitting
should not require hflush from filesystem
Key: HBASE-21544
URL: https://issues.apache.org/jira/browse/HBASE-21544
Project: HBase
Issue Type: Bug
Components: wal
Reporter: Josh Elser
Assignee: Josh Elser
Fix For: 3.0.0, 2.2.0, 2.1.2, 2.0.4
Been talking through this with a bunch of folks. [~enis] brought me back from
the cliff of despair though.
Context: running HBase on top of a filesystem that doesn't have hflush for
hfiles. In our case, on top of Azure's Hadoop-compatible filesystems (WASB,
ABFS).
When a RS fails and we have an SCP running for it, you'll see log splitting get
into an "infinite" loop where the master keeps resubmitting and the RS which
takes the action deterministically fails with the following:
{noformat}
2018-11-26 20:59:18,415 ERROR
[RS_LOG_REPLAY_OPS-regionserver/wn2-b831f9:16020-0-Writer-2]
wal.FSHLogProvider: The RegionServer write ahead log provider for FileSystem
implementations relies on the ability to call hflush for proper operation
during component failures, but the current FileSystem does not support doing
so. Please check the config value of 'hbase.wal.dir' and ensure it points to a
FileSystem mount that has suitable capabilities for output streams.
2018-11-26 20:59:18,415 WARN
[RS_LOG_REPLAY_OPS-regionserver/wn2-b831f9:16020-0-Writer-2]
wal.AbstractProtobufLogWriter: WALTrailer is null. Continuing with default.
2018-11-26 20:59:18,467 ERROR
[RS_LOG_REPLAY_OPS-regionserver/wn2-b831f9:16020-0-Writer-2] wal.WALSplitter:
Got while writing log entry to log
java.io.IOException: cannot get log writer
at
org.apache.hadoop.hbase.wal.FSHLogProvider.createWriter(FSHLogProvider.java:96)
at
org.apache.hadoop.hbase.wal.FSHLogProvider.createWriter(FSHLogProvider.java:61)
at
org.apache.hadoop.hbase.wal.WALFactory.createRecoveredEditsWriter(WALFactory.java:370)
at
org.apache.hadoop.hbase.wal.WALSplitter.createWriter(WALSplitter.java:804)
at
org.apache.hadoop.hbase.wal.WALSplitter$LogRecoveredEditsOutputSink.createWAP(WALSplitter.java:1530)
at
org.apache.hadoop.hbase.wal.WALSplitter$LogRecoveredEditsOutputSink.getWriterAndPath(WALSplitter.java:1501)
at
org.apache.hadoop.hbase.wal.WALSplitter$LogRecoveredEditsOutputSink.appendBuffer(WALSplitter.java:1584)
at
org.apache.hadoop.hbase.wal.WALSplitter$LogRecoveredEditsOutputSink.append(WALSplitter.java:1566)
at
org.apache.hadoop.hbase.wal.WALSplitter$WriterThread.writeBuffer(WALSplitter.java:1090)
at
org.apache.hadoop.hbase.wal.WALSplitter$WriterThread.doRun(WALSplitter.java:1082)
at
org.apache.hadoop.hbase.wal.WALSplitter$WriterThread.run(WALSplitter.java:1052)
Caused by:
org.apache.hadoop.hbase.util.CommonFSUtils$StreamLacksCapabilityException:
hflush
at
org.apache.hadoop.hbase.regionserver.wal.ProtobufLogWriter.initOutput(ProtobufLogWriter.java:99)
at
org.apache.hadoop.hbase.regionserver.wal.AbstractProtobufLogWriter.init(AbstractProtobufLogWriter.java:165)
at
org.apache.hadoop.hbase.wal.FSHLogProvider.createWriter(FSHLogProvider.java:77)
... 10 more{noformat}
This is the sanity check added by HBASE-18784, failing on creating the writer
for the recovered.edits file.
The odd-ball here is that our recovered.edits writer is just a WAL writer
class. The WAL writer class thinks it always should have hflush support;
however, we don't _actually_ need that for writing out the recovered.edits
files. If {{close()}} on the recovered.edits file would fail, we're trash any
intermediate data in the filesystem and rerun the whole process.
It's my understanding that this check is over-bearing and we should not make
the check when the ProtobufLogWriter is being used for the recovered.edits file.
[~zyork], [~busbey] fyi
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