Duo Zhang created HBASE-27632:
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Summary: Refactor WAL.Reader implementation so we can better
support WAL splitting and replication
Key: HBASE-27632
URL: https://issues.apache.org/jira/browse/HBASE-27632
Project: HBase
Issue Type: Improvement
Components: Replication, wal
Reporter: Duo Zhang
WAL splitting and replication has completely different requirements on WAL
reader, the latter one is much comlicated as it wants to tail a WAL file which
is currently being written.
I think split them into two classes is better here.
But we exposes two configurations out
'hbase.regionserver.hlog.reader.impl'
'hbase.regionserver.hlog.writer.impl'
which indicates that we only have one implementation for wal reader.
These two configurations are inrtoduced in 0.96, for reading the pre 0.94
sequence file format WAL file. And starting from 2.0.0, we have already dropped
the support of reading sequence file format WAL file, so I think the
configurations are useless now.
Now we stil require users to specify SecureProtobufLogReader and
SecureProtobufLogWriter when enable WAL encryption, but actually they are both
the only choice, so just use 'hbase.regionserver.wal.encryption' to determine
whether we need to use SecureProtobufLogWriter to write WAL. And for reading, I
do not think we should rely on the configuration, we should detect whether the
WAL file itself is encrypted(I believe we have already done this in
SecureProtobufLogReader.readHeader.
So in general, I prefer we just mark these two configurations deprecated and do
not use them in our code base, so we can have different Reader implementations
for WAL splitting and replication.
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