While discussing how to deal with the problem in HBASE-27621, we proposed to introduce two types of WAL readers, one for WAL splitting, and the other for WAL replication, as replication needs to tail the WAL file which is currently being written, so the logic is much more complicated. We do not want to affect WAL splitting logic and performance while tweaking the replication related things, as all HBase users need WAL splitting but not everyone needs replication.
But when reviewing the related code, I found that we have two configurations for specifying the WAL reader class and WAL write class, which indicates that we could only have one implementation for the WAL reader. They are 'hbase.regionserver.hlog.reader.impl' and 'hbase.regionserver.hlog.writer.impl'. We mentioned these two configurations several times in our ref guide. HBase 2.0+ can no longer read Sequence File based WAL file. HBase can no longer read the deprecated WAL files written in the Apache > Hadoop Sequence File format. The hbase.regionserver.hlog.reader.impl and > hbase.regionserver.hlog.writer.impl configuration entries should be set to > use the Protobuf based WAL reader / writer classes. This implementation has > been the default since HBase 0.96, so legacy WAL files should not be a > concern for most downstream users. Configure WAL encryption. Configure WAL encryption in every RegionServer’s hbase-site.xml, by setting > the following properties. You can include these in the HMaster’s > hbase-site.xml as well, but the HMaster does not have a WAL and will not > use them. > <property> > <name>hbase.regionserver.hlog.reader.impl</name> > > <value>org.apache.hadoop.hbase.regionserver.wal.SecureProtobufLogReader</value> > </property> > <property> > <name>hbase.regionserver.hlog.writer.impl</name> > > <value>org.apache.hadoop.hbase.regionserver.wal.SecureProtobufLogWriter</value> > </property> > <property> > <name>hbase.regionserver.wal.encryption</name> > <value>true</value> > </property> So in fact, do not consider encryption, the configurations are useless as we do not support reading sequence file format WAL any more, the only valid options are protobuf based reader and write. And for security, I think the configuration is redundant as if encryption is enabled, we should use SecureProtobufLogWriter for writing, no matter what the configuration value is. And for readers, I do not think we should use a configuration to specify the implementation, we should detect whether the file is encrypted and choose a secure or normal reader to read the file. So here, I propose we just deprecated these two configurations because they are useless now. Thanks.
