Lars Hofhansl created HBASE-9158:
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Summary: Serious bug in cyclic replication
Key: HBASE-9158
URL: https://issues.apache.org/jira/browse/HBASE-9158
Project: HBase
Issue Type: Bug
Affects Versions: 0.94.10, 0.95.1, 0.98.0
Reporter: Lars Hofhansl
Priority: Critical
While studying the code for HBASE-7709, I found a serious bug in the current
cyclic replication code. The problem is here in HRegion.doMiniBatchMutation:
{code}
Mutation first = batchOp.operations[firstIndex].getFirst();
txid = this.log.appendNoSync(regionInfo, this.htableDescriptor.getName(),
walEdit, first.getClusterId(), now, this.htableDescriptor);
{code}
Now note that edits replicated from remote cluster and local edits might
interleave in the WAL, we might also receive edit from multiple remote
clusters. Hence that <walEdit> might have edits from many clusters in it, but
all are just labeled with the clusterId of the first Mutation.
Fixing this in doMiniBatchMutation seems tricky to do efficiently (imagine we
get a batch with cluster1, cluster2, cluster1, cluster2, ..., in that case each
edit would have to be its own batch). The coprocessor handling would also be
difficult.
The other option is create batches of Puts grouped by the cluster id in
ReplicationSink.replicateEntries(...), this is not as general, but equally
correct. This is the approach I would favor.
Lastly this is very hard to verify in a unittest.
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