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From "Aleksey Yeschenko (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-9673) Improve batchlog write path
Date Tue, 25 Aug 2015 23:50:46 GMT


Aleksey Yeschenko commented on CASSANDRA-9673:

As for migration, my preference would be to make it happen at the borders only. So I'd ask
you again to move this live upgrade batchlog mutation conversion to {{MutationVerbHandler}},
and away from {{Keyspace::apply}}. The latter is just too deep.

A standalone test for {{LegacyBatchMigrator::converBatchEntries}} would be nice.

I would also prefer to move the whole package to o.a.c.batchlog instead of o.a.c.db.batch.
o.a.c.db is overpopulated, and, frankly, meaningless. I've been depopulating it slowly - with
schema and hints being separate top-level packages already.

> Improve batchlog write path
> ---------------------------
>                 Key: CASSANDRA-9673
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Aleksey Yeschenko
>            Assignee: Stefania
>              Labels: performance
>             Fix For: 3.0 beta 2
>         Attachments: 9673_001.tar.gz, 9673_004.tar.gz, gc_times_first_node_patched_004.png,
> Currently we allocate an on-heap {{ByteBuffer}} to serialize the batched mutations into,
before sending it to a distant node, generating unnecessary garbage (potentially a lot of
> With materialized views using the batchlog, it would be nice to optimise the write path:
> - introduce a new verb ({{Batch}})
> - introduce a new message ({{BatchMessage}}) that would encapsulate the mutations, expiration,
and creation time (similar to {{HintMessage}} in CASSANDRA-6230)
> - have MS serialize it directly instead of relying on an intermediate buffer
> To avoid merely shifting the temp buffer to the receiving side(s) we should change the
structure of the batchlog table to use a list or a map of individual mutations.

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