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From "Stefania (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9673) Improve batchlog write path
Date Tue, 25 Aug 2015 01:55:46 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14710437#comment-14710437
] 

Stefania commented on CASSANDRA-9673:
-------------------------------------

This is done, I'm just waiting for the CI results:

http://cassci.datastax.com/view/Dev/view/stef1927/job/stef1927-9673-3.0-dtest/
http://cassci.datastax.com/view/Dev/view/stef1927/job/stef1927-9673-3.0-testall/

You are correct, the previous strategy was to handle legacy mutations by invoking {{LegacyBatchMigrator.convertBatchEntries}}
every time before replaying: 

_For replaying legacy mutations, I've opted for a conversion done before replaying, which
is not very efficient, but keeps the code clean. I figured mixed version clusters are transient
but if it concerns you I can enhance it._

I changed it so that legacy mutations are converted on-the-fly before being applied.

I created a new class, {{Batch}}, and moved the {{BatchStoreMessage}} logic there, so the
messages are only concerned with serialization. The static remove method, I actually prefer
to have it in {{Batch}} rather than {{BatchLogManager}} but you can move it if you prefer
it in {{BatchlogManager}}. The remaining nits should also be addressed.

> Improve batchlog write path
> ---------------------------
>
>                 Key: CASSANDRA-9673
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9673
>             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,
gc_times_first_node_trunk_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
it).
> 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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