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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-13983) Support a means of logging all queries as they were invoked
Date Tue, 31 Oct 2017 18:03:00 GMT
Ariel Weisberg created CASSANDRA-13983:
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             Summary: Support a means of logging all queries as they were invoked
                 Key: CASSANDRA-13983
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13983
             Project: Cassandra
          Issue Type: New Feature
          Components: CQL, Observability, Testing, Tools
            Reporter: Ariel Weisberg
            Assignee: Ariel Weisberg
             Fix For: 4.0


For correctness testing it's useful to be able to capture production traffic so that it can
be replayed against both the old and new versions of Cassandra while comparing the results.

Implementing this functionality once inside the database is high performance and presents
less operational complexity.

In [this patch|https://github.com/apache/cassandra/compare/trunk...aweisberg:fql-trunk-temp?expand=1]
there is an implementation of a full query log that logs uses chronicle-queue (apache licensed,
the maven artifacts are labeled incorrectly in some cases, dependencies are also apache licensed)
to implement a rotating log of queries.

* Single thread asynchronously writes log entries to disk to reduce impact on query latency
* Heap memory usage bounded by a weighted queue with configurable maximum weight sitting in
front of logging thread
* If the weighted queue is full producers can be blocked or samples can be dropped
* Disk utilization is bounded by deleting old log segments once a configurable size is reached
* The on disk serialization uses a flexible schema binary format (chronicle-wire) making it
easy to skip unrecognized fields, add new ones, and omit old ones.
* Can be enabled and configured via JMX, disabled, and reset (delete on disk data), logging
path is configurable via both JMX and YAML
* Introduce new {{fqltool}} in /bin that currently implements {{Dump}} which can dump in a
human readable format full query logs as well as follow active full query logs

Follow up work:
* Introduce new {{fqltool}} command Replay which can replay N full query logs to two different
clusters and compare the result and check for inconsistencies. <- Actively working on getting
this done
* Log not just queries but their results to facilitate a comparison between the original query
result and the replayed result. <- Really just don't have specific use case at the moment
* "Consistent" query logging allowing replay to fully replicate the original order of execution
and completion even in the face of races (including CAS). <- This is more speculative



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