Christopher L. Shannon created AMQ-9343:
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Summary: Reduce inflight transaction memory footprint in KahaDB
Key: AMQ-9343
URL: https://issues.apache.org/jira/browse/AMQ-9343
Project: ActiveMQ
Issue Type: Improvement
Components: KahaDB
Reporter: Christopher L. Shannon
Assignee: Christopher L. Shannon
Fix For: 6.0.0, 5.18.3
When transacted messages are sent KahaDB tracks the inflight and prepared (for
XA) add commands in a map so that when the transaction is eventually committed
the commands can be used to update the KahaDB index. Currently the entire
message is kept inside the map while the transaction is pending. This is not a
problem for small/quick transactions but for transactions that are long running
and/or have a lot of pending (or big) messages before commit this can use up a
decent amount of memory and cause GC pressure.
To reduce memory we can go ahead and just clear the message from the command
after it is stored in the journal. The pending operations that are queued up to
be processed on commit only need metadata from the add command (such as message
id and destination) so the actual messages are no longer needed and can be
cleared. This is a pretty easy change and should help for edge cases with a
large number of pending message sends or big messages.
Note that on broker restart/recovery the messages are loaded again for pending
transactions and processed (such as XA in the prepared state) and the messages
are needed for processing recovery for XA transactions so the memory will be
higher again as the inflight and prepared maps will track the entire message
again (just like before this change) but this should be fine as it is just
during recovery and once finished and the broker is online again it will clear
the new incoming messages.
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