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From "Alan Conway" <acon...@redhat.com>
Subject Re: Review Request 17563: QPID-5528: HA Clean up error messages around rolled-back transactions.
Date Thu, 30 Jan 2014 23:14:17 GMT

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/17563/
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(Updated Jan. 30, 2014, 11:14 p.m.)


Review request for qpid and Gordon Sim.


Bugs: QPID-5528
    https://issues.apache.org/jira/browse/QPID-5528


Repository: qpid


Description
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QPID-5528: HA Clean up error messages around rolled-back transactions.

A simple transaction test generates a lot of errors and rollback notices in the
broker logs even though the test code never rolls back a transaction. E.g.

  qpid-cluster-benchmark -b 20.0.20.200 -n1 -m 1000 -q3 -s2 -r2 --send-arg=--tx --send-arg=10
--receive-arg=--tx --receive-arg=10

The errors are caused by queues being deleted while backup brokers are using
them. This happens a lot in the transaction test because a transactional session
must create a new transaction when the previous one closes. When the session
closes the open transaction is rolled back automatically. Thus there is almost
always an empty transaction that is created then immediately rolled back at the
end of the session. Backup brokers may still be in the process of subscribing to
the transaction's replication queue at this point, causing (harmlesss) errors.

We'd like to clean this up completely but unfortunately there are some error
messages that are not easy to remove. This commit does the following:

- Remove misleading "backup disconnected" message for cancelled transactions.
- Include TxReplicator destroy in QueueReplicator mutex. Idempotence check before any destroy.
- Remove spurious warning about ignored unreplicated dequeues.
- Remove log messages about rolling back/destroying empty transactions.
- Log incoming execution exceptions as errors to explain subsequent session detached errors.

There should be no more unexpected log messages about rollbacks since we no
longer log rollback of an empty transaction.

The following errors remain, they are harmless and can be ignored. They are not
necessarily related to transactions and can occur in other situations where
queues are deleted while still replicating.

Queue deleted, replication in progress (happens in the test, not related to TX)

On primary, the following errors:
- [Protocol] error Incoming Execution exception: not-found: Exchange not found: qpid.ha-q:...
- [Protocol] error Channel exception: not-attached: Channel xxx is not attached

On backup:
- [Protocol] error Execution exception: not-found: Exchange not found: qpid.ha-q:...

Queue deleted while backup is in the process of subscribing (in the test happens
because of empty tx)

On primary:
 [Protocol] error Execution exception: not-found: Queue not found: qpid.ha-tx:...

On backup:
[Broker] error Incoming execution exception: not-found: Queue not found: qpid.ha-tx:...

Note the "Incoming exception exception" error was actually added by this commit,
since otherwise there's no way to tell the cause of the "channel not attached"
errors.

This is not a satisfactory situation. The "harmless" error messages might
sometimes indicate real error situations and the clutter makes debugging
harder. I will leave this JIRA open for now and try to come up with a better
solution.


Diffs
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  /trunk/qpid/cpp/src/qpid/Exception.cpp 1562539 
  /trunk/qpid/cpp/src/qpid/broker/SessionAdapter.cpp 1562539 
  /trunk/qpid/cpp/src/qpid/ha/PrimaryTxObserver.h 1562539 
  /trunk/qpid/cpp/src/qpid/ha/PrimaryTxObserver.cpp 1562539 
  /trunk/qpid/cpp/src/qpid/ha/QueueReplicator.h 1562539 
  /trunk/qpid/cpp/src/qpid/ha/QueueReplicator.cpp 1562539 
  /trunk/qpid/cpp/src/qpid/ha/TxReplicator.h 1562539 
  /trunk/qpid/cpp/src/qpid/ha/TxReplicator.cpp 1562539 

Diff: https://reviews.apache.org/r/17563/diff/


Testing
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Thanks,

Alan Conway


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