After some brief discussion in #openstack-nova I've moved this to
oslo.log. The issue here appears to be that we spawn multiple separate
conductor processes writing to the same nova-conductor.log file. We
don't want to stop doing this, as it would break people.
It seems that by default python logging uses thread logs rather than
external locks:
https://docs.python.org/2/library/multiprocessing.html#logging
Suggest the fix might be to explicitly use multiprocessing.get_logger(),
or at least provide an option to do this when we know it's required.
** Project changed: nova => oslo.log
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https://bugs.launchpad.net/bugs/1718439
Title:
Apparent lack of locking in conductor logs
Status in oslo.log:
New
Bug description:
I'm looking at conductor logs generated by a customer running RH OSP
10 (Newton). The logs appear to be corrupt in a manner I'd expect to
see if 2 processes were writing to the same log file simultaneously.
For example:
===
2017-09-14 15:54:39.689 120626 ERROR nova.servicegroup.drivers.db return
self.dbapi.connect(*cargs, **cparams)
2017-09-14 15:54:39.689 120626 ERROR nova.s2017-09-14 15:54:39.690 120562
ERROR nova.servicegroup.drivers.db [-] Unexpected error while reporting service
status
2017-09-14 15:54:39.690 120562 ERROR nova.servicegroup.drivers.db Traceback
(most recent call last):
===
Notice how a new log starts part way through the second line above.
This also results in log entries in the wrong sort order:
===
2017-09-14 15:54:39.690 120562 ERROR nova.servicegroup.drivers.db return
self.dbapi.connect(*cargs, **cparams)
2017-09-14 15:54:39.690 120562 ERROR nova.servicegroup.drivers.db File
"/usr/lib/python2.7/site-packages/pymysql/__init__.py", line 88, in Connect
2017-09-14 15:54:39.689 120626 ERROR nova.servicegroup.drivers.db return
Connection(*args, **kwargs)
2017-09-14 15:54:39.689 120626 ERROR nova.servicegroup.drivers.db File
"/usr/lib/python2.7/site-packages/pymysql/connections.py", line 657, in __init__
===
Note how the first 2 lines are after the last 2 by timestamp, as
presumably the last 2 are a continuation of a previous log entry. This
confounds merge sorting of log files, which is exceptionally useful.
We also see truncated lines with no timestamp which aren't a
continuation of the previous line:
===
2017-09-14 15:54:39.690 120607 ERROR nova.servicegroup.drivers.db
DBConnectionError: (pymysql.err.OperationalError) (2013, 'Lost connection to
MySQL server during query') [SQL: u'SELECT 1']
2017-09-14 15:54:39.690 120607 ERROR nova.servicegroup.drivers.db
elf._execute_and_instances(context)
===
I strongly suspect this is because multiple conductors are running in
separate processes, and are therefore not benefiting from the thread
safety of python's logging.
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