Good catch John, and good work Angus! ;) This will save a lot of headaches.
----- Original Message ----- > On Mon, 8 Sep 2014 05:25:22 PM Jay Pipes wrote: > > On 09/07/2014 10:43 AM, Matt Riedemann wrote: > > > On 9/7/2014 8:39 AM, John Schwarz wrote: > > >> Hi, > > >> > > >> Long story short: for future reference, if you initialize an eventlet > > >> Timeout, make sure you close it (either with a context manager or simply > > >> timeout.close()), and be extra-careful when writing tests using > > >> eventlet Timeouts, because these timeouts don't implicitly expire and > > >> will cause unexpected behaviours (see [1]) like gate failures. In our > > >> case this caused non-deterministic failures on the dsvm-functional test > > >> suite. > > >> > > >> > > >> Late last week, a bug was found ([2]) in which an eventlet Timeout > > >> object was initialized but not closed. This instance was left inside > > >> eventlet's inner-workings and triggered non-deterministic "Timeout: 10 > > >> seconds" errors and failures in dsvm-functional tests. > > >> > > >> As mentioned earlier, initializing a new eventlet.timeout.Timeout > > >> instance also registers it to inner mechanisms that exist within the > > >> library, and the reference remains there until it is explicitly removed > > >> (and not until the scope leaves the function block, as some would have > > >> thought). Thus, the old code (simply creating an instance without > > >> assigning it to a variable) left no way to close the timeout object. > > >> This reference remains throughout the "life" of a worker, so this can > > >> (and did) effect other tests and procedures using eventlet under the > > >> same process. Obviously this could easily effect production-grade > > >> systems with very high load. > > >> > > >> For future reference: > > >> 1) If you run into a "Timeout: %d seconds" exception whose traceback > > >> > > >> includes "hub.switch()" and "self.greenlet.switch()" calls, there might > > >> be a latent Timeout somewhere in the code, and a search for all > > >> eventlet.timeout.Timeout instances will probably produce the culprit. > > >> > > >> 2) The setup used to reproduce this error for debugging purposes is a > > >> > > >> baremetal machine running a VM with devstack. In the baremetal machine I > > >> used some 6 "dd if=/dev/zero of=/dev/null" to simulate high CPU load > > >> (full command can be found at [3]), and in the VM I ran the > > >> dsvm-functional suite. Using only a VM with similar high CPU simulation > > >> fails to produce the result. > > >> > > >> [1] > > >> http://eventlet.net/doc/modules/timeout.html#eventlet.timeout.eventlet.ti > > >> meout.Timeout.Timeout.cancel > > >> > > >> [2] https://review.openstack.org/#/c/119001/ > > >> [3] > > >> http://stackoverflow.com/questions/2925606/how-to-create-a-cpu-spike-with > > >> -a-bash-command > > >> > > >> > > >> > > >> -- > > >> John Schwarz, > > >> Software Engineer, Red Hat. > > >> > > >> > > >> _______________________________________________ > > >> OpenStack-dev mailing list > > >> OpenStack-dev@lists.openstack.org > > >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > > > > > Thanks, that might be what's causing this timeout/gate failure in the > > > nova unit tests. [1] > > > > > > [1] https://bugs.launchpad.net/nova/+bug/1357578 > > > > Indeed, there are a couple places where eventlet.timeout.Timeout() seems > > to be used in the test suite without a context manager or calling > > close() explicitly: > > > > tests/virt/libvirt/test_driver.py > > 8925: raise eventlet.timeout.Timeout() > > > > tests/virt/hyperv/test_vmops.py > > 196: mock_with_timeout.side_effect = etimeout.Timeout() > > If it's useful for anyone, I wrote a quick pylint test that will catch all > the > above cases of "misused" context managers. > > (Indeed, it will currently trigger on the "raise Timeout()" case, which is > probably too eager but can be disabled in the usual #pylint meta-comment way) > > Here: https://review.openstack.org/#/c/120320/ > > -- > - Gus > > _______________________________________________ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > _______________________________________________ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
