[openstack-dev] Can we get some sanity in the Neutron logs please?

Armando M. armamig at gmail.com
Tue Nov 10 18:51:33 UTC 2015


On 10 November 2015 at 10:33, Matt Riedemann <mriedem at linux.vnet.ibm.com>
wrote:

> Let me qualify by saying I'm not a Neutron person.
>
> We know that gate-tempest-dsvm-neutron-full is failing hard as of the last
> 24 hours [1].
>
> An error that's been showing up in tempest runs with neutron a lot is:
>
> "AssertionError: 0 == 0 : No IPv4 addresses found in: []"
>
> So checking logstash [2] it's hitting a lot. It's only recent because that
> failure message is new to Tempest in the last day or so, but it has a lot
> of hits, so whatever it is, it's failing a lot.
>
> So the next step is usually digging into service logs looking for errors.
> I check the q-svc logs first. Not many errors but a bazillion warnings for
> things not found (networks and devices). [3]
>
> For example:
>
> 2015-11-10 17:13:02.542 WARNING neutron.plugins.ml2.rpc
> [req-15a73753-1512-4689-9404-9658a0cd0c09 None None] Device
> aaa525be-14eb-44a5-beb0-ed722896be93 requested by agent
> ovs-agent-devstack-trusty-rax-iad-5785199 not found in database
>
> 2015-11-10 17:14:17.754 WARNING neutron.api.rpc.handlers.dhcp_rpc
> [req-3d7e9848-6151-4780-907f-43f11a2a8545 None None] Network
> b07ad9b2-e63e-4459-879d-3721074704e5 could not be found, it might have been
> deleted concurrently.
>
> Are several hundred of these warnings useful to an operator trying to
> debug a problem? The point of the CI gate testing is to try and simulate a
> production cloud environment. When something goes wrong, you check the
> logs. With the amount of warning/error level logging that is in the neutron
> logs, finding a real problem is like looking for a needle in a haystack.
> Since everything is async, 404s are expected when racing to delete a
> resource and they should be handled gracefully.
>
> Anyway, the server log isn't useful so I go digging in the agent logs and
> stacktraces there are aplenty. [4]
>
> Particularly this:
>
> "Exception: Port tapcea51630-e1 is not ready, resync needed"
>
> That's due to a new change landing in the last 24 hours [5]. But the trace
> shows up over 16K times since it landed [6].
>
> Checking the code, it's basically a loop processing events and when it
> hits an event it can't handle, it punts (breaking the loop so you don't
> process the other events after it - which is a bug), and the code that
> eventually handles it is just catching all Exception and tracing them out
> assuming they are really bad.
>
> At this point, as a non-neutron person, i.e. not well versed in the
> operations of neutron or how to debug it in great detail, I assume
> something is bad here but I don't really know - and the logs are so full of
> noise that I can't distinguish real failures.
>
> I don't mean to pick on this particular change, but it's a good example of
> a recent thing.
>
> I'd like to know if this is all known issue or WIP type stuff. I've
> complained about excessively noisey neutron logs in channel before and I'm
> usually told that they are either necessary (for whatever reason) or that
> rather than complain about the verbosity, I should fix the race that is
> causing it - which is not likely to happen since I don't have the async rpc
> happy nature of everything in neutron in my head to debug it (I doubt many
> do).
>

I am not sure that's a fair statement: we usually pinpoint that just
lowering log levels is not really solving the underlying issue (whichever
it may be), and that comment really should apply to any project, not just
Neutron. That said, we had examples where we took your input and drove the
right fix ourselves.

We have a 'logging' tag for Neutron bugs that we use to identify these type
of cleanups. We'd need your attention to details to alert us of issues like
these; we'll take care of the right fixes. Currently, the queue is pretty
dry. If you can top it up, that'll be great. Going off on a log cleanup
rampage doesn't seem like the best course of action; I'd rather knock
issues one by one as they come, like the one you just mentioned.

[1] https://bugs.launchpad.net/neutron/+bugs?field.tag=logging


>
> Anyway, this is a plea for sanity in the logs. There are logging
> guidelines for openstack [7]. Let's please abide by them. Let's keep
> operators in mind when we're looking at logs and be proactive about making
> them useful (which includes more granular error handling and less global
> try/except Exception: LOG.exception constructs).
>

Your point is duly noted. We have documented this, and we are being more
meticulous during reviews.


> [1] http://tinyurl.com/ne3ex4v
> [2]
> http://logstash.openstack.org/#dashboard/file/logstash.json?query=message:%5C%22AssertionError:%200%20==%200%20:%20No%20IPv4%20addresses%20found%20in:%20%5B%5D%5C%22%20AND%20tags:%5C%22console%5C%22
> [3]
> http://logs.openstack.org/85/239885/2/gate/gate-tempest-dsvm-neutron-full/602d864/logs/screen-q-svc.txt.gz?level=TRACE
> [4]
> http://logs.openstack.org/85/239885/2/gate/gate-tempest-dsvm-neutron-full/602d864/logs/screen-q-agt.txt.gz?level=TRACE
> [5] https://review.openstack.org/#/c/164880/
> [6]
> http://logstash.openstack.org/#dashboard/file/logstash.json?query=message:%5C%22Exception:%20Port%5C%22%20AND%20message:%5C%22is%20not%20ready,%20resync%20needed%5C%22%20AND%20tags:%5C%22screen-q-agt.txt%5C%22
> [7]
> http://specs.openstack.org/openstack/openstack-specs/specs/log-guidelines.html
>
> --
>
> Thanks,
>
> Matt Riedemann
>
>
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