Hi,
Yair and I were discussing a change that I initiated and was
incorporated into the test_network_basic_ops test. It was intended as a
configuration control point for floating IP address assignments before
actually testing connectivity. The question we were discussing was
whether this check was a valid pass/fail criteria for tests like
test_network_basic_ops.
The initial motivation for the change was that test_network_basic_ops
had a less than 50/50 chance of passing in my local environment for
whatever reason. After looking at the test, it seemed ridiculous that it
should be failing. The problem is that more often than not the data that
was available in the logs all pointed to it being set up correctly but
the ping test for connectivity was timing out. From the logs it wasn't
clear that the test was failing because neutron did not do the right
thing, did not do it fast enough, or is something else happening? Of
course if I paused the test for a short bit between setup and the checks
to manually verify everything the checks always passed. So it's a timing
issue right?
Two things: adding more timeout to a check is as appealing to me as
gargling glass AND I was less "annoyed" that the test was failing as I
was that it wasn't clear from reading logs what had gone wrong. I tried
to find an additional intermediate control point that would "split"
failure modes into two categories: neutron is too slow in setting things
up and neutron failed to set things up correctly. Granted it still is
adding timeout to the test, but if I could find a control point based on
"settling" so that if it passed, then there is a good chance that if the
next check failed it was because neutron actually screwed up what it was
trying to do.
Waiting until the query on the nova for the floating IP information
seemed a relatively reasonable, if imperfect, "settling" criteria before
attempting to connect to the VM. Testing to see if the floating IP
assignment gets to the nova instance details is a valid test and,
AFAICT, missing from the current tests. However, Yair has the reasonable
point that connectivity is often available long before the floating IP
appears in the nova results and that it could be considered invalid to
use non-network specific criteria as pass/fail for this test.
In general, the validity of checking for the presence of a floating IP
in the server details is a matter of interpretation. I think it is a
given that it must be tested somewhere and that if it causes a test to
fail then it is as valid a failure than a ping failing. Certainly I have
seen scenarios where an IP appears, but doesn't actually work and others
where the IP doesn't appear (ever, not just in really long while) but
magically works. Both are bugs. Which is more appropriate to tests like
test_network_basic_ops?
Currently, the polling interval for the checks in the gate should be
tuned. They are borrowing other polling configuration and I can see it
is ill-advised. It is currently polling at an interval of a second and
if the intent is to wait for the entire system to settle down before
proceeding then polling nova that quickly is too often. It simply
increases the load while we are waiting to adapt to a loaded system. For
example in the course of a three minute timeout, the floating IP check
polled nova for server details 180 times.
All this aside it is granted that checking for the floating IP in the
nova instance details is imperfect in itself. There is nothing that
assures that the presence of that information indicates that the
networking backend is done its work.
Comments, suggestions, queries, foam bricks?
Cheers,
Brent
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