Use of parse.urlencode with dict in nova/tests/unit/scheduler/client/test_report.py can result in unpredictable query strings and thus unreliable tests

[Chris Dent]

In nova/tests/unit/scheduler/client/test_report.py there are several tests which confirm the URLs that get passed to the placement service. These create query strings by using code like:

        expected_url = '/allocation_candidates?%s' % parse.urlencode(
            {'resources': 'MEMORY_MB:1024,VCPU:1',
             'required': 'CUSTOM_TRAIT1',
             'limit': 1000})

This results in a query string that will have an unpredictable order. Similarly, the code which is doing the actual query string creation is using the same form.

Most of the time the results are the same, and the tests pass, but sometimes they do not.

There are at least two potential ways to work around this:

* build the query strings using a sequence of tuples and set the 'doseq' param to urlencode to True. This will preserve order.
* Parse the expected_url's query params in the tests back to a dict and compare dicts

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/540420

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/540420
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=cab811b89030d6e49f8ef85e29783fce94c763fc
Submitter: Zuul
Branch: master

commit cab811b89030d6e49f8ef85e29783fce94c763fc
Author: Chris Dent <email address hidden>
Date: Fri Feb 2 15:34:59 2018 +0000

    Don't rely on parse.urlencode in url comparisons

    The tests for allocation_candidates query parameters in test_report.py
    relied on urlencode with a dict arg to create the expected_url that is
    compared with the actual URL that the report client creates when
    communicating with the placement service.

    This is risky because the ordering of the query parameters is
    not reliable when the source data is a dict. This change expands
    the tests where it was used to do more explicit comparisons.

    Change-Id: I2e51a4574b20c0634ad83a53c0e68261bbf0ac82
    Closes-Bug: #1747001

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 17.0.0.0rc1 release candidate.