test_always_same_order in TestOrdered in deployment_graph.py fails randomly

[Maciej Kwiek]

./run_tests.sh -t nailgun/nailgun/test/unit/test_graph_serializer.py::TestOrdered::test_always_same_order sometimes fails, sometimes don't.

Error is:
    def test_always_same_order(self):
        self.assertEqual(
            [n['id'] for n in self.graph.topology],
> ['a', 'c', 'b', 'd', 'e'])
E AssertionError: Lists differ: ['a', 'd', 'c', 'b', 'e'] != ['a', 'c', 'b', 'd', 'e']
E
E First differing element 1:
E d
E c
E
E - ['a', 'd', 'c', 'b', 'e']
E + ['a', 'c', 'b', 'd', 'e']

It seems that inner structure of graph is not completely deterministic and in some cases may be sorted in a wrong way (`nx.topological_sort` call in `topology` property of `DeploymentGraph` class.

My proposal for a fix: make TASKS graph definition in the test linear (but I don't know why the test was there to begin with, so this may not be a proper approach).

It is possible to reproduce this on master on commit a3c259a4875787274fa01f0eba6514cc01b34308

[Dima Shulyak (dshulyak)]

Topology should be deterministic, that is why i added

 https://github.com/stackforge/fuel-web/blob/master/nailgun/nailgun/orchestrator/deployment_graph.py#L56

The problem is that dictionaries are used for internal data structures

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/169896

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/169896
Committed: https://git.openstack.org/cgit/stackforge/fuel-web/commit/?id=a1310a1f18b5bc3feaa6e4aca12948e661bf93f1
Submitter: Jenkins
Branch: master

commit a1310a1f18b5bc3feaa6e4aca12948e661bf93f1
Author: Dmitry Shulyak <email address hidden>
Date: Wed Apr 1 12:26:36 2015 -0700

    Fix issue with non-determenistic ordering in networkx sorting

    In current master of networkx it is possible to specify fabric
    that will be used for internal graph data structures.

    To avoid non determinitic issues with ordering we need to use
    OrderedDict that will return same order of keys even with different
    hash seeds. OrderedDict should be used for storing order of
    nodes inserted in graph, and for dependencies between nodes
    in graph.

    Changed tests to verify that order will be same with different
    hash seeds.

    Networkx 1.9.1 (one which we are using)

      http://bit.ly/1CcgdBs

    Networkx change with fixed code

      http://bit.ly/1al6Tpq

    Change-Id: I16a880fe996a03645c0f79e3156ae403b9f006f5
    Closes-Bug: 1438203