ifacemgr: remove stale connections on startup

[stolowski]

Remove stale conns left from old snapd releases at startup; I decided to do that in separate method rather than in reloadConnections to have it isolated.

[zyga]

Nitpick: use past tense please, removed. Alternatively we could log the actually deleted connections because after seeing this message I will only wonder, "gee which connections were removed?"

[zyga]

LGTM but please add a unit test first.

[zyga]

There are some real test failures from unit tests affected by this feature:

----------------------------------------------------------------------
FAIL: ifacestate_test.go:2147: interfaceManagerSuite.TestCoreConnectionsRenamed

ifacestate_test.go:2176:
    c.Assert(conns, DeepEquals, map[string]interface{}{
        "core:core-support-plug core:core-support": map[string]interface{}{
            "interface": "core-support", "auto": true,
        },
        "snap:unrelated core:unrelated": map[string]interface{}{
            "interface": "unrelated", "auto": true,
        },
    })
... obtained map[string]interface {} = map[string]interface {}{}
... expected map[string]interface {} = map[string]interface {}{"core:core-support-plug core:core-support":map[string]interface {}{"interface":"core-support", "auto":true}, "snap:unrelated core:unrelated":map[string]interface {}{"interface":"unrelated", "auto":true}}


----------------------------------------------------------------------
FAIL: ifacestate_test.go:1513: interfaceManagerSuite.TestDoDiscardConnsPlug

ifacestate_test.go:1514:
    s.testDoDicardConns(c, "consumer")
ifacestate_test.go:1563:
    c.Check(removed, DeepEquals, map[string]interface{}{
        "consumer:plug producer:slot": map[string]interface{}{"interface": "test"},
    })
... obtained map[string]interface {} = map[string]interface {}{}
... expected map[string]interface {} = map[string]interface {}{"consumer:plug producer:slot":map[string]interface {}{"interface":"test"}}


----------------------------------------------------------------------
FAIL: ifacestate_test.go:1517: interfaceManagerSuite.TestDoDiscardConnsSlot

ifacestate_test.go:1518:
    s.testDoDicardConns(c, "producer")
ifacestate_test.go:1563:
    c.Check(removed, DeepEquals, map[string]interface{}{
        "consumer:plug producer:slot": map[string]interface{}{"interface": "test"},
    })
... obtained map[string]interface {} = map[string]interface {}{}
... expected map[string]interface {} = map[string]interface {}{"consumer:plug producer:slot":map[string]interface {}{"interface":"test"}}


----------------------------------------------------------------------
FAIL: ifacestate_test.go:654: interfaceManagerSuite.TestStrayConnectionsIgnored

ifacestate_test.go:684:
    c.Assert(logLines, HasLen, 2)
... obtained []string = []string{"2018/04/03 13:01:38.510085 helpers.go:292: removed stale connections: consumer:plug producer:slot", "2018/04/03 13:01:38.510644 helpers.go:146: error trying to compare the snap system key: system-key missing on disk", ""}
... n int = 2


----------------------------------------------------------------------
FAIL: ifacestate_test.go:1521: interfaceManagerSuite.TestUndoDiscardConnsPlug

ifacestate_test.go:1522:
    s.testUndoDicardConns(c, "consumer")
ifacestate_test.go:1609:
    c.Check(conns, DeepEquals, map[string]interface{}{
        "consumer:plug producer:slot": map[string]interface{}{"interface": "test"},
    })
... obtained map[string]interface {} = map[string]interface {}{}
... expected map[string]interface {} = map[string]interface {}{"consumer:plug producer:slot":map[string]interface {}{"interface":"test"}}


----------------------------------------------------------------------
FAIL: ifacestate_test.go:1525: interfaceManagerSuite.TestUndoDiscardConnsSlot

ifacestate_test.go:1526:
    s.testUndoDicardConns(c, "producer")
ifacestate_test.go:1609:
    c.Check(conns, DeepEquals, map[string]interface{}{
        "consumer:plug producer:slot": map[string]interface{}{"interface": "test"},
    })
... obtained map[string]interface {} = map[string]interface {}{}
... expected map[string]interface {} = map[string]interface {}{"consumer:plug producer:slot":map[string]interface {}{"interface":"test"}}

[zyga]

We cannot land this before we fix the other bug (the one when snapd starts and there are no interfaces at all) because we would remove all of the stored connections in that case.

[codecov-io]

Codecov Report

Merging #4968 into master will decrease coverage by 0.02%.
The diff coverage is 53.57%.

@@            Coverage Diff             @@
##           master    #4968      +/-   ##
==========================================
- Coverage   79.05%   79.03%   -0.03%     
==========================================
  Files         489      489              
  Lines       36656    36684      +28     
==========================================
+ Hits        28980    28993      +13     
- Misses       5385     5394       +9     
- Partials     2291     2297       +6

Impacted Files	Coverage Δ
overlord/ifacestate/helpers.go	65.38% <53.57%> (-1.29%)	⬇️
overlord/hookstate/hookmgr.go	74.87% <0%> (-1.03%)	⬇️

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[zyga]

I don't think this is blocked anymore. We should merge mater to see that it passes and merge this branch.