worker/statushistorypruner: data race

[Dave Cheney]

lucky(~/src/github.com/juju/juju/worker/statushistorypruner) % bash ~/stress.bash
==================
WARNING: DATA RACE
Write by goroutine 18:
  github.com/juju/juju/worker/statushistorypruner_test.(*statusHistoryPrunerSuite).TestWorker.func1()
      /home/dfc/src/github.com/juju/juju/worker/statushistorypruner/worker_test.go:57 +0x3e
  github.com/juju/juju/worker/statushistorypruner.(*pruneWorker).doPruning()
      /home/dfc/src/github.com/juju/juju/worker/statushistorypruner/worker.go:52 +0x97
  github.com/juju/juju/worker/statushistorypruner.(*pruneWorker).(github.com/juju/juju/worker/statushistorypruner.doPruning)-fm()
      /home/dfc/src/github.com/juju/juju/worker/statushistorypruner/worker.go:48 +0x45
  github.com/juju/juju/worker.(*periodicWorker).run()
      /home/dfc/src/github.com/juju/juju/worker/periodicworker.go:86 +0x1a2
  github.com/juju/juju/worker.NewPeriodicWorker.func1()
      /home/dfc/src/github.com/juju/juju/worker/periodicworker.go:73 +0x79

Previous read by goroutine 16:
  github.com/juju/juju/worker/statushistorypruner_test.(*statusHistoryPrunerSuite).TestWorker()
      /home/dfc/src/github.com/juju/juju/worker/statushistorypruner/worker_test.go:84 +0x6b5
  runtime.call32()
      /home/dfc/go/src/runtime/asm_amd64.s:442 +0x3d
  reflect.Value.Call()
      /home/dfc/go/src/reflect/value.go:300 +0xcd
  gopkg.in/check%2ev1.(*suiteRunner).forkTest.func1()
      /home/dfc/src/gopkg.in/check.v1/check.go:772 +0x5e0
  gopkg.in/check%2ev1.(*suiteRunner).forkCall.func1()
      /home/dfc/src/gopkg.in/check.v1/check.go:666 +0x80

Goroutine 18 (running) created at:
  github.com/juju/juju/worker.NewPeriodicWorker()
      /home/dfc/src/github.com/juju/juju/worker/periodicworker.go:74 +0xea
  github.com/juju/juju/worker/statushistorypruner.NewPruneWorker()
      /home/dfc/src/github.com/juju/juju/worker/statushistorypruner/export_test.go:17 +0x1ad
  github.com/juju/juju/worker/statushistorypruner_test.(*statusHistoryPrunerSuite).TestWorker()
      /home/dfc/src/github.com/juju/juju/worker/statushistorypruner/worker_test.go:77 +0x388
  runtime.call32()
      /home/dfc/go/src/runtime/asm_amd64.s:442 +0x3d
  reflect.Value.Call()
      /home/dfc/go/src/reflect/value.go:300 +0xcd
  gopkg.in/check%2ev1.(*suiteRunner).forkTest.func1()
      /home/dfc/src/gopkg.in/check.v1/check.go:772 +0x5e0
  gopkg.in/check%2ev1.(*suiteRunner).forkCall.func1()
      /home/dfc/src/gopkg.in/check.v1/check.go:666 +0x80

Goroutine 16 (running) created at:
  gopkg.in/check%2ev1.(*suiteRunner).forkCall()
      /home/dfc/src/gopkg.in/check.v1/check.go:667 +0x486
  gopkg.in/check%2ev1.(*suiteRunner).forkTest()
      /home/dfc/src/gopkg.in/check.v1/check.go:804 +0x126
  gopkg.in/check%2ev1.(*suiteRunner).runTest()
      /home/dfc/src/gopkg.in/check.v1/check.go:809 +0x38
  gopkg.in/check%2ev1.(*suiteRunner).run()
      /home/dfc/src/gopkg.in/check.v1/check.go:615 +0x481
  gopkg.in/check%2ev1.Run()
      /home/dfc/src/gopkg.in/check.v1/run.go:92 +0x50
  gopkg.in/check%2ev1.RunAll()
      /home/dfc/src/gopkg.in/check.v1/run.go:84 +0x133
  gopkg.in/check%2ev1.TestingT()
      /home/dfc/src/gopkg.in/check.v1/run.go:72 +0x4b5
  github.com/juju/juju/worker/statushistorypruner_test.TestPackage()
      /home/dfc/src/github.com/juju/juju/worker/statushistorypruner/package_test.go:13 +0x2e
  testing.tRunner()
      /home/dfc/go/src/testing/testing.go:456 +0xdc
==================

----------------------------------------------------------------------
FAIL: worker_test.go:54: statusHistoryPrunerSuite.TestWorker

worker_test.go:84:
    c.Assert(passedMaxLogs, gc.Equals, 3)
... obtained int = 0
... expected int = 3

OOPS: 0 passed, 1 FAILED
--- FAIL: TestPackage (0.01s)
FAIL

[Horacio Durán (hduran-8)]

I proposed https://github.com/juju/juju/pull/3214 as a solution.