update mockbeat to reveals a data race when stopping the application

[cyrilleverrier]

When this patch is applied, running

cd $GOPATH/src/github.com/elastic/beats/libbeat/
RACE_DETECTOR=1 make system-tests

This triggers the following data race detection:

2016/01/27 10:22:46.388070 beat.go:242: DBG  Initializing output plugins
2016/01/27 10:22:46.388145 geolite.go:30: INFO GeoIP disabled: No paths were set under output.geoip.paths
2016/01/27 10:22:46.388186 file.go:48: INFO File output base filename set to: mockbeat
2016/01/27 10:22:46.388219 file.go:60: INFO Rotate every bytes set to: 1024000
2016/01/27 10:22:46.388245 file.go:69: INFO Number of files set to: 7
2016/01/27 10:22:46.388350 outputs.go:129: INFO Activated file as output plugin.
2016/01/27 10:22:46.388379 publish.go:273: DBG  Create output worker
2016/01/27 10:22:46.388552 publish.go:327: DBG  No output is defined to store the topology. The server fields might not be filled.
2016/01/27 10:22:46.388603 publish.go:347: INFO Publisher name: dell
2016/01/27 10:22:46.388925 async.go:91: INFO Flush Interval set to: -1ms
2016/01/27 10:22:46.388954 async.go:99: INFO Max Bulk Size set to: -1
2016/01/27 10:22:46.388993 beat.go:254: INFO Init Beat: mockbeat; Version: 9.9.9
2016/01/27 10:22:46.389394 beat.go:283: INFO mockbeat sucessfully setup. Start running.
2016/01/27 10:22:46.471014 service.go:33: DBG  Received sigterm/sigint, stopping
2016/01/27 10:22:46.471087 beat.go:333: INFO Start exiting beat
2016/01/27 10:22:46.471137 beat.go:301: INFO Stopping Beat
==================
WARNING: DATA RACE
Read by goroutine 8:
  github.com/elastic/beats/libbeat/beat.(*Beat).Stop()
      github.com/elastic/beats/libbeat/beat/_obj/beat.go:303 +0x9a
  github.com/elastic/beats/libbeat/beat.Run()
      github.com/elastic/beats/libbeat/beat/_obj/beat.go:145 +0x144
  github.com/elastic/beats/libbeat.main()
      github.com/elastic/beats/libbeat/_test/_obj_test/libbeat.go:14 +0xd3
  github.com/elastic/beats/libbeat.TestSystem()
      /home/cyrille/code/go/workspace/src/github.com/elastic/beats/libbeat/libbeat_test.go:17 +0x54
  testing.tRunner()
      /usr/lib/go/src/testing/testing.go:456 +0xdc

Previous write by goroutine 9:
  github.com/elastic/beats/libbeat/beat.(*Beat).Run()
      github.com/elastic/beats/libbeat/beat/_obj/beat.go:285 +0x492
  github.com/elastic/beats/libbeat/beat.(*Beat).Start()
      github.com/elastic/beats/libbeat/beat/_obj/beat.go:186 +0x27e
  github.com/elastic/beats/libbeat/beat.Run.func1()
      github.com/elastic/beats/libbeat/beat/_obj/beat.go:127 +0x68

Goroutine 8 (running) created at:
  testing.RunTests()
      /usr/lib/go/src/testing/testing.go:561 +0xaa3
  testing.(*M).Run()
      /usr/lib/go/src/testing/testing.go:494 +0xe4
  main.main()
      github.com/elastic/beats/libbeat/_test/_testmain.go:270 +0x38d

Goroutine 9 (running) created at:
  github.com/elastic/beats/libbeat/beat.Run()
      github.com/elastic/beats/libbeat/beat/_obj/beat.go:139 +0xb6
  github.com/elastic/beats/libbeat.main()
      github.com/elastic/beats/libbeat/_test/_obj_test/libbeat.go:14 +0xd3
  github.com/elastic/beats/libbeat.TestSystem()
      /home/cyrille/code/go/workspace/src/github.com/elastic/beats/libbeat/libbeat_test.go:17 +0x54
  testing.tRunner()
      /usr/lib/go/src/testing/testing.go:456 +0xdc
==================
2016/01/27 10:22:46.471560 beat.go:311: INFO Cleaning up mockbeat before shutting down.
2016/01/27 10:22:46.471679 beat.go:146: INFO Exit beat completed
PASS
coverage: 11.3% of statements in github.com/elastic/beats/libbeat/...
Found 1 data race(s)

The variable b.state in beat.go is read and written by 2 go routines: Run() and the go func started by Run()

[elasticsearch-release]

Jenkins standing by to test this. If you aren't a maintainer, you can ignore this comment. Someone with commit access, please review this and clear it for Jenkins to run; then say 'jenkins, test it'.

[ruflin]

To fix this we should probably introduce a function updateState with a mutex.

[cyrilleverrier]

Or communicating the state to the main go proc through a dedicated state channel ?

[ruflin]

That is probably the more go-like way to do it. It would also allow to change the state for example from inside a beat. Can you add this to your PR?

[andrewkroh]

jenkins, test it

[ruflin]

@cyrilleverrier I took your changes and implemented them in #885 I went with the mutex option as I felt a channel would be overkill. It is easy to change it later to a channel if needed.

[ruflin]

Closing as I think this issue was resolved by #885 Thanks for bringing it up (and provide the solution :-) ).