Issue

• Why does docker containerd throws an error message on RHEL 7?

  Feb  1 02:07:53 testlabdockerd[3616]: panic: close of nil channel
  Feb  1 02:07:53 testlabdockerd[3616]: goroutine 34 [running]:
  Feb  1 02:07:53 testlabdockerd[3616]: panic(0x887ae0, 0xc4203300c0)
  Feb  1 02:07:53 testlabdockerd[3616]: /usr/lib/golang/src/runtime/panic.go:531 +0x1cf fp=0xc42030fe88 sp=0xc42030fdf0
  Feb  1 02:07:53 testlabdockerd[3616]: runtime.closechan(0x0)
  Feb  1 02:07:53 testlabdockerd[3616]: /usr/lib/golang/src/runtime/chan.go:322 +0x343 fp=0xc42030ff10 sp=0xc42030fe88
  Feb  1 02:07:53 testlabdockerd[3616]: github.com/docker/containerd/supervisor.(*Supervisor).execExit.func1(0xc420336000, 0xc420202340, 0x0)
  Feb  1 02:07:53 testlabdockerd[3616]: /builddir/build/BUILD/docker-9a813fad75217ff3a3c1e0c1ecf5a9dd9dfbccf1/_build/src/github.com/docker/containerd/supervisor/exit.go:92 +0x10c fp=0xc42030ffc8 sp=0xc42030ff10
  Feb  1 02:07:53 testlabdockerd[3616]: runtime.goexit()
  Feb  1 02:07:53 testlabdockerd[3616]: /usr/lib/golang/src/runtime/asm_amd64.s:2197 +0x1 fp=0xc42030ffd0 sp=0xc42030ffc8
  Feb  1 02:07:53 testlabdockerd[3616]: created by github.com/docker/containerd/supervisor.(*Supervisor).execExit
  Feb  1 02:07:53 testlabdockerd[3616]: /builddir/build/BUILD/docker-9a813fad75217ff3a3c1e0c1ecf5a9dd9dfbccf1/_build/src/github.com/docker/containerd/supervisor/exit.go:93 +0x198
  Feb  1 02:07:53 testlabdockerd[3616]: goroutine 1 [chan receive]:
  Feb  1 02:07:53 testlabdockerd[3616]: runtime.gopark(0x936188, 0xc420091258, 0x91c076, 0xc, 0xc420155817, 0x3)
  Feb  1 02:07:53 testlabdockerd[3616]: /usr/lib/golang/src/runtime/proc.go:271 +0x13a fp=0xc4201557d8 sp=0xc4201557a8
  Feb  1 02:07:53 testlabdockerd[3616]: runtime.goparkunlock(0xc420091258, 0x91c076, 0xc, 0xc420155817, 0x3)
  Feb  1 02:07:53 testlabdockerd[3616]: /usr/lib/golang/src/runtime/proc.go:277 +0x5e fp=0xc420155818 sp=0xc4201557d8
  Feb  1 02:07:53 testlabdockerd[3616]: runtime.chanrecv(0x858000, 0xc420091200, 0xc420155a08, 0xc4201eba01, 0xc4201ee250)
  Feb  1 02:07:53 testlabdockerd[3616]: /usr/lib/golang/src/runtime/chan.go:513 +0x371 fp=0xc4201558b8 sp=0xc420155818
  Feb  1 02:07:53 testlabdockerd[3616]: runtime.chanrecv2(0x858000, 0xc420091200, 0xc420155a08, 0x34)
  Feb  1 02:07:53 testlabdockerd[3616]: /usr/lib/golang/src/runtime/chan.go:400 +0x35 fp=0xc4201558f0 sp=0xc4201558b8
  Feb  1 02:07:53 testlabdockerd[3616]: main.daemon(0xc420119540, 0xd, 0x0)
  Feb  1 02:07:53 testlabdockerd[3616]: /builddir/build/BUILD/docker-9a813fad75217ff3a3c1e0c1ecf5a9dd9dfbccf1/containerd-89a5d2ce19344c8c8bbfef03b43434f60a4afcc2/containerd/main.go:191 +0x583 fp=0xc420155a88 sp=0xc4201558f0
  Feb  1 02:07:53 testlabdockerd[3616]: main.main.func2(0xc420119540)
  Feb  1 02:07:54 testlabdockerd[3616]: /builddir/build/BUILD/docker-9a813fad75217ff3a3c1e0c1ecf5a9dd9dfbccf1/containerd-89a5d2ce19344c8c8bbfef0:
  

• Docker went into a hang state with the following message:

  Apr 09 14:51:19 testlabdockerd dockerd-current[1541]: time="2018-04-09T14:51:19.229223532-04:00" level=error msg="Handler for POST /v1.26/containers/601e0bf46120440ff58ac5416619b719a647cded17d15f19106dc890e72e732e/start returned error: grpc: the connection is unavailable"