Major - P3 Didn't try to reproduce but I suspect any variation of the following will do the trick:
1.) start standalone mongod on 27017
2.) mongostat 4
3.) gracefully stop the mongod
4.) restart mongod after a short while
Terminal output example
insert query update delete getmore command flushes mapped vsize res faults qr|qw ar|aw netIn netOut conn time
10 31 10 *0 0 20|0 0 21.1G 45.0G 1.2G 1 0|0 0|0 21k 91k 42 2016-09-02T09:58:09-04:00
7 3 3 *0 0 2|0 1 21.1G 45.0G 1.2G 2 0|0 0|0 4k 12k 42 2016-09-02T09:58:13-04:00
2 5 2 *0 0 9|0 0 21.1G 44.9G 1.2G 0 0|0 0|0 4k 20k 20 2016-09-02T09:58:17-04:00
*0 *0 *0 *0 0 0|0 0 21.1G 44.9G 1.2G 0 0|0 0|0 56b 8k 17 2016-09-02T09:58:21-04:00
*0 *0 *0 *0 0 0|0 0 21.1G 44.9G 1.2G 0 0|0 0|0 19b 4k 17 2016-09-02T09:58:25-04:00
*0 *0 *0 *0 0 2|0 0 21.1G 44.9G 1.2G 0 0|0 0|0 167b 9k 17 2016-09-02T09:58:29-04:00
*0 *0 *0 *0 0 0|0 0 21.1G 44.9G 1.2G 0 0|0 0|0 19b 4k 17 2016-09-02T09:58:33-04:00
no reachable servers
no reachable servers
no reachable servers
insert query update delete getmore command % dirty % used flushes vsize res qr|qw ar|aw netIn netOut conn time
no reachable servers
no reachable servers
no reachable servers
no reachable servers
no reachable servers
no reachable servers
no reachable servers
no reachable servers
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x4055b2b]
goroutine 11 [running]:
github.com/mongodb/mongo-tools/mongostat.NewStatLine(0xecf5b7c89, 0x90bc0c6, 0x46b2960, 0xc2081941e0, 0x1e, 0xc208130a20, 0x6, 0xc208130a40, 0x6, 0x9d0, ...)
/data/mci/src/src/mongo-tools-repo/.gopath/src/github.com/mongodb/mongo-tools/mongostat/stat_types.go:843 +0xc8b
github.com/mongodb/mongo-tools/mongostat.(*NodeMonitor).Poll(0xc208047090, 0x0, 0x0, 0x4, 0x0)
/data/mci/src/src/mongo-tools-repo/.gopath/src/github.com/mongodb/mongo-tools/mongostat/mongostat.go:283 +0xb51
github.com/mongodb/mongo-tools/mongostat.func·005()
/data/mci/src/src/mongo-tools-repo/.gopath/src/github.com/mongodb/mongo-tools/mongostat/mongostat.go:319 +0x201
created by github.com/mongodb/mongo-tools/mongostat.(*NodeMonitor).Watch
/data/mci/src/src/mongo-tools-repo/.gopath/src/github.com/mongodb/mongo-tools/mongostat/mongostat.go:327 +0x16a
goroutine 1 [chan receive, 1418 minutes]:
github.com/mongodb/mongo-tools/mongostat.(*MongoStat).Run(0xc2080b8060, 0x0, 0x0)
/data/mci/src/src/mongo-tools-repo/.gopath/src/github.com/mongodb/mongo-tools/mongostat/mongostat.go:378 +0x185
main.main()
/data/mci/src/src/mongo-tools-repo/mongostat/main/mongostat.go:125 +0xd90
goroutine 5 [syscall, 1418 minutes]:
os/signal.loop()
/usr/local/go/src/os/signal/signal_unix.go:21 +0x1f
created by os/signal.init·1
/usr/local/go/src/os/signal/signal_unix.go:27 +0x35
goroutine 10 [chan receive, 1418 minutes]:
github.com/mongodb/mongo-tools/common/signals.Handle()
/data/mci/src/src/mongo-tools-repo/.gopath/src/github.com/mongodb/mongo-tools/common/signals/signals_unix.go:16 +0x209
created by main.main
/data/mci/src/src/mongo-tools-repo/mongostat/main/mongostat.go:18 +0x34
goroutine 17 [syscall, 1418 minutes, locked to thread]:
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:2232 +0x1
goroutine 13 [sleep]:
gopkg.in/mgo%2ev2.(*mongoCluster).syncServersLoop(0xc20808a600)
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/cluster.go:368 +0x291
created by gopkg.in/mgo%2ev2.newCluster
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/cluster.go:78 +0x20b
goroutine 18 [chan receive]:
github.com/mongodb/mongo-tools/mongostat.func·001()
/data/mci/src/src/mongo-tools-repo/.gopath/src/github.com/mongodb/mongo-tools/mongostat/mongostat.go:133 +0x99
created by github.com/mongodb/mongo-tools/mongostat.(*SyncClusterMonitor).Monitor
/data/mci/src/src/mongo-tools-repo/.gopath/src/github.com/mongodb/mongo-tools/mongostat/mongostat.go:148 +0x11c
goroutine 6557 [IO wait]:
net.(*pollDesc).Wait(0xc2080fb640, 0x72, 0x0, 0x0)
/usr/local/go/src/net/fd_poll_runtime.go:84 +0x47
net.(*pollDesc).WaitRead(0xc2080fb640, 0x0, 0x0)
/usr/local/go/src/net/fd_poll_runtime.go:89 +0x43
net.(*netFD).Read(0xc2080fb5e0, 0xc2081197a0, 0x24, 0x24, 0x0, 0x478bc38, 0xc208178400)
/usr/local/go/src/net/fd_unix.go:242 +0x40f
net.(*conn).Read(0xc20803e4b8, 0xc2081197a0, 0x24, 0x24, 0x0, 0x0, 0x0)
/usr/local/go/src/net/net.go:121 +0xdc
gopkg.in/mgo%2ev2.fill(0x478e398, 0xc20803e4b8, 0xc2081197a0, 0x24, 0x24, 0x0, 0x0)
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/socket.go:530 +0x75
gopkg.in/mgo%2ev2.(*mongoSocket).readLoop(0xc2081d5420)
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/socket.go:547 +0x126
created by gopkg.in/mgo%2ev2.newSocket
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/socket.go:194 +0x3d3
goroutine 6538 [sleep]:
gopkg.in/mgo%2ev2.(*mongoServer).pinger(0xc208120d20, 0x1)
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/server.go:296 +0x169
created by gopkg.in/mgo%2ev2.newServer
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/server.go:89 +0x194
goroutine 1030 [IO wait]:
net.(*pollDesc).Wait(0xc20823ad80, 0x77, 0x0, 0x0)
/usr/local/go/src/net/fd_poll_runtime.go:84 +0x47
net.(*pollDesc).WaitWrite(0xc20823ad80, 0x0, 0x0)
/usr/local/go/src/net/fd_poll_runtime.go:93 +0x43
net.(*netFD).connect(0xc20823ad20, 0x0, 0x0, 0x478d358, 0xc20824eca0, 0xecf5b7de1, 0x39df7b4b, 0x46b2960, 0x0, 0x0)
/usr/local/go/src/net/fd_unix.go:114 +0x24b
net.(*netFD).dial(0xc20823ad20, 0x478e3f8, 0x0, 0x478e3f8, 0xc2081195c0, 0xecf5b7de1, 0x39df7b4b, 0x46b2960, 0x0, 0x0)
/usr/local/go/src/net/sock_posix.go:139 +0x37a
net.socket(0x4480910, 0x3, 0x2, 0x1, 0x0, 0xc208119500, 0x478e3f8, 0x0, 0x478e3f8, 0xc2081195c0, ...)
/usr/local/go/src/net/sock_posix.go:91 +0x422
net.internetSocket(0x4480910, 0x3, 0x478e3f8, 0x0, 0x478e3f8, 0xc2081195c0, 0xecf5b7de1, 0x39df7b4b, 0x46b2960, 0x1, ...)
/usr/local/go/src/net/ipsock_posix.go:137 +0x148
net.dialTCP(0x4480910, 0x3, 0x0, 0xc2081195c0, 0xecf5b7de1, 0x39df7b4b, 0x46b2960, 0xc20822ff90, 0x0, 0x0)
/usr/local/go/src/net/tcpsock_posix.go:156 +0x125
net.dialSingle(0x4480910, 0x3, 0xc20823c480, 0xf, 0x0, 0x0, 0x478e368, 0xc2081195c0, 0xecf5b7de1, 0x39df7b4b, ...)
/usr/local/go/src/net/dial.go:235 +0x3f5
net.func·016(0xecf5b7de1, 0xe39df7b4b, 0x46b2960, 0x0, 0x0, 0x0, 0x0)
/usr/local/go/src/net/dial.go:163 +0x12c
net.dial(0x4480910, 0x3, 0x478e368, 0xc2081195c0, 0xc20817fa98, 0xecf5b7de1, 0xe39df7b4b, 0x46b2960, 0x0, 0x0, ...)
/usr/local/go/src/net/fd_unix.go:40 +0x6f
net.(*Dialer).Dial(0xc20824dc40, 0x4480910, 0x3, 0xc20823c480, 0xf, 0x0, 0x0, 0x0, 0x0)
/usr/local/go/src/net/dial.go:170 +0x4be
net.DialTimeout(0x4480910, 0x3, 0xc20823c480, 0xf, 0x37e11d600, 0x0, 0x0, 0x0, 0x0)
/usr/local/go/src/net/dial.go:150 +0xe6
gopkg.in/mgo%2ev2.(*mongoServer).Connect(0xc2082320e0, 0x37e11d600, 0xc208164900, 0x0, 0x0)
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/server.go:164 +0x295
gopkg.in/mgo%2ev2.(*mongoServer).AcquireSocket(0xc2082320e0, 0x0, 0x37e11d600, 0xc20824ec00, 0x37864d00, 0x0, 0x0)
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/server.go:129 +0x278
gopkg.in/mgo%2ev2.(*mongoServer).pinger(0xc2082320e0, 0x1)
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/server.go:299 +0x1e4
created by gopkg.in/mgo%2ev2.newServer
/data/mci/src/src/mongo-tools-repo/vendor/src/gopkg.in/mgo.v2/server.go:89 +0x194