Null pointer dereference

[qed-]

I received the following panic, not doing anything in particular, there were two active alerts at the time, one silenced. Let me know if there's any further information I can provide.

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x4e532d]

goroutine 15 [running]:
github.com/prometheus/alertmanager/manager.(*memoryAlertManager).removeExpiredAggregates(0xc208054280)
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/github.com/prometheus/alertmanager/manager/manager.go:282 +0x23d
github.com/prometheus/alertmanager/manager.(*memoryAlertManager).runIteration(0xc208054280)
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/github.com/prometheus/alertmanager/manager/manager.go:395 +0x33
github.com/prometheus/alertmanager/manager.(*memoryAlertManager).Run(0xc208054280)
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/github.com/prometheus/alertmanager/manager/manager.go:408 +0x9a
created by main.main
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/main.go:111 +0xd50

goroutine 1 [chan receive, 15 minutes]:
github.com/prometheus/alertmanager/manager.(*notifier).Dispatch(0xc2080fc420)
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/github.com/prometheus/alertmanager/manager/notifier.go:813 +0x54
main.main()
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/main.go:157 +0x15c0

goroutine 14 [chan receive]:
main.func·001()
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/main.go:85 +0x84
created by main.main
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/main.go:90 +0x659

goroutine 16 [IO wait, 3 minutes]:
net.(*pollDesc).Wait(0xc208108fb0, 0x72, 0x0, 0x0)
        /usr/lib/golang/src/net/fd_poll_runtime.go:84 +0x47
net.(*pollDesc).WaitRead(0xc208108fb0, 0x0, 0x0)
        /usr/lib/golang/src/net/fd_poll_runtime.go:89 +0x43
net.(*netFD).accept(0xc208108f50, 0x0, 0x7fb150e92e40, 0xc208276768)
        /usr/lib/golang/src/net/fd_unix.go:419 +0x40b
net.(*TCPListener).AcceptTCP(0xc20802e5b0, 0x63ab5e, 0x0, 0x0)
        /usr/lib/golang/src/net/tcpsock_posix.go:234 +0x4e
net/http.tcpKeepAliveListener.Accept(0xc20802e5b0, 0x0, 0x0, 0x0, 0x0)
        /usr/lib/golang/src/net/http/server.go:1976 +0x4c
net/http.(*Server).Serve(0xc208032a20, 0x7fb150e95528, 0xc20802e5b0, 0x0, 0x0)
        /usr/lib/golang/src/net/http/server.go:1728 +0x92
net/http.(*Server).ListenAndServe(0xc208032a20, 0x0, 0x0)
        /usr/lib/golang/src/net/http/server.go:1718 +0x154
net/http.ListenAndServe(0x904bd0, 0x5, 0x0, 0x0, 0x0, 0x0)
        /usr/lib/golang/src/net/http/server.go:1808 +0xba
github.com/prometheus/alertmanager/web.WebService.ServeForever(0xc2080fd050, 0xc2080fd080, 0xc20808c640, 0xc208030c30, 0x904bd0, 0x5, 0x9041d0, 0x1, 0x0, 0x0)
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/github.com/prometheus/alertmanager/web/web.go:78 +0x8e6
created by main.main
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/main.go:145 +0x12f1

goroutine 17 [select, 15 minutes]:
github.com/prometheus/alertmanager/config.(*fileWatcher).Watch(0xc2080aa430, 0xc2080fd0b0)
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/github.com/prometheus/alertmanager/config/watcher.go:49 +0x8fb
created by main.main
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/main.go:154 +0x14b0

goroutine 19 [syscall, 15 minutes]:
syscall.Syscall(0x0, 0x3, 0xc20816fee0, 0x10000, 0x0, 0x850f70, 0x7fb150e95560)
        /usr/lib/golang/src/syscall/asm_linux_amd64.s:21 +0x5
syscall.read(0x3, 0xc20816fee0, 0x10000, 0x10000, 0x0, 0x0, 0x0)
        /usr/lib/golang/src/syscall/zsyscall_linux_amd64.go:867 +0x6e
syscall.Read(0x3, 0xc20816fee0, 0x10000, 0x10000, 0xffffffffffffffff, 0x0, 0x0)
        /usr/lib/golang/src/syscall/syscall_unix.go:136 +0x58
gopkg.in/fsnotify%2ev0.(*Watcher).readEvents(0xc2080325a0)
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/gopkg.in/fsnotify.v0/fsnotify_linux.go:219 +0x12c
created by gopkg.in/fsnotify%2ev0.NewWatcher
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/gopkg.in/fsnotify.v0/fsnotify_linux.go:126 +0x420

goroutine 20 [chan receive, 15 minutes]:
gopkg.in/fsnotify%2ev0.(*Watcher).purgeEvents(0xc2080325a0)
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/gopkg.in/fsnotify.v0/fsnotify.go:21 +0x55
created by gopkg.in/fsnotify%2ev0.NewWatcher
        /home/mavdev/dave/prometheus/alertmanager/alertmanager/.build/gopath/src/gopkg.in/fsnotify.v0/fsnotify_linux.go:127 +0x43a

[juliusv]

@qed- Thanks! Yep, known bug unfortunately in the experimental Alertmanager version, but it should only happen if you have alerts which are not matched by any aggregation_rule.

See also: #82 (comment)

Basically, make sure that every incoming alert has a matching aggregation_rule, and you should be fine. In case you do, and that still happened, it would be interesting to hear.