Runtime error after first run

[0atman]

I'm trying to test dockerise using the nginx example, but when my container runs

ADD nginx.conf.tmpl /etc/nginx/nginx.conf.tmpl #my test tmpl, which doesn't use any 
CMD dockerize -template /etc/nginx/nginx.conf.tmpl:/etc/nginx/sites-available/default -stdout /var/log/nginx/access.log -stderr /var/log/nginx/error.log nginx

I get this scary stacktrace:

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x403566]

goroutine 9 [running]:
main.tailFile(0x7fa0318de540, 0xc82004a340, 0x7ffc2a7adf0c, 0x18, 0xc820026018)
        /Users/jason/go/src/github.com/jwilder/dockerize/tail.go:34 +0x4f6
created by main.main
        /Users/jason/go/src/github.com/jwilder/dockerize/dockerize.go:131 +0xb83

goroutine 1 [semacquire]:
sync.runtime_Semacquire(0x6de90c)
        /usr/local/go/src/runtime/sema.go:43 +0x26
sync.(*WaitGroup).Wait(0x6de900)
        /usr/local/go/src/sync/waitgroup.go:126 +0xb4
main.main()
        /Users/jason/go/src/github.com/jwilder/dockerize/dockerize.go:134 +0xbb2

goroutine 5 [syscall]:
os/signal.loop()
        /usr/local/go/src/os/signal/signal_unix.go:22 +0x18
created by os/signal.init.1
        /usr/local/go/src/os/signal/signal_unix.go:28 +0x37

goroutine 7 [runnable]:
os/exec.(*Cmd).Start(0xc8200a0000, 0x0, 0x0)
        /usr/local/go/src/os/exec/exec.go:318 +0xb01
main.runCmd(0x7fa0318de540, 0xc82004a340, 0xc82000e4b0, 0x7ffc2a7adf25, 0x5, 0xc82000a1f0, 0x0, 0x0)
        /Users/jason/go/src/github.com/jwilder/dockerize/exec.go:23 +0x1d5
created by main.main
        /Users/jason/go/src/github.com/jwilder/dockerize/dockerize.go:121 +0x986

goroutine 8 [runnable]:
github.com/hpcloud/tail/watch.(*InotifyTracker).NewWatcher(0xc8200b2000, 0x0, 0x0, 0x0)
        /Users/jason/go/src/github.com/hpcloud/tail/watch/inotify_tracker.go:27 +0xe0
github.com/hpcloud/tail.TailFile(0x7ffc2a7adeea, 0x19, 0x0, 0x1, 0x0, 0x1, 0x0, 0xc8200101e0, 0x0, 0x0, ...)
        /Users/jason/go/src/github.com/hpcloud/tail/tail.go:106 +0x5af
main.tailFile(0x7fa0318de540, 0xc82004a340, 0x7ffc2a7adeea, 0x19, 0xc820026010)
        /Users/jason/go/src/github.com/jwilder/dockerize/tail.go:19 +0x123
created by main.main
        /Users/jason/go/src/github.com/jwilder/dockerize/dockerize.go:126 +0xa75

goroutine 10 [runnable]:
gopkg.in/fsnotify%2ev0.(*Watcher).readEvents(0xc820014360)
        ?:0
created by gopkg.in/fsnotify%2ev0.NewWatcher
        ?:0 +0x40b

goroutine 11 [runnable]:
gopkg.in/fsnotify%2ev0.(*Watcher).purgeEvents(0xc820014360)
        /Users/jason/go/src/gopkg.in/fsnotify.v0/fsnotify.go:20
created by gopkg.in/fsnotify%2ev0.NewWatcher
        ?:0 +0x42d

goroutine 17 [runnable]:
gopkg.in/fsnotify%2ev0.(*Watcher).readEvents(0xc8200ac180)
        ?:0
created by gopkg.in/fsnotify%2ev0.NewWatcher
        ?:0 +0x40b

goroutine 18 [runnable]:
gopkg.in/fsnotify%2ev0.(*Watcher).purgeEvents(0xc8200ac180)
        /Users/jason/go/src/gopkg.in/fsnotify.v0/fsnotify.go:20
created by gopkg.in/fsnotify%2ev0.NewWatcher
        ?:0 +0x42d

[0atman]

Do I need some kind of go standard library?

[0atman]

Could this be causing trouble?

/var/log/nginx# ls -al
total 8
drwxr-xr-x 2 root root 4096 Oct 28 22:01 .
drwxr-xr-x 9 root root 4096 Nov 10 15:06 ..
lrwxrwxrwx 1 root root   11 Oct 28 22:01 access.log -> /dev/stdout
lrwxrwxrwx 1 root root   11 Oct 28 22:01 error.log -> /dev/stderr

[0atman]

If I leave off -stdout /var/log/nginx/access.log -stderr /var/log/nginx/error.log it runs (though I'm not sure yet if it works)

[0atman]

Oh! the offical docker nginx repo makes these links:

https://github.com/nginxinc/docker-nginx/blob/4e5332fa50a1f8f73657417c6bfe249bbb3b110d/Dockerfile#L15

RUN ln -sf /dev/stdout /var/log/nginx/access.log
RUN ln -sf /dev/stderr /var/log/nginx/error.log

Is that what's causing the failure?

[0atman]

Can confirm that replacing the links with regular files fixes the stacktrace, when using -stdout /var/log/nginx/access.log -stderr /var/log/nginx/error.log

[0atman]

Proposed fix:

Defensively code the part that redirects log files to stdout/error.

[0atman]

I'd do it, but I'm no go pro!

[sstarcher]

Could this be related to overlayfs?
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/882147
moby/moby#11705

[ghost]

RUN ln -sf /dev/stdout /var/log/nginx/access.log
RUN ln -sf /dev/stderr /var/log/nginx/error.log

It's have same effect like dockerize's -stdout /var/log/nginx/access.log -stderr /var/log/nginx/error.log, but the ln -sf way is better, because dockerzie don't cleans already forwarded lines from logs and container continues growing.