Docker and Docker-Compose tricks – nginx

docker-compose.sh

# *CASE:* 
# Debug start up problems by appending logs to `up` job
[1 (master *) ~/projects/DockerCompose] docker-compose up -d && docker-compose logs

# *Example* output:
[2 (master *) ~/projects/DockerCompose]: docker-compose up -d && docker-compose logs
web is up-to-date
logs is up-to-date
Creating nginx
Attaching to nginx, logs, web
logs  | / # 
nginx | nginx: [emerg] "proxy_cache_path" directive is not allowed here in /etc/nginx/nginx.conf:100
web   | / # 
ERROR: Couldn't connect to Docker daemon - you might need to run `docker-machine start default`.

# *Conclusion:*
# A wrong docker nginx proxy cache config

# ------------

# *CASE:* 
# Debug nginx configuration in a slim Debian/Busybox/Scratch container where nginx has PID 1
# Container is already running, admin changed the config, now needs to check it
# Logging into the container is not wanted
[3 (master *) ~/projects/DockerCompose]: docker exec -it <CONTAINER NAME> nginx -t

# Output will tell if config is ok or not

# ------------

# *CASE:* 
# Reloading of nginx conf is needed after config changed
# Logging into the container is not wanted
[4 (master *) ~/projects/DockerCompose]: docker exec -it <CONTAINER NAME> nginx -s reload

# Reload, stop, …
# see command line docs for "signals" https://www.nginx.com/resources/wiki/start/topics/tutorials/commandline/

# ------------

# *CASE:*
# Find ports: *PRIVILEGED* is important, else no PID is shown
$ docker exec -it --privileged <CONTAINER NAME> nodejs /bin/sh

# List processes, ports and PIDs
$ netstat -tulpn

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 127.0.0.11:52166        0.0.0.0:*               LISTEN      -
tcp        0      0 127.0.0.1:3000          0.0.0.0:*               LISTEN      47/node
tcp        0      0 :::3001                 :::*                    LISTEN      35/gulp
tcp        0      0 :::3002                 :::*                    LISTEN      35/gulp
udp        0      0 127.0.0.11:37556        0.0.0.0:*                           -

# Find process PID that opened <PORT>
$ fuser <PORT>/tcp
<PID>

# Find location of process that is running stuff on <PORT>
$ ls -l /proc/<PID>/exe
lrwxrwxrwx    1 root     root             0 Mar 11 03:31 /proc/47/exe -> /usr/bin/node

# Find current working directory of <PID>
$ ls -l /proc/47/cwd
lrwxrwxrwx    1 root     root             0 Mar 11 04:01 /proc/47/cwd -> /usr/src/app
# alternate solution:
$ pwdx 47
47: /usr/src/app

# Find owner of process
$ ps aux |grep <PID>
<PID> root       0:00 node ./deploy/server.js
  106 root       0:00 grep <PID>

# Get <PID> environment variables
$ cat /proc/<PID>/environ
…endless mess of string…
# Shorten to what we search for
$ grep -w -a HOSTNAME /proc/<PID>/environ
HOSTNAME=3b5aeb05e6d9