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Watchful NginX

Watchful NginX container -- nginx docker container that watches for logrotated logfiles using inotify and makes sure nginx reloads them when needed. A nasty, but functional, kludge of a work-around for lack of PID namespaces in docker.

Building

The image can be built with either nginx package installed from nginx.org repository, or any of nginx-light, nginx-full, nginx-extras installed from official Debian repository. This is controlled by NGINX_PACKAGE build argument.

By default, nginx package from nginx.org is being installed. If NGINX_PACKAGE is set to anything else than nginx, packages from default Debian repositories are used instead.

The NGINX_VERSION build argument controls the nginx package version that is going to be installed. By default, version 1.13* (the latest) is used.

NOTICE: package versions in official Debian repositories are much older than on nginx.org; hence, when using them, remember to set NGINX_VERSION accordingly. As of this writing Debian jessie package version is at 1.10*.

Environment variables

More documentation needed here

  • NGINX_BOOT (default: unset)
    if set to string "false", the entrypoint script will exit immediately before running nginx, in effect making it possible to use the image to generate dhparam file and quit (curtesy @cguess).

  • NO_DHPARAM (default: unset)
    if set to string "true", dhparam generation will be skipped entirely; this is not a good idea, and should be used only for internal/utility nginx instances that run behind another webserver with TLS support.

  • PID_FILE (default: "/var/run/nginx.pid")

  • WATCH_FILE (default: "/srv/logs/nginx/logrotate")

  • DHPARAM_FILE (default: "/etc/ssl/nginx/dhparam.pem") these control the locations where the run.sh script expects to find the nginx pidfile, the file to watch for logrotate signalling, and the SSL DH parameters files; these should reflect nginx config.

Examples

Building the image with nginx package from nginx.org, version 1.13.x (i.e. the default):

docker build ./
# equivalent to
docker build --build-arg=NGINX_PACKAGE=nginx --build-arg=NGINX_VERSION=1.13* --no-cache ./

Building the image with nginx-extras package from the Debian repository, version 1.10*:

docker build --build-arg=NGINX_PACKAGE=nginx-extras --build-arg=NGINX_VERSION=1.10* --no-cache ./

Operation

Upon start it creates a dhparam file in $DHPARAM_FILE (if the file does not exist) and sets an inotify watch on $WATCH_FILE. Once the watch discovers that the watchfile has been modified, it sends the USR1 signal to nginx, which causes it to reload the logfiles.

Use by volume-mounting the watchfile in this container and in a container that logrotate runs in, and making sure logrotate touches/modifies that file, for instance by using the following in your logrotate config files:

postrotate
      /bin/date > /srv/logs/nginx/logrotate # or whatever is in $WATCH_FILE

ToDo

  • watch the logfiles themselves and remove the need for the explicit logrotate flag file
  • more configuration options (logfile/watchfile locations, etc)