Container

utpp was intended to be used inside containers. It is a single binary that can be used to modify configuration files and dynamically execute JavaScript.

info

The following real world example can be found in the adrianschubek/dir-browser repo.

/server/init.sh

utpp "/etc/nginx/**;/etc/supervisor/**;/usr/local/etc/php*/**;/var/www/html/index.php" && /usr/bin/supervisord -c /etc/supervisor/conf.d/supervisord.conf

In the example above we are using utpp to modify various configuration files such as PHP, Nginx, and Supervisor config files. These modifications are done at container startup and a user can configure it by setting environment variables.

/server/supervisor/supervisord.conf

[program:nginx]
command=nginx -g 'daemon off;'
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0
autorestart=unexpected
startretries=0

$[if `!process.env.NO_DL_COUNT`]$
[program:redis]
command=redis-server /etc/redis.conf --save 60 1
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0
autorestart=unexpected
startretries=0
$[end]$

Here if a user runs the container with the NO_DL_COUNT environment variable set to true the redis process will not be started by the supervisor (and saves resources).

/server/php/php.ini

memory_limit=${{`process.env.MEM_LIMIT ?? '256M'`}}$
display_errors=${{`process.env.DISPLAY_ERRORS ?? 'Off'`}}$

User can also configure php.ini settings by specifiying environment variables. In the example above the MEM_LIMIT and DISPLAY_ERRORS environment variables are used to configure the memory_limit and display_errors settings. If the environment variables are not set the default values will be used.

tip

Remember that you can use any JavaScript expression between apostrophes ` js here `. This will be evaluted using Node.js eval function, so you have access to all Node.js APIs like process.