Utility to simplify running applications in docker containers.
dockerize is a utility to simplify running applications in docker containers. It allows you to generate application configuration files at container startup time from templates and container environment variables. It also allows log files to be tailed to stdout and/or stderr.
The typical use case for dockerize is when you have an application that has one or more configuration files and you would like to control some of the values using environment variables.
For example, a Python application using Sqlalchemy might not be able to use environment variables directly.
It may require that the database URL be read from a python settings file with a variable named
SQLALCHEMY_DATABASE_URI
. dockerize allows you to set an environment variable such as
DATABASE_URL
and update the python file when the container starts.
Another use case is when the application logs to specific files on the filesystem and not stdout
or stderr. This makes it difficult to troubleshoot the container using the docker logs
command.
For example, nginx will log to /var/log/nginx/access.log
and
/var/log/nginx/error.log
by default. While you can sometimes work around this, it's tedious to find
the a solution for every application. dockerize allows you to specify which logs files should
be tailed and where they should be sent.
See A Simple Way To Dockerize Applications
Download the latest version in your container:
For Ubuntu Images:
RUN apt-get update && apt-get install -y wget
ENV DOCKERIZE_VERSION v0.2.0
RUN wget https://github.com/jwilder/dockerize/releases/download/$DOCKERIZE_VERSION/dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz \
&& tar -C /usr/local/bin -xzvf dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz
dockerize works by wrapping the call to your application using the ENTRYPOINT
or CMD
directives.
This would generate /etc/nginx/nginx.conf
from the template located at /etc/nginx/nginx.tmpl
and
send /var/log/nginx/access.log
to STDOUT
and /var/log/nginx/error.log
to STDERR
after running
nginx
, only after waiting for the web
host to respond on tcp 8000
:
CMD dockerize -template /etc/nginx/nginx.tmpl:/etc/nginx/nginx.conf -stdout /var/log/nginx/access.log -stderr /var/log/nginx/error.log -wait tcp://web:8000 nginx
You can specify multiple templates by passing using -template
multiple times:
$ dockerize -template template1.tmpl:file1.cfg -template template2.tmpl:file3
Templates can be generated to STDOUT
by not specifying a dest:
$ dockerize -template template1.tmpl
You can tail multiple files to STDOUT
and STDERR
by passing the options multiple times.
$ dockerize -stdout info.log -stdout perf.log
If inotify
does not work in you container, you use -poll
to poll for file changes instead.
$ dockerize -stdout info.log -stdout perf.log -poll
If your file uses {{
and }}
as part of it's syntax, you can change the template escape characters using the -delims
.
$ dockerize -delims "<%:%>"
If the destination file already exists, dockerize will refuse to overwrite it. The -force flag overrides this behaviour.
$ dockerize -force -template template1.tmpl:file
It is common when using tools like Docker Compose to depend on services in other linked containers, however oftentimes relying on links is not enough - whilst the container itself may have started, the service(s) within it may not yet be ready - resulting in shell script hacks to work around race conditions.
Dockerize gives you the ability to wait for services on a specified protocol (tcp
, tcp4
, tcp6
, http
, and https
) before starting your application:
$ dockerize -wait tcp://db:5432 -wait http://web:80
You can optionally specify how long to wait for the services to become available by using the -timeout #
argument (Default: 10 seconds). If the timeout is reached and the service is still not available, the process exits with status code 1.
$ dockerize -wait tcp://db:5432 -wait http://web:80 -timeout 10s
See this issue for a deeper discussion, and why support isn't and won't be available in the Docker ecosystem itself.
Templates use Golang text/template. You can access environment
variables within a template with .Env
.
{{ .Env.PATH }} is my path
There are a few built in functions as well:
default $var $default
- Returns a default value for one that does not exist.{{ default .Env.VERSION "0.1.2" }}
contains $map $key
- Returns true if a string is within another stringexists $path
- Determines if a file path exists or not.{{ exists "/etc/default/myapp" }}
split $string $sep
- Splits a string into an array using a separator string. Alias forstrings.Split
.{{ split .Env.PATH ":" }}
replace $string $old $new $count
- Replaces all occurrences of a string within another string. Alias forstrings.Replace
.{{ replace .Env.PATH ":" }}
parseUrl $url
- Parses a URL into it's protocol, scheme, host, etc. parts. Alias forurl.Parse
atoi $value
- Parses a string $value into an int.{{ if (gt (atoi .Env.NUM_THREADS) 1) }}
add $arg1 $arg
- Performs integer addition.{{ add (atoi .Env.SHARD_NUM) -1 }}
MIT