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
- Tail multiple log files to stdout and/or stderr
- Wait for other services to be available using TCP, HTTP(S), unix before starting the main process.
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.
In addition, it can also delay the starting of the python application until the database container is running and listening on the TCP port.
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 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:
curl -sfL https://github.com/powerman/dockerize/releases/download/v0.7.0/dockerize-`uname -s`-`uname -m` | install /dev/stdin /usr/local/bin/dockerize
The powerman/dockerize
image is a base image based on alpine linux
. dockerize
is installed in the $PATH
and can be used directly.
FROM powerman/dockerize
...
ENTRYPOINT dockerize ...
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
Template may also be a directory. In this case all files within this directory are recursively processed as template and stored with the same name in the destination directory.
If the destination directory is omitted, the output is sent to STDOUT
. The files in the source directory are processed in sorted order (as returned by ioutil.ReadDir
).
$ dockerize -template src_dir:dest_dir
If the destination file already exists, dockerize will overwrite it. The -no-overwrite flag overrides this behaviour.
$ dockerize -no-overwrite -template template1.tmpl:file
You can tail multiple files to STDOUT
and STDERR
by passing the options multiple times.
$ dockerize -stdout info.log -stdout perf.log
If your file uses {{
and }}
as part of it's syntax, you can change the template escape characters using the -delims
.
$ dockerize -delims "<%:%>"
Http headers can be specified for http/https protocols.
$ dockerize -wait http://web:80 -wait-http-header "Authorization:Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ=="
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 (file
, tcp
, tcp4
, tcp6
, http
, https
, unix
, and job
) before starting your application:
$ dockerize -wait tcp://db:5432 -wait http://web:80 -wait file:///tmp/generated-file
Job corresponds to a kubernetes job, and can be authenticated with -remote-cluster
and -kube-config=$KUBE_PATH
, or by launching it into a pod:
$ dockerize -wait job://custom_namespace:my_job
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.
$ dockerize -skip-tls-verify -wait https://web:80
You can load defaults for missing env vars from INI file.
Multiline flag allows parsing multiline INI entries.
File with header must contain single string with Header: value
.
$ dockerize -env /path/to/file.ini -env-section SectionName -multiline …
$ dockerize -env http://localhost:80/file.ini \
-env-header "Header: value" -env-header /path/to/file/with/header …
Templates use Golang text/template. You can access environment
variables within a template with .Env
.
{{ .Env.PATH }} is my path
In template you can use a lot of functions provided by Sprig plus a few built in functions as well:
exists $path
- Determines if a file path exists or not.{{ exists "/etc/default/myapp" }}
parseUrl $url
- Parses a URL into it's protocol, scheme, host, etc. parts. Alias forurl.Parse
isTrue $value
- Parses a string $value to a boolean value.{{ if isTrue .Env.ENABLED }}
jsonQuery $json $query
- Returns the result of a selection query against a json document.
WARNING! Incompatibility with original dockerize v0.6.1! These template functions was changed because of adding Sprig functions, so carefully review your templates before upgrading:
default
- order of params has changed.contains
- now it works on string instead of map, usehasKey
instead.split
- now it split into map instead of list, usesplitList
instead.replace
- order and amount of params has changed.loop
- removed, useuntilStep
instead.
Objects and fields are accessed by name. Array elements are accessed by index in square brackets (e.g. [1]
). Nested elements are separated by dots (.
).
Examples:
With the following JSON in .Env.SERVICES
{
"services": [
{
"name": "service1",
"port": 8000,
},{
"name": "service2",
"port": 9000,
}
]
}
the template expression jsonQuery .Env.SERVICES "services.[1].port"
returns 9000
.