encab 0.0.2

Docker entypoint tool

Encab: A Docker Entrypoint Tool

Encab is essentially a replacement for complex, hand-written Docker Container Entrypoint scripts, especially when dockerizing complex legacy applications.

Add it as your Dockerfile Entrypoint, together with the encab configuration file encab.yml,

   ...
   ADD encab.yml .
   ENTRYPOINT ["encab"]

define what you want to run in your container in encab.yml,

   programs:
      cron:
         command: cron -f
      main:
         command: httpd-foreground

and encab cares for the rest. Run it and you'll always know who's logging what...

   INFO  encab: encab 0.0.1
   INFO  encab: Using configuration file ./encab.yml, source: Default location.
   ERROR main: AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
   ERROR main: AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
   ERROR main: [Wed Jan 18 09:47:12.417275 2023] [mpm_event:notice] [pid 12:tid 140142563044672] AH00489: Apache/2.4.54 (Unix) configured -- resuming normal operations
   ERROR main: [Wed Jan 18 09:47:12.417830 2023] [core:notice] [pid 12:tid 140142563044672] AH00094: Command line: 'httpd -D FOREGROUND'
   INFO  cron: Hello Wed Jan 18 09:48:01 UTC 2023

It shares some similarities with supervisord which I've used before I wrote encab but supervisord is a process controll system not designed to run in a Container environment.

Note

This tool is still under development. Sufficient for local experiments but not mature enough for production use!

Features

• run multiple programs in a container at a time with transparent logging
• run programs as different users
• handle environment variables in a flexible way
• simplify container debugging
• load, build, validate environment variables

Documentation

Encab Documentation

Installation

From Source

Encab is not yet at pypi so installation from source is the only option right now.

Prerequisites

• Docker from your Linux distribution or Docker Desktop.
• git distributed version control system
• Python Version >= 3.7
• activated Python virtual environment such as miniconda or virtualenv

Download

   git clone https://github.com/skuebeck/encab.git
   cd encab
   pip install -r requirements.txt

Build Wheel

   make dist

If all goes well, the encab wheel file will be in the dist directory.

It's named encab-<version>-py3-none-any.whl

Testing (optional)

run unit tests:

   make test

run localy:

   python -m encab

It'll use the sample encab.yml file. The result will be something like this:

INFO  encab: encab 0.0.1
INFO  encab: Using configuration file ./encab.yml, source: Default location.
INFO  encab: Dry run. No program will be started.
INFO  encab: settings are valid.
INFO  encab: settings are valid.
INFO  encab: settings are valid.
INFO  encab: Dry run succeeded. Exiting.

Deployment

1. Copy the generated wheel file into your Docker project directory.

2. Create a configuration file encab.yml(see Configuration section for details).

      programs:
         main:
            sh: echo 'Hello World'
   

3. Add Encab to your Docker file.

   FROM python:3.10.8-slim-bullseye
   
   # --------------------------------------------
   # Install Encab 
   #
   ARG ENCAB_WHEEL=encab-0.0.1-py3-none-any.whl
   
   ENV PATH=$PATH:/root/.local/bin
   RUN python3 -m pip install --user pipx
   ADD ${ENCAB_WHEEL} .
   RUN python3 -m pipx install ./${ENCAB_WHEEL}
   
   # -------------------------------------------
   # add configuration file
   #
   ADD encab.yml .
   
   # -------------------------------------------
   # set encab as entrypoint
   ENTRYPOINT ["encab"]
   

4. Build container

   docker build --build-arg ENCAB_WHEEL=`ls encab-*.whl` -t encab_minimum .
   

5. Run container

   docker run encab_minimum
   

   Result:

   INFO  encab: encab 0.0.1
   INFO  encab: Using configuration file ./encab.yml, source: Default location.
   INFO  main: Hello world!
   INFO  main: Exited with rc: 0
   

Similar Projects

• supervisord
• supervisord Github