Encab: A Simple Process Manager

Encab is a process manager that simplifies running multiple services in a container or from the command line.

It's essentially a replacement for complex, hand-written Docker Container Entrypoint scripts, especially when dockerizing complex legacy applications.

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

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

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

   programs:
      cron:
         command: cron -f
         restart_delay: 1
      main:
         command: httpd-foreground

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

   INFO  encab: encab 1.0.5
   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 control system not designed to run in a Container environment.

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

Install locally

Prerequisites

• Python Version >= 3.7
• activated Python virtual environment such as miniconda or virtualenv

   pip install -U encab

Run locally

1. Create sample encab file encab.yml

   encab:
      dry_run: false
   programs:
      main:
         sh:
            - echo "Hello Encab!"

2. Run locally:

   encab

The result will be something like this:

INFO  encab: encab 1.0.5
INFO  encab: Using configuration file ./encab.yml, source: Default location.
INFO  main: Hello Encab!
INFO  main: Exited with rc: 0

Install in Container

Prerequisites

• Docker from your Linux distribution or Docker Desktop.

Run in Container

1. Create sample encab file encab.yml

   encab:
      dry_run: false
   programs:
      main:
         sh:
            - echo "Hello Encab!"

2. Add Encab to your Docker file.

   FROM python:3.10.8-slim-bullseye
   # --------------------------------------------
   # Install Venv 
   #
   ENV VIRTUAL_ENV=/opt/encabenv
   ENV PATH="$VIRTUAL_ENV/bin:$PATH"
   RUN python3 -m venv $VIRTUAL_ENV && \
      pip install --upgrade pip
   # --------------------------------------------
   # Install Encab 
   #
   
   RUN pip install encab
   
   # -------------------------------------------
   # add configuration file
   #
   ADD encab.yml .
   
   # -------------------------------------------
   # set encab as entrypoint
   ENTRYPOINT ["encab"]
   

3. Build container

   docker build -t encab_minimum .
   

4. Run container

   docker run encab_minimum
   

   Result:

   INFO  encab: encab 1.0.5
   INFO  encab: Using configuration file ./encab.yml, source: Default location.
   INFO  main: Hello world!
   INFO  main: Exited with rc: 0
   

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