======================================
Docker base image for Monasca services
======================================

This image is used as a starting point for images of all Monasca services.


Building monasca-base
=====================

You need to have Docker installed (minimum supported version is ``17.09``).
Then you could build image inside of this folder:

``docker build --no-cache -t monasca-base:1.0.0 .``


Building child image
--------------------

In the ``example`` folder you could file sample of how to start building
new child image using ``monasca-base`` as start.

Requirements
~~~~~~~~~~~~

Every child image need to provide two files:

start.sh
  In this starting script provide all steps that direct to proper service
  start. Including usage of wait scripts and templating of configuration files.
  You also could provide ability to allow running container after service died
  for easier debugging.

health_check.py
  This file will be used for checking status of application running in the
  container. It will be useful for programs like Kubernetes or Docker Swarm
  to properly handle services that are still running but stopped being
  responsive. Avoid using `curl` directly and instead use `health_check.py`
  written with specific service in mind. It will provide more flexibility
  like when creating JSON request body.


Wait scripts
------------

Some Python libraries are already preinstalled: `pykafka` and `PyMySQL`.
They are used by wait scripts and in the process of creating child image
`pip3` will reinstall them to proper versions confronting to upper constraints
file.

This wait scripts will be available in every child image and could be used in
`start.sh` to avoid unnecessary errors and restarts of containers when they
are started.

::

    python3 /kafka_wait_for_topics.py || exit 1
    python3 /mysql_check.py || exit 1
    /wait_for.sh 192.168.10.6:5000 || exit 1

Please, check content of every of this files for documentation of what
environment variables are used and more usage examples.


Useful commands
---------------

List all labels on image (you need to have ``jq`` installed):

``docker inspect monasca-api:master | jq .[].Config.Labels``

Get all steps from what Docker image was build:

::

    docker history --no-trunc <IMAGE_ID>
    docker history --no-trunc monasca-base:1.0.0