Metadata-Version: 2.0
Name: ruamel.dcw
Version: 0.2.3
Summary: docker-compose wrapper allowing for user data and env. var defaults
Home-page: https://bitbucket.org/ruamel/dcw
Author: Anthon van der Neut
Author-email: a.van.der.neut@ruamel.eu
License: MIT
Platform: UNKNOWN
Classifier: Development Status :: 4 - Beta
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python
Requires-Dist: docker-compose (>=1.6.0,<1.7.0)
Requires-Dist: ruamel.showoutput
Requires-Dist: ruamel.std.pathlib
Requires-Dist: ruamel.yaml (>=0.11)

docker-compose wrapper allowing for user data and env. var defaults
===================================================================

``dcw`` can be invoked with exactly the same commands as
docker-compose.  If ``-f``/``--file`` is specified as the first option
the filename to be read will be taken from the argument. Otherwise
``docker-compose.yml`` is assumed (currently the alternative default
files are not tested/read) the YAML file.

The YAML file has to be in the version: "2" format.

``dcw`` loads and processes the YAML file and invokes
``docker-compose --file=-`` and the original commandline arguments,
then pipes in the processed data (as YAML).

The examples in usage refer to a container `smtp` that implements an SMTP
"filter", accepting material on an incoming port, filtering spam and
viruses, and sending mail on to a relay for delivery.

processing
==========

The following subsections describe the processing that ``dcw`` does
and the reasons for doing so.

reading defaults
----------------

The key value pairs under ``user-data -> env-defaults`` are taken
to populate ``os.environ``, unless the key already exists. This means 
you can set defaults for the environment variables used in the 
docker-compose YAML file.


For `smtp` this allows you to have specific ports that will be used on
the deployment machine "backed in", while on the development machine
(where there is the need for uninterrupted "normal" mail during
testing) some environment variables can be set, for port-numbers and
directories, that override the values in the YAML file.


stripping user-data
-------------------

Any existing top-level key "user-data" or starting with "user-data-" is
removed. This allows for storing additional data in the file 
(which would require yet another configuration file or extraction
from YAML comments).

including defaults in Dockerfile actions
----------------------------------------

All of the environment variables specified in `env-defaults` are
written to the file ``.dcw_env_vars.inc`` (if the YAML file is newer
than that file). They are written with the environment variable value
if that is available, otherwise with the default as specified in the
YAML file.

The file looks like::

  export DOCKER_SMTP_HOST="some_host_name"
  export DOCKER_SMTP_DOMAIN="your_domain.com"
  export DOCKER_SMTP_RELAY="192.168.0.101"

and this file can be mapped in the Dockerfile with::

  ADD .dcw_env_vars.inc /tmp/env_vars.inc

and then used in some script in later (RUN) stanzas with::

  source /tmp/env_vars.inc




Example
=======

This is the first part of one of my ``docker-compose.yml`` files::

  version: '2'
  user-data:
    author: Anthon van der Neut <a.van.der.neut@ruamel.eu>
    description: postfix container
    env-defaults:
      PORT: 587    # override during development
  services:
    submission:
      container_name: submission
      build: .
      ports:
      - ${PORT}:587


The "author" and "description" information can easily be extracted and
used by other processes.

While developing I cannot use the submission port (587) as that is
already taken, and there I do `export PORT=10587`. On my deployment machine
I don't want to have to set PORT to the default value. With ``dcw``
the PORT env. var is set to 587 because there is no environment var "PORT"
defined on that machine.




