build(all): Decouple Docker from Maven

[igbanam]

While building out the utilities, we want to vend some packages as Docker images.

Our current build builds like this

┌─────────┐     ┌───────┐          ┌────────┐     ┌───────┐
│ machine │ ··> │ maven │ ·······> │ docker │ ··> │ image │
└─────────┘     └───────┘  :       └────────┘     └───────┘
                           :       ┌────────┐
                           └·····> │  app   │
                                   └────────┘

Ideally, we want to be able to build like this

┌─────────┐     ┌───────┐     ┌─────┐
│ machine │ ··> │ maven │ ··> │ app │
└─────────┘     └───────┘     └─────┘
┌─────────┐     ┌───────┐
│ docker  │ ··> │ image │
└─────────┘     └───────┘

…a clean separation of concerns.

This would also remove the dependence on the docker-compose plugin which uses the deprecated docker-compose command.

[igbanam]

Summary from Slack:

• The image produced by the PR doesn't work™

Suggested changes

• Bring back the empty properties files
• Undo docker.context.xml renaming because this affects the metrics URL

Questions for @ademarcqrtsl

• Why do we need 4 empty properties files?
  • why not just one?
  • why not more than four?
• Could we have some documentation on how to run this?

[ademarcqrtsl]

@igbanam ,

The empty properties deletion is harmless. What broke the image was renaming /app/rtsl/prom_db_exporter/prom_db_exporter.5.docker.properties to /app/rtsl/prom_db_exporter/docker.properties without reflecting the change in /usr/local/tomcat/conf/Catalina/localhost/*.xml

The empty properties deletion should be undone because they are placeholders, and it will be easier for people to find them if they are empty files (we can discuss it if you have better ideas on this and/or comments)

[ademarcqrtsl]

More context regarding the empty files.

That app loads its config by merging X properties files to get its final consolidated configuration. In order it loads (from file https://github.com/simpledotorg/rtsl_utils/blob/igbanam/sc-13779/extract-pde-image-build/Webapps/PrometheusDatabaseExporterWar/src/main/resources/spring.main.xml ):

1. default.properties (inside the war itself, contains defaults described in the documentation)
2. X properties with paths injected by environment variables / tomcat context XML

/app/rtsl/prom_db_exporter/prom_db_exporter.5.docker.properties Is loaded last and should contain all the things we want to more or less hard code in image. (like paths, mapping with environment variables ...)

Docker being by design made to be extended (layers), we're having more than one file to make this easy to extend by just COPY on property file that we want for each layer.

Classical layers for images in delivery can be

• solution (dhis2/simple ...)
• project (india/ nigeria ...)
• environment (test/ production ...)

This part can be discussed if you find it complex to understand.

I'm taking the point for updating the documentation on image usage / extension

[ademarcqrtsl]

Also, the content of the Image has been merged with the content of the WAR. This is not something we want as the two set of configuration serve different purpose.

• With this change the original content of https://github.com/simpledotorg/rtsl_utils/tree/master/docker_content/prometheus_db_exporter ends up being present in the WAR, resulting in inert files that are mainly going to confuse people. (they are there, but not used)
• There was two logback.xml files for a reason. Merging them changed the behaviour of the image by changing the log files location.