In this short post, I'd like to describe how to leverage Apache in containers, drawing on personal experiences with Spring Boot and WebSphere administration.

Though I always worked on the Dev side of IT, I was also interested in the Ops side. I even had a short experience being a WebSphere admin: I used it several times, helping Ops deal with the Admin console while being a developer.

Providing a single package that Ops can configure and deploy in different environments is very important. As a JVM developer, I've been happy using Spring Boot and its wealth of configuration options: command-line parameters, JVM parameters, files, profiles, environment variables, etc.

File-based configuration​

The foundation of configuring Apache is file-based. The default values are found in the /usr/local//conf//config-default.yaml configuration file. For example, by default, Apache runs on port 9080, and the admin port is 9180. That's because of the default configuration:

:  node_listen:    - 9080           #1#...deployment:  admin:    admin_listen:      ip: 0.0.0.0      port: 9180     #2

1. Regular port
2. Admin port

To override values, we need to provide a file named config.yaml in the /usr/local//conf/ directory:

:  node_listen:    - 9090           #1deployment:  admin:    admin_listen:      port: 9190     #1

1. Override values

Now, Apache should run on port 9090, and the admin port should be 9190. Here's how to run the Apache container with the above configuration:

docker run -it --rm apache/:3.4.1-debian \                 -p 9090:9090 -p 9190:9190 \                 -v ./config.yaml:/usr/local//conf//config.yaml

Environment-based configuration​

The downside of a pure file-based configuration is that you must provide a dedicated file for each environment, even if only a single parameter changes. Apache allows replacement via environment variables in the configuration file to account for that.

:  node_listen:    - ${{_NODE_LISTEN:=}}                  #1deployment:  admin:    admin_listen:      port: ${{DEPLOYMENT_ADMIN_ADMIN_LISTEN:=}} #1

1. Replace the placeholder with its environment variable value at runtime

We can reuse the same file in every environment and hydrate it with the context-dependent environment variables:

docker run -it --rm apache/:3.4.1-debian \                 -e _NODE_LISTEN=9090 \                 -e DEPLOYMENT_ADMIN_ADMIN_LISTEN=9190 \                 -p 9090:9090 -p 9190:9190 \                 -v ./config.yaml:/usr/local//conf//config.yaml

Icing on the cake, we can also offer a default value:

:  node_listen:    - ${{_NODE_LISTEN:=9080}}                  #1deployment:  admin:    admin_listen:      port: ${{DEPLOYMENT_ADMIN_ADMIN_LISTEN:=9180}} #1

1. If no environment variable is provided, use those ports; otherwise, use the environment variables' value

The trick works in standalone mode with the . yaml file. You can parameterize every context-dependent variable and secrets with it:

routes:  - uri: /*    upstream:      nodes:        "httpbin:80": 1    plugins:      openid-connect:        client_id:         client_secret: ${{OIDC_SECRET}}        discovery: https://${{OIDC_ISSUER}}/.well-known/openid-configuration        redirect_uri: http://localhost:9080/callback        scope: openid        session:          secret: ${{SESSION_SECRET}}

Conclusion​

When configuring Apache , we should ensure it's as operable as possible. In this post, I've described several ways to make it so.

Happy Apache !

To go further:

• Default configuration
• Configuration file switching based on environment variables