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Production

Docker

We currently deploy all apps using Docker. This project contains Docker infrastructure and a GitHub action that automatically builds and tags a Docker image on each commit. The image name is pcic/plan2adapt-v2-frontend.

Configuration, environment variables, and Docker

It is best practice to configure a web app externally, at run-time, typically using environment variables for any simple (atomic, e.g., string) configuration values.

Here we run into a problem introduced by CRA: CRA injects environment variables only at build time, not at run time. "The environment variables are embedded during the build time. Since Create React App produces a static HTML/CSS/JS bundle, it can’t possibly read them at runtime.".

We containerize our apps with Docker. A natural approach to deploying apps with Docker is to build the app as part of the image build, and then just serve it from a container. However, because of CRA's build-time injection of environment variables, this means that such Docker images cannot be configured at run-time, that is, when a container is run. Only static, build-time environment variables are available to CRA apps inside such images.

It therefore takes some extra effort to inject run-time environment variables (or configuration generally) into these Dockerized applications. There are two basic approaches:

  1. Build the app, and inject run-time environment variables, as part of the image run (i.e., the command run by the image includes building the app, which then has access to environment variables provided via the docker run command).

    • This is simple but it means that containers are slow to start up and contain a lot of infrastructure (Node.js, etc.) needed to build the image. This isn't an issue for us, because we don't start many instances and we don't start them often.

  2. Fetch the environment variables (or a configuration file) from the server.

    • This approach has several variants, which are outlined in this CRA issue.

A key requirement is to be able to configure at run time the the URL at which the app is deployed. CRA provides a (build-time) environment variable for this, PUBLIC_URL.

Option 2 makes setting PUBLIC_URL much harder to accomplish, and would require significant changes to the codebase.

Option 1 makes setting PUBLIC_URL simple and requires no change to the codebase; as noted we don't care about the cost of using such containers.

Therefore we have chosen option 1.

Deployment

See the contents of the docker directory for an example of how to run the Docker image. The Makefile shows how to run the image using docker-compose. You may wish to copy and modify docker-compose.yaml to construct a production deployment.