Why is the mfe image not pre-built

[iamCristYe]

Well… this may be a stupid question, but why is the mfe image not pre-built? As of now, it’s required by every maple distribution and every tutor local quickstart, it would make sense to pre-built the image right?

[iamCristYe]

I understand that mfe image is built on top of many apps, and users may choose to add their own app, but providing a pre-built image including default enabled mfe apps would be appreciated, isn’t it?

[regis]

Great question. The problem is that the MFE image depends on every user’s specific configuration. For instance, the value of LMS_HOST is required to build the static assets. Thus, it is not possible to provide a single image that could be used by just anyone.

This is a very strong limitation of microfrontends that I did not understand when we first started talking about them a couple years ago. The general idea was that MFEs would be very easy to build and deploy, and in a sense they are. But building the MFE image is costly, and at the time I did not realize that.

Honestly, I feel like now is a good time to reflect on what works and what doesn’t with MFEs. We probably need to have a conversation with the community. Among the other issues that I would like to raise is the size of the MFE static assets: it’s not normal that we have to download 1-2Mb of static js files to access each and every MFE.

[kdmccormick]

@regisb Until there’s a reasonable way to pre-build and host the tutor-mfe image, would it be possible to remove the remote-image hook from tutor-mfe? With the mfe plugin enabled, I hit an error when I try to pull all images:

$ tutor images pull all
Pulling image docker.io/overhangio/openedx:13.1.5-nightly
...
...
Pulling image docker.io/overhangio/openedx-mfe:13.0.2
docker pull docker.io/overhangio/openedx-mfe:13.0.2
Error response from daemon: manifest for overhangio/openedx-mfe:13.0.2 not found: manifest unknown: manifest unknown
Error: Command failed with status 1: docker pull docker.io/overhangio/openedx-mfe:13.0.2
$

[regis]

I’m bummed about this one… The “remote-image” hook was added to the tutor-mfe plugin to allow users to push their image to a custom registry, in particular in the context of deploying a Kubernetes cluster: fix: missing remote-image hook by shimulch · Pull Request #33 · overhangio/tutor-mfe · GitHub
I honestly don’t know how to resolve this one. It’s definitely an issue, but we need to account for two different, contradictory scenarios:

1. The image should not be pulled if it’s built locally.
2. The image should be pulled if it exists in a remote Docker registry.

I think that this issue emphasises the deeper underlying problem that we have when dealing with MFEs, which is that we don’t know how to “properly” build them.

[kdmccormick]

@regis, in lieu of the MFE build story being generally improved, I think the flexibility of the V1 Plugin API might lead us to a temporary solution:

@hooks.Filters.APP_TASK_IMAGES_PUSH.add()
@hooks.Filters.APP_TASK_IMAGES_PULL.add()
def _add_remote_image_iff_customized(
    remote_images: List[Tuple[str, str]], config: Config
) -> List[Tuple[str, str]]:
    """
    Register MFE image for pushing & pulling if and only if it has
    been set to something other than the default.

    This is work-around to an upstream issue with MFE config. Briefly:
    User config is baked into MFE builds, so Tutor cannot host a generic
    pre-built MFE image. Howevever, individual Tutor users may want/need to
    build and host their own MFE image. So, as a compromise, we tell Tutor
    to push/pull the MFE image if the user has customized it to anything
    other than the default image URL.    
    """
    default_registry = get_typed(config, "DOCKER_REGISTRY", str)
    default_image_prefix = f"{default_registry}overhangio/openedx-mfe:"
    configured_image = get_typed(config, "MFE_DOCKER_IMAGE", str)
    if configured_image.startswith(default_image_prefix):
        # Image is plugin-supplied default. Do nothing.
        return remote_images
    else:
        # Image has been customized. Add to list for pulling/pushing.
        return remote_images + [("mfe", configured_image)]

Then, using hooks.Filters.APP_TASK_IMAGES_BUILD, we would just add the MFE image for building in the normal manner.

[regis]

This is really cool! I love it.

[kdmccormick]

Great! I captured it here: Rewrite the tutor-mfe plugin to use the V1 API · Issue #59 · overhangio/2u-tutor-adoption · GitHub