chap-core

Enabling Optional Model Services

Some models require an external service to be running alongside Chap. These services are not started by default but can be enabled using a Docker Compose overlay file.

!!! note This page covers models that are not in the CHAP Model Marketplace. Marketplace models are installed with chap-admin install-all (see First-time Setup) and need no config edits or rebuild. Use the steps below only for additional services like ewars_plus or chtorch. chtorch is a chapkit service: it registers a model template on its own but gets no configuration, so add one as described in Give it a configuration.

To add a model service of your **own**, see [Running Your Own Model](/chap-core/docs/modeling-app/running-your-own-model.html).

Available Optional Services

Service	Image	Port	Description
ewars_plus	maquins/ewars_plus_api:Upload	3288	EWARS Plus R-based prediction API
chtorch	ghcr.io/dhis2-chap/chtorch:chapkit2-8f17ee3	5001	Deep learning model using chapkit

Setup

Chap ships with a compose.override.yml.example file that defines these optional services.

!!! warning “Pass -f compose.override.yml explicitly” Compose only merges compose.override.yml on its own when you run a bare docker compose with no -f flags at all. As soon as you pass any -f — as First-time Setup does — the override file is ignored, silently and with no error, so the optional services never start. The commands below assume the compose.marketplace.yml file that chap-admin writes in that guide; adjust them to match how you started Chap, keeping compose.override.yml last.

1. Copy the overlay file

cp compose.override.yml.example compose.override.yml

2. Edit the overlay (optional)

Open compose.override.yml and remove any services you do not need. For example, to enable only EWARS Plus:

services:
  ewars_plus:
    image: maquins/ewars_plus_api:Upload
    container_name: ewars_plus
    ports:
      - "3288:3288"

3. Add the model to configured models

The model also needs to be registered so that Chap seeds it on startup. Create or edit a YAML file in config/configured_models/ (do not edit default.yaml):

# config/configured_models/local.yaml
- url: https://github.com/dhis2-chap/ewars_plus_python_wrapper/
  versions:
    v1: "@<commit-sha>"  # the full sha of the commit to run; branches are rejected

See Managing models for details on the configured models format.

4. Rebuild and start

After adding the overlay and the model configuration, rebuild the Chap images (so the new config is included) and start all services:

docker compose -f compose.yml -f compose.marketplace.yml -f compose.override.yml build chap worker
docker compose -f compose.yml -f compose.marketplace.yml -f compose.override.yml up -d

5. Verify

Check that the service is running and the model appears in the API:

docker compose -f compose.yml -f compose.marketplace.yml -f compose.override.yml ps
curl http://localhost:8000/v1/crud/configured-models

The model (e.g. ewars_plus) should appear in the list of configured models.

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