Viewing Logs

When something goes wrong with a Docker Compose deployment of Chap Core, the logs are usually the first place to look. There are two complementary places to check.

Service logs (docker compose logs)

The REST API and worker log to their container output (stdout/stderr), so use docker compose logs to read them.

To stream logs from all services:

docker compose logs -f

To view logs from a specific service:

docker compose logs -f chap
docker compose logs -f worker
docker compose logs -f postgres

The most relevant services are:

• chap: the Chap Core REST API
• worker: the Celery worker that runs the models. Check this if a model run fails
• postgres: the database

Per-task log files

In addition to the service output, the worker writes a log file for each task (typically a model run) into the directory given by the CHAP_LOGS_DIR environment variable. In the default Docker Compose setup this is /data/logs, backed by a named logs volume shared between the chap and worker services:

• task_{task_id}.debug.txt: the complete log for the task, including progress messages, library output and, for a failed chapkit model run, the model's stdout and stderr. The tail of this file is what GET /v1/jobs/{task_id}/logs returns

{task_id} is the internal Celery task id. Because these files live inside the container's volume rather than in the repository on the host, read them through the running container, for example:

# List the task log files
docker compose exec worker ls /data/logs

# View the debug log for a specific task
docker compose exec worker cat /data/logs/task_<task_id>.debug.txt