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Process background tasks with the rq worker

We've got our queue and we've added tasks to it, but they won't run until we start consuming them and popping them off the queue.

To do this, we'll run a background worker whose job it is to pop items off the queue one at a time, and run the associated Python function with the associated arguments.

MacOS or Linux?

If you are using MacOS or Linux, you can run the background worker for testing using this command (make sure your virtual environment is active):

rq worker -u <insert your Redis url here> emails

The rq executable is available after installing the rq library with pip. The -u flag gives it the Redis URL to connect to. The emails at the end is the name of the queue that it should consume from. Make sure it matches the name of the queue you defined in resources/

Running on MacOS

You may get an error when running rq worker directly using MacOS (without Docker):

objc[21400]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.

If so, try running this command before starting your rq worker:


The most reliable way to run the worker though, is using Docker.

We are already used to running our API using Docker, so now we can use the same Docker image to run our worker.

First, build the image:

docker build -t rest-apis-flask-smorest-rq .

Then run a container, but instead of running the default entrypoint (defined by the CMD line in the Dockerfile), we'll tell it to run the rq program:

docker run -w /app rest-apis-flask-smorest-rq sh -c "rq worker -u <insert your Redis url here> emails"

This ensures one of the considerations that the rq documentation suggests: that the worker and the work generator (our API) share exactly the same source code.

Run another Docker container for your API, and try to register!

docker run -p 5000:5000 rest-apis-flask-smorest-rq sh -c "flask run --host"