The Greeter Example

This is a simple example of a stateful functions application implemented in Python.

In this example, we imagine a service that computes personalized greetings. Our service, consist out of the following components:

• playground ingress - Ingestion point for messages. Messages are sent to the specified target function.

• person - This function is triggered by the ingress defined above. This function keeps track of the number of visits, and triggers the next functions:

• greeter - This function, computes a personalized greeting, based on the name and the number of visits of that user. The output of that computation is forward to a Kafka egress defined below.

• playground egress - Queryable endpoint that collects the emitted greetings in the greetings topic. The greeting is utf-8 encoded.

Running the example

$ docker-compose build
$ docker-compose up

Play around!

The greeter application allows you to do the following actions:

• Create a greeting for a user via sending a GreetRequest message to the person function

In order to send messages to the Stateful Functions application you can run:

$ curl -X PUT -H "Content-Type: application/vnd.example/GreetRequest" -d '{"name": "Bob"}' localhost:8090/example/person/Bob

To consume the customized greeting, as they appear in the greetings playground topic, run in a separate terminal:

$ curl -X GET localhost:8091/greetings

Messages

The messages are expected to be encoded as JSON.

• GreetRequest: {"name": "Bob"}, name is the id of the person function

What's next?

Feeling curious? add the following print to the person function at functions.py:

print(f"Hello there {context.address.id}!", flush=True)

Then, rebuild and restart only the functions service.

docker-compose build functions
docker-compose up functions