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:
kafka ingress - This component forwards messages produced to the names kafka topic, to the person stateful function. Messages produced to this topic has the following schema { "name" : "bob"}.
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.
kafka egress - This wraps a Kafka producer that emits utf-8 greetings to the greetings Kafka topic.
docker-compose build docker-compose up
To observe the customized greeting, as they appear in the greetings Kafka topic, run in a separate terminal:
docker-compose exec kafka kafka-console-consumer \
--bootstrap-server kafka:9092 \
--isolation-level read_committed \
--from-beginning \
--topic greetings
Try adding few more input lines to input-example.json, and restart the producer service.
docker-compose restart producer
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