Sending webhooks (Kafka to HTTP)

This example showcases the use of the HTTP Publisher to call webhooks with HTTP POST requests. It consists of three services:

producer publishes messages on Kafka. The messages come in three varieties: Foo, Bar, and Baz. The event type is encoded in metadata, under the key event_type.
webhook_server is a HTTP server that listens for requests and prints the path, method, and payload on stdout.
router consumes the Kafka messages, and uses the HTTP producer to send requests to webhook_server. To illustrate how one message can spawn multiple webhooks, the following paths are called based on event_type:
1. /foo for events of type Foo
2. /foo_or_bar for events of type Foo or Bar
3. /all for all events.

Additionally, the kafka service (a Redpanda broker) is present to provide backend for the Kafka producer and subscriber.

Requirements

To run this example you will need Docker and docker-compose installed. See installation guide at https://docs.docker.com/compose/install/

To run all services, execute:

docker-compose up

To filter messages from a specific service, execute:

docker-compose logs [-f] {service}

in a separate terminal window while the services are running. Use the -f flag to emulate tail -f behavior, i.e. follow the output.