Catow: Camunda Topic Watcher

Catow is a small webservice based on fastapi. It checks, if a topic in Camunda BPMN platform as more than 0 tokens. If so, an HTTP-GET is triggered. In combination with robotframework webservice, this can trigger a robot task. When the robot tasks uses CamundaLibrary, it can consume the token provided by Camunda.

Run with Python

Installation

Camunda Topic Watcher is not yet available on pypi. But you can install it directly from github:

pip install git+https://github.com/Noordsestern/catow.git

Usage

python -m Catow.main -t <topic to be subsribed to> -r <url to be triggered>

You can also add:

• -p specifying the port Camunda Topic Watcher should run on (used later for heath checks) (default: 5003)
• -i definying the polling interval in seconds (default: 3 seconds)
• -c setting the url to Camunda (default: http://localhost:8080)

Run with Docker

Installation

docker pull ghcr.io/noordsestern/catow:master

Usage

docker run -d --name catow --env CAMUNDA_TOPIC=<external task topic> --env DESTINATION_URL=<my-destination-rul> --env POLLING_INTERVAL=10 ghcr.io/noordsestern/catow:master

Concept

Catow is under development and currently in Alpha.

Catow helps you when running robotframework tasks with CamundaLibrary tomake sure that the task has actually tokens to fetch from Camunda:

Run demo

Pre assumption

Python installed

Make sure you have python installed. Recommended is 3.9.

Camunda installed

You already have Camunda platform running on http://localhost:8080. You can find installation instractions at Camunda Documentation.

1. Install Robot Framework and CamundaLibrary

Run

pip install robotframework-camunda

robotframework-camunda will automatically pull the apropriate version of Robot Framework.

2. Upload demo model

While having Camunda platform running, upload the model by running:

robot -d logs tests/demo_upload_model.robot

3. Start demo process

Produce a few demo process instances by running:

robot -d logs tests/demo_producer.robot

You can verify in Camunda cockpit that you now have demo tokens waiting in the process:

3. Start Robotframework webservice

First install robotframework-webservice with pip

pip install robotframework-webservice

create a logs folder:

mkdir logs

and start the webservice while providing the demo consumer:

 python -m RobotFrameworkService.main -p 5004 -t tests/demo_consumer.robot

The last call starts the webservice listening on port 5004 and having tests/demo_consumer.robot ready to be executed.

4. Start Catow

Install Catow dependencies with:

pip install -r requirements.txt

Start catow with

python -m Catow.main

5. Review the output from Catow

Catow should produce the following output:

INFO:     Started server process [15228]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
{"count":3}
Start Robot!
INFO:     Uvicorn running on http://0.0.0.0:5003 (Press CTRL+C to quit)
{"count":2}
Start Robot!
{"count":1}
Start Robot!
{"count":0}
Nothing to do here.

You can see that the count goes down for each time Catow triggers the robotframework webservice. Once the count is at 0, it prints Nothing to do here. every time the count is polled.

You can now re-run the demo_producer.robot task in order to repeat the experiment.

Vision

Catow is a very simple service that shall make Robot tasks scalable: