Example NestJS microservice project

!!! WARNING: Currently not working, see the known issues section.

Description

This is an example project how to write microservices with NestJS. The program use the Open meteo API to poll the current weather of a hungarian village called Lovas, and store it in memory. The program contains two microservice. The data-streams provide an /start http rest endpoint to start a request to the Open meteo for the current weather info, and also provide a /list endpoint where the previously asked whether information can be viewed. The other microservice called worker, that is used by the data-streams to fetch the weather information.

DEMO

Here you can see a demo how to use the tool: https://drive.google.com/file/d/1rDEnCS4oeyYWXEGoOWJZScnPPRV3BMTx/view?usp=drive_link

How to install

• Install the latest nodejs: https://nodejs.org/en/learn/getting-started/how-to-install-nodejs
• Install yarn package manager: https://classic.yarnpkg.com/lang/en/docs/install/
• Run the yarn install command: https://classic.yarnpkg.com/en/docs/cli/install

How to use

Start the data-streams with the following command. It will listen on the 5000 TCP port

yarn start

Start the data-streams with the following command. It will listen on the 5001 TCP port

yarn start worker

Now you can use the http://localhost:5000/start to start a weather information fetch. In the workers log, you can see the fetched data. Unfortunatelly, currently the /list endpoint not working, cause the worker -> data-streams communication is broken.

Known issues

• When worker triggers the store_temperature event, then the data-streams not getting triggered.
• Maybe the yarn install will fail with the following issue, then try to remove the yarn.lock file. yarnpkg/yarn#8994

Possible future development

• Add tests
• Add docker-compose support
• Replace in memory weather info store in data-streams with an external storage service
• Add scheduling feature to ask whether info in periods
• Add exception handling
• Add improved logging
• Separate data-streams into to microservice, so the users and the worker service wont use the same TCP port

Licence

Open meteo non-commercial licence mentions the following:

By using the Free API for non-commercial use you agree to following terms:

• Less than 10'000 API calls per day, 5'000 per hour and 600 per minute.
• You may only use the free API services for non-commercial purposes.
• You accept to the CC-BY 4.0 license, as specified in the license conditions.
• We reserve the right to block applications and IP addresses that misuse our service without prior notice.

https://open-meteo.com/en/terms