Gleam OpenFaaS function templates

This repository contains OpenFaaS function templates for writing serverless functions in the Gleam programming language.

Usage

1. Make sure OpenFaaS has been deployed to your Kubernetes cluster and the OpenFaaS CLI tool has been installed. See here and here for a brief introduction on how to do this.

2. Download the Gleam function templates from this repo:

faas-cli template pull https://github.com/nicklasxyz/gleam_openfaas#main

3. Create a new function:

faas-cli new --lang gleam test-function

Note: This essentially creates a usual Gleam project stucture, but with a pre-defined module name and files. The main functionality should be implemented in the files contained in the test-function/function directory. Extra dependencies should be added to the rebar.config file in the root of the test-function directory. The project can be compiled and tested locally as usual.

4. Add new functionality to the function that is going to be deployed and managed by OpenFaaS:

vi test-function/function/src/function.gleam
# ... Extend or add whatever you want to the file

5. Make sure a valid container registry, to where functions can be pushed, has been defined in the test-function.yml file:

vi test-function.yml

6. Finally, build, push and deploy the function:

# Authenticate with OpenFaaS (assuming kubectl is used with the k3s Kubernetes distribution):
PASSWORD=$(k3s kubectl -n openfaas get secret basic-auth -o jsonpath="{.data.basic-auth-password}" | base64 --decode) && \
echo "OpenFaaS admin password: $PASSWORD"
faas-cli login --gateway http://localhost:31112 --password=$PASSWORD

# Build, push and deploy:
faas-cli build -f test-function.yml
faas-cli push -f test-function.yml
faas-cli deploy -f test-function.yml --gateway=http://localhost:31112

# ... or just:
faas-cli up -f test-function.yml --gateway=http://localhost:31112

# To remove function deployments run:
faas-cli remove -f test-function.yml --gateway=http://localhost:31112

7. Wait a few seconds, then we can invoke the function by sending a request through curl:

### Example GET request
curl -k \
    http://localhost:31112/function/test-function; \
    echo

# If nothing was changed in the 'test-function/function/src/function.gleam' file before
# deployment then we should just see the default response:
>> Hello from Gleam & OpenFaaS!

### Example POST request:
curl -k \
    -d "{\"value\": {\"name\": \"YourNameHere\"}}" \
    -H "Content-Type: application/json" \
    -X POST http://localhost:31112/function/test-function; \
    echo

# If nothing was changed in the 'test-function/function/src/function.gleam' file before
# deployment then we should just see the default response:
>> {"int_field":42,"string_field":"Hello YourNameHere, from Gleam & OpenFaaS!"}

8. If we just want to check that the requests were handled properly then we can check the logs:

faas-cli logs test-function --gateway http://localhost:31112

The function can also be invoked through the public interface at http://localhost:31112/ui/ using username admin and the previously defined password contained in environment variable $PASSWORD.

Acknowledgements

The general webserver setup is taken from this repository by gleam-lang.