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feat(triggers): NATS example (#54)
* Working example * Clean-up * Add link to top-level README * README fixes
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‎README.md

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| **[PostgreSQL Python](functions/postgre-sql-python/README.md)** <br/> A Python function to perform a query on a PostgreSQL managed database. | python310 | [Serverless Framework] |
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| **[Terraform Python](functions/terraform-python-example/README.md)** <br/> A Python function deployed with Terraform. | python310 | [Terraform] |
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| **[Triggers Getting Started](functions/triggers-getting-started/README.md)** <br/> Simple SQS trigger example for all runtimes. | all | [Terraform] |
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| **[Triggers NATS](functions/triggers-nats/README.md)** <br/> Simple NATS trigger example using Terraform. | all | [Terraform] |
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| **[Typescript with Node runtime](functions/typescript-with-node/README.md)** <br/> A Typescript function using Node runtime. | node18 | [Serverless Framework] |
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| **[Serverless Gateway Python Example](functions/serverless-gateway-python/README.md)** <br/> A Python serverless API using Serverless Gateway. | python310 | [Python API Framework] |
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‎functions/triggers-nats/.gitignore

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# Nats credentials
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files/nats-creds
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# Local .terraform directories
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**/.terraform/*
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# .tfstate files
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*.tfstate
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*.tfstate.*
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# Crash log files
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crash.log
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crash.*.log

‎functions/triggers-nats/README.md

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# Triggers NATS example
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Simple example showing how to use NATS triggers with Scaleway Functions.
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For complete examples of triggers in all function languages, see [triggers-getting-started](../triggers-getting-started).
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The example function is triggered by a message to a NATS topic, and will log the message body.
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## Requirements
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This example requires [Terraform](https://www.scaleway.com/en/docs/tutorials/terraform-quickstart/).
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Also, NATS **must** be [activated](https://www.scaleway.com/en/docs/serverless/messaging/how-to/get-started/#how-to-create-a-nats-account) on your project.
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## Setup
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The Terraform configuration will create an example function, a NATS account, and a trigger. It will also write the NATS credentials to a file (`files/nats-creds`).
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To authenticate with Scaleway, you can either set up the [Scaleway CLI](https://www.scaleway.com/en/cli/), from which Terraform can extract credentials, or you can export `SCW_ACCESS_KEY`, `SCW_SECRET_KEY` and `SCW_DEFAULT_PROJECT_ID`.
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Once auth is set up, you can run:
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```console
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terraform init
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terraform apply
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```
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You should be able to see your resources in the Scaleway console:
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- NATS accounts can be found in the [MnQ section](https://console.scaleway.com/messaging/protocols/fr-par/nats/accounts)
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- Functions can be found in the `triggers-nats` namespace in the [Serverless functions section](https://console.scaleway.com/functions/namespaces)
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## Running
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You can trigger your functions by sending messages to the NATS topic associated to the trigger (`triggers-nats-topic`). Below is a description of how to do this with our dummy `tests/send_messages.py` script.
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### Setup
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First you need to extract your NATS endpoint from Terraform:
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```console
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export NATS_ENDPOINT=$(terraform output -raw nats_endpoint)
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```
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Then you can set up a Python environment in the `tests` directory, e.g.
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```console
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cd tests
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python3 -m venv venv
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source venv/bin/activate
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pip3 install -r requirements.txt
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```
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### Sending messages
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Now you can run the `send_messages.py` script to send a message to the NATS topic:
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```console
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python3 send_messages.py
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```
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### Viewing function logs
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In your [Cockpit](https://console.scaleway.com/cockpit), you can access the logs from your NATS topics and functions.
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Navigate from your Cockpit to Grafana, and find the `Serverless Functions Logs` dashboard. There you should see logs from your function, printing the body of the NATS message.
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## Cleanup
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To delete all the resources used in this example, you can run the following from the root of the project:
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```console
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terraform destroy
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```

‎functions/triggers-nats/files/function.zip

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‎functions/triggers-nats/function/handler.py

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def handle(event, context):
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# The content of the NATS message is passed in the body
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msg_body = event.get("body")
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print(f"Received message: {msg_body}")
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return "Hello NATS!"

‎functions/triggers-nats/main.tf

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resource "scaleway_function_namespace" "main" {
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name = "triggers-nats"
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}
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data "archive_file" "source_zip" {
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type = "zip"
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source_dir = "${path.module}/function"
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output_path = "${path.module}/files/function.zip"
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}
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resource "scaleway_function" "main" {
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namespace_id = scaleway_function_namespace.main.id
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name = "nats-target"
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runtime = "python310"
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handler = "handler.handle"
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zip_file = data.archive_file.source_zip.output_path
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zip_hash = filesha256(data.archive_file.source_zip.output_path)
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privacy = "public"
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deploy = true
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memory_limit = 512 # MB / 280 mVCPU
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min_scale = 0
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}
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resource "scaleway_function_trigger" "main" {
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function_id = scaleway_function.main.id
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name = "nats-trigger"
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nats {
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account_id = scaleway_mnq_nats_account.main.id
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subject = "triggers-nats-topic"
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}
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}

‎functions/triggers-nats/messaging.tf

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resource "scaleway_mnq_nats_account" "main" {
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name = "nats-account"
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}
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resource "scaleway_mnq_nats_credentials" "main" {
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account_id = scaleway_mnq_nats_account.main.id
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name = "triggers-nats"
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}
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resource "local_sensitive_file" "nats" {
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filename = "files/nats-creds"
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content = "${scaleway_mnq_nats_credentials.main.file}"
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}

‎functions/triggers-nats/outputs.tf

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output "nats_endpoint" {
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value = scaleway_mnq_nats_account.main.endpoint
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sensitive = true
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}
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‎functions/triggers-nats/provider.tf

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terraform {
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required_providers {
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scaleway = {
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source = "scaleway/scaleway"
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version = ">= 2.31"
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}
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archive = {
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source = "hashicorp/archive"
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version = ">= 2.4"
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}
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}
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required_version = ">= 0.13"
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}

‎functions/triggers-nats/tests/requirements.txt

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asyncio~=3.4.3
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boto3~=1.28.40
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nats-py~=2.5.0
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nkeys~=0.1.0
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requests~=2.31.0

‎functions/triggers-nats/tests/send_messages.py

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import asyncio
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import os
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import nats
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NATS_ENDPOINT = os.environ.get("NATS_ENDPOINT")
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NATS_CREDS_PATH = "../files/nats-creds"
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NATS_TOPIC = "triggers-nats-topic"
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async def main():
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print(f"Connecting to NATS account at {NATS_ENDPOINT}")
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# Connect to NATS
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nc = await nats.connect(servers=[NATS_ENDPOINT], user_credentials=NATS_CREDS_PATH)
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# Publish a message
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await nc.publish(NATS_TOPIC, b"Hello from the NATS trigger!")
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# Close NATS connection
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await nc.close()
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if __name__ == "__main__":
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asyncio.run(main())

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