Azure Functions Lab

A Lab to tryout workflows with C# Azure Functions using HTTP and Azure Service Bus Triggers

Implementation

The lab consisting in:

• A 0-StartingIntegrationFunction function exposing a HTTP API to start the process flow;
• 0-StartingIntegrationFunction function publish a message in the messagedispatched Azure Service Bus Topic;
• 1-DispatchedMessagesPublisherFunction function listen the topic via MessageDispatchedSubscription and POST data to a HTTP API exposed by 2-DispatchedMessagesProcessor function;
• 2-DispatchedMessagesProcessor function publish another processed message into messagesprocessed Azure Service Bus Topic;
• 3-ProcessedMessagesSubscriberFunction listen the topic via MessagesProcessedSubscription;

All the functions has instructions (Failure.AtRateOf(xx);) to fail at some "rate" to simulate failures and prove process resiliency via retries.
Functions triggered by HTTP handles retries via attribute decoration ([FixedDelayRetry(xx, "hh:mm:ss")]) while Service Bus triggered Functions retries automatically whenever the function fails based on MaxDeliveryCount of the Service Bus Topic`s Subscription.
Functions writes Message's metadata into CosmosDb with MongoDb API and Message's body into Azure Storage Account to keep track of the process state, these data are expose by a REST API maded of HTTP triggered Azure Functions.

Local Configuration

After running Terraform infrastructure automation, you should create and fill some configuration values in local.settings.json file at project's root. This file should not be uploaded to the repository as it contains sensitive data.

{
	"IsEncrypted": false,
	"Values": {
		"MessageProcessorServiceUrl": "http://localhost:7071/api/",
		"FUNCTIONS_WORKER_RUNTIME": "dotnet",
		"AzureWebJobsStorage": "UseDevelopmentStorage=true",
		"BrokerConnectionString": "<run: terraform output BrokerConnectionString>",
		"DatabaseConnectionString": "<run: terraform output DatabaseConnectionString>",
		"StorageConnectionString": "<run: terraform output StorageConnectionString>",
		"DatabaseCollection": "integrations",
		"DatabaseName": "dbintegrationlab",
		"StorageContainerName": "messages"
	}
}

Running

# '~' is used to represent the project`s root folder
# create adjacent infrastructure
$ cd ~/environment/terraform
$ az login
$ terraform init
$ terraform apply
$ terraform output <property> (for sensitive data)

# running the project locally
$ cd ~/SomeExampleFunctions
$ func start --verbose

Dependencies

• .Net 5.0
• Azure Functions Core Tools 3.0
• Azure CLI 2.28
• Terraform 1.0
• Free Azure Account (services used in this lab aren`t free)