How do I post a message to a Azure Service Bus from my Azure function? - azure

Question

I am playing around with Azure functions and trying to setup an intricate construct of pipes and filters (the pattern). I am using Azure functions for this.
My starting point is a HTTP triggered Azure function. That collects some JSON from the body of the request and should pass this message to a Azure Service Bus.
I must be missing something here (I have done this before in RabbitMQ with console apps) but how do I post a message to a service bus from a HTTP triggered Azure function.
I found several references talking about configuring my function.json (what ever that is - im building in Visual Studio).
How does this input/output (trigger/binding) thing work - im guessing that is the problem here...or??
I have my first Azure function in place and is receiving the data from the HTTP - so far so good. But how to proceed?
** Update **
Still cant get it to Work. Got this code and it fails with an http500. (it also says i need to see the og - where is that log?)
public static class EI_WooCommerce_Hub
{
[FunctionName("EI_WooCommerce_Hub")]
[return: ServiceBus("eilogging", Connection = "EIIntegrationServiceBusConnection")]
public async static Task<string> Run([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = "EIWooCommerceHub/name/")]HttpRequestMessage req, TraceWriter log)
{
log.Info("Webhook triggered from: ");
return "Hello World to queue";
}
}
** Update 2 **
This seems to be a config problem. In the application settings on the function app I kept getting an authorization error for the servicebus. I added the default "AzureWebJobsServiceBus" setting with the connectionstring, then it worked. It could not pick up my own connection string for some reason.

Answer 1

You should use Service Bus output binding. Since you mentioned Visual Studio, I assume C#. The simplest ever example looks like this:
[FunctionName("ServiceBusOutput")]
[return: ServiceBus("myqueue", Connection = "ServiceBusConnection")]
public static string ServiceBusOutput([HttpTrigger] dynamic input)
{
return input.Text;
}
Then add an application setting called ServiceBusConnection with the connection string to a namespace with queue myqueue (or rename in attribute constructor).
You can find more in Azure Service Bus bindings for Azure Functions - Output.

Answer 2

When you build in Visual Studio, then the function.json is created automatically. All you have to do is to define your triggers and output as attributes of the function parameters (see here: https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-service-bus#output)
A minimalistic example:
[FunctionName("HttpTriggerCSharp")]
public static async Task<HttpResponseMessage> Run(
[HttpTrigger(AuthorizationLevel.Function, "get")] HttpRequestMessage req,
[ServiceBus("myqueue")] out string sbMessage,
TraceWriter log)
{
log.Info("C# HTTP trigger function processed a request.");
// parse query parameter
string name = req.GetQueryNameValuePairs()
.FirstOrDefault(q => string.Compare(q.Key, "name", true) == 0)
.Value;
sbMessage = name;
}