Is it possible to execute Event Hub triggered Azure Functions locally without using an actual Event Hub?

Question

I just want to ask if it is possible to execute an Azure Function (Event Hub trigger) purely on my local machine without depending on any Azure Event Hubs resource? I've been following Microsoft's process in developing Azure Functions locally (Link) but it seems that I need to fill in Event Hub connection string and name.

public static async Task Run([EventHubTrigger("samples-workitems", Connection = "eventhub-connectionstring")] EventData[] events, ILogger log)

Is there any way for this to be possible?

Answer 1

Each binding has an HTTP endpoint for local testing and debugging.

• https://localhost:7071/admin/functions/{FUNCNAME}

That's available for QueueTrigger, ServiceBusTrigger, TimerTrigger, EventHubTrigger at least.

Send a POST request with the expected data as JSON.

{ "input": "YOUR JSON SERIALIZED AND ESCAPED DATA" }

For triggers that need data put the data as serialized string into "input". See EventHubTrigger example further below.

TimerTrigger

For TimerTrigger use this:

{ "input": null }

EventGridTrigger

To execute this on some triggers it's bit tricky. Here it is for EventGridTrigger:

• https://localhost:7071/runtime/webhooks/EventGrid/functionName={FUNCNAME}

Send a POST request to execute. See here for details. The object must be an array.

EventHubTrigger

The EventHubTrigger receives data like the other triggers, as single JSON object. The structure follows the EventData class, but the only required field is "SystemProperties". There seems no serializer specific settings, property names do not change case etc.

Post this as body;

{
    "input": "{\"SystemProperties\":{},\"SomeId\":\"123\",\"Status\":\"Available\"}"
}

The event hub's body is the escaped and serialized value of "input".

Note that the same applies for the IoT Hub

Meta Data

For ALL triggers you can get meta data with a GET request. For an EventHubTrigger this could look like this:

{
    "name": "StateChange",
    "script_root_path_href": "http://localhost:7071/admin/vfs/StateChange/",
    "script_href": "http://localhost:7071/admin/vfs/bin/MyApp.Notifications.Functions.dll",
    "config_href": "http://localhost:7071/admin/vfs/StateChange/function.json",
    "test_data_href": null,
    "href": "http://localhost:7071/admin/functions/StateChange",
    "invoke_url_template": null,
    "language": "DotNetAssembly",
    "config": {
        "generatedBy": "Microsoft.NET.Sdk.Functions-3.0.11",
        "configurationSource": "attributes",
        "bindings": [
            {
                "type": "eventHubTrigger",
                "consumerGroup": "regular",
                "connection": "EventHub_Hub_Status",
                "eventHubName": "%EventHub_Status%",
                "name": "statusUpdateMessage"
            }
        ],
        "disabled": false,
        "scriptFile": "../bin/MyApp.Notifications.Functions.dll",
        "entryPoint": "MyApp.Notifications.Functions.StateChange.Run"
    },
    "files": null,
    "test_data": null,
    "isDisabled": false,
    "isDirect": true,
    "isProxy": false
}

And, of course you can use all the paths to retrieve the data, including the binaries. Very handy to write sophisticated integration tests.