Azure Functions Binding Expression in Java not resolving when deployed

Question

I have an Azure Java Function App (Java 11, gradle, azure-functions-java-library 1.4.0) that is tied to an event hub trigger. There are parameters that I can inject into the annotation by surrounding with % as per https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-expressions-patterns. The connection isn't using the % since it's a special param that is always taken from the app properties.

When I run my function locally, using ./gradlew azureFunctionsRun it runs as expected. But once it's deployed to an Azure Function App, it complains that it can't resolve the params.

The error in Azure:

2021-05-27T18:25:37.522 [Error] Microsoft.Azure.WebJobs.Host: Error indexing method 'Functions.EventHubTrigger'. Microsoft.Azure.WebJobs.Host: '%app.eventhub.name%' does not resolve to a value.

The Trigger annotation looks like:

@FunctionName("EventHubTrigger")
    public void run(
        @EventHubTrigger(name = "event",
                connection = "app.eventhub.connectionString",
                eventHubName = "%app.eventhub.name%",
                consumerGroup = "%app.eventhub.consumerGroup%",
                cardinality = Cardinality.MANY)
                List<Event> event,
        final ExecutionContext context
    ) {
        // logic
     }

Locally in local.settings.json I have values for:

 "app.eventhub.connectionString": "Endpoint=XXXX",
 "app.eventhub.name": "hubName",
 "app.eventhub.consumerGroup": "consumerName"

And in Azure for the function app, I have Configuration (under Settings) for each of the above.

Any ideas what I'm missing?

andre · Accepted Answer · 2021-05-27 20:42:42Z

After some further investigation, I managed to get things working in Azure Function Apps by changing my naming convention, from using . as separators to _.

This ended up working both locally and when deployed:

@FunctionName("EventHubTrigger")
    public void run(
        @EventHubTrigger(name = "event",
                connection = "app_eventhub_connectionString",
                eventHubName = "%app_eventhub_name%",
                consumerGroup = "%app_eventhub_consumerGroup%",
                cardinality = Cardinality.MANY)
                List<Event> event,
        final ExecutionContext context
    ) {
        // logic
     }

With configuration settings in local.settings.json as:

 "app_eventhub_connectionString": "Endpoint=XXXX",
 "app_eventhub_name": "hubName",
 "app_eventhub_consumerGroup": "consumerName"

And corresponding updates made to the App configuration.

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