Java EventHubTrigger not working

N Senthil 1

I am facing a situation with Java EventHub Trigger. I created one using VS Code and pointed to the Event Hub namespace that I had previously created. I see that the connection string is applied correctly. After deploying this function app I send a batch of messages to the event hub. I can see that the messages are received in Azure monitor dashboard. But the trigger is not triggered. When I monitor the trigger function the access count shows zero. What may be wrong in my Java eventhub trigger?

Krish G 2,331

Hello @N Senthil , can you please share your function annotation code snippet? For example:

@FunctionName("ehprocessor")  
public void eventHubProcessor(  
  @EventHubTrigger(name = "msg",  
                  eventHubName = "myeventhubname",  
                  connection = "myconnvarname") String message,  
       final ExecutionContext context )  
 {  
      //...  
 }

And also your function.json file.

Also, is it working when you debug locally?

Nalla 1

The java function and function.json are auto-generated by VS Code:

@FunctionName("EventHubTriggerJava1")
public void run(
    @EventHubTrigger(name = "message", eventHubName = "nallatrgrfn-evthub", connection = "nallatrgrfnns_RootManageSharedAccessKey_EVENTHUB", consumerGroup = "$Default", cardinality = Cardinality.MANY) List<String> message,
    final ExecutionContext context
) {
    context.getLogger().info("Java Event Hub trigger function executed.");
    context.getLogger().info("Length:" + message.size());
    message.forEach(singleMessage -> context.getLogger().info(singleMessage));
}

I'll post the function.json in the next note.

Nalla 1

function.jso

{
  "scriptFile" : "../nalla2-trgr-fn-1.0-SNAPSHOT.jar",
  "entryPoint" : "com.function.EventHubTriggerJava1.run",
  "bindings" : [ {
    "type" : "eventHubTrigger",
    "direction" : "in",
    "name" : "message",
    "connection" : "nallatrgrfnns_RootManageSharedAccessKey_EVENTHUB",
    "eventHubName" : "nallatrgrfn-evthub",
    "cardinality" : "MANY"
  } ]
}

I did not debug locally. I'll try that.

1 answer

Krish G 2,331 Reputation points

2020-08-04T16:58:50.16+00:00
@N Senthil , I suspect the possible cause of your issue is when the event is received, there might be a deserialization error:

Exception while executing function: Functions.EventHubExample. Microsoft.Azure.WebJobs.Host: Exception binding parameter message. Microsoft.Azure.WebJobs.Host: Binding parameters to complex objects (such as Object) uses Json.NET serialization.

Bind the parameter type as string instead of Object to get the raw values and avoid JSON deserialization, or

Change the queue payload to be valid json. The JSON parser failed: Unexpected character encountered while parsing value: H. Path , line 0, position 0.

Since dataType is not specified in the EventHubTrigger parameter, it is assuming that the message to be json format and trying to deserialize which fails if it is not. Adding dataType = string in the EventHubTrigger arguments like below fixed the issue since your example has List of string as input. Or if the message is in json format and input is pojo, setting datatype is not required which is the default. You can read more about that here.

@EventHubTrigger(name = "message", eventHubName = "nallatrgrfn-evthub", connection = "nallatrgrfnns_RootManageSharedAccessKey_EVENTHUB", consumerGroup = "$Default", cardinality = Cardinality.MANY, dataType = "string") List<String> message,
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1 person found this answer helpful.
Nalla 1 Reputation point

2020-08-04T17:28:09.92+00:00

The message I am oublishing is one EventData for one simple string not JSON. So I thought I should use List<EventData> message. But that gave " Bind the parameter type as string instead of Object to get the raw values and avoid JSON deserialization" so I changed that to List<String> message. Then I don't get the error message but the trigger is triggering.

I have enabled "Log Analitics Workspace" and the app insights logs did not have any messages that I could use to fix the situation.

Nalla 1 Reputation point

2020-08-04T17:30:33.55+00:00

oops I meant to type trigger is not triggering.

Krish G 2,331 Reputation points

2020-08-04T17:53:48.96+00:00

Have you now tried setting the dataType = "string" in the EventHubTrigger params as I mentioned?
Also I hope you have the app insight integration as per this.

Nalla 1 Reputation point

2020-08-04T18:06:03.147+00:00

oops, I did not see your new attribute dataType="string". Let me try that and get back here in a bit.

Nalla 1 Reputation point

2020-08-04T21:51:44.347+00:00

Yes, the attribute dataType="string" fixed the issue. The trigger worked fine in local debugging.

Thanks for your hint.

Krish G 2,331 Reputation points

2020-08-04T22:39:45.567+00:00

Glad that you could solve it. To help community members who might face similar issue, request you to click the "Accept" option of the answer if you don't mind.

Nalla 1 Reputation point

2020-08-12T16:53:14.187+00:00

Where is the "Accept" option? I cannot see it anywhere on this page.

By the way, when I deploy the Java trigger using VS Code it is not getting triggered. Is there any edits I need to make after deploying? (I did stop my local Run/Debug after deploying so only one version is running). Thanks.

Krish G 2,331 Reputation points

2020-08-12T18:55:19.09+00:00

Do you see any error in App Insights?

Nalla 1 Reputation point

2020-08-12T20:10:02.83+00:00

I viewed the 4 charts in Application Insights for this app and all of them are empty. When I run access count query it returns "No results found".

Krish G 2,331 Reputation points

2020-08-12T20:26:48.657+00:00

That's bit strange. Can you please verify configuration of the Function App in portal that app insights is correctly configured? https://learn.microsoft.com/en-us/azure/azure-functions/functions-monitoring

Nalla 1 Reputation point

2020-08-12T20:53:32.733+00:00

Yes, I do have those two items for my function app. There is a check mark in the last column (Deployment Slot Setting) for the first row but no check for the second row.

Krish G 2,331 Reputation points

2020-08-12T20:55:45.593+00:00

Can you turn off the slot settings for both and redeploy.

Nalla 1 Reputation point

2020-08-12T23:05:27.497+00:00

I see that one default product slot is created and I do not see a delete option for that.

I looked into all the Function App/Settings options for the Slot option to turn off but I did not find any. Please suggest the menu navigation path that would give me the screen to turn off the default slot. Thanks.

Krish G 2,331 Reputation points

2020-08-13T03:10:57.71+00:00

I meant turn off slot settings for the 2 app insights settings:
Function App->Configuration->Application Settings->Edit particular setting->Deployment slot settings

And, please confirm you are trying to check app insights exception log in correct place:
Your app insights instance->Failures->Exceptions

Nalla 1 Reputation point

2020-08-13T12:30:10.187+00:00

I have now turned off the "Deployment Slot setting" for the first row and redeployed the function app. But it is still not triggered.

I do see one exception in the Exceptions tab you have referred above. The exception is:
Microsoft.Azure.WebJobs.EventHubs.EventHubOptions.AddReceiver

Error indexing method 'Functions.ProcessEventHub' Value cannot be null. Parameter name: receiverConnectionString

I have attached Call Stack details in the attached text.17501-azure-app-exception.txt

Krish G 2,331 Reputation points

2020-08-13T12:36:44.573+00:00

Great! So clearly the EvenHub Connection string is not setup correctly in deployed environment. You should have app settings (Function App->Configuration->Application Settings) for the connection string with the same key name as you mentioned in your function. In your example code you provided few days back it was "nallatrgrfnns_RootManageSharedAccessKey_EVENTHUB"

Nalla 1 Reputation point

2020-08-13T12:45:09.373+00:00

Based on the "receiverConnectionString" and based on a discussion here:
https://github.com/Azure/azure-functions-host/issues/4788

I also added a connection string called "receiverConnectionString" in the application settings page. However, the drop down presented did not have Event Hub so I picked Custom. It also had a deployment slot option. I tried on and off.

I restarted the app after each of the above changes. But the trigger is still not triggered.

Krish G 2,331 Reputation points

2020-08-13T12:50:11.357+00:00

No. What is your function code saying about the connection name in the EventHubTrigger? The app setting should have same key as that. Function code looks up the name in app setting you specify in your code. And the value in the app settings should be you connection string itself.

@EventHubTrigger(name = "message", eventHubName = "nallatrgrfn-evthub", connection = "nallatrgrfnns_RootManageSharedAccessKey_EVENTHUB", consumerGroup = "$Default", cardinality = Cardinality.MANY, dataType = "string") List<String> message,

The comment in the github issue you followed is just a random comment, not a solution.

I suggest you to read the documentation https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-event-hubs-trigger?tabs=java

Nalla 1 Reputation point

2020-08-13T13:53:08.253+00:00

I have now updated the value of APPLICATIONINSIGHTS_CONNECTION_STRING to the same string that I am using in my EventHubTrigger Function code. I restarted, redeployed and still no luck.

Nalla 1 Reputation point

2020-08-13T14:23:31.11+00:00

I have now added a name value property in the "Function App/Configuation/Application settings" like:

nallatrgrfnns_RootManageSharedAccessKey_EVENTHUB = "Endpoint=sb://<<actua lEvent Hub connection string >>"

When I redeployed I am not seeing any exceptions now but the trigger is still not triggered

Nalla 1 Reputation point

2020-08-13T14:52:06.223+00:00

My access count is working now. I think I am all set now. Thanks for your help.
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