Troubleshooting Common Issues

1. Events Not Arriving

This is a common scenario. Several factors can contribute to events not reaching their destination.

Possible Causes and Solutions:

• Incorrect Connection String or Endpoint:

  Verify that the connection string used by your sender application is correct and points to the right Event Hubs namespace and event hub name. Double-check for typos or missing parameters.

  Example of a connection string:

  Endpoint=sb://your-namespace.servicebus.windows.net/;SharedAccessKeyName=RootManageSharedAccessKey;SharedAccessKey=YOUR_KEY

• Authentication/Authorization Errors:

  Ensure the Shared Access Signature (SAS) key or Azure AD credentials used have the necessary 'Send' permissions for the event hub. Check the access policies configured on your Event Hubs namespace.

• Throttling or Quota Exceeded:

  If you are exceeding the event hub's capacity (e.g., message ingress limits, number of connections), events might be dropped or delayed. Monitor your Event Hubs metrics in Azure Monitor for throttling indicators.

  Consider increasing the number of Throughput Units (TUs) or Processing Units (PUs) for your namespace.

• Network Connectivity Issues:

  Ensure that your sending application has outbound network access to the Event Hubs endpoint. Firewalls or network security groups might be blocking traffic.

  Test connectivity using tools like telnet or curl to the Event Hubs endpoint (e.g., telnet your-namespace.servicebus.windows.net 5671 for AMQP).

• Application Logic Errors:

  Review your sender application's code. Ensure that events are being correctly serialized, batched (if applicable), and sent without exceptions.

  Add robust logging within your sender application to track the lifecycle of events.

2. Consumers Not Receiving Events

If events are being sent successfully but not consumed, the issue usually lies with the consumer application or consumer group configuration.

Possible Causes and Solutions:

• Incorrect Consumer Group Name:

  Ensure your consumer application is using the correct consumer group name. If no consumer group is specified, it defaults to $Default. Create custom consumer groups for different applications to avoid conflicts.

• Consumer Lagging Behind:

  If the consumer application is offline or unable to process events as quickly as they are being produced, it will fall behind. Monitor the Last Enqueued Sequence Number and the Offset of your consumer using Event Hubs metrics or SDKs.

  You can check consumer lag by comparing the latest event offset with the last enqueued offset for a partition. If the lag is significant, consider:

  • Increasing the processing power of your consumer instances.
  • Optimizing your event processing logic.
  • Using event batching more effectively.
• Incorrect Starting Offset:

  When a consumer starts, it needs to know where to begin reading events. Ensure it's configured to read from the correct offset (e.g., latest, earliest, or a specific sequence number). If the consumer is trying to read from an offset that no longer exists (due to retention policies), it might fail.

• Partition Idling or Issues:

  Check if a specific partition is not receiving events or if there are issues with the consumer reading from that partition. Azure Monitor can show event ingress per partition.

• Connection Issues for Consumers:

  Similar to senders, consumers need network access to the Event Hubs endpoint. Verify firewalls and network configurations.

• Checkpointing Problems:

  For stateful processing, checkpointing is crucial. If checkpointing fails or is not implemented correctly, consumers might restart from an old offset, losing progress.

3. High Latency

Latency can affect real-time processing scenarios.

Possible Causes and Solutions:

• Network Latency:

  The physical distance between your application and the Azure region hosting Event Hubs can be a factor. Deploy your applications in the same region as your Event Hubs namespace where possible.

• Under-provisioned Throughput Units (TUs):

  If your event hub is experiencing high traffic and is not provisioned with enough TUs, it can lead to throttling and increased latency.

• Inefficient Batching:

  Sending individual events can incur higher overhead than sending batched events. Optimize your batching strategy for both sending and receiving.

• Serialization/Deserialization Overhead:

  Complex or inefficient serialization/deserialization logic can add latency. Use efficient formats like Avro or Protobuf where appropriate.

• Client SDK Configuration:

  Review the configuration of your Event Hubs SDK. Settings like maxBatchSize, retryOptions, and connection pooling can impact performance.

4. Event Hubs Namespace Unreachable

When you cannot connect to your Event Hubs namespace at all.

Possible Causes and Solutions:

• Azure Service Health:

  Check the Azure Service Health dashboard for any ongoing incidents or advisories related to Azure Event Hubs in your region.

• Firewall Rules:

  Ensure that your client's IP address is allowed access if you have configured IP filtering on your Event Hubs namespace. Also, check your local network's firewall.

• Private Endpoint Issues:

  If you are using Private Endpoints, verify the network configuration of the Private Endpoint and its associated VNet, including DNS resolution.

• Service Limits:

  While rare, check if you have hit any subscription-level or namespace-level service limits.

If you continue to experience issues, consult the official Azure Event Hubs troubleshooting guide or contact Azure Support.