Common Issues and Solutions
This document outlines common issues encountered when working with Azure Event Hubs and provides steps to diagnose and resolve them.
1. Connectivity Issues: Can't Connect to Event Hubs
Symptoms: Timeouts, connection refused errors, or general inability to send/receive messages.
- Check Firewall and Network Restrictions: Ensure that your client or application can reach the Event Hubs endpoint. Verify that any firewalls, network security groups (NSGs), or proxy servers are configured to allow traffic on the necessary ports (usually 5671 for AMQP, 443 for HTTPS).
- Verify Connection String/Endpoint: Double-check the connection string or endpoint URL used to connect to Event Hubs. Ensure it's correct and that you have the appropriate permissions.
- Authentication and Authorization: Confirm that your credentials (Shared Access Signature - SAS key, Azure AD identity) are valid and have the necessary permissions (e.g., "Listen," "Send," "Manage") for the specific Event Hub or consumer group.
- Service Health: Check the Azure Service Health dashboard for any ongoing incidents affecting Azure Event Hubs in your region.
- DNS Resolution: Ensure that your system can resolve the DNS name for the Event Hubs namespace.
Tip: Use tools like ping or telnet (on port 5671/443) from your client's environment to test basic network connectivity to the Event Hubs namespace.
2. Message Sending Failures: Events Not Arriving
Symptoms: Applications report successful sends, but messages are not visible in Event Hubs or being consumed.
- Check Throughput Limits: Event Hubs has throughput quotas (ingress/egress events, ingress/egress data). If you're exceeding these limits, messages might be throttled or rejected. Monitor your Event Hubs metrics in the Azure portal.
- Partition Key Distribution: If you're using partition keys, ensure they are distributed evenly. A heavily skewed partition key can lead to "hot partitions" and potential throttling.
- Event Size: Event Hubs has limits on the maximum size of an event (including metadata). Ensure your events are within these limits.
- Client-Side Buffering/Retries: Verify how your client library handles buffering and retries. Infinite retry loops without backoff can exacerbate throughput issues.
- Consumer Lag (If applicable): While this relates to receiving, if no messages are being received, it might indicate a sending issue or a problem with how messages are being processed.
Tip: Review the ServerBusyException or similar throttling-related exceptions in your application logs.
3. Message Receiving/Consumption Issues: Events Not Being Processed
Symptoms: Consumers aren't receiving messages, or there's a significant lag in message processing.
- Consumer Group Configuration: Ensure your consumer is using the correct consumer group name. Each consumer group maintains its own read position within the Event Hub partitions.
- Checkpointing and Offsets: Verify your checkpointing mechanism. If checkpoints are not being saved correctly or are stale, consumers might re-process messages or get stuck.
- Partition Ownership: In scenarios with multiple consumers in a consumer group, ensure partitions are being distributed and owned correctly. Event Hubs uses an "epoch" mechanism for this.
- Client Library Version: Ensure you are using a recent and supported version of the Event Hubs SDK for your programming language. Older versions might have bugs or performance issues.
- Application Logic: Debug your consumer application's logic. Ensure it's correctly handling message deserialization, processing, and is not crashing or blocking.
- Long-Running Operations: If your consumer performs long-running operations per message, it can lead to lag. Consider asynchronous processing or batching.
Tip: Use the "Consumer group" diagnostics in the Azure portal to see the latest offsets and potential consumer lag.
4. Latency Problems: Messages Arrive with Delays
Symptoms: Messages take longer than expected to appear in Event Hubs or to be delivered to consumers.
- Network Latency: High network latency between your application and Event Hubs, or between Event Hubs and your consumers, is a primary cause. Check network performance metrics.
- Throughput Bottlenecks: If Event Hubs or your consumers are at their throughput limits, latency will increase as requests are queued.
- Batching Configuration: If using batching for sending or receiving, a suboptimal batch size can impact latency. Experiment with batch sizes.
- Client SDK Configuration: Some client SDKs have settings related to message send/receive timeouts or buffer sizes that can affect latency.
- Throttling: As mentioned, being throttled will significantly increase latency.
5. Metrics and Monitoring
Symptoms: Unclear what is happening with Event Hubs; inability to diagnose issues without data.
- Enable Diagnostic Settings: Configure diagnostic settings for your Event Hubs namespace to send logs and metrics to Log Analytics, Storage, or another endpoint.
- Key Metrics to Monitor:
IncomingRequests / OutgoingRequestsIncomingBytes / OutgoingBytesIncomingEvents / OutgoingEventsThrottledRequests (crucial for performance issues)UserErrors / ServerErrors- Consumer Group metrics like
Lag (if available in your SDK/tooling)
- Log Analytics Queries: Utilize Kusto Query Language (KQL) in Log Analytics to slice and dice event data and diagnostics logs for deep analysis.
Tip: Set up Azure Alerts based on key metrics (e.g., high throttled requests, increased errors) to proactively identify problems.
General Troubleshooting Steps
- Simplify the Scenario: Try to isolate the issue. Can you send/receive a single message with a basic client?
- Check SDK Documentation: Refer to the official documentation for the Event Hubs SDK you are using for specific configuration options and best practices.
- Reproduce Locally: If possible, try to reproduce the issue in a controlled local environment.
- Consult Azure Status: Always check the Azure Status page for any ongoing service degradations.
- Create a Support Ticket: If you've exhausted other options, consider opening a support ticket with Microsoft Azure.