Handling Pending Messages & Failures
Explore strategies for managing pending messages, recovering from consumer failures, and re-processing.
Understanding Pending Messages
In Redis Streams, a Consumer Group allows multiple consumers to process messages from a stream.
When a consumer reads a message using XREADGROUP, the message isn't immediately removed. Instead, it's marked as pending for that consumer.
If a consumer crashes or fails to acknowledge a message (using XACK), that message remains pending. This ensures no data loss, but it also means the message isn't fully processed.
Inspecting Pending Messages
Redis provides the XPENDING command to see which messages are pending for a specific consumer group, or even for a specific consumer within that group.
- It helps identify messages that haven't been acknowledged.
- You can see which consumer is responsible for a message.
- It reveals how long a message has been pending.
This is crucial for monitoring the health and progress of your stream processing.
All lessons in this course
- Introduction to Consumer Groups
- Implementing Consumer Group Logic
- Handling Pending Messages & Failures
- Monitoring Consumer Group Lag