Brief Explanation
The "Max inflight events reached" error in Logstash occurs when the number of events being processed simultaneously in a pipeline exceeds the configured maximum limit. This error is typically a sign of backpressure in the Logstash pipeline.
Impact
This error can significantly impact the performance and stability of your Logstash pipeline:
- Event processing may slow down or stall
- Increased memory usage and potential out-of-memory errors
- Potential data loss if input buffers overflow
Common Causes
- Insufficient resources (CPU, memory) for the current workload
- Slow or unresponsive output destinations
- Complex or inefficient filter configurations
- Mismatched input and output throughput capacities
- Inadequate pipeline worker settings
Troubleshooting and Resolution Steps
Check system resources: Monitor CPU and memory usage to ensure Logstash has sufficient resources.
Review pipeline configuration:
- Optimize filter plugins for efficiency
- Ensure output destinations can handle the incoming event rate
Adjust pipeline settings:
- Increase
pipeline.workers
if resources allow - Tune
pipeline.batch.size
andpipeline.batch.delay
- Increase
Enable persistent queues:
- Configure persistent queues to handle backpressure
- Adjust queue settings like
queue.type: persisted
andqueue.max_bytes
Scale horizontally:
- Consider distributing the workload across multiple Logstash instances
Monitor and tune outputs:
- Ensure output plugins are configured optimally
- Check if output destinations are responsive and can handle the load
Use the Logstash monitoring API:
- Monitor pipeline metrics to identify bottlenecks
Best Practices
- Regularly monitor Logstash performance and adjust configurations as needed
- Implement a robust monitoring solution for your Logstash deployment
- Use Logstash's persistent queue feature for better resilience against backpressure
- Consider implementing a buffer (like Redis or Kafka) between your data source and Logstash for high-volume scenarios
Frequently Asked Questions
Q: How can I determine the current number of inflight events?
A: You can use the Logstash monitoring API to check the pipeline.events.in_flight
metric, which shows the current number of events being processed in the pipeline.
Q: What's the default max inflight events limit in Logstash?
A: The default limit is typically calculated based on the pipeline.workers
and pipeline.batch.size
settings. It's usually pipeline.workers * pipeline.batch.size * 1.5
.
Q: Can increasing pipeline.workers
always solve this error?
A: Not always. While increasing workers can help, it also increases resource usage. It's important to balance this with available system resources and identify the actual bottleneck in your pipeline.
Q: How do persistent queues help with this error?
A: Persistent queues act as a buffer, allowing Logstash to handle temporary spikes in event flow and backpressure from outputs, reducing the likelihood of reaching the max inflight events limit.
Q: Is it possible to dynamically adjust the max inflight events limit?
A: The limit is not directly configurable, but you can influence it by adjusting pipeline.workers
and pipeline.batch.size
. These changes typically require a Logstash restart to take effect.