The network.breaker.inflight_requests.overhead setting in Elasticsearch is part of the circuit breaker framework. It controls the overhead factor for the in-flight requests circuit breaker, which helps prevent out-of-memory errors by limiting the memory usage of in-flight requests.
- Default value: 1 (100% overhead)
- Possible values: Any positive decimal value
- Recommendation: Keep the default unless you have specific memory constraints or requirements
This setting determines the amount of additional memory to allocate for in-flight requests beyond their estimated size. An overhead of 1 means the breaker will allocate twice the amount of memory estimated for the request. This extra allocation helps account for unexpected memory usage during request processing.
Example
To change the in-flight requests overhead to 1.5 (150% overhead):
PUT /_cluster/settings
{
"persistent": {
"network.breaker.inflight_requests.overhead": 1.5
}
}
You might want to increase this value if you're experiencing frequent circuit breaker trips for in-flight requests despite having available memory. Conversely, you might decrease it if you need to conserve memory and are confident in your request size estimates.
Common Issues and Misuses
- Setting the value too low can lead to frequent circuit breaker trips, causing request failures.
- Setting the value too high can result in inefficient memory usage, potentially leading to out-of-memory errors.
Do's and Don'ts
Do:
- Monitor circuit breaker trips and adjust the setting gradually if needed.
- Consider this setting in conjunction with other circuit breaker settings for a holistic approach to memory management.
Don't:
- Drastically change this setting without understanding its impact on your cluster's memory usage.
- Ignore other potential causes of memory issues when adjusting this setting.
Frequently Asked Questions
Q: How does this setting interact with other circuit breaker settings?
A: This setting specifically affects the in-flight requests circuit breaker. While it operates independently, it's part of the overall circuit breaker framework in Elasticsearch. Adjusting this setting may impact the effectiveness of other breakers, so it's important to consider the entire memory management picture.
Q: Can changing this setting improve my cluster's performance?
A: While this setting primarily affects memory management, it can indirectly impact performance. If set too low, it may cause unnecessary request failures. If set too high, it might lead to memory pressure. Optimal setting can help maintain stable performance by preventing out-of-memory errors.
Q: How can I determine if I need to adjust this setting?
A: Monitor your cluster for circuit breaker events, particularly those related to in-flight requests. If you see frequent tripping of this breaker despite having available memory, you might consider increasing the overhead. Conversely, if you're experiencing memory pressure, you might consider decreasing it.
Q: Is this setting node-specific or cluster-wide?
A: This setting can be applied cluster-wide through the cluster settings API, as shown in the example. However, it can also be set on a per-node basis in the elasticsearch.yml configuration file if you need different settings for specific nodes.
Q: How does this setting affect Elasticsearch's ability to handle large requests?
A: This setting helps Elasticsearch manage memory for in-flight requests more effectively. A higher overhead value provides more buffer for large or unpredictable requests, potentially reducing the likelihood of circuit breaker trips for these requests. However, it also means less memory available for other operations, so it's a balance that needs to be struck based on your specific use case and request patterns.
