The http.compression_level setting in Elasticsearch controls the level of compression applied to HTTP responses. It determines how aggressively Elasticsearch compresses the data before sending it over the network, affecting the balance between CPU usage and network bandwidth consumption.
Description
- Default value: 3
- Possible values: 1-9
- Recommendations: The default value of 3 provides a good balance between compression ratio and CPU usage. Higher values increase compression but require more CPU resources.
This setting affects all HTTP responses from Elasticsearch, including search results, cluster state information, and other API responses. It's particularly useful for optimizing network performance in environments with limited bandwidth or when dealing with large response payloads.
Example
To change the compression level using the cluster settings API:
PUT /_cluster/settings
{
"persistent": {
"http.compression_level": 5
}
}
Increasing the compression level to 5 might be beneficial in scenarios where network bandwidth is at a premium, and the extra CPU usage for compression is acceptable. This change could result in smaller response sizes, potentially improving overall response times for clients with slower network connections.
Common Issues and Misuses
- Setting the compression level too high (e.g., 9) can lead to increased CPU usage and potentially slower response times, especially for small payloads.
- Disabling compression entirely (by setting it to 0) may significantly increase network bandwidth usage, particularly for large responses.
Do's and Don'ts
- Do monitor CPU usage and network performance after changing this setting.
- Do consider the trade-off between CPU usage and network bandwidth when adjusting this value.
- Don't set the compression level to the maximum (9) without careful consideration of the CPU impact.
- Don't frequently change this setting; find a balance that works for your specific use case and infrastructure.
Frequently Asked Questions
Q: How does http.compression_level affect Elasticsearch performance?
A: It impacts the balance between CPU usage and network bandwidth. Higher levels increase compression, reducing network traffic but requiring more CPU resources for compression and decompression.
Q: Can changing http.compression_level improve search response times?
A: Potentially, yes. In network-constrained environments, higher compression can lead to faster data transfer, potentially improving overall response times despite the additional CPU overhead.
Q: Is it better to use a high compression level for all Elasticsearch clusters?
A: Not necessarily. The optimal setting depends on your specific infrastructure, network conditions, and workload. It's important to test and monitor the impact in your environment.
Q: How can I determine the best http.compression_level for my Elasticsearch cluster?
A: Start with the default (3) and gradually adjust while monitoring CPU usage, network throughput, and response times. The optimal setting balances these factors for your specific use case.
Q: Does http.compression_level affect all Elasticsearch HTTP responses equally?
A: The setting applies to all HTTP responses, but its impact may vary depending on the response size and content. Larger responses typically benefit more from higher compression levels.
