The http.tcp.keep_alive setting in Elasticsearch controls whether to enable TCP keep-alive packets for HTTP client connections. This setting helps maintain long-lived connections and detect disconnected clients more quickly.
Description
- Default value:
true - Possible values:
trueorfalse - Recommendation: Keep the default value unless you have specific network requirements
The http.tcp.keep_alive setting is enabled by default, which allows Elasticsearch to send TCP keep-alive packets periodically. This helps in detecting and closing stale connections, preventing resource leaks and improving overall system stability.
Example
To disable TCP keep-alive for HTTP connections, you can use the cluster settings API:
PUT _cluster/settings
{
"persistent": {
"http.tcp.keep_alive": false
}
}
Disabling this setting might be necessary in environments where network policies or firewalls interfere with TCP keep-alive packets. However, this can lead to increased resource consumption due to lingering inactive connections.
Common Issues
- Increased number of stale connections when disabled
- Potential firewall issues if keep-alive packets are blocked
- Slight increase in network traffic due to keep-alive packets
Do's and Don'ts
- Do: Keep the default setting unless you have specific network requirements
- Do: Monitor connection counts and resource usage when changing this setting
- Don't: Disable this setting without understanding the implications on your network and application
- Don't: Confuse this with HTTP keep-alive, which is a different concept
Frequently Asked Questions
Q: How does http.tcp.keep_alive differ from HTTP keep-alive?
A: http.tcp.keep_alive operates at the TCP level, maintaining the underlying network connection. HTTP keep-alive, on the other hand, is an application-layer protocol feature that allows multiple HTTP requests to use the same TCP connection.
Q: Can enabling http.tcp.keep_alive impact performance?
A: The performance impact is generally minimal. It can slightly increase network traffic due to keep-alive packets, but it helps in maintaining cleaner connection states and can improve overall system stability.
Q: How often are TCP keep-alive packets sent?
A: The frequency of TCP keep-alive packets is determined by the operating system, not Elasticsearch. Typical intervals range from 30 seconds to 2 hours, depending on the OS configuration.
Q: Does this setting affect internal node-to-node communication?
A: No, this setting specifically applies to HTTP client connections. Node-to-node communication uses different transport-layer settings.
Q: Can I change this setting dynamically?
A: Yes, you can change the http.tcp.keep_alive setting dynamically using the cluster settings API. However, the change will only affect new connections; existing connections will maintain their original keep-alive state.
