v.21.7Improvement
Detect Linux Kernel Version at Runtime for Async Socket Functionality
Detect Linux kernel version at runtime (for worked nested epoll, that is required forasync_socket_for_remote/use_hedged_requests, otherwise remote queries may stuck). #25067 (Azat Khuzhin).
Why it matters
This feature solves the problem of remote queries potentially getting stuck due to lack of support for nested epoll in certain Linux kernel versions. By detecting the kernel version at runtime, ClickHouse can safely enableasync_socket_for_remote and use_hedged_requests, improving reliability and performance of remote query execution.How to use it
The kernel version detection is automatic at runtime. Users simply need to enableasync_socket_for_remote and/or use_hedged_requests settings in their ClickHouse configuration or queries to benefit from this fix without manual intervention.