open_log_file_cache
The `open_log_file_cache` directive enhances logging performance by caching log file descriptors.
Description
The open_log_file_cache directive is utilized within the http, server, and location contexts to improve the performance associated with accessing log files. By caching file descriptors for log files, it minimizes the overhead of file access, especially when writing logs concurrently. This directive accepts up to four parameters, which can define settings such as the cache size, timeout, and the maximum cache entries allowed.
The parameters are specified in the following format: open_log_file_cache zone=name:size timeout=duration max=number;. The zone parameter defines a name and size for the shared memory segment used by the cache. The timeout parameter determines how long the cache is valid before a file is re-validated for its state, while the max parameter restricts the maximum number of file items that can be cached.
When configured correctly, utilizing this directive can lead to reduced latency for log writing, especially under high server load or a significant number of simultaneous write operations. However, careful consideration must be given to the cache size and expiration settings to optimize both performance and memory usage effectively.
Config Example
http {
open_log_file_cache zone=logs_cache:10m timeout=30s max=1000;
}If the cache size is too small, it can lead to frequent cache misses, negating the performance benefits.
Incorrect timeout values may lead to stale log entries if log file descriptors are not refreshed in time.