What does open_file_cache_events do?
nginx-forum at nginx.us
Wed May 12 14:57:24 MSD 2010
I'm looking to document directives that are missing from the Wiki.
I found loads in the source code, especially thanks to Manlio Perillo.
I've stumbled upon "open_file_cache_events" declared in ngx_http_core_module.c.
I investigated what this does, here is what I found:
- it's a on/off directive
- it's off by default
- its main purpose is from 1 file, ngx_open_file_cache.c
That's where it's mostly used:
* we ignore any possible event setting error and
* fallback to usual periodic file retests
ngx_cached_open_file_t *file, ngx_open_file_info_t *of, ngx_log_t *log)
if (!(ngx_event_flags & NGX_USE_VNODE_EVENT)
|| of->fd == NGX_INVALID_FILE
|| file->uses < of->min_uses)
basically of->events takes the value of open_file_cache_events before this function is called.
When called, if of->events is false, the flow returns immediately and the function is not processed.
So it prevents Nginx from "adding an event", I presume for the specified file.
Now I understand what the open file cache does, but I don't understand what exactly what this directive does.
When the directive is enabled, does Nginx process some kind of event-based cache invalidation?
Eg. Nginx would subscribe to events for this file, when the file is deleted, Nginx gets notified with an event, and then updates the cache entry?
Thanks a lot in advance for helping me clear it out!
Posted at Nginx Forum: http://forum.nginx.org/read.php?2,85785,85785#msg-85785
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