nginx cache loader process

[Maxim Dounin]

Hello!

On Tue, Jul 09, 2013 at 07:50:32PM -0400, badtzhou wrote:

> We are running nginx 1.2.9. What will happen if cache loader is running. The
> file on disk haven't been loaded into the cache zone yet and someone try to
> access the same file. Will it cause any issue? How will it affect cache
> loader process.

If the cache isn't yet loaded, nginx will try to check if a cache 
file is there by a looking into disk directly from a worker 
process.  That is, it will work without problems and will use 
cached responses, but will be slightly less effective.

> If I don't want any file on the disk to be loaded, can I simply kill the
> cache loader process? Will that cause any problem?

It's not a good idea.  In a worst case, if you'll kill it with 
kill -9 at a wrong time, shared memory zone will be corrupted, 
resulting in completely non-working nginx.

If cache loader causes too high load on your server, may want to 
tune it's settings to make it less aggressive.  See 
http://nginx.org/r/proxy_cache_path for details.

-- 
Maxim Dounin
http://nginx.org/en/donation.html