Hi Maxim,
Does the allocated memory from connection memory pool for a given connection grow as the number of request grows? If so could you elaborate on how much it grows for a new request? If not, I guess the main reason to limit the request number is to limit the lifetime of a connection so the connection pool size is under control, right? Is there an parameter to control the lifetime of a http2 connection instead?
Thanks, ChienHsing
--------------------------------------------------------------------------------------------------------------------
Maxim Dounin mdounin at mdounin.ru<mailto:nginx-devel%40nginx.org?Subject=Re%3A%20HTTP/2%3A%20allow%20unlimited%20number%20of%20requests%20in%20connection&In-Reply-To=%3C20190712142454.GM1877%40mdounin.ru%3E>
Fri Jul 12 14:24:54 UTC 2019
Hello!
On Mon, Jul 01, 2019 at 11:24:28AM +0200, Michael Würtinger wrote:
> thanks a lot for your reply. Could you please elaborate a little bit
> which memory resources need to be freed periodically? How much memory
> can be held by a connection? What's the worst case scenario?
> We are currently running it in production with http2_max_requests set
> to a value so high that the connection practically lives forever and
> so far we cannot spot any problems but maybe we're missing something?
And example of "wost case" can be seen here:
http://mailman.nginx.org/pipermail/nginx/2018-July/056525.html
Memory can be allocated from the connection memory pool. And this
memory have to be freed at some point - so you have to close
the connection to do this. And that's why number of requests in a
particular connection is limited by default.
Whether or not memory allocations happens in your particular use
case - doesn't really matter, especially given that things can
change with seamingly minor configuration and/or client behaviour
changes.
In most cases we try to limit allocations from the connection
memory pool to a minimum, yet it is not always possible/convinient to
completely avoid allocations from connection memory pool. This
allows processing of thousands of requests on a single connection
without observable memory impact. Likely millions will also work
except may be in some specific use cases, yet I wouldn't recommend
allowing that many requests, just to be on the safe side.
--
Maxim Dounin
http://mdounin.ru/
_______________________________________________
nginx-devel mailing list
nginx-devel@nginx.org
http://mailman.nginx.org/mailman/listinfo/nginx-devel
