scoreboard and http2

[Stefan Eissing <st...@greenbytes.de>]

For the next 2.4 release, I would like to add scoreboard support to mod_http2.

There are several options for doing so and I would like your feedback on which
route we should take. I try to outline what options I see:

A) Make mod_http2 workers general MPM workers. They would then become
   part of scoreboard without changes to the board itself.
B) Extend scoreboard to handle "thread sets", where MPM threads are the set it has
   not. mod_http2 would register a new set. scoreboard handles, an opaque struct
   pointer for everyone, would get an additional "set id".
C) Mix both. MPM has thread sets and scoreboard learns to handle them. 

Discussion:
1. A), doing it naively, will mess heavily with MPM module code. MPM modules now
   use for(0...num_threads) {} heavily to setup threads that handle sockets and
   pollsets and other nice things. This is not relevant for the http2 workers which
   are, framed more generally, "slave connection workers", whereas the current MPM
   threads are "master connection workers".
2. B) will not mess with MPM at all, just extend scoreboard and mod_status. mod_http2
   would register itself for a new thread set and update the status regularly. This
   approach offers least API disturbance for a backport to 2.4.x
3. C) is an extension of B). Thread sets get registered at MPM, scoreboard interrogates
   the new MPM sets and can hand out "scoreboard handles" for them. Bringing these sets
   into the MPM could be done, so that spare threads are shared between different sets.
   Don't know if that's desirable.
4. For mod_http2, the existing status indicators will continue to work, as slave 
   connection workers do the same tasks as MPM threads, more or less. For more flexible
   use, one could provide for status indicators provided by the registrar.

Thoughts?

//Stefan

AW: scoreboard and http2

[Plüm, Rüdiger, Vodafone Group <ru...@vodafone.com>]

> -----Ursprüngliche Nachricht-----
> Von: Graham Leggett [mailto:minfrin@sharp.fm]
> Gesendet: Mittwoch, 9. Dezember 2015 14:58
> An: dev@httpd.apache.org
> Betreff: Re: scoreboard and http2
> 
> On 09 Dec 2015, at 3:49 PM, Stefan Eissing
> <st...@greenbytes.de> wrote:
> 
> > For the next 2.4 release, I would like to add scoreboard support to
> mod_http2.
> >
> > There are several options for doing so and I would like your feedback
> on which
> > route we should take. I try to outline what options I see:
> >
> > A) Make mod_http2 workers general MPM workers. They would then become
> >   part of scoreboard without changes to the board itself.
> 
> It is the goal of the MPM to care about the architecture of the machine,
> and know about processes/threads/etc.
> 
> Option A is the only real option - we cannot allow the h2 stuff to mess
> up the clean separation between the architecture of each platform and
> the core of the server itself.

+1

Regards

Rüdiger

Re: scoreboard and http2

[Graham Leggett <mi...@sharp.fm>]

On 09 Dec 2015, at 3:49 PM, Stefan Eissing <st...@greenbytes.de> wrote:

> For the next 2.4 release, I would like to add scoreboard support to mod_http2.
> 
> There are several options for doing so and I would like your feedback on which
> route we should take. I try to outline what options I see:
> 
> A) Make mod_http2 workers general MPM workers. They would then become
>   part of scoreboard without changes to the board itself.

It is the goal of the MPM to care about the architecture of the machine, and know about processes/threads/etc.

Option A is the only real option - we cannot allow the h2 stuff to mess up the clean separation between the architecture of each platform and the core of the server itself.

Regards,
Graham
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