On 01 Feb 2010, at 6:09 PM, yle lists wrote:
I'd like to submit a patch (against 2.2.14) that provides mod_proxy
sessions handling, that is, the ability to bind backend connections
(resources) to a session-id.
When proxy sessions are enabled, the backend connections are
recycled in a per-session reslist.
The worker uses a hashmap for the acquired sessions, and recycles
the released ones in a reslist.
One can use the sessions to limit, per-client (provided the client
can be identified, by IP or cookie or whatever), the number of
connections to the backend, or to forward statefull over-http-
protocols.
The session-id used for a particular request is given by the "proxy-
session-id" note (r->notes), so that the other modules (or a Rewrite/
SetEnv rule) can set it to a client identifier.
Another note ("proxy-session-client", true/false) can be used to
bind the session to the client connection (the connection-id is the
session-id), like mod_proxy 2.0.
I use it to forward client NTLM connections, since the backend
connections will be per-client connection.
For the sessions to be enabled, one can use the worker parameter
SessionsCache=on, and the SessionsCache(S)Max|Min parameters control
the sessions reslist.
The Session(S)Max|Min parameters control the number of connections
per session.
Finally, the patch also includes the functions apr_reslist_create_ex
and apr_reslist_clear which would allow one to clear a reslist with
a given clearor function.
I also included comments in the patch regarding the destructor of
the proxy connection which, IMHO, is broken in httpd-2.2x.
Some comments based on a quick once over.
Many small patches are easier to review than one big patch. Small
patches are likely to be accepted quickly, leaving time for issues
with other patches to be resolved.
Changes to APR should be packaged separately and submitted to the APR
project, httpd and APR split from each other some time ago, and httpd
doesn't keep it's own private changes to APR. The extensions you
propose to reslist look interesting, and are definitely worth picking
up there.
The patch should be to trunk rather than httpd v2.2, as all changes
must be made to the trunk first before being considered for backport
to v2.2.
Your changes to ap_proxy_acquire_connection() and friends changes the
ABI of the code, and as such cannot be backported as is to v2.2 as it
stands.
Another potential issue is that this patch extends mod_proxy instead
of adding a new module called mod_proxy_session. mod_proxy already
contains too much non-abstracted code, and this makes it worse.
Ideally, the bulk of the code should be in a module of its own.
I also don't fully see why the ABI of ap_proxy_acquire_connection()
and friends was changed, can you clarify what you were trying to do?
Regards,
Graham
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