The mailing list for listmasters using Sympa

[Olivier Salaun <address@concealed>]

Hi Luca,

Luca Maranzano wrote:

> we are testing Sympa for its LDAP features, but we are having some
> problems with long LDAP include, i.e. about 4000 subscribers.

> We have tryed to configure a list with 5 subscribers via LDAP and
> all works fine; then we tryed a list with 50 subscribers and
> all works fine. With a list of almost 4000 subscribers we have the
> folloing symptoms:
> 
> Accessing via Web sometimes is very slow, it seems that Sympa is
> updating the list of the subscribers in its (memory?) cache, 
> [...]
> 
> having lot of lists (from 50 to 100) configured to make LDAP query
> and some being possibly huge with thousands of members, can Sympa
> manage this load and can be usable through the Web interface?
> 
> The caching of the LDAP query is done only for the Web Interface, right?

No, web and mail server are based on the same low-level libraries ; they
are both caching LDAP queries. The problem is obvious on the web side
because the web client expects a fast response from the server. This
mainly occurs for the first request after Apache was restarted, because
wwsympa was also restarted.     

> Supposing that the huge lists contains data that don't change quite
> often, putting a TTL to 86400 seconds (1 day) should improve things?

You're right ; making the TTL longer will reduce the risks for the end-user
to have a slow HTTP response.

Currently, the solution for your 50-100 LDAP-based MLs consists in :
        + setting a long TTL for the lists (24 h)
        + setting a long idle-timeout for the FastCGI (so it supports slow 
responses)
        + at Apache startup, intiliazing wwsympa's LDAP cache 
          (by clicking 'Your subscriptions' for instance)

How we could improve Sympa's design to improve big LADP-based MLs management 
----------------------------------------------------------------------------

Currently Sympa uses a memory cache that :
        - cannot be used by different processes
        - needs to be initialized by all processes
This cache is stored in an in-memory DB_FIle structure.

=> this structure could be on-disk

The main disadvantage of this solution is that is will make (LDAP-related) 
queries 
slower.

We'll test this as soon as possible...

--
Olivier Salaün
Comité Réseau des Universités