Re: Question about conn_max_pending configuration options

[Howard Chu <hyc@symas.com>]

TechnoSophos wrote:
> On the conn_max_pending and conn_max_pending_auth params, what exactly
> is a "pending request"? Is this a request that slapd has not yet
> processed? For example, is a search request "pending" if slapd is in
> the process of evaluating it, but has not yet returned?

Pending means it is queued; it has not started at all. As a loose 
restriction to prevent a single client from hogging all of the server 
resources, no connection is allowed to use more than half of the total 
number of server threads. E.g., with the default of 16 threads in the 
thread pool, any connection can have only 8 operations executing at 
once. When it reaches that limit, new requests are queued on that 
connection - these are the pending operations.

Of course this is a pretty loose control, and if you have more active 
connections than you have server threads, it becomes somewhat 
meaningless. I.e., requests get pulled off a connection's pending 
operation queue to be submitted to the thread pool, and may continue to 
wait there until a thread becomes available.

--
  -- Howard Chu
  Chief Architect, Symas Corp.  http://www.symas.com
  Director, Highland Sun        http://highlandsun.com/hyc
  OpenLDAP Core Team            http://www.openldap.org/project/