Zetan Drableg wrote:
> openldap 2.4.57 on 16 core OracleLinux VMs with NVME disk.
> 8 nodes in n-way multi master configuration, MDB backend, 50k unique DNs.
> We see about 10,000 auths per minute per node.
> 
> Under heavy client load, the log shows many "deferring operation: binding" 
> messages in the same second. slapd is using only 400% cpu (of 1600 possible).

Probably you could increase # of listeners. In a pure Bind-only workload slapd 
ought to be able to utilize 100% of all cores.
> 
> [2021-04-13 19:15:58] connection_input: conn=150474 deferring operation: 
> binding
> 
> When I write LDIFs to one node like delete user or remove user from group, we 
> see spikes in authentication latency metrics (what's normally .2 - .5 second
> response time goes up to 15-30 seconds) across all nodes in the cluster at 
> the same time.
> 
> What knobs can be adjusted to allow for more concurrency? It seems like 
> writes are impacting reads.

You need more information, like I/O wait %, network % utilization, to identify 
the cause of these latency spikes.

Nobody can suggest what to tune without knowing why the bottleneck occurs.

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

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