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Re: slapd does not answer in time

Hans Moser wrote:

> I have a 4 cpu machine with SLES 9 and OpenLDAP 2.3.35.
> This is master to about 65 slaves via syncreplication.
> These slave were set up subsequently without any problem. In the last
> time every now and then the master cannot answer searches in time.
> Clients time out - i.e. Postfix doing address verification. This may
> have to do with writes to the master and the replication.
> The worst time was, when I had to reinitialize about 15 to 20 slaves and
> these slave checked the master to get in sync.* Other clients got no
> answer for a long long time. :(
> The iron is idle. Load average is 0.00.
> There were limiting factors like file number etc, which limited process
> numbers, but this was solved in the mean time.
> Which number of connections to the master does a replication slave open?
> How can I find out, what is limiting slapd and keep him from responding
> in time? Log files does not give me a hint, but I don't really know what
> to search for.
> * I take a "top level" ldif file to start the server up - ou=bla,o=foo,
> ou=log,ou=bla,o=foo and ou=humans,ou=bla,o=foo -
> and the latest hourly branch dump (these slave only replicate one branch
> from the master server) - ou=humans,ou=bla,o=foo - from the master to
> fill the server. In this case the slave contains all the data, but
> checks ALL entries to be "up to date". Is there a way to prevent this?
> The slave does only have to check for changes that happened in the last
> hour (since the dump).

There is no connection number limit (except for OS limits on number of
file descriptors and so); bu 65 replicas re-syncing simultaneously, with
operations that may require hours, will eat up all threads if configured
as the default.  If you need to have so many replicas, you might
consider unloading the master from bulk search load, dedicating it to
centralizing writes, and configure it with lots of threads, so that it
can simultaneously deal with syncs and writes (e.g. 8 threads plus the
number of consumers, to be conservative).


Ing. Pierangelo Masarati
OpenLDAP Core Team

SysNet s.r.l.
via Dossi, 8 - 27100 Pavia - ITALIA
Office:  +39 02 23998309
Mobile:  +39 333 4963172
Email:   pierangelo.masarati@sys-net.it