Re: (ITS#7013) OpenLDAP freezes and doesn't respond

[cgrosjean@janua.fr]

Thank you for your answer.
We actually could not wait for a solution or workaround anymore, due to 
the project planning and
the time we spent trying to find a solution with OpenLDAP.
So, we decided to test replacing OpenLDAP by OpenDJ, and the tests give 
pretty good results: we don't have the problem anymore.

Howard Chu a écrit :
> cgrosjean@janua.fr wrote:
>> Full_Name: Cyril Grosjean
>> Version: 2.4.26
>> OS: Red Hat Enterprise Linux Server release 5.4 (Tikanga)
>> URL: ftp://ftp.openldap.org/incoming/
>> Submission from: (NULL) (82.66.198.206)
>>
>>
>> My OpenLDAP server freezes, after a few requests, and I can't 
>> understand why.
>> I have a few LDAP clients (ldapsearch, a custom Java app. and
>> ApacheDirectoryStudio), running from different systems, either 
>> locally on the
>> OpenLDAP server, or on another OpenLDAP server, or on a remote 
>> workstation, and
>> none manages to get an answer from OpenLDAP. The connection is 
>> established but
>> each client gets stuck waiting for any result.
>>
>> We can reproduce the freeze, after a few requests coming from the 
>> custom Java
>> application. The problem doesn't occur if we don't use that application.
>>
>>
>> The last time, it occured only a few minutes after the OpenLDAP 
>> daemon was
>> restarted, under very low load.
>> I use OpenLDAP 2.4.26, over Red Hat Enterprise Linux Server release 5.4
>> (Tikanga), Kernel version 2.6.18-164.el5, amd64 architecture over 
>> VMWare.
>> I also use BDB 4.8.30, and OpenLDAP's been compiled with the 
>> following options:
>>
>> ./configure --prefix=/opt/openldap-2.4.26 --enable-dynamic=yes
>> --enable-dynlist=yes --enable-memberof=yes --enable-ppolicy=yes
>> --enable-accesslog=yes --enable-sssvlv=yes
>>
>> I noticed only 60 to 70 established connections on port 389 
>> (according to
>> netstat) when the freeze occurs.
>>
>> The OpenLDAP server is set in syncrepl mirror mode replication, and 
>> the other
>> OpenLDAP server (only used as a hot stand-by) works fine (but doesn't 
>> receive
>> any load). However, one can reproduce the problem with replication 
>> disabled.
>
> Looks like you have a thread blocked trying to modify a record, while 
> all the other writer threads are blocked waiting for that writer to 
> complete. The output of db_stat -CA would help to indicate why the 
> writer is blocked.
>
> It also looks like you've configured your replication with mirrormode 
> and delta-syncrepl. This combination is not yet supported in OpenLDAP, 
> certainly not in 2.4.26. It may be supported in 2.4.27, depending on 
> how our ongoing testing turns out.
>