Hi,

We have been using Meta backend with multiple AD domain controllers as targets. OpenLDAP version is 2.4.56 and installed on RHEL 8.6 Azure hosted servers. We have two such nodes with the same setup. I have been trying to find the root cause for the error "ch_malloc of 0 bytes failed on Meta backend" found on the two servers. Service was crashed on both servers after this error. After starting the OpenLDAP service, it has been working fine so far.

My observations so far: - Our Azure team did not find any abnormalities on the servers w.r.t the memory utilisation by LDAP during the incident. - Stats around the time when issue occurred sar -r kbmemfree kbavail kbmemused %memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty 01:50:01 PM 25202860 29022816 7519888 22.98 13808 5385664 4736872 14.48 2349572 4157132 64 02:00:01 PM 25195656 29018052 7527092 23.00 13808 5388120 4767748 14.57 2349572 4163232 44 02:10:00 PM 25197340 29010572 7525408 23.00 13808 5386752 4783920 14.62 2352524 4158856 3336 02:20:01 PM 25201220 29016192 7521528 22.99 13808 5388296 4789868 14.64 2352516 4154632 52 02:30:01 PM 25196500 29013836 7526248 23.00 13808 5390708 4789412 14.64 2352516 4159140 36 02:40:01 PM 25181840 29002912 7540908 23.04 13808 5402364 4782228 14.61 2352528 4173032 144 02:50:01 PM 25170748 28994608 7552000 23.08 13808 5413236 4758840 14.54 2352516 4185172 1092 03:00:01 PM 25172224 28997852 7550524 23.07 13808 5414920 4729152 14.45 2352520 4182356 48 03:10:01 PM 24976028 28806984 7746720 23.67 13808 5428036 5007976 15.30 2353012 4375608 4940

- We did not set any cache specifically as meta does not store any data - Error shows 0 bytes rather than any specific number I would really appreciate if you can share any pointer which would help dig further.

Thank you, Suman