Hi Team,

We are working on migration of nsldap C sdk to OpenLDAP C sdk for our application client code.

We are using OpenLDAP 2.6.7.

As part of this migration, we are facing one issue related to performance degradation under load on Windows platform.

In our application, we are using a single/shared connection handle to perform LDAP operation on LDAP user store servers. As part of Authentication, we are using ldap_search_ext_s call to get users and to get any user attributes from LDAP servers. We are using synchronous calls. With Mozilla NSLDAP, the same application is working well without any issues. As we are migrating to OpenLDAP, we did required changes and also we used ldap_dup() API to avoid "-4:Decoding error" issues under the load.

Now, we are facing performance degradation issues under the load with OpenLDAP library Whenever we are trying to get a user attribute from the LDAP user store server where that user attribute is not available or value for user attribute is empty, we observed performance degradation with OpenLDAP library clearly around 25-30%. In case, search for user attributes with value, no degradation observed. This degradation is happening only when the user attribute is not available or the value is empty.

Here are the snippet of runs output where performance degrade is showing:

*With search of user attribute having value at LDAP server side:*

Total Elapsed: 0:10:01

Minimum Response Time: 0:00:00.000.056 Maximum Response Time: 0:00:00.783.140 Average Response Time: 0:00:00.016.124

Total Requests: 659316 Throughput (Req/Sec): 1094.447

*With search of user attribute, not having value/does not exist at LDAP server side:*

Total Elapsed: 0:10:01

Minimum Response Time: 0:00:00.000.059 Maximum Response Time: 0:00:00.218.502 Average Response Time: 0:00:00.032.788

Total Requests: 355065 Throughput (Req/Sec): 590.258

Example search calls we are using: 1. ldap_search_ext_x() for user lookup 2. ldap_search_ext_s() for user attributes for that specific user. (filter: uid=* and base: "cn=user,dc=comain,dc=com) - Where uid attribute has some value for this user at LDAP server side 3. ldap_search_ext_s() for user attributes for that specific user. (filter: Name=* and base: "cn=user,dc=comain,dc=com) - Where Name attribute is not present for that user at LDAP server side (This is causing performance degrade)

With the same above steps, we did not see any performance issues with NSLDAP. If we remove step 3 from the above, no degradation is observed with the OpenLDAP library.

Could you please look into this issue and provide a solution to overcome this performance degradation issue? We are completely blocked here as part of OpenLDAP migration.

Note: To investigate this performance degradation with OpenLDAP, I wrote one LDAP sample code with the above 3 operations with multiple threads. I executed the sample with NSLDAP and OpenLDAP using multiple threads. In the sample runs, OpenLDAP is giving very poor performance when compared with NSLDAP. Please have a look at the sample also and provide your thoughts.

Thank you in advance for your time and help