University of Twente Student Theses


Write-intensive applications with LDAP

Bui, Cuong (2004) Write-intensive applications with LDAP.

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Abstract:LDAP (lightweight directory access protocol) is a protocol specification that can be used to access directories. OpenLDAP is an open source LDAP service implementation. By design LDAP is optimized for read (lookup) operations. The LDAP specification does allow write operations. Performance measurements have been conducted by [1] to measure the read performance of OpenLDAP. However, there is little known about the write-intensive performance of OpenLDAP. Applications using LDAP commonly have a read-intensive characteristic and research is concentrated at this aspect. This thesis will use a write-intensive applicaction case provided by OpenFortress (workflow reseller system) to conduct measurements to ensure whether OpenLDAP can support write-intensive applications in general. During the performance measurements a performance problem has been discovered. The performance of OpenLDAP decreases significantly after a number of operations. Both read and write operations generate this problem. The least recently used (LRU) cache replacement policy has been identified as the possible cause of the problem. Several replacements policies have been studied and adaptive replacement cache (ARC) has been chosen to replace the LRU implementation in Open-LDAP because ARC is more efficient with smaller cache sizes and can withstand certain cache flushes. OpenLDAP with the ARC implementation shows a significant decrease of cache misses (especially with smaller cache sizes). Cache misses result in disk access and therefore it is preferred to minimize this number. LRU is the most common cache replacement policy used at the time of writing of this thesis, ARC has been shown to be a good substitute for LRU. ARC manages limited resources more efficiently than LRU. The performance degradation issue was eventually tracked down to a bug in the Berkeley database code used by OpenLDAP. With this problem having been fixed, there’s no objection (performance wise) to use OpenLDAP with write-intensive applications.
Item Type:Essay (Bachelor)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:54 computer science
Programme:Computer Science BSc (56964)
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