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Memcached and redis cache modules for otrs

Last edited by Paweł Bogusławski
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Memcached and Redis cache modules for OTRS

We've designed OTRS extensions (introduced in 4e855eba and 4efaffca for OTRS 3 and #14 for OTRS 5) that allow one to implement enterprise, multiserver OTRS installations with shared cache moved from slow NFS-like solutions to faster Memcached or Redis server.

In our multiserver OTRS setups we prefer Memcached - seems to be faster with more active user sessions. If you use simple, one server OTRS installation, standard FileStorable cache backed may be best choice. In OTRS 3 you can use the otrs.CacheBenchmark.pl tool we've designed in d5eafa66 to test and choose the best backend for your setup. In OTRS 5 our tool was already merged by upstream - just use otrs.Console.pl Dev::Tools::CacheBenchmark to test. We recommend testing cache on non-production systems only.

Sample results we've got on OTRS 3, modern server, localhost TCP communication to Memcached/Redis and cached object size 256B:

Sessions(*)         Redis     Memcached    FileStorable(Local FS)   FileStorable(NFS)
----------- ------------- ------------- ------------------------- -------------------
          2     5604 op/s     4914 op/s                20300 op/s            949 op/s
         16    20952 op/s    15104 op/s                82464 op/s           9992 op/s
         64    22944 op/s    34464 op/s               568512 op/s           8032 op/s

(*) Parallel otrs.CacheBenchmark.pl exectutions on the same machine.

Results may differ for smaller/bigger object sizes - see otrs.CacheBenchmark.pl results.

As you can see putting shared cache on NFS is not the best option. If you have larger, multiserver OTRS setup with hundreds of agents working at the same time - using Memcached or Redis may be the best way to go.

Installation

Warnings:

  • Always test changes in test OTRS installation and create all necessary backups before applying to production systems.
  • Memcached/Redis communication is not encrypted so better communicate over safe subnet - cached OTRS data may be sensitive.
  • This instruction is for experienced OTRS admins/developers. Use it on your own risk.

Install Memcached and/or Redis server. In case of Memcached, tune its config to allow caching objects up to 10MB (see -I parameter in Memcached manual).

OTRS 3.3

Install extensions (4e855eba, 4efaffca, d5eafa66); patching required - we don't provide opm packages; you can buy our help if required - see below, rebuild OTRS config and delete its cache.

Go to SysConfig and search for memcached or redis; configure connection to cache server and set Memcached or Redis cache module in Cache::Module.

OTRS 5

Please note: we don't provide Redis module for OTRS 5. If you need Redis for OTRS 5 - you can buy our help in porting this module to OTRS 5 - see below.

For Memcached module to work install extension bd77abd6; patching required - we don't provide opm packages; you can buy our help if required - see below, rebuild OTRS config and delete its cache.

Go to SysConfig and search for memcached; configure connection to cache server and set Memcached cache module in Cache::Module.

Commercial support

In case you need further help with these extensions setup, we also provide professional, commercial support and services for OTRS system. Please contact us if you need our staff to help you.

Enjoy!