Apache Tuning

The goal of this page is to give some details about Apache tuning for Nebulous.

Introduction

Apache Configuration

We use the following mpm_prefork_module configuration for Apache.

<IfModule mpm_prefork_module>
        StartServers            5
        MinSpareServers         5
        MaxSpareServers         10
        MaxClients              150
        MaxRequestsPerChild     10000
</IfModule>

For convenience, the Apache log level has been set to debug.

Experiment

I wrote a small utility script that starts nbProcesses processes. Each process attempts to create nbFiles files in Nebulous using neb-touch. To ensure that files do not previously exist in Nebulous, each instance of the utility script is called with an index argument (let's call it experimentNb). Each experiment is run this way:

  python startNebFilesCreation.py <experimentNb> <nbProcesses> <nbFiles>

and creates <nbProcesses>*<nbFiles> files in Nebulous named:

  neb:///<a path to have a total path length of 200 bytes>/<experimentNb>/<processId>/<fileIdWithProcess>

The path length is adjusted through the <a path to have a total path length of 200 bytes> which is basically a sequence of "1234567890/" strings to have a total length of about 200 bytes which is the average size of a Nebulous instance entry.

Operating Conditions

The experiments are performed on ippc01 where a local Nebulous database has been installed. To avoid any conflict with existing tools, a local neb-touch was used (URL: ​https://svn.pan-starrs.ifa.hawaii.edu/repo/ipp/tags/ipp-20110218/Nebulous/bin/neb-touch; Revision: 30846).