The Glidein Factory Daemon

Description

This document describes the internals of a glideinWMS Factory Daemon.

Index

• Glidein Factory Overview

• Program flow

• Source code distribution

• Configuration files

Glidein Factory Overview

A Glidein Factory is composed of a Factory Daemon and several Factory Entry Daemons. Each Entry Daemon is autonomous; it advertises itself and processes the incoming requests. The main Factory Daemon just launches and monitors the Factory Entry Daemons.
See the picture below for a logical overview.




All daemons of a Glidein Factory share the same directory tree. The root of the tree contains the common startup and configuration files, while each entry point has a few additional configuration files on its own.

Program flow

The main tasks of the Factory Daemon are the startup up the Entry Daemons and the aggregation of statistics from the entries.
See picture below for an overview.

The only non trivial operation in the statistics aggregation. The Factory Daemon reads the XML files produced by the Factory Daemons, aggregates them, and writes out an aggregate XML file. It also updates the RRD files used to keep the history and creates the rrdtool graphs and HTML pages for human consumption.
See picture below for an overview.

Source code distribution

The Factory Daemon is implemented as a series of python scripts, and it does not need to be pre-compiled.

The code is spread over several python modules, some specific to the factory other shared between different parts of the glideinWMS. There are also an external dependency on the rrdtool python libraries.
The picture below shows the dependency tree.

glideFactory.py is executable.

The glideinWMS common libraries are in glideinWMS/lib directory.

Configuration files

The Factory daemon reads a single configuration file:
glidein.descript
located in the root of the factory configuration tree.

Only two elements of this configuration file are used:

• Entries - The list of entries, used to launch the Entry Daemons.

• LoopDelay - How long should it sleep between iterations.

Warning: The configuration file should never be changed by hand. It is generated and maintained by a dedicated tool.