This document is for users and system administrators that are unfamiliar with the OWLIM-Enterprise software. The information contained in the following pages should be enough to get started with OWLIM-Enterprise, i.e. to install and configure the software on both master and worker nodes.
A cluster is made up of two basic node types: masters and workers. A master node is responsible for:
Worker nodes are based on OWLIM-SE and are set up using the Sesame HTTP server (a Web application running inside a servlet container, e.g. Apache Tomcat). Master nodes do not store or manage any RDF data themselves (although it is possible to run a master and a worker instance on the same physical machine). From an external point of view, a master behaves exactly like any other Sesame repository that is exposed via the Sesame HTTP server, but internally utilises worker nodes (also exposed via the Sesame HTTP server) to store and manage RDF data. In this way, parallel query execution performance can be increased by having worker nodes answer queries in parallel.
The rest of this guide gives detailed step by step instructions for installing and configuring an OWLIM-Enterprise cluster that contains both master and worker nodes.
OWLIM will normally be built against the latest version of the Aduna OpenRDF Sesame framework. If using OWLIM with this version then the easiest way to deploy an OWLIM server instance is to copy the re-packaged Sesame Web applications (.war files) in to the Tomcat webapps directory. These can be found in the sesame_owlim directory in the OWLIM distribution ZIP file. These Web applications have been modified as follows:
The repackaged openrdf-sesame.war Web application must be deployed to all cluster nodes. The openrdf-workbench.war Web application need only be deployed on a single machine and this does not have to be a machine taking part in the cluster. However, for simplicity, it is more straightforward to deploy the workbench to all nodes simultaneously with the Sesame server.
After deployment, OWLIM-Enterprise master and worker nodes can be created using the workbench application as follows:
The last steps to get the cluster connected and running are:
This longer install process should be used when a different or modified version of Sesame is being used. In this case, all the OWLIM-Enterprise files need to be installed alongside Sesame in a step-by-step process as follows.
A suitable application server must be installed. The examples in this guide assume Apache Tomcat version 6.x is used. Importantly, the user must have sufficient privileges to write to the Tomcat webapps directory and to stop and start the Tomcat daemon.
No part of this guide is intended to supersede the documentation published with these 3rd party software components and the reader is strongly advised to familiarise himself/herself with these.
Assuming that an instance of Tomcat is available on all cluster nodes, the installation proceeds as follows:
One thing to remember is that although workers behave like a standard OWLIM-SE instance, worker nodes need to expose a cluster management end-point (when necessary) using a port number that is given by the Tomcat port number plus 10, i.e. usually 8080 + 10 = 8090. You must make sure that no other software is listening on this port number.
Installation of worker nodes precedes exactly the same as when installing OWLIM-SE using the Sesame HTTP server, see the OWLIM-SE installation section. However, there are several important differences:
At this point the master node is running, but the cluster it manages has no attached worker nodes.
As soon as one or more workers have been attached. the cluster can now be used as a read-only repository, notifications and statistics can be monitored through the JMX client.
When a master is brought online, it will be in read-only mode, otherwise known as 'hot-standby'. To put the master in to read-write mode, attach to its JMX interface (using jconsole) and set the ConfiguredWritable attribute to true. If there is no problem, then the IsWritable attribute should now also change to true. At this point, the cluster can be used like any other OWLIM-SE repository shared over HTTP.
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