GT 4.2.0 Index Service: Public Interface Guide

Index Service queries are performed using resource property requests; consult Java WS Core for details.

The contents of an index are maintained using the aggregator framework programming model, and can receive data from any aggregator source. Information about how to configure existing aggregator sources (such as the aggregator sources distributed with the Globus Toolkit, which include one that polls for resource property information, one that collects resource property information through subscription/notification, and one that collects information by executing an executable program) is found in the Aggregator Sources Reference; information about how to create new aggregator sources can be found in Developer's Guide.

The Aggregator Framework builds on the WS-ServiceGroup and WS-ResourceLifetime specifications. Those specifications should be consulted for details on the syntax of each operation.

Each Aggregator Framework is represented as a WS-ServiceGroup (specifically, an AggregatorServiceGroup).

Resources may be registered to an AggregatorServiceGroup using the AggregatorServiceGroup Add operation. Each registration will be represented as a ServiceGroupEntry resource. Resources may beregistered to an AggregatorServiceGroup using the service group add operation, which will cause an entry to be added to the service group.

The entry will include configuration parameters for the aggregator source; when the registration is made, the following will happen:

The method of collection by source and processing by the sink is dependent on the particular instantiation of the aggregator framework (see per-source documentation for source information and per-service documentation for sink information - for example the Index Service and the Trigger Service.)

The Aggregator Framework throws standard WS-ServiceGroup, WS-ResourceLifetime, and WS-ResourceProperties faults and does not define any new faults of its own.

Other relevant source files are the:

For a basic installation, the Index Service itself does not need any configuration changes from default; a default Index Service is available and automatically "registers" with the following GT web services based resources to allow monitoring and discovery: [CAS], [RFT], and [GRAM4] (click the links for information about what data is sent and how to change it).

	Note
	Auto-registration is turned on by default in GT 4.2.0. See the per service links above for information about configuring this capability.

In order for information to appear in the Index Service, the source of that information must be registered to the Index Service. Information sources are registered using tools like mds-servicegroup-add(1). Each registration has a limited lifetime; mds-servicegroup-add should be left running in the background so that it can continue to refresh registrations. Depending on administration preference, it may be run on the same host as the index, on the same host as a member resource, or on any other host(s).

The Index Service is built on Aggregator Framework and can use any Aggregator Sources Reference to collect information. In the most common case, the index service uses the QueryAggregatorSource to gather resource property values from the registered resource using one of the three WS-Resource Properties operations to poll for information; the polling method used depends on the configuration element supplied in the registration content.

Two other aggregator sources are supplied with the distribution: the SubscriptionAggregatorSource, which gathers resource property values through subscription/notification, and the ExecutionAggregatorSource, which executes an external program to gather information.

The aggregation sources used to collect data can be changed from default by editing the aggregatorSources parameter in the JNDI service configuration. See $GLOBUS_LOCATION/etc/globus_wsrf_mds_index/jndi-config.xml:

<resource name="configuration"
             type="org.globus.mds.aggregator.impl.AggregatorConfiguration">
  <resourceParams>
    <parameter>
      <name> factory</name>
      <value>org.globus.wsrf.jndi.BeanFactory</value>
    </parameter>
    <parameter>
      <name>aggregatorSource</name>
      <value>org.globus.mds.aggregator.impl.QueryAggregatorSource 
             org.globus.mds.aggregator.impl.SubscriptionAggregatorSource 
             org.globus.mds.aggregator.impl.ExecutionAggregatorSource
      </value>
    </parameter>
</resourceParams>

This parameter specifies one or more Java classes that may be used to collect data for the Index. By default it is set to use the QueryAggregatorSource, SubscriptionAggregatorSource, and ExecutionAggregatorSource. Details of these standard sources are in the Aggregator Sources Reference.

The ExecutionAggregatorSource, which may be used by the Index Service, has a domain-specific interface (specifically, the inputs provided to and outputs expected from the executable program).

The syntax of the execution source's domain-specific interface is described in Configuring Execution Aggregator Source.