GT 4.2.1 WS MDS Aggregator Sources Reference

The query source collects information from a registered resource by using WS-Resource Properties polling mechanisms:

The QueryAggregatorSource will attempt to detect when the data source EPR is local to the current container instance, and if so set the connection properties to use local transport.

Polls are made periodically, with both the period and target Resource Properties specified in the registration message.

The SubscriptionAggregatorSource gathers resource property values from the registered resource using WS-Notification subscriptions. Data is delivered when property values change, rather than periodically.

The SubscriptionAggregatorSource will attempt to detect when the data source EPR is local to the current container instance, and if so set the connection properties to use local transport.

The execution aggregation source provides a way to aggregate data (arbitrary XML information) about a registered resource using an arbitrary local executable (such as an external script). The executable will be passed registration information as parameters and is expected to output the gathered data.

A basic example of the use of this API is described in the [fixme link to ping test example] for the aggregator execution source.

The execution aggregation source will periodically execute an identified executable. The identity of the executable and the frequency with which it is to run are specified in the registration message.

Details of the interface between the execution source and local executables are in Chapter 6, Configuring Execution Aggregator Source

To register resources with the Index Service:

The configuration file consists of an optional defaultServiceGroupEPR, an optional defaultRegistrantEPR, and then one or more ServiceGroupRegistrationParameters blocks, each of which represents one registration.

You can use the example configuration at $GLOBUS_LOCATION/etc/globus_wsrf_mds_aggregator/example-aggregator-registration.xml, replacing the EPRs in that file with the EPRs for your resources. It includes many examples of configurations for GRAM, RFT and other situations.

The general syntax of the configuration file is:

<?xml version="1.0" encoding="UTF-8" ?>
<ServiceGroupRegistrations
  xmlns="http://mds.globus.org/servicegroup/client">

  // An optional default service group EPR.
  <defaultServiceGroupEPR>
    // Default service group EPR
  </defaultServiceGroupEPR>

  // An optional default registrant EPR.
  <defaultRegistrantEPR>
    // Default registrant EPR
  </defaultRegistrantEPR>

  // An optional default security descriptor file.
  <defaultSecurityDescriptorFile>
    // Path name of default security descriptor file
  </defaultSecurityDescriptorFile>

  // One or more service group registration blocks:

  <ServiceGroupRegistrationParameters>
    <ServiceGroupEPR>
      // EPR of the service group to register to
    </ServiceGroupEPR>
    <RegistrantEPR>
      // EPR of the entity to be monitored.
    </RegistrantEPR>
    <InitialTerminationTime>
      // Initial termination time
    </InitialTerminationTime>
    <RefreshIntervalSecs>
      // Refresh interval, in seconds
    </RefreshIntervalSecs>
    <Content type="agg:AggregatorContent">
      // Aggregator-source-specific configuration parameters
    </Content>
  </ServiceGroupRegistrationParameters>

</ServiceGroupRegistrations>

The following table describes the different blocks of the file and any parameters:

Further configuration information is detailed per source: QueryAggregatorSource, SubscriptionAggregatorSource, and ExecutionAggregatorSource.

	Note
	Using the ExecutionAggregatorSource also requires configuring the executable itself, which is also covered in the ExecutionAggregatorSource section.

If a GetResourcePropertyPollType block is used, QueryAggregatorSource will request a single resource property. The block has this form:

 <Content xsi:type="agg:AggregatorContent"
                    xmlns:agg="http://mds.globus.org/aggregator/types">
                    <agg:AggregatorConfig xsi:type="agg:AggregatorConfig">
                    <agg:GetResourcePropertyPollType>
                    <agg:PollIntervalMillis>interval_in_ms</agg:PollIntervalMillis>
                    <agg:ResourcePropertyName>rp_namespace:rp_localname</agg:ResourcePropertyName>
                    </agg:GetResourcePropertyPollType>
                    </agg:AggregatorConfig> <agg:AggregatorData/>
                    </Content>

where:

If a GetMultipleResourcePropertiesPollType block is used, QueryAggregatorSource will request one or more resource properties. The block has this form:

 <Content
                    xmlns:agg="http://mds.globus.org/aggregator/types"
                    xsi:type="agg:AggregatorContent"> <agg:AggregatorConfig
                    xsi:type="agg:AggregatorConfig">
                    <agg:GetMultipleResourcePropertiesPollType>
                    <agg:PollIntervalMillis>interval_in_ms</agg:PollIntervalMillis>
                    <agg:ResourcePropertyNames>rp1_namespace:rp1_localname</agg:ResourcePropertyNames>
                    <agg:ResourcePropertyNames>rp2_namespace:rp3_localname</agg:ResourcePropertyNames>
                    <agg:ResourcePropertyNames>rp3_namespace:rp3_localname</agg:ResourcePropertyNames>
                    </agg:GetMultipleResourcePropertiesPollType>
                    </agg:AggregatorConfig> <agg:AggregatorData/>
                    </Content>

where:

If a QueryResourcePropertiesPollType block is used, QueryAggregatorSource will request that a query be executed against the Resource Property Set of the remote resource. In the GT4 implementation of WSRF Core, the only query language that is supported is XPath. The block has this form:

                    <Content xmlns:agg="http://mds.globus.org/aggregator/types"
                    xsi:type="agg:AggregatorContent"> <agg:AggregatorConfig
                    xsi:type="agg:AggregatorConfig">
                    <agg:QueryResourcePropertiesPollType>
                    <agg:PollIntervalMillis>interval_in_ms</agg:PollIntervalMillis>
                    <agg:QueryExpressionDialect="dialect">
                    Query Expression </agg:QueryExpression>
                    </agg:QueryResourcePropertiesPollType>
                    </agg:AggregatorConfig> <agg:AggregatorData/>
                    </Content>

where:

The configuration block for ExecutionAggregatorSource (inside the Content block) looks like this:

                <Content xsi:type="agg:AggregatorContent"
                xmlns:agg="http://mds.globus.org/aggregator/types">
                <agg:AggregatorConfig xsi:type="agg:AggregatorConfig">
                <agg:ExecutionPollType>
                <agg:PollIntervalMillis>interval_in_ms</agg:PollIntervalMillis>
                <agg:ProbeName>dummy_namespace:probe_name</agg:ProbeName>
                </agg:ExecutionPollType>
                </agg:AggregatorConfig>
                <agg:AggregatorData/>
                </Content>
            

where:

If you've properly configured and registered your script for execution but are getting errors from the container because it cannot find the specified script, there are two likely causes.

First, make sure that your script/program is executable and is located in the $GLOBUS_LOCATION/libexec/aggrexec directory. When it's specified in the configuration mentioned above, only specify the name of the script/program, without any qualification or path. For example, using the ProbeName as test-script will be specifying the file $GLOBUS_LOCATION/libexec/aggrexec/test-script script.

Next, make sure that you have correctly created an executableMappings definition in the appropriate jndi-config.xml file.