GT 3.9.4 Component Guide to Public Interfaces: WS MDS Index Service

Semantics and syntax of APIs

Programming Model Overview

Index service queries are performed using resource property requests; consult the WS-Core documentation for details.

The contents of an index are maintained using the aggregator 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 MDS Index Public Interface Guide; information about how to create new aggregator sources can be found in the aggregator documentation.

Semantics and syntax of the WSDL

The WSDL interface for the Index is inherited entirely from the aggregator, and so the aggregator interface documentation should be consulted for further information.

Command-line tools

  • mds-servicegroup-add
  • Other command line tools

    • mds-servicegroup-add for WS MDS Index Service

    mds-servicegroup-add creates a set of registrations to a WS-ServiceGroup and periodically renews those registrations. It is intended primarily for registering grid resources to MDS services such as the index and trigger services.

    Registrations are defined in an XML configuration file, which is documented in the aggregator admin guide.

    Command syntax

       mds-servicegroup-add -s http://foo [options] config.xml

    Options and Arguments

    -s http://foo This dummy option is required but ignored. All end point references used by mds-servicegroup-add are read from the configuration file, not the command line.
    -a By default, mds-servicegroup-add will attempt to make an authenticated connection to each service group. This option is used to specify anonymous connections (and to prevent mds-servicegroup-add from failing if you don't have a valid Grid credential).
    config.xml the configuration file

    The other standard toolkit options [TODO -- link to standard options page] are also supported.

    The syntax of the configuration file used by mds-servicegroup-add is described in detail in the MDS Index Public Interface Guide. In addition, the Globus Toolkit distribution includes an example configuration file $GLOBUS_LOCATION/etc/globus_wsrf_mds_aggregator/example-aggregator-registration.xml. The simplest way to register services to an index is to edit the example file, replacing the EPRs in that file with the EPRs for your resources, and then to run mds-servicegroup-add to perform the registrations specified in that file.

    Limitations

    It is necessary for the tool to continue to run in order for the registrations that it maintains to be kept alive, as registrations will otherwise time out.

    Other command line tools for WS MDS Index Service

    The index service exposes information via service groups, so command line tools like wsrf-query and wsrf-get-property can be used to query it. See the GT Java WS Core User's Guide for more information about how to use these tools.

    Overview of Graphical User Interface

    There is no GUI specifically for the Index Service. The release contains a tech preview of WebMDS which can be used to display monitoring information collected in an Index Service in a normal web browser.

    Semantics and syntax of domain-specific interface

    Interface introduction

    [provide an overview of the purpose and structure of the domain-specific interface]

    Syntax of the interface

    [list and describe detailed information here]

    Configuration interface

    Configuration overview

    For a basic installation, the index service itself does not need any configuration changes from default.

    In order for member services to appear in the index, they must be registered using the mds-servicegroup-add tool. This tool should be run as a daemon to maintain 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 the MDS Aggregator Framework and can use any aggregator source to collect information. By default, 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.

    Syntax of the interface

    Specifying the Aggregator Source

    The aggregation source used to collect data can be changed from default by editing the aggregatorSource parameter in the index configuration in $GLOBUS_LOCATION/etc/globus_wsrf_mds_index/jndi-config.xml: 

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

    This parameter specifies a java class that will be used to collect data for the index. By default it is set to the QueryAggregatorSource. It can be changed to one of the other sources supplied with the toolkit, or to one installed later. Details of the supplied sources are in the Aggregator developer guide.

    Configuring the Aggregator Source

    Configuration options are specified by creating a configuration file and running mds-servicegroup-add to perform the registrations specified in that configuration file. The syntax of that file is: 
    <?xml version="1.0" encoding="UTF-8" ?>
<ServiceGroupRegistrations
  xmlns="http://mds.globus.org/servicegroup/client" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xmlns:agg="http://mds.globus.org/aggregator/types">

   <defaultServiceGroupEPR>
      Default service group EPR
   </defaultServiceGroupEPR>

   <defaultRegistrantEPR>
      Default registrant EPR
   </defaultRegistrantEPR>

   <defaultSecurityDescriptorFile>
      Path name of security descriptor file
   </defaultSecurityDescriptorFile>

   One or more of the following:
   <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>
         Aggregator-source-specific configuration parameters
      </Content>
   </ServiceGroupRegistrationParameters>

</ServiceGroupRegistrations>
    Each ServiceGroupRegistrationParameters block specifies the parameters used to register a resource to a service group. The parameters specified in this block are:
    ServiceGroupEPR The EPR of the service group to register to. This parameter may be omitted if a defaultServiceGroupEPR block is specified; in this case, the value of defaultServiceGroupEPR will be used instead.
    RegistrantEPR The EPR of the resource to register. This parameter may be omitted if a defaultRegistrantEPR block is specified; in this case, the value of defaultRegistrantEPR will be used instead.
    InitialTerminationTime The initial termination time of this registration (this may be omitted).
    RefreshIntervalSecs The refresh interval, in seconds.
    Content Aggregator-source-specific registration parameters. The content blocks for the various aggregator sources are described in detail in the following sections.

    The defaultServiceGroupEPR block provides a convenient way to register a number of resources to a single service group -- for example, if you wish to register several resources to your default VO index, you can specify that index as the default service group and omit the ServiceGroupEPR blocks from each ServiceGroupRegistrationParameters block.

    The defaultRegistrantEPR block provides a convenient way to register a single resource to several service groups -- for example, if you wish to register your local GRAM server to several index servers, you can specify your GRAM server as the default registrant and omit the RegistrantEPR blocks from each ServiceGroupRegistrationParameters block.

    ServiceGroupRegistration Content Blocks for QueryAggregatorSource

    The QueryAggregatorSource can use one of the following three configuration blocks.
    GetResourcePropertyPollType
    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>
    The PollIntervalMillis parameter is the poll refresh period in milliseconds; the ResourcePropertyName parameter is the QName of the resource property to poll for.
    GetMultipleResourcePropertiesPollType
    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>
    The PollIntervalMillis parameter is the poll refresh period in milliseconds; the ResourcePropertyNames parameters are the QNames of the resource properties to poll for. There is no limit on the number of ResourcePropertyNames that may be specified.
    QueryResourcePropertiesPollType
    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 GT3.9.4 implementation of 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:QueryExpression Dialect="dialect">
               Query Expression
            </agg:QueryExpression>
         </agg:QueryResourcePropertiesPollType>
      </agg:AggregatorConfig>
      <agg:AggregatorData/>
   </Content>
    The PollIntervalMillis parameter is the poll refresh period in milliseconds. The QueryExpression is an xsd:any element; the Dialect attribute specifies the dialect of the query expression.

    ServiceGroupRegistration Content Blocks for SubscriptionAggregatorSource

    The SubscriptionAggregatorSource gathers resource property values from the registered resource using WS-Notification subscriptions. The configuration block for SubscriptionAggregatorSource looks like this: 
    
   <Content
        xmlns:agg="http://mds.globus.org/aggregator/types"
        xsi:type="agg:AggregatorContent">
      <agg:AggregatorConfig xsi:type="agg:AggregatorConfig">
         <agg:AggregatorSubscriptionType>
             <TopicExpression Dialect="dialect">
                Topic Expression
             </TopicExpression>
             <Precondition Dialect="dialect">
                Precondition
             </Precondition>
             <Selector Dialect="dialect">
                Selector
             </Selector>
             <SubscriptionPolicy>
                Subscription Policy
             </SubscriptionPolicy>
             <InitialTerminationTime>time</InitialTerminationTime>
         </agg:AggregatorSubscriptionType>
      </agg:AggregatorConfig>
      <agg:AggregatorData/>
   </Content>
    The only required parameter is the TopicExpression, which specifies the topic expression to use in the subscription request. [TODO: link to generic notification/subscription docs].

    ServiceGroupRegistration Content Blocks for ExecutionAggregatorSource

    The ExecutionAggregatorSource gathers arbitrary XML information about a registered resource by executing an external script and passing registration as parameters. The configuration block for ExecutionAggregatorSource 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:filename</agg:ProbeName>
         </agg:ExecutionPollType>
      </agg:AggregatorConfig>
      <agg:AggregatorData/>
   </Content>
    The PollIntervalMillis parameter is the poll refresh period in milliseconds. The ProbeName parameter specifies the path name to the executable file, relative to the $GLOBUS_LOCATION/libexec/aggrexec directory. The path name should be specified as the local name part of this QName; the namespace part is ignored.

    Environment variable interface

    • provide details on settings and effect of env var #1
    • ...
    • provide details on settings and effect of env var #n