Chapter 26. Technical Service

26.1. Context

For effective components, non-functional aspects must be added to the application functional code. Likewise enterprise middleware and component platforms, in the context of Grids, services must be deployed at execution in the component containers in order to implement those aspects. This work proposes an architecture for defining, configuring, and deploying such Technical Services in a Grid platform.

26.2. Overview

A technical service is a non-functional requirement that may be dynamically fulfilled at runtime by adapting the configuration of selected resources.

From the programmer point of view, a technical service is a class that implements the TechnicalService interface. This class defines how to configure a node.

package org.objectweb.proactive.core.descriptor.services;
			
public interface TechnicalService { 
	public void init(HashMap argValues);
	public void apply(Node node);
}

From the deployer point of view, a technical service is a set of ”variable-value” tuples, each of them configuring a given aspect of the application environment.

<technical-service id="myService" class="services.Service1">
  <arg name="name1" value="value1" />
  <arg name="name2" value="value2" />
</technical-service>

The class attribute defines the implementation of the service, a class which must implement the TechnicalService interface.

The configuration parameters of the service are specified by arg tags in the deployment descriptor. Those parameters are passed to the init method as a map associating the name of a parameter as a key and its value. The apply method takes as parameter the node on which the service must be applied. This method is called after the creation or acquisition of a node, and before the node is used by the application.

Note

	Note
Two or several technical services could be combined if they touch separate aspects. Indeed, two different technical services, which are conceptually orthogonal, could be incompatible at source code level . That is why a virtual node can be configured by only one technical service. However, combining two technical services can be done at source code level, by providing a class extending `TechnicalService` that defines the correct merging of two concurrent technical services.

Two or several technical services could be combined if they touch separate aspects. Indeed, two different technical services, which are conceptually orthogonal, could be incompatible at source code level .

That is why a virtual node can be configured by only one technical service. However, combining two technical services can be done at source code level, by providing a class extending TechnicalService that defines the correct merging of two concurrent technical services.

26.3. Progamming Guide

26.3.1. A full XML Descriptor File

<ProActiveDescriptor>
  <componentDefinition>
    <virtualNodesDefinition>
      <virtualNode name="master" property="multiple" serviceRefid="ft-master" />
      <virtualNode name="slaves" property="multiple" serviceRefid="ft-slaves" />
    </virtualNodesDefinition>
  </componentDefinition>
  ...
  <infrastructure>
    <processes>
      <processDefinition id="localJVM">
        <jvmProcess class="JVMNodeProcess" />
      </processDefinition>
    </processes>
    <aquisition>
      <aquisitionDefinition id="p2pservice">
        <P2PService nodesAsked="100000">
          <peerSet>
            <peer>rmi://registry1:3000</peer>
          </peerSet>
        </P2PService>
      </acquisitionDefinition>
    </services>
  </infrastructure>
  <technicalServiceDefinitions>
    <service id="ft-master" class="services.FaultTolerance">
      <arg name="proto" value="pml" />
      <arg name="server" value="rmi://host/FTServer1" />
      <arg name="TTC" value="60" />
    </service>
    <service id="ft-slaves" class="services.FaultTolerance">
      <arg name="proto" value="cic" />
      <arg name="server" value="rmi://host/FTServer2" />
      <arg name="TTC" value="600" />
    </service>
  </technicalServiceDefinitions>
</ProActiveDescriptor>

26.3.2. Nodes Properties

In order to help programmers for implementing their owns technical services, we have added a property system to the nodes. This is usefull for configuring technical services.

Get the current node:

Node localNode = ProActive.getNode();

Using properties:

String myProperty = localNode.getProperty(myKeyAsString);
localNode.setProperty(myKeyAsString, itsValueAsString);

26.4. Further Information

The seminal paper [ CDD06c ] .

The first presentation of this work is available here .

The work of this paper [ CCDMCompFrame06 ] is based on Technical Services.

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