2004-10-19
This article is suitable for friends who are interested in grid computing and GT. Although GT4 is now implementation of the class, it is still necessary to understand GT3 is still very necessary. The change in GT3-> GT4 is not big. GT3 CORE is Grid Service (hereinafter referred to as GS), GS is inherently Web Service (hereinafter referred to as WS). It adds some features on the basis of WS. Compared to other distributed computing technologies (such as Corba, RMI, EJB), WS advantage: 1. It is based on standard XML, which makes it platform independent. 2. It uses HTTP as a communication protocol, the Internet, the agent's firewall does not limit HTTP.ws Disadvantages: 1. Lack of some Features (lifecycle management, notification, persistent stability). 2.ws is stateless, making it impossible to remember what a call did. And GS will improve WS, add some functions. Bottom a GS ratio What is WS? 1. Sustained HSL Grid Service and Temporary Service Instance GS Use the factory method to replace the single stateless WS instance shared by all users. For any GS, when it is deployed to the Server, it will generate a plant when it is deployed to the Server. This factory will manage all Service instances. For example, when a user wants to use a service, it allows the factory to produce an instance, once an instance created, a GSH (Grid Service Handle) is also generated, give this instance. Gsh is like An address, specifying the service's location. Users want to know how to communicate with Service, send GSH to Handle Resolver, GSR (Grid Service Reference) will return to the user, GSR includes the details of GS (such as Methods, Message Types), If you use SOAP binding, this GSR is WSDL File. Each service instance is temporary, there are life cycles, different users can communicate with his own service, if necessary, a service instance can also be more User service. 2 Service Data We know that in the UDDI directory, we can find service to meet our needs, but if there are multiple similar services, we don't know which one is more appropriate. You can make a decision through WSDL, but there are two problems using WSDL, one is WSDL contains a lot of complex technical details so that it is not easy to query, and the other is the continuous-changing service, WSDL is not easy to dynamically modify. Service Data is a service related to service. Each service instance has its own data set, including one or more SDE (Service Data Elements). SDE can be a simple named value, or a complex structure. In GT3 CORE, each SDE is implemented as a Java Class, just like java bean. We pass the GET, SET method to access the value of the SDE. A file called SDD (Service Data Description) will be transmitted along with WSDL to illustrate SDE. 3 Lifecycle Management GT3 Core There are two ways to define the service instance LifeCyle. First, before the instance and the service factory negotiation, the second is to give the instance to instance, this message includes requestterminationBefore, requestterminationAfter.gt3 Core Some Callback methods allow customers to get notifications when they change their life. Lifecycle Monitor also provides management of life. 4 Notification Notice Mechanism Allows the customer when the GS's Service Data changes. That is to say, different programs and users can communicate through service data. Users can book and start listening, as long as changes have changed, the predetermined user will be notified immediately.
