計(jì)算機(jī)外文翻譯--weblogic server clustering 介紹

1、- 1 -外文原文Understanding WebLogic Server ClusteringThis section is a brief introduction to WebLogic Server clusters. It contains the following information: ? “What Is a WebLogic Server Cluster?” on page 2-1 ? “How Does a C

2、luster Relate to a Domain?” on page 2-2? “What Are the Benefits of Clustering?” on page 2-3 ? “What Are the Key Capabilities of a Cluster?” on page 2-3? “What Types of Objects Can Be Clustered?” on page 2-5 ? “What Types

3、 of Objects Cannot Be Clustered?” on page 2-8What Is a WebLogic Server Cluster?A WebLogic Server cluster consists of multiple WebLogic Server server instances running simultaneously and working together to provide increa

4、sed scalability and reliability. A cluster appears to clients to be a single WebLogic Server instance. The server instances that constitute a cluster can run on the same machine, or be located on different machines. You

5、can increase a cluster’s capacity by adding additional server instances to the cluster on an existing machine, or you can add machines to the cluster to host the incremental server instances. Each server instance in a cl

6、uster must run the same version of WebLogic Server.How Does a Cluster Relate to a Domain?A cluster is part of a particular WebLogic Server domain. A domain is an interrelated set of WebLogic Server resources that are man

7、aged as a unit. A domain includes one or more WebLogic Server instances, which can be clustered, non-clustered, or a combination of clustered and non-clustered instances. A domain can include multiple clusters. A domain

8、also contains the application components deployed in the domain, and the resources and services required by those application components and the server instances in the domain. Examples of the resources and services used

9、 by applications and server instances include machine definitions, optional network channels, connectors, and startup classes.You can use a variety of criteria for organizing WebLogic Server instances into domains. For i

10、nstance, you might choose to allocate resources to multiple domains based on logical divisions of the hosted application, geographical considerations, or the number or complexity of the resources under management. For ad

11、ditional information about domains see - 3 -help programmers and administrators maximize the scalability and availability of their applications. What Are the Key Capabilities of a Cluster?This section defines, in non-tec

12、hnical terms, the key clustering capabilities that enable scalability and high availability.? Application Failover Simply put, failover means that when an application component (typically referred to as an “object” in th

13、e following sections) doing a particular “job”—some set of processing tasks—becomes unavailable for any reason, a copy of the failed object finishes the job.For the new object to be able to take over for the failed objec

14、t: – There must be a copy of the failed object available to take over the job.– There must be information, available to other objects and the program that manages failover, defining the location and operational status of

15、 all objects—so that it can be determined that the first object failed before finishing its job.– There must be information, available to other objects and the program that manages failover, about the progress of jobs in

16、 process—so that an object taking over an interrupted job knows how much of the job was completed before the first object failed, for example, what data has been changed, and what steps in the process were completed.WebL

17、ogic Server uses standards-based communication techniques and facilities— including IP sockets and the Java Naming and Directory Interface (JNDI)—to share and maintain information about the availability of objects in a c

18、luster. These techniques allow WebLogic Server to determine that an object stopped before finishing its job, and where there is a copy of the object to complete the job that was interrupted.Note: For backward compatibili

19、ty with previous versions, WebLogic Server also allows you to use multicast for communications between clusters.Information about what has been done on a job is called state. WebLogic Server maintains information about s

20、tate using techniques called session replication and replica-aware stubs. When a particular object unexpectedly stops doing its job, replication techniques enable a copy of the object pick up where the failed object stop

21、ped, and finish the job. ? WebLogic Server supports automatic and manual migration of a clustered server instance from one machine to another. A Managed Server that can be migrated is referred to as a migratable server.