Chapter 1. Introduction to Domains

Table of Contents

1.1. Basic Concepts
1.2. Relationship Between JEUS and Domain
1.3. Composition
1.3.1. Domain Administration Server(DAS)
1.3.2. Managed Servers
1.4. Production and Development Modes
1.5. Domain Restrictions

This chapter describes the concepts and architecture of a domain.

A domain is the basic unit of management. It consists of multiple servers and clusters that are divided according to tasks.

Services, server locations, and security policies can be different for each domain. Each domain has a separate configuration file and does not share settings with other domains. Domains should be created with the knowledge that the security configuration, applications, and resources are shared within each domain.

Consider the following when creating a domain:

  • Role of a server

    • A domain consists of related applications.

  • Physical location of the server

    • To provide stable services, the physical location of the servers is important.

  • Load on the servers

    • Use an appropriate number of servers based on the required workload.

Each machine requires an instance of JEUS (installed in JEUS_HOME), which can contain one or more domains. A domain can be created in one instance or across multiple instances of JEUS.

Note

Usually, a single JEUS instance is installed on each server. However, it is possible for a machine to have multiple instances of JEUS installed.

For instance, a domain for personnel management and another for order management can be installed on three servers according to the applications' requirements. In the following example, Domain1 for personnel management service is installed on a single machine, Machine1. The domain for order management is installed on all three machines so that its services are still available if one of the servers fails.

The following diagram shows the relationship between JEUS domains.


A domain consists of Domain Administration Server(DAS), Managed Servers(MS), and clusters.


Machine 1 contains DAS that processes orders by communicating with WebAdmin and jeusadmin. DAS can also install JEUS on Machine 2 and Machine 3 via SSH, and can start and stop the Managed Servers.

Machine 2 and Machine 3 each contain two MSs. Managed Server 2 and Managed Server 4 in Cluster 1 share applications and resources and provide the same services, but Managed Server 1 and Managed Server 3, which are not in Cluster 1, do not.

Note

A basic domain must contain one server that acts as both DAS and MS. This domain configuration should only be used for development and testing. In the production environment, separate servers should be used for management and services and DAS should only be used to manage MSs.

Domain Administration Server must exist in every domain. It centrally manages and monitors MSs.

The major functions of DAS are:

The domain operation mode can be set to either of the following modes. The mode must be manually set in the configuration file (domain.xml). It cannot be configured through WebAdmin or jeusadmin.

  • Production mode

    This mode is suitable for the actual production environment. The auto-reload or hot-swap functions of web applications are not provided. Set the production-mode to true in the domain.xml file.

  • Development mode

    If the production-mode is set to false in the domain.xml file, the domain runs in the development mode.

Note

1. It is recommended to use the development mode during the development stage where applications are changed frequently, and to use the production mode in the actual production environment.

2. All running servers in the domain must be restarted after modifying the configuration.

The following restrictions apply to each domain.

  • Each domain must have one DAS.

    WebAdmin and jeusadmin can only manage the domain of the DAS that they are connected to. To manage another domain, WebAdmin and jeusadmin must connect to a different URL.

  • Configurations and resources cannot be shared between domains.

  • All servers in the domain must use the same version.

  • The name of each server and cluster in the domain must be unique.

  • The name of each domain on a JEUS instance must be unique.