The factors that affect how applications connect to a service integration bus so that they can use resources provided by that bus.
To connect to a service integration bus, an application actually connects to a messaging engine on the bus.
In the simplest case, you can configure the environment to automatically connect applications to any available messaging engine on the bus. You can specify extra configuration details to control the connection process; for example, to identify special bootstrap servers, or to limit connection to a subgroup of available messaging engines.
Applications that are running inside an application server can locate a suitable messaging engine themselves.
If the messaging engine is found in the same server, a connection is created that provides the application with the fastest available connection to a messaging engine. Otherwise, if a messaging engine is found in another process - on the same or a different host - a remote connection is made. If no suitable messaging engine is found the application fails to connect to the bus.
The following figure shows two applications running in application servers. Application X on server3 has connected to the messaging engine running in the same server. Application Y on server1 has connected to a messaging engine that is running in the same bus but on a different server and host, because server1 does not have a suitable messaging engine.
Client applications running outside an application server (for example, running in a client container or outside the WebSphere® Application Server environment) cannot locate a suitable messaging engine themselves and must complete a bootstrap process through a bootstrap server. A bootstrap server is an application server that is running the SIBService service, but is not necessarily running any messaging engines. The bootstrap server selects a messaging engine that is running in an application server that supports the desired target transport chain.
This figure shows a client application running outside an application server. To connect to a messaging engine, the application connects first to a bootstrap server. The bootstrap server selects a messaging engine then tells the client application to connect to that messaging engine.
A bootstrap server uses a specific port and bootstrap transport chain, which with the host name form the endpoint address of the bootstrap server.
The properties of a JMS connection factory used by a client application control the selection of a suitable messaging engine and how the client connects to the selected messaging engine. By default, a connection factory expects to use a bootstrap server that has an endpoint address of localhost:7276:BootstrapBasicMessaging. That is: the client application expects to use a bootstrap server on the same host as the client, using port 7276, and using the predefined bootstrap transport chain called BootstrapBasicMessaging.
When you create an application server, it is automatically assigned a unique non-secure bootstrap port, SIB_ENDPOINT_ADDRESS, and a secure bootstrap port, SIB_ENDPOINT_SECURE_ADDRESS. If you want to use an application server as a bootstrap server, and the server has been assigned a non-secure port other than 7276, or you want to use the secure port, then you must specify the endpoint address of the server on the Provider endpoints property of the connection factory.
The endpoint addresses for bootstrap servers must be specified in every connection factory that is used by applications outside of an application server. To avoid having to specify a long list of bootstrap servers, you can provide a few highly-available servers as dedicated bootstrap servers. Then you only need to specify a short list of bootstrap servers on each connection factory.
The selection process is used to choose a messaging engine that an application should connect to so that it can use the resources of a service integration bus. The information that controls the selection process is configured on the connection factory (or programmatically by the application). The information is used to find the most suitable messaging engine in the bus for the application to connect to. You can configure the properties of the connection factory to restrict the range of messaging engines that applications can connect to.
The default configuration enables applications to connect to any available messaging engine in the bus. For this configuration, you only need to specify the one required connection property, Bus name, which sets the name of the bus to which the application wants to connect.
In both cases (that is, an application running in an application server and an application running outside an application server) you can restrict the range of messaging engines available for connection, to a subgroup of those available in the service integration bus. You do this by configuring the following connection properties of the connection factory:
These transport chains specify the communication protocols that can be used to communicate with the application server that the client application is connected to. The following predefined messaging engine inbound transport chains are provided:
A suitable messaging engine in the same server is selected ahead of a suitable messaging engine in the same host, and in turn ahead of a suitable messaging engine in another host.
A suitable messaging engine in the same server is selected ahead of a suitable messaging engine in the same host, and in turn ahead of a suitable messaging engine in another host.
This option should be used only in WebSphere Application Server environments that support server clusters.