High availability with the integration framework

The integration framework supports both synchronous and asynchronous message processing in a highly available environment.

The Tivoli®'s process automation engine integration framework supports various message formats and protocols for exchanging messages between the process automation engine and external systems.

Depending on the integration framework capabilities that are used, there are different ways to configure high availability.

When you use the integration framework in a high availability environment, you must pay attention to the following areas:
Integration framework error handling
The mxe.int.globaldir property defines where integration framework error logs, the schema, and Web Services Description Language (WSDL) files are stored and read from. In a clustered environment, the directory is on a shared disk and all application servers must have access to that location.
Synchronous integration
Synchronous integration does not use JMS Queues. For example, the synchronous message exchange can use HTTP, web services, and Enterprise JavaBeans. The high availability characteristics of synchronous integration are similar to the process automation engine user interface client; the web browser. If an error occurs, the request must be resubmitted to continue.
Asynchronous integration
Asynchronous integration uses JMS queues. For example, the asynchronous message exchange can use HTTP, web services, Enterprise JavaBeans, file loading, and interface tables. Queue failover must be considered: WebSphere® Application Server configures queues for failover by default in a clustered environment.
As part of asynchronous integration, the consumer of the messages and the producer of the messages must be considered:
Consumer
The process automation engine consumes messages in the queue.
  • Sequential queue: Guarantees the order of messages that are processed is based on the order that the messages are received. Only one instance of a cron task handles the consumption of messages from the queue. If the server fails, the highly available environment starts another instance of the cron task to handle the failed job on another server or node.
  • Continuous queue: Multiple instances or servers consume messages from the queue in a multi-threaded mode and the processing order is not guaranteed. If one server fails, a second server picks up the message.
Producer
An external system puts the messages in the queue. If an error occurs when the message is placed in the queue, the sender must handle the error and resend the message.


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