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How to Enable a Singleton Adapter in an ESB Cluster Environment (Doc ID 746108.1)

Last updated on OCTOBER 24, 2019

Applies to:

Oracle Enterprise Service Bus - Version to
Information in this document applies to any platform.
***Checked for relevance on 15-Mar-2012***


The purpose of this document is to explain how to configure an inbound technology adapter to operate as a singleton adapter in an ESB process.

Note to provide an explanation of what a singleton adapter is and how it functions:

In an ESB High Availability cluster the adapters are deployed (by registration of the various ESB services) into all nodes of the cluster and by default are active in all of the nodes when the nodes are up and running.

For Read and FTP inbound adapters you will only want to have one of these adapters active and polling at any time.  Otherwise multiple active Read or FTP adapters may cause a "race condition" with each other where multiple adapters will try to act on the same file, when in actuality you want each file to be acted on only one time.

This can be accomplished by configuring the inbound adapter in the ESB service to be a singleton adapter.  This means that only one instance of the adapter is active at any one time.  So for example if there are three nodes in an ESB cluster the singleton adapter will only be active on one of the three nodes, guaranteeing that there will be no "race condition" or contention between other adapters in the cluster.

If the node with the active adapter is stopped or fails for some reason the adapter will then become active on one, and only one, of the other active nodes in the cluster.  The management of which of the adapters are active or not active is handled by the JGroups configuration.  The failover of adapters is also managed by using JGroups communication.

Though configuring an adapter for singleton behavior is typically only done for the inbound Read and FTP adapters (to prevent multiple handling of the same file), it can also be configured for any of the inbound technology adapters, e.g. JMS, AQ, AQ-JMS, DB, MQ. 


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In this Document
 1.  Configuration of JGroups on the Servers
 2.  Configuring the Adapter Cluster During Design Time
 3.  Formation of an Adapter Cluster by JGroups
 4.  Adapter Activation in Only One Node in an ESB Runtime (ESBRT)

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