we are studying to change our architecture from single IS to clustered IS to ensure high availability, scalability, etc…
But such arhitecture evolution can have an impact on our existing developments.
We are questionning about the behaviour of monothreaded triggers hosted in 2 clustered-IS :
is there one thread for both clustered-IS, so only one thread for the whole platform at one time
or is there one thread for each IS of the cluster, which would mean that the ordering of document processing would not be guaranteed (2 threads at one time).
Take a look at pages 125-127 in the Publish-Subscribe Developer’s Guide (for v6.1). It talks about things “in a clustered environment” but the behavior described happens whenever two or more IS instances use the same prefix (a “broker client cluster” if you will). If the triggers are serial, and the documents published to the Broker are from the same publisher, document order will be preserved.
Thank you for your quick answer Rob. I had looked the Publish-Subscribe Developer’s Guide but I still have one question : how publishers are defined ?
Let’s say I’ve got a cluster of 2 webMethods IS (call them IS_FRONT_1 and IS_FRONT_2) used as front-end to receive Web-Services orders, and another cluster of 2 webMethods IS (call them IS_BACK_1 and IS_BACK_2) used to connect to different Back-Ends (CRM, Billing). They are all connected to the same Broker Server.
The events I receive need to be ordered from the begining to the end of the provisioning process, so my triggers are monothreaded. Does IS_FRONT_1 is considered as a different publisher as IS_FRONT_2 ? If it is the case, there is a risk that a document B received on IS_FRONT_2 after document A in IS_FRONT_1 is porcessed in IS_BACK_X before document A. If these events are on the same account, it is a strong problem for me.
So my question is :
is a webMethods cluster of 2 IS considered as a single publisher or each IS is considered as a standalone publisher ?
If IS_FRONT_1 and IS_FRONT_2 use the same Broker client prefix, they use the same publishing queue and therefore appear to the Broker to be a single publisher.