[Users] Services updating on slave nodes

[Vincent Zurczak [via Petals Forums]]

Hi,

I have just seen your posts.
I can try to give some indications. However, I am not very familliar with
Petals DSB ( http://chamerling.org/2011/10/13/petals-dsb-is-not-petals-esb/
which is not the same than Petals ESB ).

However, they have a common ancestor, so, my answer may be valid.
In fact, the nodes can see each other because they are in the same topology.
However, each node manages its own registry of services. They know their own
services but also those from the other nodes. To be aware of the services
located on other nodes, there is a synchronization process. 

This synchronization relies on the master node, which acts as a referent. A
slave node synchronizes its registry with the master node. And same thing
for all the slave nodes. It means it takes time for a service to be visible
on all the nodes of a topology. 

The delay between every synchronization is defined in the
*server.properties* file of every slave node. In Petals ESB 3.1.3, it is
possible to force a synchronization with JMX. But I don't think this feature
was back-ported in Petals DSB. So, you may have to wait so that all the
nodes are synchronized. And about the fact that sometimes, it worked when
you restarted a node, it was because when it starts, a slave node tried to
contact the master. It completely depends on the start order.

Share a registry in a distributed environement is not that simple and not
adapted to real-time use cases. In fact, it is the same problematic than a
distributed database.

I will forward this to the main developer of Petals DSB, so that he can
confirm (or not) what I said. 

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