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If I plan to install multiple instances of Orion context broker in a high availability scenario like described here, I am wondering how event notifications are handled?

So If I Register/subscribe to an specific Event, which occours then, will I be notified/called one time, or one time for each CB-instance?

Jürgen Zornig
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  • Does this answer your question? [What would be the behavior of subscriptions and notifications in an Orion Load-Balancing scenario?](https://stackoverflow.com/questions/43857300/what-would-be-the-behavior-of-subscriptions-and-notifications-in-an-orion-load-b) – Jürgen Zornig Jan 27 '20 at 12:15

2 Answers2

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In multi node deployment of Orion ContextBroker as described in referred document, there will be one notification to each event from the broker which will receive the request. The HAProxy will route each incoming request to one of multiple ContextBroker, thus one notification will be generated based on subscription made.

So If you Register/subscribe to an specific Event, then, you will be notified/called one time from one ContextBroker which has received the reuqest.

thebluemagician
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  • Thanks for the clarification! Is there any reference how Context Broker handles Notifications (that they are triggered by the one instance that received the request)? I just want to get sure and understand, that the MongoDB Store is definitely NOT involved in this process and its de facto stateless then. – Jürgen Zornig Jan 23 '20 at 10:05
  • @JürgenZornig, I am unable to find the related reference document. The above deductions about the subscriptions/notification is based on running the multi-node Orion ContextBroker and other Fiware GEs in production environment. The MongoDb is responsible for persisting entities and subscriptions, Subscription/notification is all managed by broker itself. – thebluemagician Jan 24 '20 at 04:57
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    All state is managed at MongoDB. Orion process is fully stateless (thus enabling those HA/scaling-out scenarios easily). – fgalan Jan 27 '20 at 12:05
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Some more references about Orion and HA/scaling-out, in the case they can be usefull:

fgalan
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  • thanks for the references, this is what I was looking for. I flagged my question as duplicate, as you answered this already perfectly – Jürgen Zornig Jan 27 '20 at 12:13
  • Great to know! If you find some of the referred questions/answers useful, please provide a +1 on then. That way the would be become more SEO-relevant and other users may reach them more easily :) – fgalan Jan 27 '20 at 12:27