it will be round-robin : https://opendxl.github.io/open…oc/dxlclient.service.html
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DXL Services are exposed to the DXL fabric and are invoked in a fashion similar to RESTful web services. Communication between an invoking client and the DXL service is one-to-one (request/response).
Each service is identified by the “topics” it responds to. Each of these “topics” can be thought of as a method that is being “invoked” on the service by the remote client.
Multiple service “instances” can be registered with the DXL fabric that respond to the same “topics”. When this occurs (unless explicitly overridden by the client) the fabric will select the particular instance to route the request to (by default round-robin). Multiple service instances can be used to increase scalability and fault-tolerance
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