Hi all, I am working on implementing active-passive clustering on top of the new MB4 architecture. Current message delivery implementation in MB4 is not capable to work in a multi-node environment. If we run more than one node concurrently, messages can be duplicated since all nodes start delivering messages available for a queue in the message store. We have to make the MB4 nodes cluster aware to rectify this behavior. High-level design
We are planning to use the available RDBMS leader election mechanism to decide on the active node. All the non-leader nodes will be passive nodes and will reject all incoming requests. The clients should be configured with failover URLs so that they can failover to the active node from passive nodes. Tasks to do when the active node becomes passive 1. Enable rejecting all requests to broker node except the CLOSE-OK 2. Close existing AMQ connections (both publishing and consuming) Tasks to do when the passive node becomes active 1. Start accepting all requests to broker node The assumption here is the active components like the Inbound disruptor, outbound disruptor, delivery task managers will stop working (consuming resources) when the incoming requests are stopped and subscriptions are removed in passive nodes. - Filtering message events will be handled by “InboundEventGatekeeper”. - DeliveryHandler will also be modified to stop delivering messages when a node becomes passive. - All the connections will be closed using the server connection registry Suggestions and feedback are appreciated. -- Asanka Abeyweera Senior Software Engineer WSO2 Inc. Phone: +94 712228648 Blog: a5anka.github.io <https://wso2.com/signature>
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