This documentation is for WSO2 Message Broker 3.0.0. View documentation for the latest release.
Due to a known issue do not use JDK1.8.0_151 with WSO2 products. Use JDK 1.8.0_144 until JDK 1.8.0_162-ea is released.

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The slot manager communicates with both publishers and subscribers and acts as the coordinator for distributing slots among the nodes. A slot assignment map is maintained to track the slots that are assigned to nodes at a given time. The activities of a slot manager can be illustrated as follows.

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Communicating with publishers
Each publisher belongs to a queue/topic and its messages are published in the row of the message store mapped to this queue. A publisher returns its last message ID to the slot manager node in the MB cluster after every 1000 messages or after a timeout. The slot manager updates the Hazelcast Distributed Map with these IDs and uses them to generate slots when it receives requests for slots from slot delivery worker nodes.