Fuse Message Broker uses message cursors to improve the scalability of the persistent message store. By default, a hybrid approach that uses an in memory dispatch queue for fast consumers and message cursors for slower consumers is used. Fuse Message Broker also supports two alternative cursor implementations. The type of cursor can be configured on a per-destination basis.
Message data is cached in the broker using message cursors, where a cursor instance is associated with each destination. A message cursor represents a batch of messages cached in memory. When necessary, a message cursor will retrieve persisted messages through the persistence adapter. But the key point you need to understand about message cursors is that the cursors are essentially independent of the persistence layer.
Message cursors provide a means for optimizing a persistent message store. They allow the persistent store to maintain a pointer to the next batch of messages to pull from the persistent message store. Fuse Message Broker has three types of cursors that can be used depending on the needs of your application:
Store-based cursors are used by default to handle persistent messages.
VM cursors are very fast, but cannot handle slow message consumers.
File-based cursors are used by default to handle non-persistent messages. They are useful when the message store is slow and message consumers are relatively fast.
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