This manual is for an old version of Hazelcast Jet, use the latest stable version.

Three callback methods are involved in data processing: process(), completeEdge(), and complete().

Processors can be stateful and do not need to be thread-safe. A single instance will be called by a single thread at a time, although not necessarily always the same thread.


Jet passes the items received over a given edge by calling process(ordinal, inbox). All items received since the last process() call are in the inbox, but also all the items the processor has not removed in a previous process() call. There is a separate instance of Inbox for each inbound edge, so any given process() call involves items from only one edge.

The processor should not remove an item from the inbox until it has fully processed it. This is important with respect to the cooperative behavior: the processor may not be allowed to emit all items corresponding to a given input item and may need to return from the process() call early, saving its state. In such a case the item should stay in the inbox so Jet knows the processor has more work to do even if no new items are received.


Eventually each edge will signal that its data stream is exhausted. When this happens, Jet calls the processor's completeEdge() with the ordinal of the completed edge.

The processor may want to emit any number of items upon this event, and it may be prevented from emitting all due to a full outbox. In this case it may return false and will be called again later.


Jet calls complete() after all the edges are exhausted and all the completeEdge() methods are called. It is the last method to be invoked on the processor before disposing of it. The semantics of the boolean return value are the same as in completeEdge().