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

In some special cases, unbounded data buffering must be allowed on an edge. Consider the following scenario:

A vertex sends output to two edges, creating a fork in the DAG. The branches later rejoin at a downstream vertex which assigns different priorities to its two inbound edges. Since the data for both edges is generated simultaneously, and since the lower-priority edge will apply backpressure while waiting for the higher-priority edge to be consumed in full, the upstream vertex will not be allowed to emit its data and a deadlock will occur. The deadlock is resolved by activating the unbounded buffering on the lower-priority edge.