Beams accept messages and forward them along.
Makes beams for particular intervals and partition numbers.
Beam composed of a stack of smaller beams.
Metadata stored in ZooKeeper for a ClusteredBeam.
Emits messages over http.
Partitions messages based on the output of a Partitioner, and propagates the partitioned messages via the appropriate underlying beams.
Farms out events to various beams, round-robin.
Wraps a Beam and exposes a single-message API rather than the future-batch-based API.