How big are batches in BatchMap?

[th0ger]

The Batch Map Mode states:

BatchMap is an interface that allows developers to process multiple data items in a UDF single call, rather than each item in separate calls.

But it doesn't say anything about how big batches are, or whether the size is in controlled by numaflow or the developer.

[whynowy]

The batch size is same as the readBatchSize.

[th0ger]

Just did at test with readBatchSize: 10.
But the length of BatchResponses() inside my BatchMapper gives size 1, sometimes 2.

readBatchSize seems to be an upper bound, in case the source does not yield enough events for a full batch.

[whynowy]

This is right, because readBatchSize itself is an upper bound.

[th0ger]

#2418