by Example

A push consumer provides alternate control to a pull consumer. Rather than fetching messages in controlled (and appropriately sized) batches to be processed, with a push consumer, the server will proactively push as many messages to the active subscription up to the consumer’s max ack pending limit.

In the happy path, the subscription receiving these messages can keep up and acknowledge the message prior to the ack wait time has elapsed.

Where push consumers can get unwieldy and confusing is when the subscriber cannot keep up, message processing errors start occurring, or the active subscription gets interrupted. Messages start getting redelivered and being interleaving with new messages pushed from the stream.

In practice, ephemeral push consumers can be a lightweight and useful way to do one-off consumption of a subset of messages in a stream. However, if you have a durable use case, it is recommended to access pull consumers first which provides more control and implicit support for scaling out consumption.