eventsfrom

In computing, eventsfrom is a term used in event-driven and streaming contexts to denote an operation that produces a new event stream starting at a specified origin from a given source. It describes a way to derive a focused view of events by selecting a starting point within an existing stream.

Typically, you provide a source stream and a starting point such as a timestamp, an offset, or a checkpoint. The resulting stream yields events from that point onward. The starting point can be inclusive or exclusive, and some implementations include a replay buffer to re-emit events that occurred since the checkpoint. The approach often aims to preserve event order and may involve buffering or cursors to manage late arrivals and backpressure.

Common use cases include replaying events after a failure, resuming processing after a pause, and building read models or projections from an event store. By starting from a known point, systems can reconstruct state or continue processing without reprocessing the entire history.

In practice, many libraries offer similar functionality under different names. Some frameworks provide operators like from, startFrom, or startAt that implement an equivalent concept by slicing or buffering an existing stream. The exact semantics—such as inclusivity, handling of late events, and guarantees of delivery—vary by implementation.

Key considerations include preserving event order, handling late or missing data, and choosing between at-least-once and exactly-once delivery guarantees. Performance and memory usage may depend on buffering strategies and the size of the initial window. Related concepts include event streams, event sourcing, offsets, checkpoints, and log tailing.