MemoryStore¶

MemoryStore()

A store kept in this process's memory, by the rules every store keeps (streaming.md, The rules a store keeps): each claim and each append is one step per log, and an event that does not pass the event schema is refused event-malformed. A journal for tests, notebooks and one process; logs are lost when it ends.

append(event) and extend(events) (a batch, kept whole or not at all) answer "kept" or "duplicate", or raise EventRefused; claim(tree) gives a later writer its number and the last kept event's position; read(tree, after) gives the kept events after a position.

A journal's writer sends what waits as one batch, every event through extend (a lone one as a batch of one), except to a subclass that overrides append and not extend (a transport, failures for a test): that one is sent every event alone, through its append. batches = False also sends every event alone.

Methods¶

claim¶

MemoryStore.claim(tree)

A later writer claims an unfinished log: it gets a writer number, one more than any given for this log, and the position of the last kept event, after which it numbers. Every earlier writer is fenced.

extend¶

MemoryStore.extend(events)

A batch of one log's events, checked each as if appended alone, in order, kept whole or not at all: "duplicate" when every event is one, "kept" when every event is kept or a duplicate; else nothing is kept, and the refusal names the first event refused (err.event).

read¶

MemoryStore.read(tree, after=None)

The kept events of a log after a position (all of them after None). Never fenced: a fenced writer learns what was kept by reading.

writer_of¶

MemoryStore.writer_of(tree)

The last writer number this store gave for a log (1 before any claim).