quantlab.utils.atomic

Atomic JSON and parquet file writes.

Every JSON sidecar quantlab persists (resume ledgers, acquisition watermarks, failure manifests) goes through write_json_atomically, and every parquet file written whole (raw vendor pulls, the Ticker map’s days) through write_parquet_atomically. The payload is written to a temporary file in the destination’s own directory and then renamed over the destination, so an interrupted write leaves either the previous complete file or the new one, never a truncated file that a resumed run would fail to parse.

No lock is taken: two concurrent writers still race, but the loser sees a complete file rather than a fragment. This module imports only the standard library so any layer can use it without creating an import cycle.

Functions

write_json_atomically	Serialise payload as JSON to path with an atomic replace.
write_parquet_atomically	Write frame as parquet to path with an atomic replace.