Implement RotatingFileSink in hierarchy
Overview
This question evaluates a candidate's proficiency in Python object-oriented design, file I/O and JSON serialization, concurrency control via locking, context manager protocols, custom exception handling, and adherence to Liskov substitution when implementing a rotating file sink.
Bloomberg
Sep 6, 2025, 12:00 AM
Data Engineer
Technical Screen
Other / Miscellaneous
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You are given an existing Python 3.10 codebase with an abstract base class RecordSink (from abc import ABC, abstractmethod) that defines open() -> None, write(record: dict) -> None, and close() -> None. A Pipeline class instantiates a sink, calls sink.open() once, then for each record calls sink.write(record), and finally calls sink.close(); Pipeline must not be modified. Implement a new concrete RotatingFileSink that: (
- writes each record as a compact JSON line (UTF-
- to disk, (
- rotates to a new file when either a maximum number of lines N is reached or total bytes exceed limit L, using filenames like prefix_00001.log, prefix_00002.log, etc., (
- supports use as a context manager via enter / exit while preserving existing open/close semantics, (
- is safe for concurrent write() calls from multiple threads using a lock, (
- raises a custom SinkClosedError if write() is invoked after close(), and (
- adheres to Liskov substitution so Pipeline works unchanged. Do not alter existing method signatures or the Pipeline. Provide the full class implementation and a brief unit test showing rotation and thread-safety.