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Implement RotatingFileSink in hierarchy

BloombergData Engineer · Technical Screen
MediumData EngineerTechnical ScreenSoftware Engineering Fundamentals

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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.

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: (

  1. writes each record as a compact JSON line (UTF-
  2. to disk, (
  3. 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., (
  4. supports use as a context manager via enter/exit while preserving existing open/close semantics, (
  5. is safe for concurrent write() calls from multiple threads using a lock, (
  6. raises a custom SinkClosedError if write() is invoked after close(), and (
  7. 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.