Design a multithreaded event logger

Problem Statement

Design a thread-safe EventLogger class that allows multiple threads to log messages simultaneously. The logger must ensure that logs are written to an underlying Sink (an interface with a write(message: String) method) in a way that minimizes contention while maintaining chronological ordering based on the time the logging call was made.

Requirements

1. Thread Safety: Multiple threads must be able to call log(message) concurrently without data corruption.
2. Ordering: Messages should ideally appear in the Sink in the order they were submitted.
3. Performance: Minimize the time a thread spends blocked waiting for I/O. Consider using an asynchronous or buffered approach.
4. Durability: Ensure that even if the application shuts down, pending logs in the buffer are flushed to the Sink.

Interface

class EventLogger:
    def __init__(self, sink: Sink, buffer_size: int):
        pass

    def log(self, message: str):
        """Adds a message to the logger."""
        pass

    def shutdown(self):
        """Flushes remaining logs and stops the logger."""
        pass

Constraints

• sink.write is a blocking I/O operation.
• The system must handle high throughput without overwhelming memory if sink.write becomes slow.

Examples

• Input: Thread A calls log("A"), Thread B calls log("B") shortly after.
• Output: Sink receives "A" then "B".

Edge Cases

• The logger buffer is full: should it block the caller or drop logs?
• Sudden application termination before shutdown is called.