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Design a multi-threaded synchronous log writer
Problem: Design a Multi-threaded Synchronous Log Writer
Design a log writer component that can be invoked by multiple application threads concurrently and writes log messages to a single file on disk.
Requirements:
- Concurrent Calls: The
log(message)method must support concurrent invocations from many different application threads. - Synchronous/Durable Writes: Once the
log()method returns, the message must be guaranteed to be durably persisted to disk, surviving a process crash. This implies the necessity of usingfsyncor equivalent flush operations. - Well-defined Ordering: The log messages must maintain a specific order. The candidate should state their chosen ordering strategy (e.g., FIFO based on call time across all threads, or FIFO per-thread with arbitrary interleaving between threads).
- High Throughput: The design should prioritize high throughput, specifically by avoiding an
fsyncoperation for every single log message if possible.
Tasks:
- Propose a detailed implementation approach, including the choice of data structures and the threading model.
- Clearly explain how your design ensures durability, preserves the chosen ordering, and achieves high performance.
- Discuss potential failure modes (such as the disk becoming full, partial writes, or a process crash during a write operation) and outline strategies for handling them robustly.
AI interview prep
Core dilemma
Balancing the strict requirement for synchronous, durable writes with the need for high throughput under concurrent access, all while maintaining a defined log ordering to a single file.
Mid-level signals3
Senior signals3
Red flags3
3 tradeoffs and 3 stress tests locked
Interview prep
Unlock the interviewer X-Ray rubric, tradeoff matrix, stress tests, clarifying questions, and key concepts.
Design a multi-threaded synchronous log writer
Problem: Design a Multi-threaded Synchronous Log Writer
Design a log writer component that can be invoked by multiple application threads concurrently and writes log messages to a single file on disk.
Requirements:
- Concurrent Calls: The
log(message)method must support concurrent invocations from many different application threads. - Synchronous/Durable Writes: Once the
log()method returns, the message must be guaranteed to be durably persisted to disk, surviving a process crash. This implies the necessity of usingfsyncor equivalent flush operations. - Well-defined Ordering: The log messages must maintain a specific order. The candidate should state their chosen ordering strategy (e.g., FIFO based on call time across all threads, or FIFO per-thread with arbitrary interleaving between threads).
- High Throughput: The design should prioritize high throughput, specifically by avoiding an
fsyncoperation for every single log message if possible.
Tasks:
- Propose a detailed implementation approach, including the choice of data structures and the threading model.
- Clearly explain how your design ensures durability, preserves the chosen ordering, and achieves high performance.
- Discuss potential failure modes (such as the disk becoming full, partial writes, or a process crash during a write operation) and outline strategies for handling them robustly.