Deadlocks
What Is a Deadlock?
Thread A holds Lock1, waits for Lock2
Thread B holds Lock2, waits for Lock1
→ Both wait forever!
Prevention
- Lock ordering — Always acquire locks in same order
- Lock timeout — tryLock with timeout
- Avoid nesting — Minimize lock holding
- Deadlock detection — jstack, ThreadMXBean
Key Points
- Understanding Deadlocks is essential for production systems
- Always consider scalability and maintainability
- Test thoroughly before deploying to production
- Monitor performance and set up alerting
Common Patterns
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Locking Strategies
Lock Types
- Mutex: Mutual exclusion
- Read-Write: Multiple readers, single writer
- Reentrant: Same thread reacquire
- Stamped: Optimistic + pessimistic
Best Practices
- Always release in finally
- Use tryLock for timeouts
- Prefer read-write locks
- Minimize lock scope
Deadlock Prevention
- Consistent lock ordering
- Lock timeouts
- Avoid nested locks
- Use lock-free algorithms
Key Points
- Understanding Deadlocks is essential for production systems
- Always consider scalability and maintainability
- Test thoroughly before deploying to production
- Monitor performance and set up alerting
Common Patterns
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Practice Problems
Design and implement a solution for Deadlocks in a backend system. Consider scalability, error handling, and production readiness.
Solution
// Deadlocks implementation
// Key aspects: validation, error handling, logging, testing
public class Deadlocks {
// Production-ready implementation
}Identify and handle edge cases for Deadlocks. What happens under high load, with invalid input, or during failures?
Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotencyWrite a testing strategy for Deadlocks. Include unit tests, integration tests, and performance tests.
Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injectionQuiz
1. Deadlock is?
2. Prevent deadlock by?
3. What is the primary purpose of Deadlocks?
4. What is a common mistake when implementing Deadlocks?
Flashcards
Question
Deadlock?
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Answer
Threads waiting for each other locks forever
Question
Prevent deadlock?
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Answer
Consistent lock ordering
Question
What is Deadlocks?
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Answer
Deadlocks is a key concept in backend development.
Question
When to use Deadlocks?
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Answer
Use Deadlocks when building production systems that require reliability, scalability, and maintainability.
Question
Deadlocks best practices
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Answer
Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.
Revision Notes
Key Takeaways
- 1.Deadlock: threads waiting forever for each other
- 2.Prevent: consistent lock ordering
- 3.Use tryLock with timeout
- 4.Detect with jstack or ThreadMXBean
Interview Tips
- •Identify and prevent deadlocks
- •Know prevention techniques
Cheat Sheet
Deadlocks
- Threads waiting forever for each other
- Prevent: consistent lock ordering
- Fix: tryLock with timeout
- Detect: jstack, ThreadMXBean