Unique ID Generation (Snowflake)
Introduction
Generating unique, sortable IDs at scale is a common requirement for distributed systems. Twitter's Snowflake is a well-known solution that enables decentralized, high-throughput ID generation.
Problem Statement
How can we generate unique, time-ordered IDs across multiple servers without central coordination, while ensuring high availability and performance?
System Requirements
- IDs must be unique and sortable by time.
- The system should support high throughput and low latency.
- No single point of failure.
- Should work across multiple data centers.
High-Level Design
Snowflake IDs are 64-bit integers composed of:
- Timestamp (41 bits)
- Data center ID (5 bits)
- Machine ID (5 bits)
- Sequence number (12 bits)
Each node generates IDs independently using its own machine and data center IDs, incrementing the sequence for each request within the same millisecond.
Key Components
- ID Generator Service: Runs on each node, responsible for generating IDs.
- Clock Synchronization: Ensures system clocks are accurate to avoid duplicate IDs.
- Configuration Management: Assigns unique machine/data center IDs.
Challenges
- Clock drift: If the system clock moves backward, it can cause duplicate IDs.
- Sequence overflow: If more than 4096 IDs are requested in a millisecond, the generator must wait for the next millisecond.
- Deployment: Ensuring unique machine/data center IDs across the fleet.
Conclusion
Snowflake-style ID generation is a robust solution for distributed, high-scale systems. Careful attention to clock management and configuration is essential for reliability.