# SULID: Snowflake-inspired Universally Unique Lexicographically Sortable Identifier
SULID is a unique ID generation algorithm that combines the benefits of ULID and Snowflake. It offers a highly efficient, reliable, and lexicographically sortable identifier, which ensures uniqueness across multiple data centers and machines, making it ideal for high-concurrency distributed environments.
[](https://crates.io/crates/sulid)
[](https://docs.rs/sulid)
[](https://github.com/andeya/sulid?tab=MIT-1-ov-file)
## Features
- **High Concurrency Support**: Efficiently generates unique IDs in high-concurrency environments.
- **Time Ordered**: Retains the time-ordered characteristic of ULID.
- **Distributed Uniqueness**: Ensures unique IDs across distributed environments by incorporating data center and machine IDs.
- **Readability**: Produces shorter, human-readable identifiers.
## Overview
SULID is based on the ULID (Universally Unique Lexicographically Sortable Identifier) format but incorporates additional bits for a data center ID and machine ID, similar to Snowflake. This design ensures uniqueness in distributed environments and maintains time-ordering characteristics, making it suitable for applications requiring both high concurrency and global uniqueness, such as microservice architectures, log tracking, and order generation.
## ID Format
SULIDs have a unique structure comprising the following parts, adding up to a 128-bit identifier:
1. **Timestamp**: 48 bits, representing the epoch time in milliseconds.
2. **Random Number**: 70 bits of randomness to ensure uniqueness within the same millisecond.
3. **Data Center ID**: 5 bits, identifying the data center.
4. **Machine ID**: 5 bits, identifying the machine within the data center.
Here is a visual breakdown of the SULID format:
```
## Installation
To use SULID, add the following dependencies to your `Cargo.toml` file:
```toml
[dependencies]
sulid = "0.5"
```
## Usage
Here's how you can use the `SulidGenerator` in your project:
```rust
use sulid::SulidGenerator;
fn main() {
let generator = SulidGenerator::new(1, 1);
for _ in 0..5 {
let id = generator.generate();
println!("SULID: {}", id);
}
}
```
## Example Output
Running the example code generates SULIDs such as:
```
SULID: 01J75J83RH36YXGGGWCS8JBP11
SULID: 01J75J83RHEXCA2NH96PDDJQ11
SULID: 01J75J83RHAFMZ86CBFRHTKN11
SULID: 01J75J83RHRYCTWD1QKRCJGQ11
SULID: 01J75J83RHMRDSRAW5KSN99V11
```
## Benefits
- High Concurrency Support: The algorithm is designed to generate IDs efficiently in environments with high concurrency, making it suitable for distributed systems.
- Time Ordered: SULID retains the time-ordering characteristic of ULID. This feature is beneficial for logging systems and event sourcing where chronological order is essential.
- Distributed Uniqueness: By incorporating data center and machine IDs similar to Snowflake's approach, SULID ensures IDs are unique across different machines and data centers.
- Readability: Compared to traditional UUIDs, SULID produces shorter and more human-readable identifiers, making them easier to work with in certain scenarios.
- Traceability: The time-ordered nature of SULID makes it easier to trace and debug events in distributed systems.
## How It Works
SULID leverages both ULID and Snowflake's strengths:
- `ULID`: Provides lexicographically sortable identifiers based on a timestamp and randomness.
- `Snowflake`: Adds data center and machine IDs to ensure distributed uniqueness.
By combining these two approaches, SULID generates IDs that are globally unique, time-ordered, and suitable for high-concurrency distributed environments.
## License
This project is licensed under the MIT License.