strattonbrazil / markiert

A unique-ID generator using Twitter's Snowflake specification

markiert

A unique ID generator using Twitter's Snowflake specification.

Use this generator when IDs must:

• be generated on fault-tolerant system
• fit into a 64-bit number
• be sortable

Schema of 64-bit ID

• 1 bit reserved
• 41 bits timestamp (in milliseconds from reference)
• 5 bits datacenter id
• 5 bits machine id
• 12 bits sequence number

Configuration

Most app management systems such as Kubernetes provide ways to set environment variables dynamically.

The generator uses four environment variables:

• MARKIERT_HTTP_PORT - the HTTP port to retrieve the IDs (defaults to 8080)
• MARKIERT_DATACENTER_ID - the integer ID of the datacenter (defaults to 1)
• MARKIERT_MACHINE_ID - the integer ID of the machine (defaults to 1)
• MARKIERT_EPOCH_OFFSET - the UNIX epoch value the timestamp will reference (defaults to 1288834974657, the original Snowflake epoch)
  • for example, an ID generated 3 milliseconds after the MARKIERT_EPOCH_OFFSET will have a timestamp of 3

I recommend choosing a MARKIERT_EPOCH_OFFSET relative to the current time and use that across deployments for the life of the ID space.

Here's an example one-liner to print the current epoch time:

python -c "import time; print(int(time.time()*1000))"

API Usage

Markiert provides a single REST endpoint for fetching an ID.

http://<IP_ADDRESS:PORT>/id

This endpoint provides a JSON-formatted response, which includes the 64-bit number in a string. For example:

{"id":"6816559434522038272"}

Building

mvn compile package

Unit Testing

mvn test

Integration Testing

There's a simple integration test for verifying unique and sequencial ids.

Start the packaged jar file:

java --jar target/markiert-1.0-SNAPSHOT-fat.jar

And then launch the script in a separate terminal:

nodejs ./request_test.js