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CruftFlake

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A stab at a version of Twitter Snowflake but in PHP with a simple ZeroMQ interface (rather than Thrift).

Implementation

This project was motivated by personal curiosity and also my inability to get Twitter's project to build.

The implementation copies Twitter - generating 64 bit IDs.

  • time - 41 bits
  • configured machine ID - 10 bits
  • sequence number - 12 bits

Has a custom epoch that means it can generate IDs until 2081-09-06 (not the same epoch as Snowflake).

ZooKeeper for config coordination (optional)

Each machine must have a unique 10 bit machine ID. ZooKeeper can be used to keep a list of all registered machine IDs, allowing new machines to self-assign a new unique machine ID.

When using ZooKeeper, when a new node starts up for the first time it must be able to contact the ZooKeeper cluster and create a new node. It will look at all the existing nodes and then (if it can't find its own Mac Address) attempt to claim a free one.

I was using Ephemeral nodes for this - similar(ish) to a lock pattern but this had the issue that the node needed to remain connected to ZK throughout its lifetime -- this way it doesn't.

The downside is that potentially the 1024 possible machine IDs will "fill up" and need to be manually pruned.

Running

Git clone and then execute composer update to install the dependencies. You should run the tests to verify things are OK:

vendor/bin/phpunit

There are two scripts provided for playing about with.

  1. The generator (the server)

    ./examples/cruftflake.php

Or to specify a manually configured machine ID:

./examples/cruftflake.php -m 1

  1. A client that will generate N IDs and dump to STDOUT

    ./examples/client.php -n 100