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‎LICENSE

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The MIT License (MIT)
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Copyright © 2019 Ennexa Technologies Private Limited, https://www.ennexa.com <[email protected]>
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Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

‎README.md

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### Snowflake ID Generator
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An implementation of [Snowflake](https://blog.twitter.com/engineering/en_us/a/2010/announcing-snowflake.html) ID generator that works without a dedicated daemon.
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The generator can be used with `PHP-FPM` or `mod_php`.
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### Installation
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composer require ennexa/snowflake
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### Usage
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// First we need to create a store for saving the state
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$store = new Snowflake\Store\RedisStore(new \Redis);
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// $store = new Snowflake\Store\FileStore('/path/to/store/state');
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// Create a generator with the created store
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$generator = new Snowflake\Generator($store, $instanceId = 0);
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// Use Generator::nextId to generate the next unique id
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echo $generator->nextId();
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### Credits
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This generator was originally created for use on [Prokerala.com](https://www.prokerala.com).

‎composer.json

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{
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"name": "ennexa/snowflake",
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"description": "Snowflake ID Generator that does not require a daemon",
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"type": "library",
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"require": {
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"php": ">=5.6.0"
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},
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"license": "MIT",
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"authors": [
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{
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"name": "Prokerala",
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"email": "[email protected]",
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"homepage": "https://www.prokerala.com"
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}
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],
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"minimum-stability": "stable",
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"autoload": {
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"psr-4": {
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"Ennexa\\Snowflake\\": "src/Snowflake"
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}
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}
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}

‎src/Snowflake/.DS_Store

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‎src/Snowflake/Exception/InvalidArgumentException.php

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<?php
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namespace Ennexa\Snowflake\Exception;
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class InvalidArgumentException
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extends \InvalidArgumentException
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implements \Ennexa\Snowflake\ExceptionInterface {
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}

‎src/Snowflake/Exception/InvalidSystemClockException.php

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<?php
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namespace Ennexa\Snowflake\Exception;
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class InvalidSystemClockException
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extends \Exception
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implements \Ennexa\Snowflake\ExceptionInterface {
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}

‎src/Snowflake/Exception/RuntimeException.php

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<?php
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namespace Ennexa\Snowflake\Exception;
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class RuntimeException
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extends \RuntimeException
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implements \Ennexa\Snowflake\ExceptionInterface {
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}

‎src/Snowflake/ExceptionInterface.php

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<?php
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namespace Ennexa\Snowflake;
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interface ExceptionInterface {
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}

‎src/Snowflake/Generator.php

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<?php
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namespace Ennexa\Snowflake;
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use Exception\InvalidArgumentException;
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use Exception\InvalidSystemClockException;
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class Generator {
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const NODE_LEN = 8;
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const WORKER_LEN = 8;
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const SEQUENCE_LEN = 8;
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private $instanceId = 0;
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private $startEpoch = 1546300800000;
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private $sequenceMax;
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private $store;
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private static function getMaxValue(int $len)
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{
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return -1 ^ (-1 << $len);
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}
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public static function generateInstanceId($nodeId = 0, $workerId = 0)
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{
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$nodeIdMax = $this->getMaxValue(self::NODE_LEN);
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if ($nodeId < 0 || $nodeId > $nodeIdMax) {
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throw InvalidArgumentException("Node ID should be between 0 and $nodeIdMax");
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}
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$workerIdMax = $this->getMaxValue(self::WORKER_LEN);
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if ($workerId < 0 || $workerId > $workerIdMax) {
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throw InvalidArgumentException("Worker ID should be between 0 and $workerIdMax");
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}
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return $nodeId << self::WORKER_LEN | $workerId;
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}
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public function __construct(StoreInterface $store, int $instanceId = 0, ?int $startEpoch = null)
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{
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$this->setInstanceId($instanceId);
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$this->setStore($store);
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if (!is_null($startEpoch)) {
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$this->startEpoch = $startEpoch;
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}
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$this->sequenceMask = -1 ^ (-1 << self::SEQUENCE_LEN);
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$this->sequenceMax = -1 & $this->sequenceMask;
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$this->tickShift = self::NODE_LEN + self::WORKER_LEN + self::SEQUENCE_LEN;
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}
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/**
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* Set the sequence store
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*
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* @param int Instance Id
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* @return void
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*/
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public function setStore(StoreInterface $store)
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{
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$this->store = $store;
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}
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/**
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* Get the current generator instance id
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*
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* @param int Instance Id
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* @return void
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*/
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public function getInstanceId()
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{
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return $this->instanceId >> self::SEQUENCE_LEN;
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}
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/**
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* Set the instance id for the generator instance
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*
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* @param int Instance Id
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* @return void
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*/
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public function setInstanceId(int $instanceId)
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{
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$this->instanceId = $instanceId << self::SEQUENCE_LEN;
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}
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/**
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* Get the next sequence
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*
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* @return array timestamp and sequence number
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*/
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public function nextSequence()
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{
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return $this->store->next($this->instanceId);
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}
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/**
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* Generate a unique id based on the epoch and instance id
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*
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* @return int unique 64-bit id
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* @throws InvalidSystemClockException
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*/
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public function nextId()
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{
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list($timestamp, $sequence) = $this->nextSequence();
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if ($sequence < 0) {
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$ticks = $timestamp - $this->startEpoch;
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throw new InvalidSystemClockException("Clock moved backwards or wrapped around. Refusing to generate id for $ticks ticks");
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}
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$ticks = ($timestamp - $this->startEpoch) << $this->tickShift;
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return (string)($ticks | $this->instanceId | $sequence);
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}
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}

‎src/Snowflake/Store/FileStore.php

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<?php
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namespace Ennexa\Snowflake\Store;
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use Ennexa\Snowflake\StoreInterface;
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use Ennexa\Snowflake\Exception\RuntimeException;
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class FileStore implements StoreInterface
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{
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public function __construct($cacheDir)
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{
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$this->cacheDir = $cacheDir;
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if (!file_exists($cacheDir)) {
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$status = mkdir($cacheDir, 0700, true);
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if (!$status) {
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throw new RuntimeException("[Snowflake] Failed to created directory - {$cacheDir}");
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}
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}
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}
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public function next(int $instanceId):array
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{
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$timestamp = (int)floor(microtime(true) * 1000);
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$file = "last_ts_{$instanceId}.fc";
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$fp = fopen("{$this->cacheDir}/{$file}", "c+");
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if (!$fp) {
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throw new RuntimeException('[Snowflake] Failed to open file');
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}
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$counter = 100;
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do {
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// Try to acquire exclusive lock. Fails after 5ms
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$locked = flock($fp, LOCK_EX | LOCK_NB);
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usleep(50);
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} while($counter--);
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if (!$locked) {
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throw new RuntimeException('[Snowflake] Failed to acquire lock');
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}
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try {
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fseek($fp, 0);
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$content = fread($fp, 50);
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$lastTimestamp = $sequence = 0;
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if ($content) {
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list($lastTimestamp, $sequence) = unserialize($content);
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}
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if ($lastTimestamp > $timestamp) {
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$sequence = -1;
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} else if ($lastTimestamp < $timestamp) {
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$sequence = 0;
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} else {
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$sequence++;
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}
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if ($sequence >= 0) {
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fseek($fp, 0);
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ftruncate($fp, 0);
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fwrite($fp, serialize([$timestamp, $sequence]));
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fflush($fp);
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}
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} finally {
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flock($fp, LOCK_UN);
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fclose($fp);
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}
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return [$timestamp, $sequence];
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}
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}

‎src/Snowflake/Store/RedisStore.php

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<?php
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namespace Ennexa\Snowflake\Store;
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use Ennexa\Snowflake\StoreInterface;
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use Ennexa\Snowflake\Exception\RuntimeException;
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class RedisStore implements StoreInterface
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{
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private $backend;
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public function __construct(\Redis $redis)
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{
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$this->backend = $redis;
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}
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private function getLuaScript()
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{
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return <<<LUA
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redis.replicate_commands()
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local ts = redis.call('time')
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local old_ts = tonumber(redis.call('get',KEYS[1] .. '.ts')) or 0
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local new_ts = ts[1] * 1000 + (ts[2] - ts[2] % 1000) / 1000
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redis.call('set', KEYS[1] .. '.ts', new_ts)
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redis.log(3, old_ts .. '|' .. new_ts)
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if (old_ts < new_ts) then
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redis.call('set', KEYS[1] .. '.seq', 0)
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return {new_ts, 0}
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else
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return {new_ts, redis.call('incr', KEYS[1] .. '.seq')}
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end
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LUA;
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}
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public function next(int $instanceId):array
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{
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try {
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return $this->backend->eval($this->getLuaScript(), [
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"snowflake_{$instanceId}"
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], 1);
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} catch (\RedisException $e) {
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throw new RuntimeException('[Snowflake] Failed to generate sequence', null, $e);
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}
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}
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}

‎src/Snowflake/StoreInterface.php

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<?php
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namespace Ennexa\Snowflake;
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interface StoreInterface {
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public function next(int $instanceId):array;
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}

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