A cross-process lock.

.circleci/config.yml

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+version: 2.0
+jobs:
+  build:
+    environment:
+      CC_TEST_REPORTER_ID: b0e2dc22a6c4744ffb6a4a8597af2062cce268cbfd8c9baaaa660d79ed33a803
+    docker:
+      - image: circleci/php:7-cli-node-browsers-legacy
+    working_directory: ~/repo
+    steps:
+      - checkout
+      - run:
+          name: Setup dependencies
+          command: |
+            sudo composer self-update
+            composer install -n --prefer-dist
+      - run:
+          name: Setup Code Climate test-reporter
+          command: |
+            curl -L https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64 > ./cc-test-reporter
+            chmod +x ./cc-test-reporter
+      - run:
+          name: Run tests
+          command: |
+            ./cc-test-reporter before-build
+            vendor/bin/phpunit --testsuite all --coverage-clover clover.xml
+            ./cc-test-reporter after-build --coverage-input-type clover --exit-code $?

README.md

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+# Locker
+![CircleCI (all branches)](https://img.shields.io/circleci/project/github/fmizzell/datastore.svg)
+[![Maintainability](https://api.codeclimate.com/v1/badges/c04818119efc862221cd/maintainability)](https://codeclimate.com/github/fmizzell/locker/maintainability)
+[![Test Coverage](https://api.codeclimate.com/v1/badges/c04818119efc862221cd/test_coverage)](https://codeclimate.com/github/fmizzell/locker/test_coverage)
+[![GPLv3 license](https://img.shields.io/badge/License-GPLv3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0.en.html)
+
+A cross-process lock.

composer.json

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+{
+    "name": "fmizzell/locker",
+    "description": "A cross-process lock.",
+    "license": "GPL-3.0-only",
+    "authors": [
+        {
+            "name": "fmizzell",
+            "email": "[email protected]"
+        }
+    ],
+    "autoload": {
+        "psr-4": {
+            "Locker\\": "src/"
+        }
+    },
+    "require-dev": {
+        "phpunit/phpunit": "^7.4"
+    }
+}

phpunit.xml

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+<phpunit
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/6.3/phpunit.xsd"
+    verbose="false">
+
+    <testsuites>
+        <testsuite name="all">
+            <directory suffix="Test.php" phpVersion="7.2" phpVersionOperator=">=">test</directory>
+        </testsuite>
+    </testsuites>
+
+    <filter>
+        <whitelist processUncoveredFilesFromWhitelist="true">
+            <directory suffix=".php">src</directory>
+        </whitelist>
+    </filter>
+
+</phpunit>

src/Locker.php

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+<?php
+
+namespace Locker;
+
+
+class Locker
+{
+
+  private $timeWaited = -1;
+  private $name;
+  private $expire;
+  private $wait;
+
+  /**
+   * Constructor.
+   *
+   * @param string $name
+   *   The locks name.
+   *
+   * @param int $expire
+   *   When the lock is set, it will automatically expire after
+   *   this amount of time has passed if the lock is not released.
+   *
+   * @param int $wait
+   *   Time we are willing to wait for the lock before we bail.
+   */
+  public function __construct($name, $expire = 30, $wait = 5)
+  {
+    $this->name = $name;
+    $this->expire =  $expire;
+    $this->wait = $wait;
+  }
+
+  /**
+   * Wait until we get the lock, or we get tired of waiting.
+   */
+  public function getLock() {
+    do {
+      $this->wait();
+      if ($this->timeWaited > $this->wait) {
+        $this->timeWaited = -1;
+        throw new \Exception("The lock was not acquire after {$this->wait} second(s).");
+      }
+      $this->lockExpired();
+    } while (!$this->lockCreated());
+
+    $this->timeWaited = -1;
+    return TRUE;
+  }
+
+  /**
+   * Release the lock.
+   */
+  public function releaseLock() {
+    $path = "/tmp/{$this->name}.lock";
+    if (file_exists($path)) {
+      array_map('unlink', glob("{$path}/*.*"));
+      rmdir($path);
+    }
+  }
+
+  private function wait() {
+    if ($this->timeWaited >= 0) {
+      sleep(1);
+    }
+    $this->timeWaited++;
+  }
+
+  private function lockExpired() {
+    $file = "/tmp/{$this->name}.lock/expire.txt";
+    if (file_exists($file) && file_get_contents($file) < time()) {
+      $this->releaseLock();
+      return TRUE;
+    }
+    return FALSE;
+  }
+
+  private function lockCreated() {
+    $lock_path = "/tmp/{$this->name}.lock";
+    if (@mkdir($lock_path, 0700)) {
+      file_put_contents("{$lock_path}/expire.txt", (time() + $this->expire));
+      return TRUE;
+    }
+    return FALSE;
+  }
+}

test/LockerTest.php

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+<?php
+
+
+class LockerTest extends \PHPUnit\Framework\TestCase
+{
+  private $locker;
+
+  protected function setUp()
+  {
+    $this->locker = new \Locker\Locker("test", 5, 1);
+  }
+
+  public function testReleaseAndWait() {
+    $this->assertTrue($this->locker->getLock());
+
+    try {
+      $this->locker->getLock();
+    }
+    catch(\Exception $e) {
+      $this->assertEquals($e->getMessage(), "The lock was not acquire after 1 second(s).");
+    }
+
+    $this->locker->releaseLock();
+    $this->assertTrue($this->locker->getLock());
+  }
+
+  public function testExpiration() {
+    $this->assertTrue($this->locker->getLock());
+    sleep(6);
+    $this->assertTrue($this->locker->getLock());
+  }
+
+  protected function tearDown()
+  {
+    $this->locker->releaseLock();
+  }
+
+}