feat(core): 新增一个一主双备缓存工具

#351

app/Cache/DoubleBackup.php

@@ -0,0 +1,98 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Zhiyi\Plus\Cache;
+
+use Closure;
+use Zhiyi\Plus\Support\Setting;
+use Illuminate\Contracts\Cache\Factory as CacheInterface;
+
+class DoubleBackup
+{
+    /**
+     * Cache manager.
+     * @var \Illuminate\Contracts\Cache\Factory
+     */
+    protected $cache;
+
+    /**
+     * Setting util.
+     * @var \Zhiyi\Plus\Support\Setting
+     */
+    protected $setting;
+
+    /**
+     * Create a double backup cacher.
+     * @param \Illuminate\Contracts\Cache\Factory $cache
+     */
+    public function __construct(CacheInterface $cache)
+    {
+        $this->cache = $cache;
+        $this->setting = $this->createSetting();
+    }
+
+    /**
+     * Get cache.
+     * @param string $index
+     * @param int $minutes
+     * @param \Closure $task
+     * @return mixed
+     */
+    public function get(string $index, int $minutes, Closure $task)
+    {
+        $mainIndex = $index.'/main';
+        $backupIndexes = [
+            $index.'/backup-0',
+            $index.'/backup-1',
+        ];
+
+        if ($this->cache->has($mainIndex)) {
+            return $this->randomRead(array_merge($backupIndexes, [$mainIndex]), function (array $indexes) {
+                return $this->randomRead($indexes);
+            });
+        } elseif ($this->setting->get($taskKey = 'cache://tasks/'.$index)) {
+            return null;
+        }
+
+        $this->setting->set($taskKey, true);
+        $this->cache->put($mainIndex, $contents = $task(), $expiresAt = now()->addMinutes($minutes));
+        foreach ($backupIndexes as $key => $value) {
+            $temExpiresAt = $expiresAt->addMinutes(
+                $minutes / ($key + 1) / 2
+            );
+            $this->cache->put($value, $contents, $temExpiresAt);
+        }
+
+        return $contents;
+    }
+
+    /**
+     * Create a setting util.
+     * @return \Zhiyi\Plus\Support\Setting
+     */
+    public function createSetting(): Setting
+    {
+        return Setting::create('cache://double-backup');
+    }
+
+    /**
+     * Random read cache.
+     * @param array $indexes
+     * @param \Closure $next
+     * @return mixed
+     */
+    protected function randomRead(array $indexes, Closure $next)
+    {
+        $indexKey = rand(0, count($indexes) - 1);
+        $index = $indexes[$indexKey];
+
+        if ($this->cache->has($index)) {
+            return $this->cache->get($index);
+        }
+
+        unset($indexes[$indexKey]);
+
+        return $next(array_values($indexes));
+    }
+}