[7.x] Cache::lock support for the database cache driver

src/Illuminate/Cache/CacheManager.php

@@ -214,7 +214,11 @@ protected function createDatabaseDriver(array $config)
 
         return $this->repository(
             new DatabaseStore(
-                $connection, $config['table'], $this->getPrefix($config)
+                $connection,
+                $config['table'],
+                $this->getPrefix($config),
+                $config['lock_table'] ?? 'cache_locks',
+                $config['lock_lottery'] ?? [2, 100]
             )
         );
     }

src/Illuminate/Cache/DatabaseLock.php

@@ -0,0 +1,138 @@
+<?php
+
+namespace Illuminate\Cache;
+
+use Illuminate\Database\Connection;
+use Illuminate\Database\QueryException;
+
+class DatabaseLock extends Lock
+{
+    /**
+     * The database connection instance.
+     *
+     * @var \Illuminate\Database\Connection
+     */
+    protected $connection;
+
+    /**
+     * The database table name.
+     *
+     * @var string
+     */
+    protected $table;
+
+    /**
+     * The prune probability odds.
+     *
+     * @var string
+     */
+    protected $lottery;
+
+    /**
+     * Create a new lock instance.
+     *
+     * @param  \Illuminate\Database\Connection  $connection
+     * @param  string  $table
+     * @param  string  $name
+     * @param  int  $seconds
+     * @param  string|null  $owner
+     * @param  array  $lottery
+     * @return void
+     */
+    public function __construct(Connection $connection, $table, $name, $seconds, $owner = null, $lottery = [2, 100])
+    {
+        parent::__construct($name, $seconds, $owner);
+
+        $this->connection = $connection;
+        $this->table = $table;
+        $this->lottery = $lottery;
+    }
+
+    /**
+     * Attempt to acquire the lock.
+     *
+     * @return bool
+     */
+    public function acquire()
+    {
+        $acquired = false;
+
+        try {
+            $this->connection->table($this->table)->insert([
+                'id' => $this->name,
+                'owner' => $this->owner,
+                'expires_at' => $this->expiresAt(),
+            ]);
+
+            $acquired = true;
+        } catch (QueryException $e) {
+            $updated = $this->connection->table($this->table)
+                ->where('id', $this->name)
+                ->where(function ($query) {
+                    return $query->where('owner', $this->owner)->orWhere('expires_at', '<=', time());
+                })->update([
+                    'owner' => $this->owner,
+                    'expires_at' => $this->expiresAt(),
+                ]);
+
+            $acquired = $updated >= 1;
+        }
+
+        if (random_int(1, $this->lottery[1]) <= $this->lottery[0]) {
+            $this->connection->table($this->table)->where('expires_at', '<=', time())->delete();
+        }
+
+        return $acquired;
+    }
+
+    /**
+     * Get the UNIX timestamp indicating when the lock should expire.
+     *
+     * @return int
+     */
+    protected function expiresAt()
+    {
+        return $this->seconds > 0 ? time() + $this->seconds : now()->addDays(1)->getTimestamp();
+    }
+
+    /**
+     * Release the lock.
+     *
+     * @return bool
+     */
+    public function release()
+    {
+        if ($this->isOwnedByCurrentProcess()) {
+            $this->connection->table($this->table)
+                        ->where('id', $this->name)
+                        ->where('owner', $this->owner)
+                        ->delete();
+
+            return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * Releases this lock in disregard of ownership.
+     *
+     * @return void
+     */
+    public function forceRelease()
+    {
+        $this->connection->table($this->table)
+                    ->where('id', $this->name)
+                    ->delete();
+    }
+
+    /**
+     * Returns the owner value written into the driver for this lock.
+     *
+     * @return string
+     */
+    protected function getCurrentOwner()
+    {
+        return optional($this->connection->table($this->table)->where('id', $this->name)->first())->token;
+    }
+}

src/Illuminate/Cache/DatabaseStore.php

@@ -35,19 +35,41 @@ class DatabaseStore implements Store
      */
     protected $prefix;
 
+    /**
+     * The name of the cache locks table.
+     *
+     * @var string
+     */
+    protected $lockTable;
+
+    /**
+     * A array representation of the lock lottery odds.
+     *
+     * @var string
+     */
+    protected $lockLottery;
+
     /**
      * Create a new database store.
      *
      * @param  \Illuminate\Database\ConnectionInterface  $connection
      * @param  string  $table
      * @param  string  $prefix
+     * @param  string  $lockTable
+     * @param  array  $lockLottery
      * @return void
      */
-    public function __construct(ConnectionInterface $connection, $table, $prefix = '')
+    public function __construct(ConnectionInterface $connection,
+                                $table,
+                                $prefix = '',
+                                $lockTable = 'cache_locks',
+                                $lockLottery = [2, 100])
     {
         $this->table = $table;
         $this->prefix = $prefix;
         $this->connection = $connection;
+        $this->lockTable = $lockTable;
+        $this->lockLottery = $lockLottery;
     }
 
     /**
@@ -205,6 +227,38 @@ public function forever($key, $value)
         return $this->put($key, $value, 315360000);
     }
 
+    /**
+     * Get a lock instance.
+     *
+     * @param  string  $name
+     * @param  int  $seconds
+     * @param  string|null  $owner
+     * @return \Illuminate\Contracts\Cache\Lock
+     */
+    public function lock($name, $seconds = 0, $owner = null)
+    {
+        return new DatabaseLock(
+            $this->connection,
+            $this->lockTable,
+            $this->prefix.$name,
+            $seconds,
+            $owner,
+            $this->lockLottery
+        );
+    }
+
+    /**
+     * Restore a lock instance using the owner identifier.
+     *
+     * @param  string  $name
+     * @param  string  $owner
+     * @return \Illuminate\Contracts\Cache\Lock
+     */
+    public function restoreLock($name, $owner)
+    {
+        return $this->lock($name, 0, $owner);
+    }
+
     /**
      * Remove an item from the cache.
      *