feat: Add memcache_customprefix

Signed-off-by: Martin <31348196+Earl0fPudding@users.noreply.github.com>

config/config.sample.php

@@ -1758,6 +1758,16 @@ $CONFIG = [
 	 */
 	'memcache.distributed' => '\\OC\\Memcache\\Memcached',
 
+	/**
+	 * Cache Key Prefix for Redis or Memcached
+	 *
+	 * * Used for avoiding collisions in the cache system
+	 * * May be used for ACL restrictions in Redis
+	 *
+	 * Defaults to ``''`` (empty string)
+	 */
+	'memcache_customprefix' => 'mycustomprefix',
+
 	/**
 	 * Connection details for Redis to use for memory caching in a single server configuration.
 	 *

lib/private/Memcache/Factory.php

@@ -115,6 +115,7 @@ class Factory implements ICacheFactory {
 	protected function getGlobalPrefix(): string {
 		if ($this->globalPrefix === null) {
 			$config = Server::get(SystemConfig::class);
+			$customprefix = $config->getValue('memcache_customprefix', '');
 			$maintenanceMode = $config->getValue('maintenance', false);
 			$versions = [];
 			if ($config->getValue('installed', false) && !$maintenanceMode) {
@@ -131,7 +132,7 @@ class Factory implements ICacheFactory {
 			// Include instanceid in the prefix, in case multiple instances use the same cache (e.g. same FPM pool)
 			$instanceid = $config->getValue('instanceid');
 			$installedApps = implode(',', array_keys($versions)) . implode(',', array_values($versions));
-			$this->globalPrefix = hash('xxh128', $instanceid . $installedApps);
+			$this->globalPrefix = $customprefix . hash('xxh128', $instanceid . $installedApps);
 		}
 		return $this->globalPrefix;
 	}
@@ -145,9 +146,11 @@ class Factory implements ICacheFactory {
 	public function withServerVersionPrefix(\Closure $closure): void {
 		$backupPrefix = $this->globalPrefix;
 
+		$config = Server::get(SystemConfig::class);
+		$customprefix = $config->getValue('memcache_customprefix', '');
 		// Include instanceid in the prefix, in case multiple instances use the same cache (e.g. same FPM pool)
-		$instanceid = Server::get(SystemConfig::class)->getValue('instanceid');
-		$this->globalPrefix = hash('xxh128', $instanceid . implode('.', $this->serverVersion->getVersion()));
+		$instanceid = $config->getValue('instanceid');
+		$this->globalPrefix = $customprefix . hash('xxh128', $instanceid . implode('.', $this->serverVersion->getVersion()));
 		$closure($this);
 		$this->globalPrefix = $backupPrefix;
 	}