From b64e3f8db609b1f65ec23f467da7488abf92c05a Mon Sep 17 00:00:00 2001
From: Robin McCorkell <rmccorkell@owncloud.com>
Date: Sat, 5 Sep 2015 20:02:49 +0100
Subject: [PATCH] Fallback to complete Memcached flush if getAllKeys fails

Newer Memcached's do not support the underlying protocol commands that
getAllKeys() is implemented with. We should fallback to clearing
everything in that case, as causing (temporary) performance problems for
other applications on the server is better than having stale cached data.
---
 lib/private/memcache/memcached.php |  5 +++++
 tests/lib/memcache/memcached.php   | 23 +++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/lib/private/memcache/memcached.php b/lib/private/memcache/memcached.php
index 1503851fd7..e99303ecc1 100644
--- a/lib/private/memcache/memcached.php
+++ b/lib/private/memcache/memcached.php
@@ -89,6 +89,11 @@ class Memcached extends Cache implements IMemcache {
 	public function clear($prefix = '') {
 		$prefix = $this->getNamespace() . $prefix;
 		$allKeys = self::$cache->getAllKeys();
+		if ($allKeys === false) {
+			// newer Memcached doesn't like getAllKeys(), flush everything
+			self::$cache->flush();
+			return true;
+		}
 		$keys = array();
 		$prefixLength = strlen($prefix);
 		foreach ($allKeys as $key) {
diff --git a/tests/lib/memcache/memcached.php b/tests/lib/memcache/memcached.php
index 51a78996dd..3ea9216029 100644
--- a/tests/lib/memcache/memcached.php
+++ b/tests/lib/memcache/memcached.php
@@ -26,4 +26,27 @@ class Memcached extends Cache {
 		parent::setUp();
 		$this->instance = new \OC\Memcache\Memcached($this->getUniqueID());
 	}
+
+	public function testClear() {
+		// Memcached is sometimes broken with clear(), so we don't test it thoroughly
+		$value='ipsum lorum';
+		$this->instance->set('1_value1', $value);
+		$this->instance->set('1_value2', $value);
+		$this->instance->set('2_value1', $value);
+		$this->instance->set('3_value1', $value);
+
+		$this->assertTrue($this->instance->clear('1_'));
+
+		$this->assertFalse($this->instance->hasKey('1_value1'));
+		$this->assertFalse($this->instance->hasKey('1_value2'));
+		//$this->assertTrue($this->instance->hasKey('2_value1'));
+		//$this->assertTrue($this->instance->hasKey('3_value1'));
+
+		$this->assertTrue($this->instance->clear());
+
+		$this->assertFalse($this->instance->hasKey('1_value1'));
+		$this->assertFalse($this->instance->hasKey('1_value2'));
+		$this->assertFalse($this->instance->hasKey('2_value1'));
+		$this->assertFalse($this->instance->hasKey('3_value1'));
+	}
 }