MDL-63329 core: Remove memcache session support

config-dist.php

@@ -284,16 +284,8 @@
 //      igbinary support to make the setting to work. Also, if you change the serializer you have to flush the database!
 //      $CFG->session_redis_serializer_use_igbinary = false; // Optional, default is PHP builtin serializer.
 //
-//   Memcache session handler (requires memcached server and memcache extension):
-//      $CFG->session_handler_class = '\core\session\memcache';
-//      $CFG->session_memcache_save_path = '127.0.0.1:11211';
-//      $CFG->session_memcache_acquire_lock_timeout = 120;
-//      ** NOTE: Memcache extension has less features than memcached and may be
-//         less reliable. Use memcached where possible or if you encounter
-//         session problems. **
-//
-// Please be aware that when selecting either Memcached or Memcache for sessions that it is advised to use a dedicated
-// memcache server. The memcache and memcached extensions do not provide isolated environments for individual uses.
+// Please be aware that when selecting Memcached for sessions that it is advised to use a dedicated
+// memcache server. The memcached extension does not provide isolated environments for individual uses.
 // Using the same server for other purposes (MUC for example) can lead to sessions being prematurely removed should
 // the other uses of the server purge the cache.
 //

lib/classes/session/memcached.php

@@ -74,7 +74,7 @@ public function __construct() {
         if (empty($this->savepath)) {
             $this->servers = array();
         } else {
-            $this->servers = util::connection_string_to_memcache_servers($this->savepath);
+            $this->servers = self::connection_string_to_memcache_servers($this->savepath);
         }
 
         if (empty($CFG->session_memcached_prefix)) {
@@ -268,4 +268,33 @@ public function kill_session($sid) {
         }
     }
 
+    /**
+     * Convert a connection string to an array of servers.
+     *
+     * "abc:123, xyz:789" to
+     *  [
+     *      ['abc', '123'],
+     *      ['xyz', '789'],
+     *  ]
+     *
+     * @param   string  $str save_path value containing memcached connection string
+     * @return  array[]
+     */
+    protected static function connection_string_to_memcache_servers(string $str) : array {
+        $servers = [];
+        $parts   = explode(',', $str);
+        foreach ($parts as $part) {
+            $part = trim($part);
+            $pos  = strrpos($part, ':');
+            if ($pos !== false) {
+                $host = substr($part, 0, $pos);
+                $port = substr($part, ($pos + 1));
+            } else {
+                $host = $part;
+                $port = 11211;
+            }
+            $servers[] = [$host, $port];
+        }
+        return $servers;
+    }
 }

lib/upgrade.txt

@@ -71,6 +71,8 @@ information provided here is intended especially for developers.
     - I navigate to "PATH > ITEM" in site administration
     - I navigate to course participants
     - I navigate to "TAB1 > TAB2" in the course gradebook
+* The core\session\util class has been removed. This contained one function only used by the memcached class which has
+  been moved there instead (connection_string_to_memcache_servers).
 
   If some items are not available without Navigation block at all, one can use combination of:
     - I add the "Navigation" block if not present