Improve memcache connection and failure handling; add debug option to trace memcache activity for session storage

program/include/rcmail.php

@@ -336,21 +336,42 @@ class rcmail
       }
 
       $this->memcache = new Memcache;
-      $mc_available = 0;
+      $this->mc_available = 0;
+      
+      // add alll configured hosts to pool
+      $pconnect = $this->config->get('memcache_pconnect', true);
       foreach ($this->config->get('memcache_hosts', array()) as $host) {
         list($host, $port) = explode(':', $host);
         if (!$port) $port = 11211;
-        // add server and attempt to connect if not already done yet
-        if ($this->memcache->addServer($host, $port) && !$mc_available)
-          $mc_available += intval($this->memcache->connect($host, $port));
+        $this->mc_available += intval($this->memcache->addServer($host, $port, $pconnect, 1, 1, 15, false, array($this, 'memcache_failure')));
       }
+      
+      // test connection and failover (will result in $this->mc_available == 0 on complete failure)
+      $this->memcache->increment('__CONNECTIONTEST__', 1);  // NOP if key doesn't exist
 
-      if (!$mc_available)
+      if (!$this->mc_available)
         $this->memcache = false;
     }
 
     return $this->memcache;
   }
+  
+  /**
+   * Callback for memcache failure
+   */
+  public function memcache_failure($host, $port)
+  {
+    static $seen = array();
+    
+    // only report once
+    if (!$seen["$host:$port"]++) {
+      $this->mc_available--;
+      raise_error(array('code' => 604, 'type' => 'db',
+        'line' => __LINE__, 'file' => __FILE__,
+        'message' => "Memcache failure on host $host:$port"),
+        true, false);
+    }
+  }
 
 
   /**

program/include/rcube_session.php

@@ -55,6 +55,7 @@ class rcube_session
     $this->start = microtime(true);
     $this->ip = $_SERVER['REMOTE_ADDR'];
     $this->logging = $config->get('log_session', false);
+    $this->mc_debug = $config->get('memcache_debug', false);
 
     $lifetime = $config->get('session_lifetime', 1) * 60;
     $this->set_lifetime($lifetime);
@@ -255,8 +256,9 @@ class rcube_session
    */
   public function mc_read($key)
   {
-    if ($value = $this->memcache->get($key)) {
-      $arr = unserialize($value);
+    $value = $this->memcache->get($key);
+    if ($this->mc_debug) write_log('memcache', "get($key): " . strlen($value));
+    if ($value && ($arr = unserialize($value))) {
       $this->changed = $arr['changed'];
       $this->ip      = $arr['ip'];
       $this->vars    = $arr['vars'];
@@ -289,8 +291,15 @@ class rcube_session
 
     $newvars = $oldvars !== false ? $this->_fixvars($vars, $oldvars) : $vars;
     
-    if ($newvars !== $oldvars || $ts - $this->changed > $this->lifetime / 2)
-      return $this->memcache->set($key, serialize(array('changed' => time(), 'ip' => $this->ip, 'vars' => $newvars)), MEMCACHE_COMPRESSED, $this->lifetime);
+    if ($newvars !== $oldvars || $ts - $this->changed > $this->lifetime / 2) {
+      $value = serialize(array('changed' => time(), 'ip' => $this->ip, 'vars' => $newvars));
+      $ret = $this->memcache->set($key, $value, MEMCACHE_COMPRESSED, $this->lifetime);
+      if ($this->mc_debug) {
+        write_log('memcache', "set($key): " . strlen($value) . ": " . ($ret ? 'OK' : 'ERR'));
+        write_log('memcache', "... get($key): " . strlen($this->memcache->get($key)));
+      }
+      return $ret;
+    }
     
     return true;
   }
@@ -303,7 +312,9 @@ class rcube_session
    */
   public function mc_destroy($key)
   {
-    return $this->memcache->delete($key);
+    $ret = $this->memcache->delete($key);
+    if ($this->mc_debug) write_log('memcache', "delete($key): " . ($ret ? 'OK' : 'ERR'));
+    return $ret;
   }