Add config option to disable strict session timeout to be able to use read_and_close

Fixed https://github.com/nextcloud/server/issues/29356

Signed-off-by: Julius Härtl <jus@bitgrid.net>

config/config.sample.php

@@ -256,6 +256,17 @@ $CONFIG = [
  */
 'session_lifetime' => 60 * 60 * 24,
 
+/**
+ * `true` enabled a relaxed session timeout, where the session timeout would no longer be
+ * handled by Nextcloud but by either the PHP garbage collection or the expiration of
+ * potential other session backends like redis.
+ *
+ * This may lead to sessions being available for longer than what session_lifetime uses but
+ * comes with performance benefits as sessions are no longer a locking operation for concurrent
+ * requests.
+ */
+'session_relaxed_expiry' => false,
+
 /**
  * Enable or disable session keep-alive when a user is logged in to the Web UI.
  * Enabling this sends a "heartbeat" to the server to keep it from timing out.

lib/base.php

@@ -455,7 +455,9 @@ class OC {
 			\OC::$server->getUserSession()->logout();
 		}
 
+		if (!self::hasSessionRelaxedExpiry()) {
 			$session->set('LAST_ACTIVITY', time());
+		}
 		$session->close();
 	}
 
@@ -466,6 +468,13 @@ class OC {
 		return \OC::$server->getConfig()->getSystemValue('session_lifetime', 60 * 60 * 24);
 	}
 
+	/**
+	 * @return bool true if the session expiry should only be done by gc instead of an explicit timeout
+	 */
+	public static function hasSessionRelaxedExpiry(): bool {
+		return \OC::$server->getConfig()->getSystemValue('session_relaxed_expiry', false);
+	}
+
 	/**
 	 * Try to set some values to the required Nextcloud default
 	 */

lib/private/Session/Internal.php

@@ -178,7 +178,7 @@ class Internal extends Session {
 	 */
 	public function reopen(): bool {
 		if ($this->sessionClosed) {
-			$this->startSession();
+			$this->startSession(false, false);
 			$this->sessionClosed = false;
 			return true;
 		}
@@ -225,7 +225,11 @@ class Internal extends Session {
 		}
 	}
 
-	private function startSession(bool $silence = false) {
-		$this->invoke('session_start', [['cookie_samesite' => 'Lax']], $silence);
+	private function startSession(bool $silence = false, bool $readAndClose = true) {
+		$sessionParams = ['cookie_samesite' => 'Lax'];
+		if (\OC::hasSessionRelaxedExpiry()) {
+			$sessionParams['read_and_close'] = $readAndClose;
+		}
+		$this->invoke('session_start', [$sessionParams], $silence);
 	}
 }