Prior to #828, index.php contained:

if(!session_id()) {
    session_start();
}

However, session_start() was always called because session_id() returns a string; even an empty string (""), would mean the conditional evaluated to true.

This isn't necessarily wrong as it either starts or resumes an existing session. In fact, it masks a problem where MySQL is configured with a low limit on concurrent connections. By calling session_start() in index.php, requests associated with the same session are funneled in serial fashion.

See comments:

• http://ca.php.net/manual/en/function.session-start.php#90968
• http://ca.php.net/manual/en/function.session-start.php#31262

Following #828, the session_start() call was removed. We are starting to see reports of "SQLSTATE![ User xxxxxx already has more than 'max_user_connections' active connections" appearing in some dashboard widgets.

Proposed patch:

Index: index.php
===================================================================
--- index.php   (revision 1329)
+++ index.php   (working copy)
@@ -37,6 +37,7 @@
 session_cache_limiter('nocache');
 @date_default_timezone_set(date_default_timezone_get());
 require_once PIWIK_INCLUDE_PATH .'/core/Loader.php';
+Zend_Session::start();

 if(!defined('PIWIK_ENABLE_ERROR_HANDLER') || PIWIK_ENABLE_ERROR_HANDLER)
 {

This duplicates the functionality of "session.auto_start=On" (see #881), but is Zend Framework-friendly.

Pros:

• Mitigates the connection limit problem.
• Potentially lowers peak load on the server.

Cons:

• A long-loading widget delays the loading of other widgets. This gives the appearance that the dashboard is taking longer to load.