TechNote: Lasso 9 - Resolving XML error when activating MySQL Session Storage

Lasso 9 can store session data in Memory, SQLite (default), or MySQL and each has specific benefits. The session data is stored encoded as XML. On CentOS, Lasso 9 leverages the libxml2 library to handle XML.

• The memory session driver provides the benefit of speed.
• The SQLite session driver provides persistance of sessions through instance restarts.
• MySQL session storage is the most appropriate option when sharing sessions between websites on different instances or servers.

The most typical scenario where MySQL session storage would be used is in sharing session data between nodes of a High Availability (HA) cluster. Each node instance in the cluster must be configured to use the same MySQL database and table for session storage if the sessions are to be common to all nodes.

Platforms affected:

CentOS 5.6 32-bit and 64-bit
Lasso Server 9.1.4

Symptom:

Activating MySQL session storage results in deadlocked Lasso 9 for pages using sessions.

Steps to reproduce:

In Lasso 9 Admin -> Sessions, select "MySQL" as default session driver.
Error will be regardless of MySQL database and table selected or created.

Error output in lasso.out.txt:

(usually if output is wrapped in protect/handle blocks)

​libxml error while parsing document: Start tag expected, '<' not found

Error stack: 

4:37 xml.lasso
172:38 session.lasso
…

Solution:

Update to latest libxml2 
At the time of writing libxml2 is at version 2.6.26-2.1.12.
This version of libxml2 resolves the error.

Author: Jonathan Guthrie
Created: 25 Oct 2011
Last Modified: 25 Oct 2011