What is Session Clustering?

Question

We have currently started using tomcat 7.0 in our development environment. Following are the configuration Details :

Tomcat Version : 7.0.55
Java Version :1.7.0.67

We have a requirement to implement clustering for one of our applications . The same application's active but idle sessions need to be persisted to a JDBC store . We have a small cluster of just two nodes so as recommended we need to use DeltaManager but for session persistence we need to use PersistentManager . PersistentManager is not recommended for clustering as the session data is not swapped out in real time.As far as I understand , we can only use one of the manager configurations .

Can you please let me know if it is possible to achieve session persistence along with clustering , If yes how can we achieve the same ?

Answer 1

Sql Server failover clustering can be conceptually explained as a smoke-and-mirrors dns hack. Thinking of clustering in familiar terms makes you realize how simple a technology it really is.
Simplified description of Sql Server Failover Clustering

Imagine you have two computers: SrvA and SrvB

You plug an external HD (F:) into SrvA, Install Sql Server and configure it to store its database files on f:\ (The executable is under C:\Program Files).

Unplug the HD, plug it into SrvB, Install Sql Server and configure it to store its database files on F:\ in the exact same location.

Now, you create a dns alias "MyDbServer" that points to SrvA, plug the external HD back into SrvA, and start sql server.

All is good until one day when the power supply fails on SrvA and the machine goes down.

To recover from this disaster you do the following:

Plug the external drive into SrvB
Start sql server on SrvB
Tweak the dns entry for "MyDbServer" to point to SrvB.

You're now up and going on SrvB, and your client applications are blissfully unaware that SrvA failed because they only ever connected using the name "MyDbServer".

Answer 2

Session clustering is used to provide scalability for keeping the session data in synch across a “cluster” of PHP servers. The sessions reside on the machine in which they are created. These sessions are then delivered from one machine to another. This delivery is fully distributed. The Zend Session manager is used for transferring sessions from the system (session storage) to remote addresses.