database

Database Session State

Stores session data as comitted data in the database.

• Overview
• How It Works
• When to Use It

Overview

When a call goes out from the client to the server, the server object first pulls the data required for the request from the database. In order to pull information from the database, the server object will need some information about the session, which requires at least a session ID number to be stored on the client.

The data involved is typically a mix of session data that's only local to the current interaction and committed data that's relevant to all interactions.

How It Works

• Session data is usually considered local to the session and shouldn't affect other parts of the system until the session as a whole is comitted.

  • Adding a field to each database row that may have session data is one route (isPending).
  • Store a session ID as a pending field, makes it much easier to find all the data for a particular session.
  • Separate set of pending tables.

• You'll need a mechanism to clean out the session data if a session is canceled or abandoned.

  • Using a session ID you can find all data with it and delete it.
  • If a user abandon the session without telling you, you'll need some kind of timeout mechanism (e.g., a daemon that runs every few minutes).

When To Use It

• You'll gain by using stateless objects on the server, thus enabling pooling and easy clustering. This is usually more straightforward than with Server Session State.

• You'll pay with the time needed to pull the data in and out of the database with each request. You can reduce this cost by caching the server object.

• Programming effort, especially around handling session state, is considerable.