Session handling in visitor group criteria

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Note

This content applies to Optimizely Content Management System (CMS) versions 11.9.0 and higher.

You can use the built-in Optimizely visitor group criteria without requiring session state on the server side by manually turning off ASP.NET session states. The visitor group system can autodetect if the session state was disabled and switch to a cookie-based approach for visitor group criteria that previously used sessions. You can also customize the storage of users' visitor group sessions.

RaiseStartSession event

If the session is enabled, then the RaiseStartSession event is raised by AspNet session start event. If the session is disabled, then the RaiseStartSession event is raised by HttpApplication AcquireRequestState event.

Session State

The session-based visitor group criterion saves its session state inside a session, cookie, or customized state storage. If the session is enabled and there is no registered custom storage, then it uses the HTTP session object as storage. If the session is disabled and there is no registered custom storage, then it uses the HTTP cookie as storage.

Enable and disable session state

By default, CMS uses the HTTP session object if the AspNet session state mode is not Off. You can change it explicitly by setting the property EnableSession to false on the VisitorGroupOptions options.

Customize State storage

To customize storage, implement the IStateStorage interface and register it. This sample code shows customized state storage and disabling session state.

internal class InMemoryStateStorage: IStateStorage {
  IDictionary<string, string> _states = new Dictionary<string, string>();
  public bool IsAvailable => true;
  public object Load(string key) {
    _states.TryGetValue(key, out string value);
    return value;
  }

  public void Save(string key, object value) {
    _states[key] = (string) value;
  }

  public void Delete(string key) {
    _states.Remove(key);
  }
}

and you can register the custom state storage in IServiceCollection in the startup, like this:

public class Startup {
  public void ConfigureServices(IServiceCollection services) {
    services.Add<VisitorGroupOptions>((s) => new VisitorGroupOptions(), ServiceInstanceScope.Singleton);
    services.Configure<VisitorGroupOptions>(s => s.EnableSession = EnableSession);
    services.Add<IStateStorage>(s => new InMemoryStateStorage(), ServiceInstanceScope.Singleton);
  }
}