ASP.NET SignalR – Beyond the Chat Application

Last January 30, I talked about ASP.NET SignalR 2.0 and what are the other uses of the technology aside from the chat application that’s widely available in the internet.

The first time I talked about SignalR (Q2 2013) is about the overview of the technology, and how it is used based on the chat application. From that point, I haven’t seen any implementation yet on how can it be used in business applications – a world where I actually work in. Although a quick check now on the project’s SignalR GitHub page, there are some projects/applications published using this technology.

Fortunately, an unfortunate incident that was reported before by a friend was a good business case where this technology can be implemented. The scenario is something like this:

Employee was working on an application where the users are located on multiple locations and multiple timezones. Employee worked with the business partner to schedule the production release of the approved enhancements. Business sent out prior notifications to the departments through e-mail and employee worked on the technical team that will assist in the release. Departments are responsible for cascading this information to their respective units as they are more aware of the specific roles for their group.

The release was made but had to be pulled out minutes after due to business reasons. The time in between the post release and the time it had to be reverted, data corruption happened and these needs to be corrected. It took a long time and large effort to reach out to different users to remediate data fixes.

A root cause analysis was conducted and one of the suggestions is that in the future releases, introduce the app_offline.htm file in the root folder of the application to make sure that no one is actually working on the application on the time of the release.

While the app_offline.htm file effectively excludes everyone from the application (aka “soft offline”), this might be costly for some who are currently working on the application. Either they had to re-upload a large file, re-input lots of data once an abrupt “activation” of the app_offline.htm file is put into place. It would be nice if these people would be notified of the upcoming outage ONLY if there’s a way to identify their current site activity and send them notices as warning to save their changes.

Building up a prototype using SignalR might be useful for these reasons:

  • Current users of the application are considered as “clients” connected to the server. Application administrators don’t need access to the web server just to get the number of users online (through perfmon) OR use an application level variable (and using that nasty Application.Lock() method) that can probably cause performance penalties.
  • I can treat the whole application as a glorified “chat session” and send broadcast messages to all or specific users (more on the sample application). I can send notifications individually or to everyone, as I desire through divs triggered according to events.

In my talk, I used two pages to demonstrate SignalR. It all started with converting a SignalR 1.x application to version SignalR 2.0.x and build the demo from that.

Client Page (signalr-Notification.aspx)

The client page provides three different ways of participating in the application session (or “chat”) – using the current windows identity, a client-input name, or a value taken from the web.config.

Image

Once you have selected your “identity”, you would see a familiar chat window similar to the chat demo. What made this demo different is that you have three functionality that builds on top of the chat demo.

The first two buttons in this page provide notification to all connected users, while the last one just provide notification to the user calling the function. The first button sends notification based on a fixed value. This could either be a standard greeting to those joining the session or any hardcoded value (e.g. name of the application, etc) that you wish to broadcast.

The second button broadcasts value from the web.config file. As indicated in the scenario above, it would have been better if the current users using the application prior the updates be notified that the application would go offline in x number of minutes. Case for example, if the website is scheduled to go offline in a specific time, you can get the value of the offline schedule (date or datetime) from the web.config and broadcast it to the users. This button is quite flexible on what data to broadcast or notify since you have control on what data to display to the connected users.

The third button simply displays how many users are connected to the application at that point. That’s just it. You would know how many people are actually having an active session with the application. Previously on ASP.NET Membership, the basis of number of users online is based on the users’ login session. However, if I say I login and close the browser after authentication, I would still be recognized as “online”.

Admin Page (signalr-Admin.aspx)

Getting through the admin page needs you to be identified again in the system. I just basically reused the first page and added admin-related items.

In the admin page, I displayed all connected users and their corresponding connection IDs. From this point, the “admin” can send individual messages to the user or broadcast to all a message. This is similar to a Facebook notification wherein people associated or a specific person gets notified for an update or message.

Admin

The demo files can be downloaded through my Skydrive folder and is provided as is.

There are other enhancements/items that I am working on this project:

  • Ability to return back to the admin who among the users have acknowledged the notification. An event can be raised and capture the current username of the user who clicked the notification.
  • Do a comparative speed/latency test on connections coming from different browsers. Note that SignalR’s mode of transport depends on the type of browser that a user uses to work with the application.

Questions? Feel free to ask them in the comments. 🙂

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s