Trouble using Azure Cache Service (Preview) with Azure Website

Question

We currently have 2 separate ASP.Net websites hosted on one of our server. These sites uses StateServer to maintain same session across both sites. We are looking to move these sites to Azure. I was able to upload both sites on Azure without any trouble but I was not able to share the session between both sites. I tried using Azure Cache Service (Preview) to maintain session but for some reason it doesn't work, it always uses different session when I redirect to the second site. I already spent quite a bit of time googling around with no avail.

To get to the bottom of the issue, I now have created 2 test sites and have uploaded it on the Azure. I changed the config to use the Cache Service (Preview) as SessionState but it still doesn't work.

The link to get to the test site is: http://sessiontestsite1.azurewebsites.net/

On the home page, please enter a value in the textbox and click "Update session variable", this will store the text into a session variable. Then, on the top right corner of the page there is a link called "Site2" which will redirect to the second site. I am hoping that second site will be able to access the session variable set in the "Site1" and vice versa. Please note on my local machine I was able to use the same session using StateServer.

I followed this link to configure cache service.

I read somewhere, people were saying that Cache Service cannot be used with Azure Websites but I think those are old posts, as per Scott Gutherie's blog (sorry, StackOverflow doesn't allow me to post more than 2 links) Cache Service can be used with Azure Websites.

Also our requirement is to use these sites as Azure Websites, we do NOT want to use WebRoles or VMs or CloudServices etc.

Answer 1

Because session sharing in our current setup doesn't work we have decided to use two sites as virtual applications.

We have now created a new website and that website has two sub folders (set as virtual applications). Both sites now sits in theses sub folders. That way session state using cache service works.

Answer 2

This is not how session works. When you put a value in the Session the server assign the client an ID and sends it to the client in a cookie. In ASP.NET it's ASP.NET_SessionId. The client (Browsers) will only send the cookie to the remote address associated with it. If you use Fiddler or browser dev tools you will see the browser sending back the ASP.NET_SessionId cookie to sessionstatesite1 and not to sessionstatesite2 because it has a different hostname.

You can either add the cookie manually (using browser dev tools for example) and test it again.

If you want to use the cache for user session and have the user access the site using 1 URL that get's routed to different Azure Website Instances, that cache will work fine for you. Again you can verify that using multiple ways. Adding the cookie manually above should show you that it's working. If you wanna do it in an end-to-end flow do this:

1. Create an Azure Website
2. Scale the site to run on multiple instances
3. Configure your site to display the Process Id or Instance Id Environment Variable
4. Configure your site to use caching as you already did before
5. Store something in session state
6. log in to kudu (https://<yoursitename>.scm.azurewebsites.net)
7. Go to process explorer view (https://<yoursitename>.scm.azurewebsites.net/ProcessExplorer) and right click on the w3wp.exe and kill it (you can also verify the PID there)
8. send a request again from the browser, it will go to a different instance and you can tell by the Process Id, but the session value will still be saved.