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SignalR as a service in Azure

May 8, 2018 - John Waters

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In a previous post, I wrote about using SignalR in AspNetCore. Today, I tried the next step up – SignalR as a service!

You will find the announcement here. This page has more details. So why would you want to run SignalR as a service, rather than embedding your Hubs in your API or Web back end? In short – scalability. If your service goes viral and expands to a farm, you would traditionally use a SignalR backplane, with Sql Server or Redis as a backing store. Turns out there is a lot of tricky programming behind getting this to work well, using sticky sessions and load balancing web sockets. Using the Azure SignalR service, this is all taken care of for you. There is a free tier, with one unit, or a paid tier, with multiple units, which will scale elastically. The free tier is good for 100 concurrent connection and 100,000 messages per day.

Switching to this service from regular SignalR is a breeze. First, you will want to add the Nuget package Microsoft.Azure.SignalR to your app (instead of Microsoft.AspnetCore.SignalR). Second, in your Startup.cs, add .AddAzureSignalR() to your AddSignalR.

Now, switch from UseSignalR to UseAzureSignalR.

Next, create you SignalR service in the Azure portal, and copy the Primary Connection String from it’s keys. For development, add this to your local User Secrets, like this:

When deploying your API to Azure, just add this same connection string as an app setting (with the key Azure:SignalR:ConnectionString).

That’s it! No changes to Hubs, or to your logic using IHubContexts. No changes to connections, groups, messages… and no changes to your client. Very straight forward. I did find though that I had to remove the explicit setting of HttpTransportType to WebSockets in my Angular client, leaving that setting as the default on both client and server worked. In my case, my JTW bearer authentication worked well out of the box too.

Welcome to SignalR as a Service!

John Waters

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