Use Azure SignalR Local Emulator for serverless development

When developing serverless applications, we provide an Azure SignalR Local Emulator to make the local development and integration easier. The emulator works only for serverless scenarios, for Default mode that the Azure SignalR Service acts as a proxy, you can directly use self-host SignalR to do local development. Also note that emulator only works for Transient transport type (the default one) and doesn't support Persistent transport type.

Features available

• Auth
• Latest Rest API support
• Upstream

Walkthrough

We use this serverless sample to show how to use the emulator.

1. Clone the sample repo to local

   git clone https://github.com/Azure/azure-functions-signalrservice-extension.git
   cd azure-functions-signalrservice-extension/samples/bidirectional-chat
   

2. Install the emulator

   dotnet tool install  -g Microsoft.Azure.SignalR.Emulator
   

   Or update the emulator to the latest preview version if it's already installed:

   dotnet tool update -g Microsoft.Azure.SignalR.Emulator
   

3. Run the emulator asrs-emulator to list all the available commands

   

4. Init the default upstream settings using:

   asrs-emulator upstream init
   

   It creates a default settings.json into the current folder, with a default upstream UrlTemplate as http://localhost:7071/runtime/webhooks/signalr, which is the URL for SignalR's local function trigger:

   {
   "UpstreamSettings": {
       "Templates": [
       {
           "UrlTemplate": "http://localhost:7071/runtime/webhooks/signalr",
           "EventPattern": "*",
           "HubPattern": "*",
           "CategoryPattern": "*"
       }
       ]
   }
   }
   

   You could edit the file to make the pattern more restricted, for example, change HubPattern from * to chat. When the file is modified, its change is hot-loaded into the emulator.

5. Start the emulator

   asrs-emulator start
   

   After the emulator is successfully started, it generates the ConnectionString to be used later, for example, the ConnectionString is Endpoint=http://localhost;Port=8888;AccessKey=ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789ABCDEFGH;Version=1.0; as the below screenshot shows.

   

   The emulator also provides advanced options when start, for example, you can use asrs-emulator start -p 8999 to customize the port the emulator used. Type asrs-emulator start --help to check the options available.

6. Go into subfolder csharp and rename local.settings.sample.json to local.settings.json, use the ConnectionString generated by the emulator to fill into the value of the AzureSignalRConnectionString in your local.settings.json. Fill into AzureWebJobsStorage your storage connection string, for example, UseDevelopmentStorage=true when using storage emulator. Save the file and run the function in the csharp subfolder with func start.

   

7. In the browser, navigate to http://localhost:7071/api/index to play with the demo.

   

Next steps

In this article, you learn how to use SignalR Service in your applications. Check the following articles to learn more about SignalR Service.

Azure SignalR Service internals

Quickstart: Create a chat room by using SignalR Service