SignalR Service Integration¶

This recipe covers adding real-time messaging to Azure Functions Java with Azure SignalR Service in serverless mode. It uses the @SignalRConnectionInfoInput annotation to implement the required negotiate endpoint and the @SignalROutput annotation to broadcast messages to connected clients.

Architecture¶

flowchart TD
    CLIENT[Browser Client] --> NEG[negotiate Function]
    NEG --> INFO[SignalRConnectionInfo Input]
    INFO --> SR[(Azure SignalR Service)]
    CLIENT -->|WebSocket| SR
    PUB[broadcast Function] --> OUT[SignalR Output]
    OUT --> SR
    SR -->|push| CLIENT

Prerequisites¶

To use the SignalR Service annotations in Java functions, add the SignalR library dependency to your pom.xml:

<dependency>
    <groupId>com.microsoft.azure.functions</groupId>
    <artifactId>azure-functions-java-library-signalr</artifactId>
    <version>1.0.0</version>
</dependency>

Configure the connection in app settings. A connection string (stored as AzureSignalRConnectionString) or an identity-based connection is supported:

az functionapp config appsettings set \
  --name $APP_NAME \
  --resource-group $RG \
  --settings "AzureSignalRConnectionString__serviceUri=https://$SIGNALR_NAME.service.signalr.net"

The SignalR Service instance must be in Serverless mode. When using an identity-based connection, grant the function app's managed identity the SignalR Service Owner role on the resource.

The negotiate Endpoint¶

Before a client connects, it calls a negotiate endpoint to obtain the service URL and a short-lived access token. The @SignalRConnectionInfoInput binding produces this payload.

@FunctionName("negotiate")
public SignalRConnectionInfo negotiate(
        @HttpTrigger(
            name = "req",
            methods = { HttpMethod.POST },
            authLevel = AuthorizationLevel.ANONYMOUS)
            HttpRequestMessage<Optional<String>> req,
        @SignalRConnectionInfoInput(
            name = "connectionInfo",
            hubName = "serverless") SignalRConnectionInfo connectionInfo) {
    return connectionInfo;
}

Output Binding: Broadcast a Message¶

The @SignalROutput annotation sends a message to all connected clients. The SignalRMessage object specifies a target (the client-side handler name) and arguments.

@FunctionName("broadcast")
@SignalROutput(name = "$return", hubName = "serverless")
public SignalRMessage broadcast(
        @HttpTrigger(
            name = "req",
            methods = { HttpMethod.POST },
            authLevel = AuthorizationLevel.FUNCTION)
            HttpRequestMessage<Optional<String>> req) {
    SignalRMessage message = new SignalRMessage();
    message.target = "newMessage";
    message.arguments.add(req.getBody().orElse(""));
    return message;
}

Sending to a Specific User or Group¶

Set userId or groupName on the SignalRMessage to target a subset of clients instead of broadcasting:

message.userId = "user1";
message.target = "newMessage";

See Also¶

• HTTP Authentication
• Managed Identity

Sources¶

• Azure Functions SignalR Service bindings (Microsoft Learn)
• SignalR Service input binding (Microsoft Learn)
• SignalR Service output binding (Microsoft Learn)