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SignalR Service output binding for Azure Functions

Use the SignalR output binding to send one or more messages using Azure SignalR Service. You can broadcast a message to:

  • All connected clients
  • Connected clients in a specified group
  • Connected clients authenticated to a specific user

The output binding also allows you to manage groups, such as adding a client or user to a group, removing a client or user from a group.

For information on setup and configuration details, see the overview.

Example

Broadcast to all clients

A C# function can be created by using one of the following C# modes:

  • Isolated worker model: Compiled C# function that runs in a worker process that's isolated from the runtime. Isolated worker process is required to support C# functions running on LTS and non-LTS versions .NET and the .NET Framework.
  • In-process model: Compiled C# function that runs in the same process as the Functions runtime.
  • C# script: Used primarily when you create C# functions in the Azure portal.

The following example shows a function that sends a message using the output binding to all connected clients. The newMessage is the name of the method to be invoked on each client.

[Function(nameof(BroadcastToAll))]
[SignalROutput(HubName = "chat", ConnectionStringSetting = "SignalRConnection")]
public static SignalRMessageAction BroadcastToAll([HttpTrigger(AuthorizationLevel.Anonymous, "post")] HttpRequestData req)
{
    using var bodyReader = new StreamReader(req.Body);
    return new SignalRMessageAction("newMessage")
    {
        // broadcast to all the connected clients without specifying any connection, user or group.
        Arguments = new[] { bodyReader.ReadToEnd() },
    };
}

Here's binding data in the function.json file:

Example function.json:

{
  "type": "signalR",
  "name": "signalROutput",
  "hubName": "hubName1",
  "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
  "direction": "out"
}
const { app, output } = require('@azure/functions');

const signalR = output.generic({
    type: 'signalR',
    name: 'signalR',
    hubName: 'hub',
    connectionStringSetting: 'AzureSignalRConnectionString',
});

// You can use any other trigger type instead.
app.http('broadcast', {
    methods: ['GET'],
    authLevel: 'anonymous',
    extraOutputs: [signalR],
    handler: (request, context) => {
        context.extraOutputs.set(signalR, {
            "target": "newMessage",
            "arguments": [request.body]
        });
    }
});

Complete PowerShell examples are pending.

Here's the Python code:

def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
    message = req.get_json()
    signalROutput.set(json.dumps({
        'target': 'newMessage',
        'arguments': [ message ]
    }))
@FunctionName("sendMessage")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRMessage sendMessage(
        @HttpTrigger(
            name = "req",
            methods = { HttpMethod.POST },
            authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req) {

    SignalRMessage message = new SignalRMessage();
    message.target = "newMessage";
    message.arguments.add(req.getBody());
    return message;
}

Send to a user

You can send a message only to connections that have been authenticated to a user by setting the user ID in the SignalR message.

[Function(nameof(SendToUser))]
[SignalROutput(HubName = "chat", ConnectionStringSetting = "SignalRConnection")]
public static SignalRMessageAction SendToUser([HttpTrigger(AuthorizationLevel.Anonymous, "post")] HttpRequestData req)
{
    using var bodyReader = new StreamReader(req.Body);
    return new SignalRMessageAction("newMessage")
    {
        Arguments = new[] { bodyReader.ReadToEnd() },
        UserId = "userToSend",
    };
}

Here's binding data in the function.json file:

Example function.json:

{
  "type": "signalR",
  "name": "signalROutput",
  "hubName": "hubName1",
  "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
  "direction": "out"
}

Complete PowerShell examples are pending.

Here's the Python code:

def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
    message = req.get_json()
    signalROutput.set(json.dumps({
        #message will only be sent to this user ID
        'userId': 'userId1',
        'target': 'newMessage',
        'arguments': [ message ]
    }))
@FunctionName("sendMessage")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRMessage sendMessage(
        @HttpTrigger(
            name = "req",
            methods = { HttpMethod.POST },
            authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req) {

    SignalRMessage message = new SignalRMessage();
    message.userId = "userId1";
    message.target = "newMessage";
    message.arguments.add(req.getBody());
    return message;
}
const { app, output } = require('@azure/functions');

const signalR = output.generic({
    type: 'signalR',
    name: 'signalR',
    hubName: 'hub',
    connectionStringSetting: 'AzureSignalRConnectionString',
});

app.http('sendToUser', {
    methods: ['GET'],
    authLevel: 'anonymous',
    extraOutputs: [signalR],
    handler: (request, context) => {
        context.extraOutputs.set(signalR, {
            "target": "newMessage",
            "arguments": [request.body],
            "userId": "userId1",
        });
    }
});

Send to a group

You can send a message only to connections that have been added to a group by setting the group name in the SignalR message.

[Function(nameof(SendToGroup))]
[SignalROutput(HubName = "chat", ConnectionStringSetting = "SignalRConnection")]
public static SignalRMessageAction SendToGroup([HttpTrigger(AuthorizationLevel.Anonymous, "post")] HttpRequestData req)
{
    using var bodyReader = new StreamReader(req.Body);
    return new SignalRMessageAction("newMessage")
    {
        Arguments = new[] { bodyReader.ReadToEnd() },
        GroupName = "groupToSend"
    };
}

Here's binding data in the function.json file:

Example function.json:

{
  "type": "signalR",
  "name": "signalROutput",
  "hubName": "hubName1",
  "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
  "direction": "out"
}
const { app, output } = require('@azure/functions');

const signalR = output.generic({
    type: 'signalR',
    name: 'signalR',
    hubName: 'hub',
    connectionStringSetting: 'AzureSignalRConnectionString',
});

app.http('sendToGroup', {
    methods: ['GET'],
    authLevel: 'anonymous',
    extraOutputs: [signalR],
    handler: (request, context) => {
        context.extraOutputs.set(signalR, {
            "target": "newMessage",
            "arguments": [request.body],
            "groupName": "myGroup",
        });
    }
});

Complete PowerShell examples are pending.

Here's the Python code:

def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
    message = req.get_json()
    signalROutput.set(json.dumps({
        #message will only be sent to this group
        'groupName': 'myGroup',
        'target': 'newMessage',
        'arguments': [ message ]
    }))
@FunctionName("sendMessage")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRMessage sendMessage(
        @HttpTrigger(
            name = "req",
            methods = { HttpMethod.POST },
            authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req) {

    SignalRMessage message = new SignalRMessage();
    message.groupName = "myGroup";
    message.target = "newMessage";
    message.arguments.add(req.getBody());
    return message;
}

Group management

SignalR Service allows users or connections to be added to groups. Messages can then be sent to a group. You can use the SignalR output binding to manage groups.

Specify SignalRGroupActionType to add or remove a member. The following example removes a user from a group.

[Function(nameof(RemoveFromGroup))]
[SignalROutput(HubName = "chat", ConnectionStringSetting = "SignalRConnection")]
public static SignalRGroupAction RemoveFromGroup([HttpTrigger(AuthorizationLevel.Anonymous, "post")] HttpRequestData req)
{
    return new SignalRGroupAction(SignalRGroupActionType.Remove)
    {
        GroupName = "group1",
        UserId = "user1"
    };
}

Note

In order to get the ClaimsPrincipal correctly bound, you must have configured the authentication settings in Azure Functions.

Here's binding data in the function.json file:

Example function.json:

{
  "type": "signalR",
  "name": "signalROutput",
  "hubName": "hubName1",
  "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
  "direction": "out"
}
const { app, output } = require('@azure/functions');

const signalR = output.generic({
    type: 'signalR',
    name: 'signalR',
    hubName: 'hub',
    connectionStringSetting: 'AzureSignalRConnectionString',
});

// The following function adds a user to a group
app.http('addUserToGroup', {
    methods: ['POST'],
    authLevel: 'anonymous',
    extraOutputs: [signalR],
    handler: (request, context) => {
        context.extraOutputs.set(signalR, {
            "userId": req.query.userId,
            "groupName": "myGroup",
            "action": "add"
        });
    }
});

// The following function removes a user from a group
app.http('removeUserFromGroup', {
    methods: ['POST'],
    authLevel: 'anonymous',
    extraOutputs: [signalR],
    handler: (request, context) => {
        context.extraOutputs.set(signalR, {
            "userId": req.query.userId,
            "groupName": "myGroup",
            "action": "remove"
        });
    }
});

Complete PowerShell examples are pending.

The following example adds a user to a group.

def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
    signalROutput.set(json.dumps({
        'userId': 'userId1',
        'groupName': 'myGroup',
        'action': 'add'
    }))

The following example removes a user from a group.

def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
    signalROutput.set(json.dumps({
        'userId': 'userId1',
        'groupName': 'myGroup',
        'action': 'remove'
    }))

The following example adds a user to a group.

@FunctionName("addToGroup")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRGroupAction addToGroup(
        @HttpTrigger(
            name = "req",
            methods = { HttpMethod.POST },
            authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req,
        @BindingName("userId") String userId) {

    SignalRGroupAction groupAction = new SignalRGroupAction();
    groupAction.action = "add";
    groupAction.userId = userId;
    groupAction.groupName = "myGroup";
    return action;
}

The following example removes a user from a group.

@FunctionName("removeFromGroup")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRGroupAction removeFromGroup(
        @HttpTrigger(
            name = "req",
            methods = { HttpMethod.POST },
            authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req,
        @BindingName("userId") String userId) {

    SignalRGroupAction groupAction = new SignalRGroupAction();
    groupAction.action = "remove";
    groupAction.userId = userId;
    groupAction.groupName = "myGroup";
    return action;
}

Attributes

Both in-process and isolated worker process C# libraries use attribute to define the function. C# script instead uses a function.json configuration file.

The following table explains the properties of the SignalROutput attribute.

Attribute property Description
HubName This value must be set to the name of the SignalR hub for which the connection information is generated.
ConnectionStringSetting The name of the app setting that contains the SignalR Service connection string, which defaults to AzureSignalRConnectionString.

Annotations

The following table explains the supported settings for the SignalROutput annotation.

Setting Description
name Variable name used in function code for connection info object.
hubName This value must be set to the name of the SignalR hub for which the connection information is generated.
connectionStringSetting The name of the app setting that contains the SignalR Service connection string, which defaults to AzureSignalRConnectionString.

Configuration

The following table explains the binding configuration properties that you set in the function.json file.

function.json property Description
type Must be set to signalR.
direction Must be set to out.
name Variable name used in function code for connection info object.
hubName This value must be set to the name of the SignalR hub for which the connection information is generated.
connectionStringSetting The name of the app setting that contains the SignalR Service connection string, which defaults to AzureSignalRConnectionString.

When you're developing locally, add your application settings in the local.settings.json file in the Values collection.

Next steps