SignalR Service input binding for Azure Functions

02/20/2020
4 minutes to read

Before a client can connect to Azure SignalR Service, it must retrieve the service endpoint URL and a valid access token. The SignalRConnectionInfo input binding produces the SignalR Service endpoint URL and a valid token that are used to connect to the service. Because the token is time-limited and can be used to authenticate a specific user to a connection, you should not cache the token or share it between clients. An HTTP trigger using this binding can be used by clients to retrieve the connection information.

For more information on how this binding is used to create a "negotiate" function that can be consumed by a SignalR client SDK, see the Azure Functions development and configuration article in the SignalR Service concepts documentation.

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

Example

The following example shows a C# function that acquires SignalR connection information using the input binding and returns it over HTTP.

[FunctionName("negotiate")]
public static SignalRConnectionInfo Negotiate(
    [HttpTrigger(AuthorizationLevel.Anonymous)]HttpRequest req,
    [SignalRConnectionInfo(HubName = "chat")]SignalRConnectionInfo connectionInfo)
{
    return connectionInfo;
}

The following example shows a SignalR connection info input binding in a function.json file and a C# Script function that uses the binding to return the connection information.

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

Example function.json:

{
    "type": "signalRConnectionInfo",
    "name": "connectionInfo",
    "hubName": "chat",
    "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
    "direction": "in"
}

Here's the C# Script code:

#r "Microsoft.Azure.WebJobs.Extensions.SignalRService"
using Microsoft.Azure.WebJobs.Extensions.SignalRService;

public static SignalRConnectionInfo Run(HttpRequest req, SignalRConnectionInfo connectionInfo)
{
    return connectionInfo;
}

The following example shows a SignalR connection info input binding in a function.json file and a JavaScript function that uses the binding to return the connection information.

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

Example function.json:

{
    "type": "signalRConnectionInfo",
    "name": "connectionInfo",
    "hubName": "chat",
    "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
    "direction": "in"
}

Here's the JavaScript code:

module.exports = async function (context, req, connectionInfo) {
    context.res.body = connectionInfo;
};

The following example shows a SignalR connection info input binding in a function.json file and a Python function that uses the binding to return the connection information.

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

Example function.json:

{
    "type": "signalRConnectionInfo",
    "name": "connectionInfo",
    "hubName": "chat",
    "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
    "direction": "in"
}

Here's the Python code:

def main(req: func.HttpRequest, connectionInfoJson: str) -> func.HttpResponse:
    return func.HttpResponse(
        connectionInfoJson,
        status_code=200,
        headers={
            'Content-type': 'application/json'
        }
    )

The following example shows a Java function that acquires SignalR connection information using the input binding and returns it over HTTP.

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

Authenticated tokens

If the function is triggered by an authenticated client, you can add a user ID claim to the generated token. You can easily add authentication to a function app using App Service Authentication.

App Service Authentication sets HTTP headers named x-ms-client-principal-id and x-ms-client-principal-name that contain the authenticated user's client principal ID and name, respectively.

You can set the UserId property of the binding to the value from either header using a binding expression: {headers.x-ms-client-principal-id} or {headers.x-ms-client-principal-name}.

[FunctionName("negotiate")]
public static SignalRConnectionInfo Negotiate(
    [HttpTrigger(AuthorizationLevel.Anonymous)]HttpRequest req, 
    [SignalRConnectionInfo
        (HubName = "chat", UserId = "{headers.x-ms-client-principal-id}")]
        SignalRConnectionInfo connectionInfo)
{
    // connectionInfo contains an access key token with a name identifier claim set to the authenticated user
    return connectionInfo;
}

You can set the userId property of the binding to the value from either header using a binding expression: {headers.x-ms-client-principal-id} or {headers.x-ms-client-principal-name}.

Example function.json:

{
    "type": "signalRConnectionInfo",
    "name": "connectionInfo",
    "hubName": "chat",
    "userId": "{headers.x-ms-client-principal-id}",
    "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
    "direction": "in"
}

Here's the C# Script code:

#r "Microsoft.Azure.WebJobs.Extensions.SignalRService"
using Microsoft.Azure.WebJobs.Extensions.SignalRService;

public static SignalRConnectionInfo Run(HttpRequest req, SignalRConnectionInfo connectionInfo)
{
    // connectionInfo contains an access key token with a name identifier
    // claim set to the authenticated user
    return connectionInfo;
}

You can set the userId property of the binding to the value from either header using a binding expression: {headers.x-ms-client-principal-id} or {headers.x-ms-client-principal-name}.

Example function.json:

{
    "type": "signalRConnectionInfo",
    "name": "connectionInfo",
    "hubName": "chat",
    "userId": "{headers.x-ms-client-principal-id}",
    "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
    "direction": "in"
}

Here's the JavaScript code:

module.exports = async function (context, req, connectionInfo) {
    // connectionInfo contains an access key token with a name identifier
    // claim set to the authenticated user
    context.res.body = connectionInfo;
};

You can set the userId property of the binding to the value from either header using a binding expression: {headers.x-ms-client-principal-id} or {headers.x-ms-client-principal-name}.

Example function.json:

{
    "type": "signalRConnectionInfo",
    "name": "connectionInfo",
    "hubName": "chat",
    "userId": "{headers.x-ms-client-principal-id}",
    "connectionStringSetting": "<name of setting containing SignalR Service connection string>",
    "direction": "in"
}

Here's the Python code:

def main(req: func.HttpRequest, connectionInfo: str) -> func.HttpResponse:
    # connectionInfo contains an access key token with a name identifier
    # claim set to the authenticated user
    return func.HttpResponse(
        connectionInfo,
        status_code=200,
        headers={
            'Content-type': 'application/json'
        }
    )

You can set the userId property of the binding to the value from either header using a binding expression: {headers.x-ms-client-principal-id} or {headers.x-ms-client-principal-name}.

@FunctionName("negotiate")
public SignalRConnectionInfo negotiate(
        @HttpTrigger(
            name = "req",
            methods = { HttpMethod.POST },
            authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Optional<String>> req,
        @SignalRConnectionInfoInput(
            name = "connectionInfo",
            hubName = "chat",
            userId = "{headers.x-ms-client-principal-id}") SignalRConnectionInfo connectionInfo) {
    return connectionInfo;
}

SignalR Service input binding for Azure Functions

Example

Authenticated tokens

Next steps

Is this page helpful?

Feedback

Is this page helpful?