Azure Web PubSub trigger and bindings for Azure Functions

Article
01/12/2024

This reference explains how to handle Web PubSub events in Azure Functions.

Web PubSub is an Azure-managed service that helps developers easily build web applications with real-time features and publish-subscribe pattern.

Action	Type
Run a function when messages come from service	Trigger binding
Bind request to target object under Http trigger for negotiation and upstream requests	Input binding
Invoke service do actions	Output binding

Source code | Package | API reference documentation | Product documentation | Samples

Add to your Functions app

Working with the trigger and bindings requires you reference the appropriate package. The NuGet package is used for .NET class libraries while the extension bundle is used for all other application types.

Language	Add by...	Remarks
C#	Installing the NuGet package, version prerelease
C# Script, JavaScript, Python, PowerShell	Explicitly install extensions, Use extension bundles	The Azure Tools extension is recommended to use with Visual Studio Code.
C# Script (online-only in Azure portal)	Adding a binding	To update existing binding extensions without having to republish your function app, see Update your extensions.

Key concepts

Diagram showing the workflow of Azure Web PubSub service working with Function Apps.

(1)-(2) WebPubSubConnection input binding with HttpTrigger to generate client connection.

(3)-(4) WebPubSubTrigger trigger binding or WebPubSubContext input binding with HttpTrigger to handle service request.

(5)-(6) WebPubSub output binding to request service do something.

Trigger binding

Use the function trigger to handle requests from Azure Web PubSub service.

WebPubSubTrigger is used when you need to handle requests from service side. The trigger endpoint pattern would be like below which should be set in Web PubSub service side (Portal: settings -> event handler -> URL Template). In the endpoint pattern, the query part code=<API_KEY> is REQUIRED when you're using Azure Function App for security reasons. The key can be found in Azure portal. Find your function app resource and navigate to Functions -> App keys -> System keys -> webpubsub_extension after you deploy the function app to Azure. Though, this key isn't needed when you're working with local functions.

<Function_App_Url>/runtime/webhooks/webpubsub?code=<API_KEY>

Screenshot of get function system keys.

Example

[FunctionName("WebPubSubTrigger")]
public static void Run(
    [WebPubSubTrigger("<hub>", WebPubSubEventType.User, "message")] UserEventRequest request, ILogger log)
{
    log.LogInformation($"Request from: {request.ConnectionContext.UserId}");
    log.LogInformation($"Request message data: {request.Data}");
    log.LogInformation($"Request message dataType: {request.DataType}");
}

WebPubSubTrigger binding also supports return value in synchronize scenarios, for example, system Connect and user event, when server can check and deny the client request, or send messages to the caller directly. Connect event respects ConnectEventResponse and EventErrorResponse, and user event respects UserEventResponse and EventErrorResponse, rest types not matching current scenario is ignored. And if EventErrorResponse is returned, service drops the client connection.

[FunctionName("WebPubSubTriggerReturnValueFunction")]
public static UserEventResponse Run(
    [WebPubSubTrigger("hub", WebPubSubEventType.User, "message")] UserEventRequest request)
{
    return request.CreateResponse(BinaryData.FromString("ack"), WebPubSubDataType.Text);
}

The following example shows a Web PubSub trigger JavaScript function.

const { app, trigger } = require('@azure/functions');

const wpsTrigger = trigger.generic({
    type: 'webPubSubTrigger',
    name: 'request',
    hub: '<hub>',
    eventName: 'message',
    eventType: 'user'
});

app.generic('message', {
    trigger: wpsTrigger,
    handler: async (request, context) => {
        context.log('Request from: ', request.connectionContext.userId);
        context.log('Request message data: ', request.data);
        context.log('Request message dataType: ', request.dataType);
    }
});

WebPubSubTrigger binding also supports return value in synchronize scenarios, for example, system Connect and user event, when server can check and deny the client request, or send message to the request client directly. In JavaScript weakly typed language, it's deserialized regarding the object keys. And EventErrorResponse has the highest priority compare to rest objects, that if code is in the return, then it's parsed to EventErrorResponse and client connection is dropped.

app.generic('message', {
    trigger: wpsTrigger,
    handler: async (request, context) => {
          return { 
              "data": "ack",
              "dataType" : "text"
          };
    }
});

Define trigger binding in function.json.

{
  "disabled": false,
  "bindings": [
    {
      "type": "webPubSubTrigger",
      "direction": "in",
      "name": "data",
      "hub": "<hub>",
      "eventName": "message",
      "eventType": "user"
    }
  ]
}

Define function in index.js.

module.exports = function (context, data) {
  context.log('Request from: ', context.bindingData.request.connectionContext.userId);
  context.log('Request message data: ', data);
  context.log('Request message dataType: ', context.bindingData.request.dataType);
}

WebPubSubTrigger binding also supports return value in synchronize scenarios, for example, system Connect and user event, when server can check and deny the client request, or send message to the request client directly. In JavaScript weakly typed language, it's deserialized regarding the object keys. And EventErrorResponse has the highest priority compare to rest objects, that if code is in the return, then it's parsed to EventErrorResponse and client connection is dropped.

module.exports = async function (context) {
  return { 
    "data": "ack",
    "dataType" : "text"
  };
}

Attributes and annotations

In C# class libraries, use the WebPubSubTrigger attribute.

Here's an WebPubSubTrigger attribute in a method signature:

[FunctionName("WebPubSubTrigger")]
public static void Run([WebPubSubTrigger("<hub>", <WebPubSubEventType>, "<event-name>")] 
    WebPubSubConnectionContext context, ILogger log)
{
    ...
}

For a complete example, see C# example.

Configuration

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

function.json property	Attribute property	Description
type	n/a	Required - must be set to `webPubSubTrigger`.
direction	n/a	Required - must be set to `in`.
name	n/a	Required - the variable name used in function code for the parameter that receives the event data.
hub	Hub	Required - the value must be set to the name of the Web PubSub hub for the function to be triggered. We support set the value in attribute as higher priority, or it can be set in app settings as a global value.
eventType	WebPubSubEventType	Required - the value must be set as the event type of messages for the function to be triggered. The value should be either `user` or `system`.
eventName	EventName	Required - the value must be set as the event of messages for the function to be triggered. For `system` event type, the event name should be in `connect`, `connected`, `disconnected`. For user-defined subprotocols, the event name is `message`. For system supported subprotocol `json.webpubsub.azure.v1.`, the event name is user-defined event name.
connection	Connection	Optional - the name of an app settings or setting collection that specifies the upstream Azure Web PubSub service. The value is used for signature validation. And the value is auto resolved with app settings "WebPubSubConnectionString" by default. And `null` means the validation is not needed and always succeed.

Usages

In C#, WebPubSubEventRequest is type recognized binding parameter, rest parameters are bound by parameter name. Check table below of available parameters and types.

In weakly typed language like JavaScript, name in function.json is used to bind the trigger object regarding below mapping table. And respect dataType in function.json to convert message accordingly when name is set to data as the binding object for trigger input. All the parameters can be read from context.bindingData.<BindingName> and is JObject converted.

Binding Name	Binding Type	Description	Properties
request	`WebPubSubEventRequest`	Describes the upstream request	Property differs by different event types, including derived classes `ConnectEventRequest`, `ConnectedEventRequest`, `UserEventRequest` and `DisconnectedEventRequest`
connectionContext	`WebPubSubConnectionContext`	Common request information	EventType, EventName, Hub, ConnectionId, UserId, Headers, Origin, Signature, States
data	`BinaryData`,`string`,`Stream`,`byte[]`	Request message data from client in user `message` event	-
dataType	`WebPubSubDataType`	Request message dataType, which supports `binary`, `text`, `json`	-
claims	`IDictionary<string, string[]>`	User Claims in system `connect` request	-
query	`IDictionary<string, string[]>`	User query in system `connect` request	-
subprotocols	`IList<string>`	Available subprotocols in system `connect` request	-
clientCertificates	`IList<ClientCertificate>`	A list of certificate thumbprint from clients in system `connect` request	-
reason	`string`	Reason in system `disconnected` request	-

Important

In C#, multiple types supported parameter MUST be put in the first, i.e. request or data that other than the default BinaryData type to make the function binding correctly.

Return response

WebPubSubTrigger respects customer returned response for synchronous events of connect and user event. Only matched response is sent back to service, otherwise, it's ignored. Besides, WebPubSubTrigger return object supports users to SetState() and ClearStates() to manage the metadata for the connection. And the extension merges the results from return value with the original ones from request WebPubSubConnectionContext.States. Value in existing key is overwrite and value in new key is added.

Return Type	Description	Properties
`ConnectEventResponse`	Response for `connect` event	Groups, Roles, UserId, Subprotocol
`UserEventResponse`	Response for user event	DataType, Data
`EventErrorResponse`	Error response for the sync event	Code, ErrorMessage
`*WebPubSubEventResponse`	Base response type of the supported ones used for uncertain return cases	-

Input binding

Our extension provides two input binding targeting different needs.

WebPubSubConnection

To let a client connect to Azure Web PubSub Service, it must know the service endpoint URL and a valid access token. The WebPubSubConnection input binding produces required information, so client doesn't need to handle this token generation itself. Because the token is time-limited and can be used to authenticate a specific user to a connection, don't cache the token or share it between clients. An HTTP trigger working with this input binding can be used for clients to retrieve the connection information.
WebPubSubContext

When using is Static Web Apps, HttpTrigger is the only supported trigger and under Web PubSub scenario, we provide the WebPubSubContext input binding helps users deserialize upstream http request from service side under Web PubSub protocols. So customers can get similar results comparing to WebPubSubTrigger to easily handle in functions. See examples in below. When used with HttpTrigger, customer requires to configure the HttpTrigger exposed url in event handler accordingly.

Example - `WebPubSubConnection`

The following example shows a C# function that acquires Web PubSub connection information using the input binding and returns it over HTTP. In below example, the UserId is passed in through client request query part like ?userid={User-A}.

[FunctionName("WebPubSubConnectionInputBinding")]
public static WebPubSubConnection Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequest req,
    [WebPubSubConnection(Hub = "<hub>", UserId = "{query.userid}")] WebPubSubConnection connection)
{
    return connection;
}

const { app, input } = require('@azure/functions');

const connection = input.generic({
    type: 'webPubSubConnection',
    name: 'connection',
    userId: '{query.userId}',
    hub: '<hub>'
});

app.http('negotiate', {
    methods: ['GET', 'POST'],
    authLevel: 'anonymous',
    extraInputs: [connection],
    handler: async (request, context) => {
        return { body: JSON.stringify(context.extraInputs.get('connection')) };
    },
});

Define input bindings in function.json.

{
  "disabled": false,
  "bindings": [
    {
      "authLevel": "anonymous",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req"
    },
    {
      "type": "http",
      "direction": "out",
      "name": "res"
    },
    {
      "type": "webPubSubConnection",
      "name": "connection",
      "userId": "{query.userid}",
      "hub": "<hub>",
      "direction": "in"
    }
  ]
}

Define function in index.js.

module.exports = function (context, req, connection) {
  context.res = { body: connection };
  context.done();
};

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("WebPubSubConnectionInputBinding")]
public static WebPubSubConnection Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequest req,
    [WebPubSubConnection(Hub = "<hub>", UserId = "{headers.x-ms-client-principal-name}")] WebPubSubConnection connection)
{
    return connection;
}

Note

Limited to the binding parameter types don't support a way to pass list nor array, the WebPubSubConnection is not fully supported with all the parameters server SDK has, especially roles, and also includes groups and expiresAfter. In the case customer needs to add roles or delay build the access token in the function, it's suggested to work with server SDK for C#.

[FunctionName("WebPubSubConnectionCustomRoles")]
public static async Task<Uri> Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequest req)
{
    var serviceClient = new WebPubSubServiceClient(new Uri(endpoint), "<hub>", "<web-pubsub-connection-string>");
    var userId = req.Query["userid"].FirstOrDefault();
    // your method to get custom roles.
    var roles = GetRoles(userId);
    return await serviceClient.GetClientAccessUriAsync(TimeSpan.FromMinutes(5), userId, roles);
}

Note

const { app } = require('@azure/functions');
const { WebPubSubServiceClient } = require('@azure/web-pubsub');
app.http('negotiate', {
    methods: ['GET', 'POST'],
    authLevel: 'anonymous',
    handler: async (request, context) => {
        const serviceClient = new WebPubSubServiceClient(process.env.WebPubSubConnectionString, "<hub>");
        let token = await serviceClient.getAuthenticationToken({ userId: req.query.userid, roles: ["webpubsub.joinLeaveGroup", "webpubsub.sendToGroup"] });
        return { body: token.url };
    },
});

Note

Define input bindings in function.json.

{
  "disabled": false,
  "bindings": [
    {
      "authLevel": "anonymous",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req"
    },
    {
      "type": "http",
      "direction": "out",
      "name": "res"
    }
  ]
}

Define function in index.js.

const { WebPubSubServiceClient } = require('@azure/web-pubsub');

module.exports = async function (context, req) {
  const serviceClient = new WebPubSubServiceClient(process.env.WebPubSubConnectionString, "<hub>");
  let token = await serviceClient.getAuthenticationToken({ userId: req.query.userid, roles: ["webpubsub.joinLeaveGroup", "webpubsub.sendToGroup"] });
  context.res = { body: token.url };
  context.done();
};

Example - `WebPubSubContext`

The following example shows a C# function that acquires Web PubSub upstream request information using the input binding under connect event type and returns it over HTTP.

[FunctionName("WebPubSubContextInputBinding")]
public static object Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequest req,
    [WebPubSubContext] WebPubSubContext wpsContext)
{
    // in the case request is a preflight or invalid, directly return prebuild response by extension.
    if (wpsContext.IsPreflight || wpsContext.HasError)
    {
        return wpsContext.Response;
    }
    var request = wpsContext.Request as ConnectEventRequest;
    var response = new ConnectEventResponse
    {
        UserId = wpsContext.Request.ConnectionContext.UserId
    };
    return response;
}

const { app, input } = require('@azure/functions');

const wpsContext = input.generic({
    type: 'webPubSubContext',
    name: 'wpsContext'
});

app.http('connect', {
    methods: ['GET', 'POST'],
    authLevel: 'anonymous',
    extraInputs: [wpsContext],
    handler: async (request, context) => {
        var wpsRequest = context.extraInputs.get('wpsContext');

        return { "userId": wpsRequest.request.connectionContext.userId };
    }
});

Define input bindings in function.json.

{
  "disabled": false,
  "bindings": [
    {
      "authLevel": "anonymous",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": ["get", "post"]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "$return"
    },
    {
      "type": "webPubSubContext",
      "name": "wpsContext",
      "direction": "in"
    }
  ]
}

Define function in index.js.

module.exports = async function (context, req, wpsContext) {
  // in the case request is a preflight or invalid, directly return prebuild response by extension.
  if (wpsContext.hasError || wpsContext.isPreflight)
  {
    return wpsContext.response;
  }
  // return an http response with connect event response as body.
  return { body: {"userId": wpsContext.connectionContext.userId} };
};

Configuration

WebPubSubConnection

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

function.json property	Attribute property	Description
type	n/a	Must be set to `webPubSubConnection`
direction	n/a	Must be set to `in`
name	n/a	Variable name used in function code for input connection binding object.
hub	Hub	Required - The value must be set to the name of the Web PubSub hub for the function to be triggered. We support set the value in attribute as higher priority, or it can be set in app settings as a global value.
userId	UserId	Optional - the value of the user identifier claim to be set in the access key token.
connection	Connection	Required - The name of the app setting that contains the Web PubSub Service connection string (defaults to "WebPubSubConnectionString").

WebPubSubContext

The following table explains the binding configuration properties that you set in the functions.json file and the WebPubSubContext attribute.

function.json property	Attribute property	Description
type	n/a	Must be set to `webPubSubContext`.
direction	n/a	Must be set to `in`.
name	n/a	Variable name used in function code for input Web PubSub request.
connection	Connection	Optional - the name of an app settings or setting collection that specifies the upstream Azure Web PubSub service. The value is used for Abuse Protection and Signature validation. The value is auto resolved with "WebPubSubConnectionString" by default. And `null` means the validation is not needed and always succeed.

Usage

WebPubSubConnection

WebPubSubConnection provides below properties.

Binding Name	Binding Type	Description
BaseUri	Uri	Web PubSub client connection uri.
Uri	Uri	Absolute Uri of the Web PubSub connection, contains `AccessToken` generated base on the request.
AccessToken	string	Generated `AccessToken` based on request UserId and service information.

WebPubSubConnection provides below properties.

Binding Name	Description
baseUrl	Web PubSub client connection uri.
url	Absolute Uri of the Web PubSub connection, contains `AccessToken` generated base on the request.
accessToken	Generated `AccessToken` based on request UserId and service information.

WebPubSubConnection provides below properties.

Binding Name	Description
baseUrl	Web PubSub client connection uri.
url	Absolute Uri of the Web PubSub connection, contains `AccessToken` generated base on the request.
accessToken	Generated `AccessToken` based on request UserId and service information.

WebPubSubContext

WebPubSubContext provides below properties.

Binding Name	Binding Type	Description	Properties
request	`WebPubSubEventRequest`	Request from client, see below table for details.	`WebPubSubConnectionContext` from request header and other properties deserialized from request body describe the request, for example, `Reason` for `DisconnectedEventRequest`.
response	`HttpResponseMessage`	Extension builds response mainly for `AbuseProtection` and errors cases.	-
errorMessage	string	Describe the error details when processing the upstream request.	-
hasError	bool	Flag to indicate whether it's a valid Web PubSub upstream request.	-
isPreflight	bool	Flag to indicate whether it's a preflight request of `AbuseProtection`.	-

For WebPubSubEventRequest, it's deserialized to different classes that provide different information about the request scenario. For PreflightRequest or not valid cases, user can check the flags IsPreflight and HasError to know. It's suggested to return system build response WebPubSubContext.Response directly, or customer can log errors on demand. In different scenarios, customer can read the request properties as below.

Derived Class	Description	Properties
`PreflightRequest`	Used in `AbuseProtection` when `IsPreflight` is true	-
`ConnectEventRequest`	Used in system `Connect` event type	Claims, Query, Subprotocols, ClientCertificates
`ConnectedEventRequest`	Used in system `Connected` event type	-
`UserEventRequest`	Used in user event type	Data, DataType
`DisconnectedEventRequest`	Used in system `Disconnected` event type	Reason

Note

Though the WebPubSubContext is a input binding provides similar request deserialize way under HttpTrigger comparing to WebPubSubTrigger, there's limitations, i.e. connection state post merge is not supported. The return response is still respected by the service side, but users require to build the response themselves. If users have needs to set the event response, you should return a HttpResponseMessage contains ConnectEventResponse or messages for user event as response body and put connection state with key ce-connectionstate in response header.

Output binding

Use the Web PubSub output binding to invoke Azure Web PubSub service to do something. You can broadcast a message to:

All connected clients
Connected clients authenticated to a specific user
Connected clients joined in a specific group
A specific client connection

The output binding also allows you to manage clients and groups, as well as grant/revoke permissions targeting specific connectionId with group.

Add connection to group
Add user to group
Remove connection from a group
Remove user from a group
Remove user from all groups
Close all client connections
Close a specific client connection
Close connections in a group
Grant permission of a connection
Revoke permission of a connection

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

Example

[FunctionName("WebPubSubOutputBinding")]
public static async Task RunAsync(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequest req,
    [WebPubSub(Hub = "<hub>")] IAsyncCollector<WebPubSubAction> actions)
{
    await actions.AddAsync(WebPubSubAction.CreateSendToAllAction("Hello Web PubSub!", WebPubSubDataType.Text));
}

const { app, output } = require('@azure/functions');
const wpsMsg = output.generic({
    type: 'webPubSub',
    name: 'actions',
    hub: '<hub>',
});

app.http('message', {
    methods: ['GET', 'POST'],
    authLevel: 'anonymous',
    extraOutputs: [wpsMsg],
    handler: async (request, context) => {
        context.extraOutputs.set(wpsMsg, [{
            "actionName": "sendToAll",
            "data": `Hello world`,
            "dataType": `text`
        }]);
    }
});

Define bindings in functions.json.

{
  "disabled": false,
  "bindings": [
    {
      "type": "webPubSub",
      "name": "actions",
      "hub": "<hub>",
      "direction": "out"
    }
  ]
}

Define function in index.js.

module.exports = async function (context) {
  context.bindings.actions = {
    "actionName": "sendToAll",
    "data": "hello",
    "dataType": "text"
  };
  context.done();
}

WebPubSubAction

WebPubSubAction is the base abstract type of output bindings. The derived types represent the action server want service to invoke.

In C# language, we provide a few static methods under WebPubSubAction to help discover available actions. For example, user can create the SendToAllAction by call WebPubSubAction.CreateSendToAllAction().

Derived Class	Properties
`SendToAllAction`	Data, DataType, Excluded
`SendToGroupAction`	Group, Data, DataType, Excluded
`SendToUserAction`	UserId, Data, DataType
`SendToConnectionAction`	ConnectionId, Data, DataType
`AddUserToGroupAction`	UserId, Group
`RemoveUserFromGroupAction`	UserId, Group
`RemoveUserFromAllGroupsAction`	UserId
`AddConnectionToGroupAction`	ConnectionId, Group
`RemoveConnectionFromGroupAction`	ConnectionId, Group
`CloseAllConnectionsAction`	Excluded, Reason
`CloseClientConnectionAction`	ConnectionId, Reason
`CloseGroupConnectionsAction`	Group, Excluded, Reason
`GrantPermissionAction`	ConnectionId, Permission, TargetName
`RevokePermissionAction`	ConnectionId, Permission, TargetName

In weakly typed language like javascript, actionName is the key parameter to resolve the type, available actions are listed as below.

ActionName	Properties
`sendToAll`	Data, DataType, Excluded
`sendToGroup`	Group, Data, DataType, Excluded
`sendToUser`	UserId, Data, DataType
`sendToConnection`	ConnectionId, Data, DataType
`addUserToGroup`	UserId, Group
`removeUserFromGroup`	UserId, Group
`removeUserFromAllGroups`	UserId
`addConnectionToGroup`	ConnectionId, Group
`removeConnectionFromGroup`	ConnectionId, Group
`closeAllConnections`	Excluded, Reason
`closeClientConnection`	ConnectionId, Reason
`closeGroupConnections`	Group, Excluded, Reason
`grantPermission`	ConnectionId, Permission, TargetName
`revokePermission`	ConnectionId, Permission, TargetName

Important

The message data property in the send message related actions must be string if data type is set to json or text to avoid data conversion ambiguity. Please use JSON.stringify() to convert the json object in need. This is applied to any place using message property, for example, UserEventResponse.Data working with WebPubSubTrigger.

When data type is set to binary, it's allowed to leverage binding naturally supported dataType as binary configured in the function.json, see Trigger and binding definitions for details.

In weakly typed language like javascript, actionName is the key parameter to resolve the type, available actions are listed as below.

ActionName	Properties
`sendToAll`	Data, DataType, Excluded
`sendToGroup`	Group, Data, DataType, Excluded
`sendToUser`	UserId, Data, DataType
`sendToConnection`	ConnectionId, Data, DataType
`addUserToGroup`	UserId, Group
`removeUserFromGroup`	UserId, Group
`removeUserFromAllGroups`	UserId
`addConnectionToGroup`	ConnectionId, Group
`removeConnectionFromGroup`	ConnectionId, Group
`closeAllConnections`	Excluded, Reason
`closeClientConnection`	ConnectionId, Reason
`closeGroupConnections`	Group, Excluded, Reason
`grantPermission`	ConnectionId, Permission, TargetName
`revokePermission`	ConnectionId, Permission, TargetName

Important

When data type is set to binary, it's allowed to leverage binding naturally supported dataType as binary configured in the function.json, see Trigger and binding definitions for details.

Configuration

WebPubSub

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

function.json property	Attribute property	Description
type	n/a	Must be set to `webPubSub`
direction	n/a	Must be set to `out`
name	n/a	Variable name used in function code for output binding object.
hub	Hub	The value must be set to the name of the Web PubSub hub for the function to be triggered. We support set the value in attribute as higher priority, or it can be set in app settings as a global value.
connection	Connection	The name of the app setting that contains the Web PubSub Service connection string (defaults to "WebPubSubConnectionString").

Troubleshooting

Setting up console logging

You can also easily enable console logging if you want to dig deeper into the requests you're making against the service.

Next steps

Use these resources to start building your own application:

Tutorial: Publish and subscribe to messages in Azure Web PubSub

Tutorial: Create a simple chatroom with Azure Web PubSub

Tutorial: Use a service-supported subprotocol for client streaming

Tutorial: Build serverless chat with Azure Functions and Web PubSub

Tutorial: Configure an event listener

Play with live demos

Explore more Azure Web PubSub samples

Share via

Azure Web PubSub trigger and bindings for Azure Functions

Add to your Functions app

Key concepts

Trigger binding

Example

Attributes and annotations

Configuration

Usages

Return response

Input binding

Example - `WebPubSubConnection`

Authenticated tokens

Example - `WebPubSubContext`

Configuration

WebPubSubConnection

WebPubSubContext

Usage

WebPubSubConnection

WebPubSubContext

Output binding

Example

WebPubSubAction

Configuration

WebPubSub

Troubleshooting

Setting up console logging

Next steps

Feedback

Feedback

Additional resources

Share via

Azure Web PubSub trigger and bindings for Azure Functions

Add to your Functions app

Key concepts

Trigger binding

Example

Attributes and annotations

Configuration

Usages

Return response

Input binding

Example - WebPubSubConnection

Authenticated tokens

Example - WebPubSubContext

Configuration

WebPubSubConnection

WebPubSubContext

Usage

WebPubSubConnection

WebPubSubContext

Output binding

Example

WebPubSubAction

Configuration

WebPubSub

Troubleshooting

Setting up console logging

Next steps

Feedback

Feedback

Additional resources

Example - `WebPubSubConnection`

Example - `WebPubSubContext`