What is Azure Web PubSub service?

Article
07/26/2024

Azure Web PubSub Service makes it easy to build web applications where server and clients need to exchange data in real-time. Real-time data exchange is the bedrock of certain time-sensitive apps developers build and maintain. Developers have used the service in a variety of applications and industries, for exmaple, in chat apps, real-time dashboards, multi-player games, online auctions, multi-user collaborative apps, location tracking, notifications, and more.

With the recent surge in interest in AI, Web PubSub has become an invaluable tool to developers building AI-enabled applications for token streaming. The service is battle-tested to scale to tens of millions of concurrent connections and offers ultra-low latency.

When an app's usage is small, developers typically opt for a polling mechanism to provide real-time communication between server and clients - clients send repeated HTTP requests to server over a time interval. However, developers often report that while polling mechanism is straightforward to implement, it suffers three important drawbacks.

Outdated data.
Inconsistent data.
Wasted bandwidth and compute resources.

These drawbacks are the primary motivations that drive developers to look for alternatives. This article provides an overview of Azure Web PubSub service and how developers can use it to build real-time communication channel fast and at scale.

What is Azure Web PubSub service used for?

Any app scenario where updates at the data resource need to be delivered to other components across network can benefit from using Azure Web PubSub. As the name suggests, the service facilities the communication between a publisher and subscribers. A publisher is a component that publishes data updates. A subscriber is a component that subscribes to data updates.

Azure Web PubSub service is used in a multitude of industries and app scenarios where data is time-sensitive. Here's a partial list of some common use cases.

Use case	Example applications
High frequency data updates	Multi-player games, social media voting, opinion polling, online auctioning
Live dashboards and monitoring	Company dashboard, financial market data, instant sales update, game leaderboard, IoT monitoring
Cross-platform chat	Live chat room, AI-assisted chatbot, online customer support, real-time shopping assistant, messenger, in-game chat
Location tracking	Vehicle asset tracking, delivery status tracking, transportation status updates, ride-hailing apps
Multi-user collaborative apps	coauthoring, collaborative whiteboard and team meeting apps
Cross-platform push notifications	Social media, email, game status, travel alert
IoT and connected devices	Real-time IoT metrics, managing charging network for electric vehicles, live concert engagement
Automation	Real-time trigger from upstream events

What are the benefits using Azure Web PubSub service?

Built-in support for large-scale client connections and highly available architectures:

Azure Web PubSub service is designed for large-scale, real-time applications. With a single Web PubSub resource, it can scale to 1 million concurrent connections, which is sufficient for most cases. When multiple resources are used together, the service allows you to scale beyond 1 million concurrent connections. Meanwhile, it also supports multiple global regions for sharding, high availability, or disaster recovery purposes.

Support for a wide variety of client SDKs and programming languages:

Azure Web PubSub service works with a broad range of clients. These clients include web and mobile browsers, desktop apps, mobile apps, server processes, IoT devices, and game consoles. Server and client SDKs are available for mainstream programming languages, C#, Java, JavaScript, and Python, making it easy to consume the APIs offered by the service. Since the service supports standard WebSocket protocol, you can use any REST capable programming languages to call Web PubSub's APIs directly if SDKs aren't available in your programming language of choice.

Offer rich APIs for different messaging patterns:

Azure Web PubSub service offers real-time, bi-directional communication between server and clients for data exchange. The service offers features to allow you to finely control how a message should be delivered and to whom. Here's a list of supported messaging patterns.

Messaging pattern	Details
Broadcast to all clients	A server sends data updates to all connected clients.
Broadcast to a subset of clients	A server sends data updates to a subset of clients arbitrarily defined by you.
Broadcast to all clients owned by a specific human user	A human user can have multiple browser tabs or device open, you can broadcast to the user so that all the web clients used by the user are synchronized.
Client pub/sub	A client sends messages to clients that are in a group arbitrarily defined by you without your server's involvement.
Clients to server	Clients send messages to server at low latency.

How to use the Azure Web PubSub service?

There are many different ways to program with Azure Web PubSub service, as some of the samples listed here:

Build serverless real-time applications: Use Azure Functions' integration with Azure Web PubSub service to build serverless real-time applications in languages such as JavaScript, C#, Java and Python.
Use WebSocket subprotocol to do client-side only Pub/Sub - Azure Web PubSub service provides WebSocket subprotocols to empower authorized clients to publish to other clients in a convenient manner.
Use provided SDKs to manage the WebSocket connections in self-host app servers - Azure Web PubSub service provides SDKs in C#, JavaScript, Java and Python to manage the WebSocket connections easily, including broadcast messages to the connections, add connections to some groups, or close the connections, etc.
Send messages from server to clients via REST API - Azure Web PubSub service provides REST API to enable applications to post messages to clients connected, in any REST capable programming languages.