Implementing WebSocket Rate Limiting in Azure API Management

Discover how to manage WebSocket connections and messages effectively within Azure API Management, including current limitations and workarounds.
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This video is based on the question https://stackoverflow.com/q/77791550/ asked by the user 'Shunsuke' ( https://stackoverflow.com/u/19167201/ ) and on the answer https://stackoverflow.com/a/77806667/ provided by the user 'Mo Haidar' ( https://stackoverflow.com/u/5069951/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Challenge of WebSocket Rate Limiting in Azure API Management

In today's world of real-time communication, WebSockets provide a powerful way to facilitate interactive data transfer between a client and server. However, when managing a high number of user connections and messages, ensuring control and efficiency becomes essential. One common challenge that developers face is the need to rate limit WebSocket connections and messages in Azure API Management.

What Is the Objective?

In an ideal scenario, we would want to achieve the following objectives when using WebSockets:

Rate limit the number of WebSocket connections each user (or API key) can have at a time.

Rate limit the number of messages that can be sent over a WebSocket connection.

Extract and log WebSocket messages, allowing for better monitoring and management.

However, the question arises: Is it truly feasible to implement such functionality in Azure API Management?

Analyzing the Solutions

Current Capabilities

Currently, the policies in Azure API Management are limited to the initial onhandshake operation. Let’s break this down:

Onhandshake Policies: Policies can only be applied during the WebSocket handshake phase. Once the connection is established, these policies are not effective anymore.

Rate Limiting:

If you apply a rate-limit or quota policy at the onhandshake stage, it will only restrict a client from making new WebSocket connections at that moment.

Once the rate-limit counter resets, users are free to create more connections irrespective of the number of active connections.

Limitation of Message Management

Unfortunately, leveraging message content or limiting the number of messages sent over an existing WebSocket connection isn't possible through the Azure API Management infrastructure:

Message Limits: There is no option currently available within Azure API Management to constrain the number of messages transmitted over a WebSocket connection.

Logging Messages: Policies for capturing or logging messages (beyond handshake requests) are also absent in Azure API Management. This means creating policies to log specific messages into EventHub is not possible.

Workarounds and Best Practices

While you may not have complete control over WebSocket connection management, here are a few strategies that could help you manage WebSocket interactions more effectively:

Backend Connection Management: Implement mechanisms on your backend WebSocket service to recycle or limit active connections. This can mitigate over-connection issues despite the limitations of Azure API Management.

Monitoring Active Connections: Utilize external monitoring tools to keep track of active connections and develop custom solutions that trigger alerts when users exceed predetermined limits.

Feedback Loop: Inform users of their connection status and any limitations to maximize user experience. Clear feedback can prevent potential overloads.

Conclusion

While Azure API Management offers many robust features, it currently has certain limitations regarding WebSocket rate limiting and message management. Understanding these constraints allows developers to strategize and create alternative methods to ensure efficient control of WebSocket interactions. With proper backend management and user notifications, you can still maintain a functional and responsive environment for real-time communications.

For now, we encourage constant monitoring of Azure API Management’s feature updates since enhancements might eventually address these limitations in the future.