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Updated on 2025-06-06 GMT+08:00
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Accessing a Real-Time Service Using Server-Sent Events

Context

Server-Sent Events (SSE) is a server push technology enabling a server to push events to a client via an HTTP connection. This technology is usually used to enable a server to unidirectionally push real-time data to a client, for example, a real-time news update or stock prices.

SSE primarily facilitates unidirectional real-time communication from the server to the client, such as streaming ChatGPT responses. In contrast to WebSockets, which provide bidirectional real-time communication, SSE is designed to be more lightweight and simpler to implement.

Key features of SSE include:

  • Easy to use: SSE is based on the HTTP protocol and is straightforward to implement. No complex configurations or additional libraries are needed, and data can be pushed in real-time over standard HTTP connections.
  • Automatic reconnection: SSE supports automatic reconnection. If the connection is interrupted, the client automatically attempts to reconnect, ensuring continuous data delivery.
  • Unidirectional communication: SSE is unidirectional, meaning the server can send events to the client, but the client cannot send data back to the server through the same connection.
  • Low resource usage: SSE uses HTTP connections, making it less resource-intensive compared to other real-time communication protocols like WebSocket. This makes SSE ideal for lightweight real-time data push scenarios.

Prerequisites

The image for importing the model is SSE-compliant.

Constraints

  • SSE supports only the deployment of real-time services.
  • It supports only real-time services deployed using models imported from custom images.
  • When you call an API to access a real-time service, the size of the prediction request body and the prediction time are subject to the following limitations:
    • The size of a request body cannot exceed 12 MB. Otherwise, the request will fail.
    • Due to the limitation of API Gateway, the prediction duration of each request does not exceed 40 seconds.

Calling an SSE Real-Time Service

The SSE protocol itself does not introduce new authentication mechanisms; it relies on the same methods as HTTP requests.

You can use one of the following authentication methods provided by ModelArts:

The following section uses GUI software Postman for prediction and token authentication as an example to describe how to call an SSE service.

Figure 1 Calling an SSE service
Figure 2 Response header Content-Type

In normal cases, the value of Content-Type in the response header is text/event-stream;charset=UTF-8.