⇧

WebSockets and SSE for communication microservice

Status

Status: Accepted Date: 2025-04-03

Context

The communication module need a realtime feature for

  • The notifications,
  • Building reactive UI, e.g. instant messaging for instance.
  • System messages, e.g. updating granted roles to users.

Pros & Cons

  • The Server-Sent Events (SSE) protocole is a lightweight, unidirectional http based protocol.
  • It is well suited when going through proxies, firewalls, or API gateways.
  • Generally considered less resource-efficient than WebSockets on the backend side.
  • Websockets can be blocked by firewalls. The fallback to SSE could be a workaround.
  • SSE is heavier than websockets.
  • SSE is unidirectional.
  • Some functionalities are not available with SSE, e.g. rooms

Decision

The decision is to use WebSockets and Server-Sent Events (SSE) as a fallback for the communication microservice.

The strategy could be this one: Websockets (nominal case) -> SSE -> Short pooling -> asynchrone.

Consequences

The choice of WebSockets and SSE has the following consequences:

  • Two implementations are needed.
  • The client need to handle both protocols.
  • SSE is currently not supported by APISIX, which may require a workaround or future adaptation