← Back to release summary

WebTransport draining

Category

Network / Connectivity

Type

Chromium catches up

Status

Proposed (Chrome Proposed)

Intent stage

None

Summary

WebTransport.draining is a promise that resolves when the server indicates that the WebTransport session will be gracefully retired. Applications can use this signal to establish a replacement session while existing streams and the current session remain usable.

Motivation

A WebTransport server may need to retire a session for maintenance, load balancing, deployment, or connection-lifetime management. Without a draining signal, an application learns about this only when the session closes, which can cause an avoidable interruption while a replacement connection is established. The draining promise gives the application advance notice without changing the lifetime or usability of the current session.

Standards & signals

• Specification: https://w3c.github.io/webtransport/#dom-webtransport-draining
• Firefox: Positive — Mozilla's position applies to WebTransport as a whole. Mozilla representatives have previously indicated that a separate standards-position request is not needed for every individual WebTransport specification member.
• Safari: Support — WebKit's position applies to WebTransport as a whole. Safari now implements WebTransport, including the current API surface.
• Web developers: No signals — Positive interest in WebTransport use cases; no draining-specific survey.
• Tracking bug: https://issues.chromium.org/issues/564353368

Docs: https://github.com/w3c/webtransport/blob/main/explainer.md#11-handling-session-draining

Explainers: https://github.com/w3c/webtransport/blob/main/explainer.md#11-handling-session-draining

View on chromestatus.com