fix: scope websocket upgrades to the proxy prefix#475
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The plugin registers a single server-wide `upgrade` listener that dispatches every WebSocket upgrade through `fastify.routing`, regardless of the prefix the proxy is mounted on. When the proxy shares the server with another `upgrade` handler (for example `@fastify/websocket`), it consumes and answers upgrades it does not own, breaking those unrelated WebSocket endpoints. Only handle upgrades whose path falls within a registered proxy prefix when the proxy coexists with other `upgrade` listeners. When the proxy is the only listener, behaviour is unchanged: every upgrade is routed as before, so out-of-prefix requests are still rejected normally. Closes fastify#414
climba03003
approved these changes
Jul 16, 2026
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Fixes #414.
@fastify/http-proxyregisters a single server-wideupgradelistener that dispatches every WebSocket upgrade throughfastify.routing, regardless of the prefix the proxy is mounted on. When the proxy shares its server with anotherupgradehandler (e.g.@fastify/websocket), it consumes and answers upgrades it does not own, corrupting those unrelated WebSocket endpoints (the reporter's "existing handlers stop working").This scopes the shared upgrade listener: when the proxy coexists with other
upgradelisteners, it only handles upgrades whose path falls within a registered proxy prefix and leaves the rest untouched for the owning handler. When the proxy is the soleupgradelistener, behaviour is unchanged — every upgrade is routed exactly as before, so out-of-prefix requests are still rejected normally (existingws-prefix-rewritebehaviour is preserved).Added
test/ws-upgrade-prefix.js, which fails onmain(an out-of-prefix upgrade is answered with a404by the proxy) and passes with this change. Full suite green at 100% coverage.Note for reviewers:
@fastify/websockethas the mirror-image global upgrade listener, so a proxy route and a@fastify/websocketroute on the same path still conflict — that needs a reciprocal change on their side. This PR fixes the http-proxy side: it no longer steals upgrades outside its own prefix.Closes #414