socketio
Downgrade engine_socket transport error "polling request overlap" to 4xx from 5xx
Describe the bug
Hi Peeps,
I am facing an issue where the sockets are in polling mode, the engine io long-polling algorithm will error out when you have two open GET requests. As of now, the error is treated as 500 error.
This could happen when a client has a faulty configuration in place. So, I am proposing we should treat this error as 400/406/409 code where it is used to tell the client that a fault has taken place on THEIR side.
https://github.com/socketio/engine.io/blob/4c306af9458d9caab36c7f8294d8c252b273b8dc/lib/transports/polling.ts#L115-L122
To Reproduce
The issue is similar to https://github.com/socketio/engine.io/issues/166 but restricted to polling only. No upgrade to WebSocket is allowed in my case.
You can reproduce the issue in the following ways
- Using a reverse proxy to proxy WebSocket
reproduced - Use a browser(firefox) to block WebSocket transport
reproduced - Using a socket client to proxy WebSocket:
not-reproduced-
transports: [ "polling"]
-
Once the browser shows the xhr requests(GET) as pending state, copy the request as curl. Execute the curl request via the terminal to reproduce the issue.
Engine.IO client version: 6.1.0
Expected behavior
it indicates a faulty implementation of the engine io long-polling algorithm when you have two open GET requests. The proposed Idea is that we could downgrade data request overlap from client error code listed below as 4xx error instead of 500
https://github.com/socketio/engine.io/blob/4c306af9458d9caab36c7f8294d8c252b273b8dc/lib/transports/polling.ts#L119
potential error codes - 400/406/409
Thanks!
One way i'd propose to solve this is to make the behaviour of this configurable/overridable so that we don't introduce a breaking change.
That sounds reasonable, let's schedule this for the next major version. :+1:
Done in https://github.com/socketio/engine.io/commit/911d0e35757ea9ee93d1807c401c734661615e96, included in version 6.4.2.