Frontend sometimes disconnect and cannot reconnect

[Hanksha]

Hi,

We've had report of users of our Theia based application about the frontend being disconnected and not able to reconnect, for some it even makes the app freeze completely. Often it's when they leave the application for a while (e.g. make the machine sleep) and go back to it. It happens both on browser and electron.

I can see this in the dev tools console when it happens:

The logs are also spammed with logs like this:

2025-05-13T00:30:53.105Z plugin-host ERROR Promise rejection not handled in one second: Error: no local service handler with id LoggerMain , reason: Error: no local service handler with id LoggerMain
2025-05-13T00:30:53.105Z plugin-host ERROR With stack trace: Error: no local service handler with id LoggerMain
    at t.RPCProtocolImpl.handleRequest (file:///home/leninadizon/Documents/martini_designer_linux/resources/app/lib/frontend/bundle.js:2:8901423)
    at c.requestHandler (file:///home/leninadizon/Documents/martini_designer_linux/resources/app/lib/frontend/bundle.js:2:8901056)
    at c.handleRequest (file:///home/leninadizon/Documents/martini_designer_linux/resources/app/lib/frontend/bundle.js:2:3105166)
    at c.handleMessage (file:///home/leninadizon/Documents/martini_designer_linux/resources/app/lib/frontend/bundle.js:2:3103072)

2025-05-13T00:31:02.423Z root ERROR Uncaught Exception: 
Error: transport error
2025-05-13T00:31:02.423Z root ERROR Error: transport error
    at /home/leninadizon/Documents/martini_designer_linux/resources/app/lib/backend/825.js:2:45683
    at Map.forEach (<anonymous>)
    at /home/leninadizon/Documents/martini_designer_linux/resources/app/lib/backend/825.js:2:45662
    at /home/leninadizon/Documents/martini_designer_linux/resources/app/lib/backend/825.js:2:15658

2025-05-13T00:33:01.010Z root WARN A command editor.action.toggleStickyScroll is already registered.
2025-05-13T00:33:01.013Z root WARN A command noop is already registered.
2025-05-13T00:33:01.013Z root WARN A command default:undo is already registered.
2025-05-13T00:33:01.013Z root WARN A command default:redo is already registered.
2025-05-13T00:33:01.013Z root WARN A command editor.action.selectAll is already registered.
2025-05-13T00:33:01.013Z root WARN A command _setContext is already registered.
2025-05-13T00:33:01.013Z root WARN A command getContextKeyInfo is already registered.
2025-05-13T00:33:01.013Z root WARN A command _generateContextKeyInfo is already registered.
2025-05-13T00:33:01.013Z root WARN A command _moveTo is already registered.
2025-05-13T00:33:01.013Z root WARN A command _moveToSelect is already registered.
2025-05-13T00:33:01.013Z root WARN A command columnSelect is already registered.
2025-05-13T00:33:01.013Z root WARN A command cursorColumnSelectLeft is already registered.
2025-05-13T00:33:01.021Z root WARN A command cursorColumnSelectRight is already registered.
2025-05-13T00:33:01.021Z root WARN A command cursorColumnSelectUp is already registered.
2025-05-13T00:33:01.021Z root WARN A command cursorColumnSelectPageUp is already registered.
2025-05-13T00:33:01.021Z root WARN A command cursorColumnSelectDown is already registered.
2025-05-13T00:33:01.021Z root WARN A command cursorColumnSelectPageDown is already registered.
2025-05-13T00:33:01.021Z root WARN A command cursorMove is already registered.
2025-05-13T00:33:01.021Z root WARN A command cursorLeft is already registered.
2025-05-13T00:33:01.021Z root WARN A command cursorLeftSelect is already registered.

Any idea what could be causing this? (I'm not familiar with this part of Theia)

[msujew]

Hey @Hanksha,

on long disconnects, the backend will kill the connection container and everything associated with it (plugin host, etc.). In that case, the frontend needs to reload to reconnect correctly. However, this behavior needs to be configured in the app configuration. See:

theia/examples/electron/package.json

Line 13 in 6d1a4a1

"reloadOnReconnect": true,

[Hanksha]

Hi @msujew , thanks for your reply.

I'll try it and see if it resolves the issue.

Wouldn't reloading the window be a problem for unsaved changes? Specially for the electron app.

[Hanksha]

I guess I could set the frontendConnectionTimeout to -1 for the electron app? Would that have a negative side effect?

[sdirix]

That's a valid configuration for Electron. We do the same in the Theia IDE, see here.

[Hanksha]

Alright, thanks, I'll give it a try!