BackendApplication#onStop is not called on electron app quit. Is it a debug glitch, bug, or a missing feature?

[kittaakos]

Hi there; when I quit a Theia-based electron app, or the Theia electron example started from sources by closing the last window with the X, the BackendApplication#onStop is not always called. When the electron app runs in cluster mode, and the Theia backend is forked from the electron main, onStop is not called from the electron app. When --no-cluster arg is set, it works.

2023-02-01T14:13:35.812Z root INFO >>> Stopping backend contributions...
2023-02-01T14:13:35.812Z root INFO <<< All backend contributions have been stopped.

When the backend app process stops, it stops the contributions. This is the happy path, and it works fine if --no-cluster is set:

theia/packages/core/src/node/backend-application.ts

Line 177 in b28c8b9

process.on('exit', () => this.onStop());

But in a bundled app, the backend process is forked from the electron main. The electron app kills the backend process on quit with the default 'SIGTERM' signal:

theia/packages/core/src/electron-main/electron-main-application.ts

Line 499 in b28c8b9

process.kill(backendProcess.pid);

Currently, the backend app does not do any cleanup on 'SIGTERM':

theia/packages/core/src/node/backend-application.ts

Line 181 in b28c8b9

process.on('SIGTERM', signalHandler);

theia/packages/core/src/node/backend-application.ts

Lines 173 to 175 in b28c8b9

	function signalHandler(signal: NodeJS.Signals): never {
	process.exit(1);
	}

For example, I want to delete a file on quit synchronously, but it does not work because the backend contributions are not stopped.

theia/packages/core/src/node/backend-application.ts

Lines 91 to 97 in b28c8b9

	/**
	* Called when the backend application shuts down. Contributions must perform only synchronous operations.
	* Any kind of additional asynchronous work queued in the event loop will be ignored and abandoned.
	*
	* @param app the express application.
	*/
	onStop?(app?: express.Application): void;

Has somebody experienced the same? Is it a bug, or am I doing something wrong? Thanks!

[msujew]

I haven't confirmed it, but from your description, it looks like a bug to me.

[dmm9]

@msujew Could you confirm this is a bug? See also #14216

[dmm9]

I am experiencing the same, onStop is not being called. I have tried both BackendApplicationContribution and ElectronMainApplicationContribution. Using theia 1.49.1.

@kittaakos did you find a solution?

[dankeboy36]

did you find a solution?

@dmm9, the Arduino IDE has patched this default Theia behavior in this commit: arduino/arduino-ide@d68bc4a#diff-54951a7f6fc1d8e5bca375af44a6874aa403c6ab0942031b7126743fc7d5ab66.