Error：Kill child process will case "kill ESRCH" when "Error in connection establishment: net::ERR_CONNECTION_REFUSED"

[zhaomenghuan]

Bug Description:

Two problems that can be reproduced stably.

• Error in connection establishment: net::ERR_CONNECTION_REFUSED
• Kill ESRCH

Steps to Reproduce:

When I opened the Electron desktop application built on Theia, and did not operate for a period of time, when I opened DevTools, I could see the following error:

I click the exit button：

Error popup will pop up：

The code that caused the error is:

process.kill(backendProcess.pid);

Additional Information

• Operating System: macOS
• Theia Version:

[vince-fugnitto]

@zhaomenghuan I believe you may have encountered the following issue: #4249

[kittaakos]

I have noticed this issue several times already; for some reason, the backed process just terminates. When closing the electron app, we try to close the forked BE process, but it's not there anymore. This issue requires two fixes:

• figuring out why the BE process terminates,
• making sure to swallow the ESRCH errors when quitting the electron app here:
  

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

  Line 426 in 57b4b67

  process.kill(backendProcess.pid);

[zhaomenghuan]

Is there any better solution to handle the failed "Error in connection establishment: net:ERR_CONNECTION_REFUSED" exception? When is the official plan to fix this problem? The application experience of this problem in the Electron environment is very affected.

[kittaakos]

"Error in connection establishment: net:ERR_CONNECTION_REFUSED" exception?

For the record, this 👆 exception is causing the Kill ESRCH problem. You have to figure out why does the backend process crash and terminate on your side. Maybe, it's a generic Theia issue.

As for the Kill ERSCH error dialog, you can customize your electron application like this to ignore the ESRCH:

your-electron-main-module.ts:

export default new ContainerModule((bind, unbind, isBound, rebind) => {
    bind(YourElectronMainApplication).toSelf().inSingletonScope();
    rebind(ElectronMainApplication).toService(ElectronMainApplication);
});

your-electron-main-application.ts:

@injectable()
export class YournElectronMainApplication extends ElectronMainApplication {

    protected async startBackend(): Promise<number> {
        // Check if we should run everything as one process.
        const noBackendFork = process.argv.indexOf('--no-cluster') !== -1;
        // We cannot use the `process.cwd()` as the application project path (the location of the `package.json` in other words)
        // in a bundled electron application because it depends on the way we start it. For instance, on OS X, these are a differences:
        // https://github.com/eclipse-theia/theia/issues/3297#issuecomment-439172274
        process.env.THEIA_APP_PROJECT_PATH = this.globals.THEIA_APP_PROJECT_PATH;
        // Set the electron version for both the dev and the production mode. (https://github.com/eclipse-theia/theia/issues/3254)
        // Otherwise, the forked backend processes will not know that they're serving the electron frontend.
        process.env.THEIA_ELECTRON_VERSION = process.versions.electron;
        if (noBackendFork) {
            process.env[ElectronSecurityToken] = JSON.stringify(this.electronSecurityToken);
            // The backend server main file is supposed to export a promise resolving with the port used by the http(s) server.
            const address: AddressInfo = await require(this.globals.THEIA_BACKEND_MAIN_PATH);
            return address.port;
        } else {
            let args = this.processArgv.getProcessArgvWithoutBin();
            // https://github.com/eclipse-theia/theia/issues/8227
            if (process.platform === 'darwin') {
                // https://github.com/electron/electron/issues/3657
                // https://stackoverflow.com/questions/10242115/os-x-strange-psn-command-line-parameter-when-launched-from-finder#comment102377986_10242200
                // macOS appends an extra `-psn_0_someNumber` arg if a file is opened from Finder after downloading from the Internet.
                // "AppName" is an app downloaded from the Internet. Are you sure you want to open it?
                args = args.filter(arg => !arg.startsWith('-psn'));
            }
            const backendProcess = fork(
                this.globals.THEIA_BACKEND_MAIN_PATH,
                args,
                await this.getForkOptions(),
            );
            return new Promise((resolve, reject) => {
                // The backend server main file is also supposed to send the resolved http(s) server port via IPC.
                backendProcess.on('message', (address: AddressInfo) => {
                    resolve(address.port);
                });
                backendProcess.on('error', error => {
                    reject(error);
                });
                app.on('quit', () => {
                    try {
                        // If we forked the process for the clusters, we need to manually terminate it.
                        // See: https://github.com/eclipse-theia/theia/issues/835
                        process.kill(backendProcess.pid);
                    } catch (e) {
                        if (e.code === 'ESRCH') {
                            console.log('Could not terminate the backend process. It was not running.');
                            return;
                        }
                        throw e;
                    }
                });
            });
        }
    }

}

Or provide us a patch with the fix.

[zhaomenghuan]

When I hibernate my computer and turn it on again, the problem can be reproduced stably. I added the close and exit events of backendProcess to ElectronMainApplication, and found that the signal values are both SIGPIPE. Node.js Process ignores SIGPIPE errors by default, but it doesn't seem to take effect in the Electron environment. I tried adding the following code to BackendApplication, which seems to solve the problem.

@injectable()
export class BackendApplication {
    ...
    constructor(
        @inject(ContributionProvider) @named(BackendApplicationContribution)
        protected readonly contributionsProvider: ContributionProvider<BackendApplicationContribution>,
        @inject(BackendApplicationCliContribution) protected readonly cliParams: BackendApplicationCliContribution
    ) {
        ...
        process.on('SIGPIPE', () => {
            console.log("No, please do not exit...");
        });
        ...
    }
    ...
}
...

electron issues reference：electron/electron#13254 (comment)
vscode code reference：https://github.com/microsoft/vscode/blob/master/src/bootstrap.js#L34