[Question] MaxListenersExceededWarning: Possible EventEmitter memory leak detected.

[paperbackdragon]

I'm in the process of moving our tests from puppeteer to playwright, and when I run them now I notice a warning in the output:

> jest --runInBand --config=./jest-playwright.config.js

 PASS  src/playwright/commands/sync-commands.test.ts (25.332s)
 PASS  src/playwright/list/list-scroll.test.ts (16.498s)
 PASS  src/playwright/notifications/notifications.test.ts (8.894s)
 PASS  src/playwright/driveStatus/drive-status-update.test.ts (8.239s)
 PASS  src/playwright/commands/view-online.test.ts (8.386s)
 PASS  src/playwright/driveStatus/drive-callout.test.ts (6.712s)
 PASS  src/playwright/commands/delete.test.ts (6.422s)
 PASS  src/playwright/settings/sync-settings-account.test.ts
 PASS  src/playwright/rootView/root-view.test.ts
 PASS  src/playwright/settings/sync-settings-general.test.ts
(node:38312) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 disconnected listeners added. Use emitter.setMaxListeners() to increase limit
 PASS  src/playwright/commands/rename.test.ts
 PASS  src/playwright/driveStatus/drive-status-button.test.ts
 PASS  src/playwright/commands/new-folder.test.ts

It always seems to be after the 10th test suite that runs so I'm assuming it has to do with the browser process. I'm using chromium.launchServer in a Jest setup script, setting that websocket endpoint to a variable in process.env, and then using const browser = chromium.connect({ wsEndpoint: process.env.WS_ENDPOINT }); in each test to get a reference to the one browser instance. I'm making sure to call page.close() after each test suite, and browser.close() in my Jest teardown script.

Is this pattern not using just one browser instance? Or would the issue be something else? I'm happy to just set process.setMaxListeners(Infinity); but I want to be sure that's safe to do.

Thanks!!

[dennis8989]

I have the same issue. I use playwright-python, I wonder how to add process.setMaxListeners(Infinity) in my code? or it has been fixed in version 1.12? Thanks

[mxschmitt]

Which version are you using? I would recommend creating a new issue with reproducible steps. Because closed issues don't get normally much attention.