Pybricks App - Fails to start.

[zoligyenge]

Hello. The team I am coaching observed that at times, the Pybricks App - fails to start, it just opens to a white screen. However, at home, I could never reproduce the problem. I am wondering whether it has anything to do with the laptop not having internet connection where the team is training?

If no internet can cause pybricks not starting, that could be quite problematic at competitions. Do you have any suggestions?

As always - Thanks for your great work...

[dlech]

It's been a while, but we had folks reporting the white screen a while back. It was due to issues with our web server. But that seems to have been resolved.

I can't seem to find it right now, but somewhere we have an issue or discussion about this with some more in-depth debugging that show what the exact failure was. IIRC, there was some file that wasn't being severed properly.

When the server is working correctly, all needed files are downloaded to your computer the first time Pybricks Code runs so that it works offline after that.

On the computer that isn't working, you could try clearing the browser cache for that site to force it to re-download everything to see if that makes it better.

[laurensvalk]

all needed files are downloaded to your computer the first time Pybricks Code runs

But does this mean that after each restart (of the computer or Pybricks app/ browser window), one needs an internet connection?

No connection is needed the second time.

You could try it out quite easily by turning off WiFi on your computer and restarting it. It will also persist the next day, and so on.

It only goes away if you clear your browser data/cookies/cache.

[zoligyenge]

That is exactly what I tried and each time the first time I open pybricks after I restart the laptop I get the white screen if I have no internet.

I am really worried about this for the Singapore WRO finals...

all needed files are downloaded to your computer the first time Pybricks Code runs

But does this mean that after each restart (of the computer or Pybricks app/ browser window), one needs an internet connection?

No connection is needed the second time.

You could try it out quite easily by turning off WiFi on your computer and restarting it. It will also persist the next day, and so on.

It only goes away if you clear your browser data/cookies/cache.

[dlech]

I figured out why I couldn't find the "old issue" - it was an email. Here is a snippet of it that shows the issue that was with our server (the bits that have status of (pending)).

I'm able to reproduce the issue as well by checking the "Disable cache" option in the "Network" tab. It looks like it is getting hung up when fetching the pyodide files. So likely still an issue with our web hosting provider. We'll keep working on it. Fortunately for most users, Pybricks works offline once it has loaded successfully once until the next update, so they won't notice this issue.

Not sure if this would work as a workaround, but seems to work for me... Changing the "No thottling" to "offline" seems to avoid the white screen issue (also don't disable cache). But I may have some files cached that you don't if the site never loaded completely for you at least once before.

[dlech]

So if you could do the same network log in the web browser dev tools, that would help us troubleshoot the issue.

Also (be sure to back up all of your files first!), you could try clearing your browser cache for the site to force it to re-download Pybricks Code and hopefully all of the files will be available offline as they should.

If things are working correctly, you should see (ServiceWorker) on every single file under Size. This means there is an "offline" copy of the file which lets the app work without an internet connection.

There is possibly one exception though where there isn't (ServiceWorker) which is highlighted in the screenshot above. I don't think this is actually a problem. This file is a separate service worker itself and I think the log entry is for running the file rather than downloading it. The same file is in the workbox-precache as it should be for offline use.

[zoligyenge]

Thanks dlech

I will make some screenshots when the issue happens again. I can't consistently reproduce the problem though.