Library scanner turns UI unresponsive

[Thomas Jarosch]

On the first mixxx invocation (without a .mixxx directory on Linux),
a dialog pops up to select the initial music library path.

Once mixxx 2.1 beta starts scanning, the whole UI becomes unresponsive,
no "Library Scanner" dialog is shown. After roughly 60 seconds (!)
the "Library Scanner" dialog is shown, but the filenames hardly get refreshed.

Something starves the UI event handling completely. The main window
also does not react to resize events.

I reinstalled mixxx 2.0, cleared the .mixxx directory and tried again.
This time the "Library Scanner" dialog instantly pops up, the main window
stays responsive and the "Library Scanner" refreshs the currently scanned file constantly.

This is on Fedora 26 x86_64 with qt 5.9.4.

[Daniel Schürmann (daschuer)]

Is it your own build made with qt5?
Is a qt4 version also effected?

[Thomas Jarosch (thomas-jarosch)]

hey Be, this is not a duplicate of #1738227.
#1738227 is about the *analyzer*, this bug report is about the *library scanner*.
The fixes for #1738227 are part of the 2.1 branch already.

Please re-open.

@daschuer: Both my 2.0 build and 2.1 build use qt5.
Only the 2.1 build shows the problem.

Not sure if I can build it with qt4, I have not tried to build with that.
Do you think it will make a difference?

Is the library scanner behaving normal for you
when you reinitialize your data directory?

[Daniel Schürmann (daschuer)]

OK, than there is no need to rebuild it with Qt4.

I can reproduce the issue somehow.
During library scanner, I can use the Mixxx GUI.
But loading Tracks via drag and drop fails.

Also creating a Playlist fails.
It appears an empty message box.

The library scanner cancel button has no effect.

[Daniel Schürmann (daschuer)]

If I start the library scanner from the menu later, everything works lieke expected

[Uwe Klotz (uklotzde-deactivatedaccount)]

We are now correctly using a dedicated, thread-local database connection for each thread. Could this issue with the library scanner be caused by internal synchronizations within SQLite that prevent to create concurrent transactions for different connections? Just a thought, we need to validate this.

[Thomas Jarosch (thomas-jarosch)]

Small correction from my side: mixxx 2.1 is linked against Qt 4.8.7.
I didn't investigate correctly yesterday.

[RJ Skerry-Ryan (rryan)]

Is this still an issue with Mixxx 2.1.4?

[Be (be.ing)]

This still happens in master.

[Be (be.ing)]

I realized this is why I turn off the option to rescan the library on startup. If that did not block the GUI, I would gladly leave that option enabled.

[Uwe Klotz (uklotzde-deactivatedaccount)]

Probably the root cause: https://bugs.launchpad.net/mixxx/+bug/1051106

Rescanning the library on startup should be removed.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/9159