Katalon Studio freezes and non-responsive

Hi There,

Katalon is great tool and love it’s API testing capability.

However, recently Katalon Studio continue to froze and became non-responsive when trying to close it.

I have to close the app from my task manager every time it freezes.

Can you take a look?

Katalon Studio
Version: 6.1.0
Build: 1
Windows 10


That’s a bug. I’ll move this thread.

I expect @devalex88/@ThanhTo et al will want to see your KS logs.


I have similar issue. While just editing test cases and test objects, Katalon will freeze. If I look at the process, it is consuming (working set 1200+ megs of ram) (Commit 3842+ Megs of ram. Working set will start to reduce the ram by about 2 megs a second. I let it sit to see what will occur, but it never recovers. Only thing I can do is kill the process.

Katalon Log shows many
!MESSAGE Unhandled event loop exception
org.eclipse.swt.SWTError: No more handles

This occurs every couple of days.

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Me too! So, you keep KS open “all the time”, too? BTW, your working set is about half mine, it seems. But yeah, I’ve done the same and once I see KS “start” to crash, there’s not much you can do to stop it. First indication I get is weird UI update issues…

Here’s my current process:

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We don’t have enough data to fix this issue, but we will add a button which you can use to dump debug information when freezing occurs. I hope it will help us improve the performance.


I just noticed that it fills 4 log files with errors starting with:

!MESSAGE Problems occurred when invoking code from plug-in: “org.eclipse.e4.ui.workbench”.


!MESSAGE An exception occurred while notifying part listeners

Followed by a few others before the repeating SWTerror.

Yes, I leave it open some days, when working on cleanup of objects.

Now it has happened 3 times in one day. It appears to be a memory leak when you’re editing many Test Cases and Test Objects by opening/saving/closing over and over. Takes about 2 hours, then wham, have to kill Katalon.

I am on a Windows Server 2016 system, with all latest updates.

I don’t edit Test Objects (don’t use them at all) but otherwise, yes, I have right now 13 (thirteen) tabs open. @devalex88 has seen how I use Katalon, stretched across two monitors. And yes, I’m convinced it’s unable to support so many editing windows open, it gets very confused. For example, I can’t execute a TC unless it occupies the tab at the far left, i.e., the one closest to the Test Explorer.

I’d advise against testing client software especially browser apps on a server operating system. #JustSayin.

Yep, I wish we could do it all on client OS, but we are unit testing Dynamics 365 CRM and it has issues installing on client OS. Regression tests are all run from Win 10 client to QA servers.

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same happened me too
NPE is bad bad bad


@devalex88 I wonder how we’re supposed to use a button if the UI is broken/unresponsive…

Wish we could use VSC.

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I agree, What can a button do on a frozen UI?

To repeat this freezing have about 60 odd objects or test cases, now work through them, opening, editing, and closing. Over and over. Won’t take long to freeze.

Could anyone please follow these steps to retrieve and send us your heapdump?

with Java Visual VM tool you are able to get thread dump or heap dump by clicking button

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@devalex88 That’s interesting. Since turning on the “Show heap status”, I can watch Katalon’s use of memory. Here are my findings.

There is a slow but inexorable trend upward for “in use” value (on the left) and an even slower trend upward for the total commit number (on the right).

From startup and opening a bunch of files (tabbed windows) I’m seeing something like 300M of 900M

Today, same session, it’s at 673M of 2003M using the same files and after having clicked the trashcan. Anytime I see the left figure climb (perhaps showing ~1000/~2000) and I’m done running tests, clicking the trashcan will certainly cleanup memory. But again, there’s a slow residual climb for both figures.

So far, clicking the trashcan has certainly allowed me to keep Katalon open/stable for longer. However, the results reveal there is definitely one or more memory leaks somewhere.

As I was writing this message, and Katalon is idle, it has crept up again, from 673M of 2003M to 682M of 2003M. So I clicked a method name and 701M of 2003M.

I know, there’s nothing you can do with this info other than confirm Katalon has a leak issue. :confused:

EDIT: And now it’s still climbing and I’m doing nothing:

673M of 2003M
682M of 2003M
701M of 2003M
708M of 2003M
819M of 2004M
Click trashcan
636M of 2007M



And look at the memory widget:


Up until this point I had been clicking the trashcan to run the garbage collector… but then I forgot for a while and bang.

I know a few people, including me, have been asking for a dark theme, but that’s not quite what I had in mind :stuck_out_tongue:

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Please try to retrieve the heapdump using Eclipse MAT. That will help us understand what had consumed all the memory.

Perhaps I wasn’t clear. When the crash happens, it’s very difficult to use any software on my desktop. Katalon is crashing so badly, it’s screwing with my display driver to a point that launching MAT and following those steps you posted would be extremely difficult - so difficult, it’s a non-starter for me. All I can do is ctrl-shit-esc (task manager) and hope to drag it clear to kill Kat.

What isn’t clear from my screenshots is all hell breaks loose when it crashes… flickering, weird updates, flashes of crazy colors, apps from different desktops show up (Dexpot: but they’re not truly there, they’re still on their proper desktop) it goes so crazy its hard to do anything beyond task manager.

I’ll add this FWIW, editing multiple files takes far more memory than executing scripts. :confused:

That sounds bad :smile:. Can you take the heapdump before that point - like when it feels that memory can no longer be released?

I’ll do my best but I can’t promise to catch it in time.