We are running several VMs with Windows on several Ubuntu Machines with QEMU+KVM.
These VMs are created/destroyed several times per hour, with different MAC/IP Addresses.
Every once in a while, a java process will return the same UUID.randomUUID() as previous VM (from the same/different hypervisor). For example, a Windows VM we created over a month ago returned the same UUID.randomUUID() as a VM created just now.
The only reason we can think of is a lack of entropy? Is there a way to seed the entropy for java.util.UUID to prevent this from happening?
Related
So I have spent the better part of two days troubleshooting a very weird issue. At no point running my application on the development workstation or a physical workstation did I ever encounter any issues running the application.
The app has reached a point in the development lifecycle were it was time to start doing more targeted regression testing. This included running the application within virtual machines as I wanted to support the application running in virtualized environments.
Well upon testing in virtualized environments I noticed a very weird issue randomly any command I had binded that opened a child window would sometimes not work. The child window will not render and the button would be greyed out due to the canexcute of the command giving false since it thought the command was still running. This issue cannot be reproduced on a physical machine and have tried greatly.
After research I saw a lot about virtual machines and wpf rendering and people stating to force software rendering instead of allowing hardware rendering. This did not work either.
Further research/testing found this didn't have to be a task that rendered a simple child window and it could be any task that would lead to this random issue.
After beating my head I have found these articles
https://www.gresearch.co.uk/2019/12/20/deep-dives-in-debugging-when-it-really-isnt-your-fault/
https://github.com/dotnet/coreclr/issues/26990
https://github.com/dotnet/coreclr/pull/10065
Long story short is that this is an issue with .net 4.8 and if I run in a virtual machine running 4.7.2 these issues are not reproducible. I am going to leave this open though as I did notice something odd after discovering this information and testing further.
I have discovered that if I run application on a virtual machine with .net 4.7.2 with TWO or more vCPUs that these random issues are not reproducible. But if I run on a virtual machine with .net 4.7.2 and ONE vCPU the issue still arises. Furthermore if I run application on .net 4.8 with TWO or more vCPUs the issue arises. Lastly if I run on .net 4.8 with ONE vCPU the issue is not reproducible.
This question is in the context of Windows Phone 8. As far as I understand, TASKHOST is a generic process which acts as a host for processes that run from DLLs rather than EXEs, and there can be many instances of TASKHOST running, as there will be one instance of TASKHOST for every DLL-based service. So, if I need to find out what apps are running under TASKHOST, is there a way to do so? For example, is there any way to get an handle of each instance of TASKHOST and find out more about the process running under each? (Basically, I need to find out if the app I'm trying to launch (not exe) is already running)
Thanks :)
No way to do this with the current API, the apps are all sandboxed.
I have a big problem.
I wrote an app for Windows Phone 7.1+, and it's also published on Windows Phone Store:
this app works well for Windows Phone 7.1 and also for Windows Phone 8, and there were no problems during app submission process (who also declares that my app is fully compatible with any OS since Windows Phone 7.5).
The problem is related only to my Scheduled Agent, which runs perfectly on Windows Phone Mango (7.1), but it is not firing at all on Windows Phone 8 (I've also tested my app on real devices, with both the OS').
When I upgraded to Visual Studio 2012 (Express for Windows Phone), I've noticed that it is possibile to add two different types of ScheduledTaskAgent project: one for Windows Phone 7.5 and one for Windows Phone 8 (obviously it wasn't so in Visual Studio 2010...and I used the only one available = the first) !
Dou you think this can be the reason while the scheduled agent is not working in WP8?
What's the difference between the two projects types?
How to manage (in code I mean) two projects of that type? Is it possible?
How can I choose which task I have to register (see code below)?
Will the submission process fail with two ScheduledTaskAgent projects (I think so)?
This is the critical part of the code, when I'm registering my task at startup:
PeriodicTask newTask = new PeriodicTask("MyTaskID");
newTask.Description = "my Description";
ScheduledActionService.Add(newTask);
#if DEBUG
Microsoft.Phone.Scheduler.ScheduledActionService.LaunchForTest("MyTaskID", TimeSpan.FromSeconds(5));
#endif
Thank you in advance.
The only difference between the two project types is (1) the Windows Phone 8 one targets Windows Phone 8 instead of 7.1 and (2) it references the Windows Phone 8 SDK instead of the Windows Phone 7 dlls.
I have an application where I have two projects (7.1 and 8.0). I also have two background agent projects (7.1 and 8.0) and I share code between them using linked files. I reference the 8.0 agent from the 8.0 project and the 7.1 agent from the 7.1 project. I used this example as a best practice for having the two versions of code.
You do not want to reference two agents since that will not work.
If you remove the #if DEBUG does your agent get called when you're debugging?
First make sure you got the proper reference in app manifest file.
<ExtendedTask Name="BackgroundTask">
<BackgroundServiceAgent Specifier="ScheduledTaskAgent" Name="MyApp.Agent" Source="MyApp.Agent" Type="MyApp.Agent.ScheduledAgent" />
</ExtendedTask>
Second the Agent library must be referenced in the main app project.
Third, make sure you are not exceeding the allowed running time or memory allocation. In WP8 the cap for background agent was raised to 11MB. Also there is a limit of app with registered background tasks, so it might be possible that there was no free slot for your task with bg agent.
We have a higher-end Win7-64 Dell precision workstation notebook with an i7, 8 gigs of ram, tons of hd space and running dedicated AMD graphics. The machine is about a month old. It was one of the highest-end we could get at the time.
What we're experiencing is when we run our WPF/SQL Server (local) app, it tends to hang and stall, sometimes completely crashing, but mostly just hanging until we force it to close. However, the exact same installer running in a VMware virtual machine running on that same machine runs flawlessly. Actually, the VM install runs better than a lot of native installs on other machines. It's very snappy with no hangs or hesitations at all. But again, same app, same installer running direct in the OS, and we're back to the issues above.
We've ran all Windows updates.... we've tried completely reinstalling everything... .NET frameworks, SQL Server, video drivers, even updated the BIOS and checked for rogue services but it still happens.
At first we thought it was Symantec AV's real-time protection because when we first shut that off, things started getting snappy again (and slowed down and froze when it auto-re-enabled itself furthering this hypothesis) but then it just started slowing down again, and more surprising, that same AV is running in the VM without issue! Checked the exceptions but there weren't any.
We even tried forcing WPF to run in software-render mode but again, nothing.
Now the odd thing is this only seems to be happening on this and a few other machines, but we can't seem to find anything in common except they're all running Win7 64-bit. As such, we have absolutely no idea where to start. And since most are hangs, not crashes, we can't even look at the crash reports.
So can anyone give us any idea what else we can look at? This is holding up us shipping a three-years-in-the-making major release of our software so to say this is a show-stopper would be an understatement. We've been stumped for about a month now and getting nowhere fast.
Found it!! Turns out there's a bug in .NET 4.0 regarding UI Automation and the changes MS introduced. Here's the info, and the fix! (Note: Even if you call MS, they will send you a link, but it's always a broken link. I managed to track this down manually.)
Note: Their article talks about a specific case that causes this behavior, but if you google around, you'll see tons of issues around hangs related to those DLLs. The latest is they're promising a fix in the .NET 4.5 runtime (from a MS post on this issue.)
Here's the KB article...
http://support.microsoft.com/kb/2484841/en-us
...and here is the actual hotfix.
http://archive.msdn.microsoft.com/KB2484841/Release/ProjectReleases.aspx?ReleaseId=5583
Apparently the VM didn't suffer from this. We weren't sure if the VM had the hotfix applied or not or if this only happens on non-virtualized machines. Still, this solved all of the issues and the app is now snappy again. (Man, was this fun to track down! Ugh!!)
We have a Java Application server installed on our client's test server. Within application server, a number of threads access the filesystem in a number of ways (using java.io classes). The application server is started as a service. After a number of hours, sometimes up to a day, the filesystem seems to have become unavailable to these threads. On looking at the folders/directories in question on the filesystem, they are still present, appear to have the correct access permissions and do not appear to have exclusive locks on them. Is this possible? Any suggestions as to clues I should look for? Most likely causes?
The Operating system in question is Windows 2003 (Service Pack 2) with 32 bit processor. Filesystem is NTFS JRE is 1.6
I have already posted this on the serverFault Q&A, but it was suggested I pose the question here instead.
Check that your applications closes streams, such as FileInputStream, correctly.