Re: [libvirt] [Qemu-devel] qemu leaving unix sockets behind after VM is shut down
On Tue, Apr 01, 2014 at 02:34:58PM -0600, Chris Friesen wrote:
When running qemu with something like this
-device virtio-serial \ -chardev socket,path=/tmp/foo,server,nowait,id=foo \ -device virtserialport,chardev=foo,name=host.port.0
the VM starts up as expected and creates a socket at /tmp/foo as expected.
However, when I shut down the VM the socket at /tmp/foo is left behind in the filesystem. Basically qemu has "leaked" a file.
With something like OpenStack where we could be creating/destroying many VMs this could end up creating a significant number of files in the specified directory.
Has any thought been given to either automatically cleaning up the unix socket in the filesystem when qemu exits, or else supporting the abstract namespace for unix sockets to allow for automatic cleanup?
Libvirt has a special case for the monitor socket in its qemuProcessStop() function. Are you using the OpenStack libvirt driver? Perhaps QEMU should support cleanup but first I think we should check the situation with libvirt. Stefan
On Tue, May 06, 2014 at 03:39:57PM +0200, Stefan Hajnoczi wrote:
On Tue, Apr 01, 2014 at 02:34:58PM -0600, Chris Friesen wrote:
When running qemu with something like this
-device virtio-serial \ -chardev socket,path=/tmp/foo,server,nowait,id=foo \ -device virtserialport,chardev=foo,name=host.port.0
the VM starts up as expected and creates a socket at /tmp/foo as expected.
However, when I shut down the VM the socket at /tmp/foo is left behind in the filesystem. Basically qemu has "leaked" a file.
With something like OpenStack where we could be creating/destroying many VMs this could end up creating a significant number of files in the specified directory.
Has any thought been given to either automatically cleaning up the unix socket in the filesystem when qemu exits, or else supporting the abstract namespace for unix sockets to allow for automatic cleanup?
Libvirt has a special case for the monitor socket in its qemuProcessStop() function.
Are you using the OpenStack libvirt driver?
Perhaps QEMU should support cleanup but first I think we should check the situation with libvirt.
We have explicit cleanup (ie unlink() call) for the monitor UNIX socket, but guess we forgot todo the same for other char device sockets. We can't rely on QEMU to cleanup since it can obviously SEGV at any time which would prevent it cleaning up after itself. So libvirt must have any neccessary cleanup itself, even if QEMU did make an effort to clean up. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
On 05/06/2014 07:39 AM, Stefan Hajnoczi wrote:
On Tue, Apr 01, 2014 at 02:34:58PM -0600, Chris Friesen wrote:
When running qemu with something like this
-device virtio-serial \ -chardev socket,path=/tmp/foo,server,nowait,id=foo \ -device virtserialport,chardev=foo,name=host.port.0
the VM starts up as expected and creates a socket at /tmp/foo as expected.
However, when I shut down the VM the socket at /tmp/foo is left behind in the filesystem. Basically qemu has "leaked" a file.
With something like OpenStack where we could be creating/destroying many VMs this could end up creating a significant number of files in the specified directory.
Has any thought been given to either automatically cleaning up the unix socket in the filesystem when qemu exits, or else supporting the abstract namespace for unix sockets to allow for automatic cleanup?
Libvirt has a special case for the monitor socket in its qemuProcessStop() function.
Are you using the OpenStack libvirt driver?
Perhaps QEMU should support cleanup but first I think we should check the situation with libvirt.
Yes, I am in fact using OpenStack/libvirt, and did eventually track down libvirt as the code that was cleaning up the monitor socket. Even so, I think this sort of change would be valid in qemu itself. qemu created the files, so really it should be up to qemu to delete them when it's done with them. They're not usable for anything with qemu not running, so there's no good reason to leave them laying around. Chris
On 05/06/2014 08:52 AM, Chris Friesen wrote:
Yes, I am in fact using OpenStack/libvirt, and did eventually track down libvirt as the code that was cleaning up the monitor socket.
Even so, I think this sort of change would be valid in qemu itself. qemu created the files, so really it should be up to qemu to delete them when it's done with them.
They're not usable for anything with qemu not running, so there's no good reason to leave them laying around.
In the case of sVirt with SELinux labeling, it's often the case that libvirt has to pre-create the file (as qemu itself is prevented from creating the file itself) - that is also an argument for libvirt doing the cleanup. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
On 05/06/2014 03:39 PM, Stefan Hajnoczi wrote:
On Tue, Apr 01, 2014 at 02:34:58PM -0600, Chris Friesen wrote:
When running qemu with something like this
-device virtio-serial \ -chardev socket,path=/tmp/foo,server,nowait,id=foo \ -device virtserialport,chardev=foo,name=host.port.0
the VM starts up as expected and creates a socket at /tmp/foo as expected.
However, when I shut down the VM the socket at /tmp/foo is left behind in the filesystem. Basically qemu has "leaked" a file.
With something like OpenStack where we could be creating/destroying many VMs this could end up creating a significant number of files in the specified directory.
Has any thought been given to either automatically cleaning up the unix socket in the filesystem when qemu exits, or else supporting the abstract namespace for unix sockets to allow for automatic cleanup?
I have sent a libvirt patch to clean up the sockets on qemu shutdown: https://www.redhat.com/archives/libvir-list/2014-May/msg00398.html Jan
Libvirt has a special case for the monitor socket in its qemuProcessStop() function.
Are you using the OpenStack libvirt driver?
Perhaps QEMU should support cleanup but first I think we should check the situation with libvirt.
Stefan
-- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
participants (5)
-
Chris Friesen -
Daniel P. Berrange -
Eric Blake -
Ján Tomko -
Stefan Hajnoczi