Re: [libvirt] [Libguestfs] Quantifying libvirt errors in launching the libguestfs appliance

On Wed, Jan 13, 2016 at 16:25:14 +0100, Martin Kletzander wrote: > On Wed, Jan 13, 2016 at 10:18:42AM +0000, Richard W.M. Jones wrote: > >As people may know, we frequently encounter errors caused by libvirt > >when running the libguestfs appliance. > > > >I wanted to find out exactly how frequently these happen and classify > >the errors, so I ran the 'virt-df' tool overnight 1700 times. This > >tool runs several parallel qemu:///session libvirt connections both > >creating a short-lived appliance guest. > > > >Note that I have added Cole's patch to fix https://bugzilla.redhat.com/1271183 > >"XML-RPC error : Cannot write data: Transport endpoint is not connected" > > > >Results: > > > >The test failed 538 times (32% of the time), which is pretty dismal. > >To be fair, virt-df is aggressive about how it launches parallel > >libvirt connections. Most other virt-* tools use only a single > >libvirt connection and are consequently more reliable. > > > >Of the failures, 518 (96%) were of the form: > > > > process exited while connecting to monitor: qemu: could not load kernel '/home/rjones/d/libguestfs/tmp/.guestfs-1000/appliance.d/kernel': Permission denied > > > >which is https://bugzilla.redhat.com/921135 or maybe > >https://bugzilla.redhat.com/1269975. It's not clear to me if these > >bugs have different causes, but if they do then potentially we're > >seeing a mix of both since my test has no way to distinguish them. > > > > It looks to me as the same problem. And as the same problem we were > talking about bunch of time and, apparently, didn't get to a conclusion. > > For each of the kernels, libvirt labels them (with both DAC and selinux > labels), then proceeds to launching qemu. If this is done parallel, the > race is pretty obvious. Could you remind me why you couldn't use > <seclabel model='none'/> or <seclabel relabel='no'/> or something that > would mitigate this? If we cannot use this, then we need to implement > the <seclabel/> element for kernel and initrd. Hmm, can't we just label kernel and initrd files the same way we label <shareable/> disk images, i.e., non-exclusive label so that all QEMU process can access them and avoid removing the label once a domain disappears?