On 05/15/2014 11:19 PM, Eric Blake wrote:
On 05/15/2014 01:22 AM, Ján Tomko wrote:
If virDomainMemoryStats is called too soon after domain startup, QEMU returns: "error":{"class":"GenericError","desc":"guest hasn't updated any stats yet"} when we try to query balloon stats.
Check for this reply and log it as OPERATION_INVALID instead of INTERNAL_ERROR. This means the daemon only logs it at the debug level, without polluting system logs.
Reported by Laszlo Pal: https://www.redhat.com/archives/libvirt-users/2014-May/msg00023.html --- v1: https://www.redhat.com/archives/libvir-list/2014-May/msg00420.html v2: return 0 in this case - even though balloon stats are not yet available, we can still return 'rss' in qemuDomainMemoryStats jump to cleanup if CheckError returns < 0
src/qemu/qemu_monitor_json.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)
+ if ((data = virJSONValueObjectGet(reply, "error"))) { + const char *klass = virJSONValueObjectGetString(data, "class"); + const char *desc = virJSONValueObjectGetString(data, "desc");
- if (ret < 0) + if (STREQ_NULLABLE(klass, "GenericError") && + STREQ_NULLABLE(desc, "guest hasn't updated any stats yet")) {
Adding qemu. Uggh - the qemu documentation of QMP states:
- The "desc" member is a human-readable error message. Clients should not attempt to parse this message.
because the contents of that field are NOT guaranteed to be stable. We're stuck parsing that field for old versions of qemu, but this is one case where upstream qemu (for future versions) should change the "class" member of that particular error case to a distinct value other than GenericError so that it is trivially obvious when this particular condition has occurred, since it is a case where libvirt wants to treat it as a non-error.
reluctant ACK, while hoping that we can do something more reliable in the future.
I have pushed the patch now. The qemu patch reporting empty stats instead of this error should be on its way: https://lists.gnu.org/archive/html/qemu-devel/2014-05/msg04295.html Jan