Re: [libvirt] cont command failing via JSON monitor on restore

Daniel P. Berrange wrote: > > > > Yep, it wasn't really intended as a fix. It was intended to make > > the error scenario clearly detectable, which has succeeded as per > > Jim's report. The fact that QMP returned an error in this way, > > means we can now reliably detect, usleep(1000), and then retry > > the 'cont' again at which point we should succeed. > > Something like the attached patch? I'm not quite sure about the retry bounds (currently 1 second). In my testing, it always succeeds on the second attempt - even with large memory vms.

0001-qemu-Retry-JSON-monitor-cont-cmd-on-MigrationExpecte.patch > From ec9109b40a4b2c45035495e0e4f65824a92dcf3d Mon Sep 17 00:00:00 2001 From: Jim Fehlig&lt;jfehlig(a)novell.com&gt; Date: Thu, 13 Jan 2011 12:52:23 -0700 Subject: [PATCH] qemu: Retry JSON monitor cont cmd on MigrationExpected error When restoring a saved qemu instance via JSON monitor, the vm is left in a paused state. Turns out the 'cont' cmd was failing with "MigrationExpected" error class and "An incoming migration is expected before this command can be executed" error description due to migration (restore) not yet complete. Detect if 'cont' cmd fails with "MigrationExpecte" error class and retry 'cont' cmd. --- src/qemu/qemu_monitor_json.c | 20 +++++++++++++++++--- 1 files changed, 17 insertions(+), 3 deletions(-) diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c index 7877731..63b736e 100644 --- a/src/qemu/qemu_monitor_json.c +++ b/src/qemu/qemu_monitor_json.c @@ -702,13 +702,27 @@ qemuMonitorJSONStartCPUs(qemuMonitorPtr mon, int ret; virJSONValuePtr cmd = qemuMonitorJSONMakeCommand("cont", NULL); virJSONValuePtr reply = NULL; + int i = 0, timeout = 3; if (!cmd) return -1; - ret = qemuMonitorJSONCommand(mon, cmd,&reply); + do { + ret = qemuMonitorJSONCommand(mon, cmd,&reply); - if (ret == 0) - ret = qemuMonitorJSONCheckError(cmd, reply); + if (ret != 0) + break; + + /* If no error, we're done */ + if ((ret = qemuMonitorJSONCheckError(cmd, reply)) == 0) + break; + + /* If error class is not MigrationExpected, we're done. + * Otherwise try 'cont' cmd again */ + if (!qemuMonitorJSONHasError(reply, "MigrationExpected")) + break; + + virJSONValueFree(reply); + } while ((++i<= timeout)&& (usleep(250000)<=0)); virJSONValueFree(cmd); virJSONValueFree(reply);