[libvirt] [PATCH v2 3/8] Add support for fetching statistics of completed jobs

[Philipp Hahn]

Hi,

FYI as tracking down that failure did cost me some time and hopefully
this summary will help other to avoid this situation:

Am 09.09.2014 um 11:54 schrieb Jiri Denemark:
> virDomainGetJobStats gains new VIR_DOMAIN_JOB_STATS_COMPLETED flag that
> can be used to fetch statistics of a completed job rather than a
> currently running job.
> 
> Signed-off-by: Jiri Denemark <jdenemar at redhat.com>
...
> --- a/src/qemu/qemu_monitor_json.c
> +++ b/src/qemu/qemu_monitor_json.c
> @@ -2500,7 +2500,8 @@ qemuMonitorJSONGetMigrationStatusReply(virJSONValuePtr reply,
...
> -    if (status->status == QEMU_MONITOR_MIGRATION_STATUS_ACTIVE) {
> +    if (status->status == QEMU_MONITOR_MIGRATION_STATUS_ACTIVE ||
> +        status->status == QEMU_MONITOR_MIGRATION_STATUS_COMPLETED) {
>          virJSONValuePtr ram = virJSONValueObjectGet(ret, "ram");
>          if (!ram) {
>              virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>                            _("migration was active, but RAM 'transferred' "
>                              "data was missing"));

This change from libvirt v1.2.9-rc1~203 breaks migration with
qemu-kvm-1.1.2, as that ancient implementation does *not* export
transfer statistics for completed jobs:

> qemuMonitorJSONCommandWithFd:286 : Send command '{"execute":"query-migrate","id":"libvirt-41"}' for write with FD -1
> qemuMonitorJSONIOProcessLine:179 : Line [{"return": {"status": "active", "ram": {"total": 2164654080, "remaining": 22474752, "transferred": 175117413}}, "id": "libvirt-41"}]
...
> qemuMonitorJSONCommandWithFd:286 : Send command '{"execute":"query-migrate","id":"libvirt-42"}' for write with FD -1
> qemuMonitorJSONIOProcessLine:179 : Line [{"return": {"status": "completed"}, "id": "libvirt-42"}]

As you can see, there is not "ram" section and the migration is aborted
with the message:
> internal error: migration was active, but no RAM info was set

qemu-kvm/qmp-commands.hx even states this:
> - "ram": only present if "status" is "active", it is a json-object with the
>   following RAM information (in bytes):
but the example some lines below is wrong:
> 2. Migration is done and has succeeded
> 
> -> { "execute": "query-migrate" }
> <- { "return": {
>         "status": "completed",
>         "ram":{
That example has been updated by v1.2.0-rc0~29^2~2, but forgot to update
the specification above.


The attached hack for libvirt makes migration work again for me by
making "ram" optional in case of "completed".

Philipp
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