I'm initiating a migration via QMP and seeing something unusual with qemu 2.0
(logs are from the QMP initiator and are doctored a little for readability):
08:49:37.047387 Sending JSON QMP:
{"execute":"migrate","arguments":{"uri":"tcp:10.157.128.51:2249"},"id":"0000000000000010"}
08:49:37.049530 Got JSON QMP: {"return": {}, "id": "0000000000000010"}
08:49:37.049639 Sending JSON QMP:
{"execute":"query-migrate","id":"0000000000000011"}
08:49:37.050628 Got JSON QMP: {"return": {}, "id": "0000000000000011"}
... initiator concludes migration has failed ...
08:49:37.050709 Sending JSON QMP:
{"execute":"migrate_cancel","id":"0000000000000012"}
08:49:37.051659 Got JSON QMP: {"return": {}, "id": "0000000000000012"}
Now, from the docs, the 'migrate' QMP command is meant to return an empty
object all the time (as far as I can tell). From the time difference, it
appears it's doing something.
'query-migrate' is specified to return an empty object only "before the
first migration" (see full extract below from qmp-commands.hx for details).
After the first migration (which I can only presume means 'after the
first migration has started') it's meant to return a status member of
either 'completed', 'active' or 'failed'. But it's doing none of these.
I am calling it a matter of microseconds after it's returned the QMP
object (see above) which I guess may be the issue.
Is this a documentation error (in which case can I safely treat no
return code as meaning in progress)? Or is this a bug? If a previous
migrate has failed is there a chance I might pick up "failed" if I
poll immediately afterwards?
Reading the code, there is a state 'setup' which doesn't seem to appear
in the docs. As far as I can see, if I poll the QMP status whilst it's
awaiting completion of the tcp non-blocking connect, it /should/ be
in the 'setup' status. But I'm not seeing "setup" here either.
Any idea how this is meant to work?
--
Alex Bligh
1. Before the first migration
-> { "execute": "query-migrate" }
<- { "return": {} }
2. Migration is done and has succeeded
-> { "execute": "query-migrate" }
<- { "return": {
"status": "completed",
"ram":{
"transferred":123,
"remaining":123,
"total":246,
"total-time":12345,
"setup-time":12345,
"downtime":12345,
"duplicate":123,
"normal":123,
"normal-bytes":123456,
"dirty-sync-count":15
}
}
}
3. Migration is done and has failed
-> { "execute": "query-migrate" }
<- { "return": { "status": "failed" } }
4. Migration is being performed and is not a block migration:
-> { "execute": "query-migrate" }
<- {
"return":{
"status":"active",
"ram":{
"transferred":123,
"remaining":123,
"total":246,
"total-time":12345,
"setup-time":12345,
"expected-downtime":12345,
"duplicate":123,
"normal":123,
"normal-bytes":123456,
"dirty-sync-count":15
}
}
}
