Hmm, looks like the snapshot code does not properly set jobInfo->statsType:

(gdb) p jobInfo
$1 = {
    status = QEMU_DOMAIN_JOB_STATUS_COMPLETED,
    operation = VIR_DOMAIN_JOB_OPERATION_SNAPSHOT,
    started = 1552567278659,
    stopped = 1552567278667,
    sent = 0,
    received = 0,
    timeElapsed = 30,
    timeDelta = 0,
    timeDeltaSet = false,
    statsType = QEMU_DOMAIN_JOB_STATS_TYPE_NONE,
    stats = {
        mig = {
            status = 6,
            total_time = 17,
            downtime_set = true,
            downtime = 22,
            setup_time_set = true,
            setup_time = 1,
            ram_transferred = 3510941,
            ram_remaining = 0,
            ram_total = 168370176,
            ram_bps = 228062937,
            ram_duplicate_set = true,
            ram_duplicate = 40339,
            ram_normal = 767,
            ram_normal_bytes = 3141632,
            ram_dirty_rate = 0,
            ram_page_size = 4096,
            ram_iteration = 2,
            ...
        },
        dump = {
            status = 6,
            completed = 17,
            total = 1
        }
    },
    mirrorStats = {
        transferred = 0,
        total = 0
    }
}

The patch was sent upstream for review: https://www.redhat.com/archives/libvir-list/2019-March/msg00971.html

This bug is fixed upstream by

commit 1c2a9260e865af8ad7dde9cdd21515800d1864e7
Refs: v5.1.0-237-g1c2a9260e8
Author:     Jiri Denemark <jdenemar>
AuthorDate: Thu Mar 14 15:33:26 2019 +0100
Commit:     Jiri Denemark <jdenemar>
CommitDate: Fri Mar 15 09:39:19 2019 +0100

    qemu: Set job statsType for external memory snapshot

    Any job which is able to provide statistics that can be queried via
    virDomainGetJob{Stats,Info} has to set an appropriate statsType.

    Without a proper statsType qemuDomainJobInfoToParams and
    qemuDomainJobInfoToInfo have no idea what statistics should be sent to
    the API caller.

    https://bugzilla.redhat.com/show_bug.cgi?id=1688774

    Signed-off-by: Jiri Denemark <jdenemar>
    Reviewed-by: Erik Skultety <eskultet>

Meet a new problem after the fix, pls help to confirm

=========================
Do following thing at the same time in different consoles:
=========================
a. (IN VM) generate some data to make the snapshot process last long:
# dd if=/dev/urandom of=/tmp/1.file bs=1K count=5000000

b. (IN HOST CONSOLE 1) create the snapshot as follow:
[root@hp-z220-02 tmp]# virsh snapshot-create-as  61a1423f-5591-4b36-94ad-be0d982c34e5 s1 --memspec file=/tmp/snap.1

c. (IN HOST CONSOLE 2) check the domjobinfo:
[root@hp-z220-02 ~]# time virsh domjobinfo 61a1423f-5591-4b36-94ad-be0d982c34e5


=========================
RESULT:
=========================
at above step c, the cmd just hangs there, will return something after step b finished, as follow:

b1:
[root@hp-z220-02 tmp]# virsh snapshot-create-as  61a1423f-5591-4b36-94ad-be0d982c34e5 s1 --memspec file=/tmp/snap.1
Domain snapshot s1 created

c1:
[root@hp-z220-02 ~]# time virsh domjobinfo 61a1423f-5591-4b36-94ad-be0d982c34e5
Job type:         None        

real	0m27.377s
user	0m0.011s
sys	0m0.005s

=========================
Problem:
=========================
During taking snapshot, the domjobinfo should display the info about the running job, something like following:
Tue Apr 10 07:03:56 EDT 2018
Job type:         Unbounded   
Operation:        Snapshot
Time elapsed:     1027         ms
Data processed:   110.118 MiB
Data remaining:   151.859 MiB
Data total:       1.126 GiB
Memory processed: 110.118 MiB
Memory remaining: 151.859 MiB
Memory total:     1.126 GiB
Memory bandwidth: 223.485 MiB/s
Dirty rate:       0            pages/s
Iteration:        1           
Constant pages:   228613      
Normal pages:     27634       
Normal data:      107.945 MiB
Expected downtime: 300          ms
Setup time:       8            ms

Hi yisun

The "hang" problem you met is a different issue and is tracked in this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1565552#c2

Actually you can only get the domjobinfo in memory snapshot phase which is very short, but you could increase the guest memory size to make the phase longer. Note: adding memory load in guest will not help, because guest is paused at the beginning.

And note that you can monitor libvirtd log when do the test, after you see libvirtd sends command "migrate" to qemu monitor, you could try to query domjobinfo immediately.

(In reply to Fangge Jin from comment #7)
> Hi yisun
> 
> The "hang" problem you met is a different issue and is tracked in this bug:
> https://bugzilla.redhat.com/show_bug.cgi?id=1565552#c2
> 
> Actually you can only get the domjobinfo in memory snapshot phase which is
> very short, but you could increase the guest memory size to make the phase
> longer. Note: adding memory load in guest will not help, because guest is
> paused at the beginning.
> 
> And note that you can monitor libvirtd log when do the test, after you see
> libvirtd sends command "migrate" to qemu monitor, you could try to query
> domjobinfo immediately.

Thx for the info
Verified with:
libvirt-5.0.0-7.module+el8+2887+effa3c42.x86_64

1. in vm run:
[root@localhost ~]# dd if=/dev/urandom of=/tmp/1.file bs=1K count=5000000

2. in host console 1 run:
[root@localhost ~]# virsh snapshot-create-as 5d9e1bfb-9342-4530-82b1-f8c2dac70e8d s1 --memspec file=/tmp/snap.1

3. in host console 2 run:
[root@localhost ~]# virsh domjobinfo 5d9e1bfb-9342-4530-82b1-f8c2dac70e8d

4. check console 1 until snapshot finished:
[root@localhost ~]# virsh snapshot-create-as 5d9e1bfb-9342-4530-82b1-f8c2dac70e8d s1 --memspec file=/tmp/snap.1
Domain snapshot s1 created

5. check console 2 make sure there is no error:
[root@localhost ~]# virsh domjobinfo 5d9e1bfb-9342-4530-82b1-f8c2dac70e8d
Job type:         None  
<=== This is hang until snapshot finished, tracked by bz565552


[root@localhost ~]# virsh domjobinfo 5d9e1bfb-9342-4530-82b1-f8c2dac70e8d --completed
Job type:         Completed   
Operation:        Snapshot    
Time elapsed:     2298         ms
Data processed:   700.835 MiB
Data remaining:   0.000 B
Data total:       1.126 GiB
Memory processed: 700.835 MiB
Memory remaining: 0.000 B
Memory total:     1.126 GiB
Memory bandwidth: 1.340 GiB/s
Dirty rate:       0            pages/s
Page size:        4096         bytes
Iteration:        3           
Postcopy requests: 0           
Constant pages:   116251      
Normal pages:     178809      
Normal data:      698.473 MiB
Total downtime:   526          ms
Setup time:       6            ms

(In reply to yisun from comment #8)
> (In reply to Fangge Jin from comment #7)
> > Hi yisun
> > 
> > The "hang" problem you met is a different issue and is tracked in this bug:
> > https://bugzilla.redhat.com/show_bug.cgi?id=1565552#c2
> > 
> > Actually you can only get the domjobinfo in memory snapshot phase which is
> > very short, but you could increase the guest memory size to make the phase
> > longer. Note: adding memory load in guest will not help, because guest is
> > paused at the beginning.
> > 
> > And note that you can monitor libvirtd log when do the test, after you see
> > libvirtd sends command "migrate" to qemu monitor, you could try to query
> > domjobinfo immediately.
> 
> Thx for the info
> Verified with:
> libvirt-5.0.0-7.module+el8+2887+effa3c42.x86_64
> 
> 1. in vm run:
> [root@localhost ~]# dd if=/dev/urandom of=/tmp/1.file bs=1K count=5000000
> 
> 2. in host console 1 run:
> [root@localhost ~]# virsh snapshot-create-as
> 5d9e1bfb-9342-4530-82b1-f8c2dac70e8d s1 --memspec file=/tmp/snap.1
> 
> 3. in host console 2 run:
> [root@localhost ~]# virsh domjobinfo 5d9e1bfb-9342-4530-82b1-f8c2dac70e8d
> 
> 4. check console 1 until snapshot finished:
> [root@localhost ~]# virsh snapshot-create-as
> 5d9e1bfb-9342-4530-82b1-f8c2dac70e8d s1 --memspec file=/tmp/snap.1
> Domain snapshot s1 created
> 
> 5. check console 2 make sure there is no error:
> [root@localhost ~]# virsh domjobinfo 5d9e1bfb-9342-4530-82b1-f8c2dac70e8d
> Job type:         None  
> <=== This is hang until snapshot finished, tracked by bz565552
<==== typo here, should be bz1565552

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2019:1293