Re: [Qemu-devel] [PATCH v2 2/3] scripts: add render_block_graph function for QEMUMachine

[Eduardo Habkost <ehabkost@redhat.com>]

On Fri, Aug 17, 2018 at 09:59:41PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> 17.08.2018 21:25, Eduardo Habkost wrote:
> > On Fri, Aug 17, 2018 at 09:04:39PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> > > Render block nodes graph with help of graphviz. This new function is
> > > for debugging, so there is no sense to put it into qemu.py as a method
> > > of QEMUMachine. Let's instead put it separately.
> > > 
> > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> > > ---
> > >   scripts/render_block_graph.py | 78 +++++++++++++++++++++++++++++++++++++++++++
> > >   1 file changed, 78 insertions(+)
> > >   create mode 100644 scripts/render_block_graph.py
> > > 
> > > diff --git a/scripts/render_block_graph.py b/scripts/render_block_graph.py
> > > new file mode 100644
> > > index 0000000000..7048a0bac8
> > > --- /dev/null
> > > +++ b/scripts/render_block_graph.py
> > > @@ -0,0 +1,78 @@
> > > +# Render Qemu Block Graph
> > [...]
> > 
> > What about making the script work from the command-line?
> > 
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> > diff --git a/scripts/render_block_graph.py b/scripts/render_block_graph.py
> > old mode 100644
> > new mode 100755
> > index 7048a0bac8..e29fe0fc41
> > --- a/scripts/render_block_graph.py
> > +++ b/scripts/render_block_graph.py
> > @@ -1,3 +1,4 @@
> > +#!/usr/bin/env python
> >   # Render Qemu Block Graph
> >   #
> >   # Copyright (c) 2017 Parallels International GmbH
> > @@ -16,8 +17,9 @@
> >   # along with this program.  If not, see <http://www.gnu.org/licenses/>.
> >   #
> > -import os
> > +import os, sys
> >   from graphviz import Digraph
> > +from qmp.qmp import QEMUMonitorProtocol
> >   def perm(arr):
> >       s = 'w' if 'write' in arr else '_'
> > @@ -27,16 +29,16 @@ def perm(arr):
> >       s += 's' if 'resize' in arr else '_'
> >       return s
> > -def render_block_graph(vm, filename, pointers=False, format='png'):
> > +def render_block_graph(qmp, filename, pointers=False, format='png'):
> >       '''
> >       Render graph in text (dot) representation into "@filename" and
> >       representation in @format into "@filename.@format"
> >       '''
> > -    nodes = vm.command('query-named-block-nodes')
> > +    nodes = qmp.command('query-named-block-nodes')
> >       nodes_info = {n['node-name']: n for n in nodes}
> > -    block_graph = vm.command('x-query-block-graph')
> > +    block_graph = qmp.command('x-query-block-graph')
> >       graph = Digraph(comment='Block Nodes Graph')
> >       graph.format = format
> > @@ -76,3 +78,9 @@ def render_block_graph(vm, filename, pointers=False, format='png'):
> >           graph.edge(str(e['parent']), str(e['child']), label=label)
> >       graph.render(filename)
> > +
> > +if __name__ == '__main__':
> > +    #TODO: use argparse for command-line arguments
> > +    qmp = QEMUMonitorProtocol(sys.argv[1])
> > +    qmp.connect()
> > +    render_block_graph(qmp, sys.argv[2])
> > 
> > 
> 
> Cool, thanks.
> 
> so, how to use it then?
> 
> for python iotest a proper parameter would be vm._qmp, yes?

Yes, assuming you just want to do it locally just for debugging.

One thing we could do later: refactor QEMUMachine and
QEMUMonitorProtocol so their method names are the same and both
'vm' and 'vm._qmp' work here.

> 
> is there a way to dump running libvirt vm graph?
> 
> I've started libvirt guest, qemu process has cmdline parameters
> -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-3-tmp/monitor.sock,server,nowait
> -mon chardev=charmonitor,id=monitor,mode=control
> 
> command
> virsh qemu-monitor-command tmp '{"execute": "x-query-block-graph"}'
> works fine,
> 
> but script hangs on connection:
> # python ./scripts/render_block_graph.py
> /var/lib/libvirt/qemu/domain-3-tmp/monitor.sock
> ^CTraceback (most recent call last):
>   File "./scripts/render_block_graph.py", line 85, in <module>
>     qmp.connect()
>   File "/work/src/qemu/up-new-fleecing/scripts/qmp/qmp.py", line 140, in
> connect
>     self.__sock.connect(self.__address)
>   File "/usr/lib64/python2.7/socket.py", line 224, in meth
>     return getattr(self._sock,name)(*args)
> KeyboardInterrupt
> 
> ./scripts/qmp/qmp-shell /var/lib/libvirt/qemu/domain-3-tmp/monitor.sock
> outputs nothing...

I don't know why it doesn't work with a running instance started
by libvirt, but it works if I run QEMU manually using "-qmp
unix:/tmp/qmp,server".

-- 
Eduardo