scripts: add render_block_graph function for QEMUMachine

#!/usr/bin/env python

#

# Render Qemu Block Graph

#

# Copyright (c) 2018 Virtuozzo International GmbH. All rights reserved.

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program.  If not, see <http://www.gnu.org/licenses/>.

#

import os

import sys

import subprocess

import json

from graphviz import Digraph

from qemu import MonitorResponseError

def perm(arr):

    s = 'w' if 'write' in arr else '_'

    s += 'r' if 'consistent-read' in arr else '_'

    s += 'u' if 'write-unchanged' in arr else '_'

    s += 'g' if 'graph-mod' in arr else '_'

    s += 's' if 'resize' in arr else '_'

    return s

def render_block_graph(qmp, filename, format='png'):

    '''

    Render graph in text (dot) representation into "@filename" and

    representation in @format into "@filename.@format"

    '''

    bds_nodes = qmp.command('query-named-block-nodes')

    bds_nodes = {n['node-name']: n for n in bds_nodes}

    job_nodes = qmp.command('query-block-jobs')

    job_nodes = {n['device']: n for n in job_nodes}

    block_graph = qmp.command('x-debug-query-block-graph')

    graph = Digraph(comment='Block Nodes Graph')

    graph.format = format

    graph.node('permission symbols:\l'

               '  w - Write\l'

               '  r - consistent-Read\l'

               '  u - write - Unchanged\l'

               '  g - Graph-mod\l'

               '  s - reSize\l'

               'edge label scheme:\l'

               '  <child type>\l'

               '  <perm>\l'

               '  <shared_perm>\l', shape='none')

    for n in block_graph['nodes']:

        if n['type'] == 'block-driver':

            info = bds_nodes[n['name']]

            label = n['name'] + ' [' + info['drv'] + ']'

            if info['drv'] == 'file':

                label += '\n' + os.path.basename(info['file'])

            shape = 'ellipse'

        elif n['type'] == 'block-job':

            info = job_nodes[n['name']]

            label = info['type'] + ' job (' + n['name'] + ')'

            shape = 'box'

        else:

            assert n['type'] == 'block-backend'

            label = n['name'] if n['name'] else 'unnamed blk'

            shape = 'box'

        graph.node(str(n['id']), label, shape=shape)

    for e in block_graph['edges']:

        label = '%s\l%s\l%s\l' % (e['name'], perm(e['perm']),

                                  perm(e['shared-perm']))

        graph.edge(str(e['parent']), str(e['child']), label=label)

    graph.render(filename)

class LibvirtGuest():

    def __init__(self, name):

        self.name = name

    def command(self, cmd):

        # only supports qmp commands without parameters

        m = {'execute': cmd}

        ar = ['virsh', 'qemu-monitor-command', self.name, json.dumps(m)]

        reply = json.loads(subprocess.check_output(ar))

        if 'error' in reply:

            raise MonitorResponseError(reply)

        return reply['return']

if __name__ == '__main__':

    obj = sys.argv[1]

    out = sys.argv[2]

    if os.path.exists(obj):

        # assume unix socket

        qmp = QEMUMonitorProtocol(obj)

        qmp.connect()

    else:

        # assume libvirt guest name

        qmp = LibvirtGuest(obj)

    render_block_graph(qmp, out)