vmdriver: static connection class and fixing pep issues.

vmdriver.py

+""" Driver for libvirt. """
 import libvirt
 import logging
 import os
@@ -8,7 +9,6 @@ from vmcelery import celery, lib_connection
 
 sys.path.append(os.path.dirname(os.path.basename(__file__)))
 
-connection = None
 
 state_dict = {0: 'NOSTATE',
               1: 'RUNNING',
@@ -21,16 +21,51 @@ state_dict = {0: 'NOSTATE',
               }
 
 
+#class Singleton(type):
+#
+#    """ Singleton class."""
+#
+#    _instances = {}
+#
+#    def __call__(cls, *args, **kwargs):
+#        if cls not in cls._instances:
+#            cls._instances[cls] = super(Singleton, cls).__call__(*args,
+#                                                                 **kwargs)
+#        return cls._instances[cls]
+
+
+class Connection(object):
+
+    """ Singleton class to handle connection."""
+
+#    __metaclass__ = Singleton
+    connection = None
+
+    @classmethod
+    def get(cls):
+        """ Return the libvirt connection."""
+
+        return cls.connection
+
+    @classmethod
+    def set(cls, connection):
+        """ Set the libvirt connection."""
+
+        cls.connection = connection
+
+
 @decorator
 def req_connection(original_function, *args, **kw):
-    '''Connection checking decorator for libvirt.
+    """Connection checking decorator for libvirt.
 
     If envrionment variable LIBVIRT_KEEPALIVE is set
     it will use the connection from the celery worker.
-    '''
+
+    Return the decorateed function
+
+    """
     logging.debug("Decorator running")
-    global connection
-    if connection is None:
+    if Connection.get() is None:
         connect()
         try:
             logging.debug("Decorator calling original function")
@@ -48,6 +83,11 @@ def req_connection(original_function, *args, **kw):
 
 @decorator
 def wrap_libvirtError(original_function, *args, **kw):
+    """ Decorator to wrap libvirt error in simple Exception.
+
+    Return decorated function
+
+    """
     try:
         return original_function(*args, **kw)
     except libvirt.libvirtError as e:
@@ -60,34 +100,34 @@ def wrap_libvirtError(original_function, *args, **kw):
 @celery.task
 @wrap_libvirtError
 def connect(connection_string='qemu:///system'):
-    '''Connect to the libvirt daemon specified in the
-    connection_string or the local root.
-    '''
-    global connection
+    """ Connect to the libvirt daemon.
+
+    String is specified in the connection_string parameter
+    the default is the local root.
+
+    """
     if os.getenv('LIBVIRT_KEEPALIVE') is None:
-        if connection is None:
-            connection = libvirt.open(connection_string)
+        if Connection.get() is None:
+            Connection.set(libvirt.open(connection_string))
             logging.debug("Connection estabilished to libvirt.")
         else:
             logging.debug("There is already an active connection to libvirt.")
     else:
-        connection = lib_connection
+        Connection.set(lib_connection)
         logging.debug("Using celery libvirt connection connection.")
 
 
 @celery.task
 @wrap_libvirtError
 def disconnect():
-    '''Disconnect from the active libvirt daemon connection.
-    '''
-    global connection
+    """ Disconnect from the active libvirt daemon connection."""
     if os.getenv('LIBVIRT_KEEPALIVE') is None:
-        if connection is None:
+        if Connection.get() is None:
             logging.debug('There is no available libvirt conection.')
         else:
-            connection.close()
+            Connection.get().close()
             logging.debug('Connection closed to libvirt.')
-            connection = None
+            Connection.set(None)
     else:
         logging.debug('Keepalive connection should not close.')
 
@@ -96,9 +136,8 @@ def disconnect():
 @req_connection
 @wrap_libvirtError
 def define(vm):
-    '''Define permanent virtual machine from xml
-    '''
-    connection.defineXML(vm.dump_xml())
+    """ Define permanent virtual machine from xml. """
+    Connection.get().defineXML(vm.dump_xml())
     logging.info("Virtual machine %s is defined from xml", vm.name)
 
 
@@ -106,14 +145,17 @@ def define(vm):
 @req_connection
 @wrap_libvirtError
 def create(vm_desc):
-    '''Create and start non-permanent virtual machine from xml
+    """ Create and start non-permanent virtual machine from xml.
+
+    Return the domain info dict.
     flags can be:
         VIR_DOMAIN_NONE = 0
         VIR_DOMAIN_START_PAUSED = 1
         VIR_DOMAIN_START_AUTODESTROY = 2
         VIR_DOMAIN_START_BYPASS_CACHE = 4
         VIR_DOMAIN_START_FORCE_BOOT = 8
-    '''
+
+    """
     vm = VMInstance.deserialize(vm_desc)
     # Setting proper hypervisor
     vm.vm_type = os.getenv("HYPERVISOR_TYPE", "test")
@@ -121,13 +163,13 @@ def create(vm_desc):
     logging.info(xml)
     # Emulating DOMAIN_START_PAUSED FLAG behaviour on test driver
     if vm.vm_type == "test":
-        connection.createXML(
+        Connection.get().createXML(
             xml, libvirt.VIR_DOMAIN_NONE)
         domain = lookupByName(vm.name)
         domain.suspend()
     # Real driver create
     else:
-            connection.createXML(
+        Connection.get().createXML(
             vm.dump_xml(), libvirt.VIR_DOMAIN_START_PAUSED)
         logging.info("Virtual machine %s is created from xml", vm.name)
     return domain_info(vm.name)
@@ -137,19 +179,17 @@ def create(vm_desc):
 @req_connection
 @wrap_libvirtError
 def shutdown(name):
-    '''Shutdown virtual machine (need ACPI support).
-    '''
+    """ Shutdown virtual machine (need ACPI support). """
+
     domain = lookupByName(name)
     domain.shutdown()
-    return _parse_info(domain.info())
 
 
 @celery.task
 @req_connection
 @wrap_libvirtError
 def delete(name):
-    '''Destroy the running called 'name' virtual machine.
-    '''
+    """ Destroy the running called 'name' virtual machine. """
     domain = lookupByName(name)
     domain.destroy()
 
@@ -158,12 +198,14 @@ def delete(name):
 @req_connection
 @wrap_libvirtError
 def list_domains():
-    '''
-    :return list: List of domains name in host
-    '''
+    """ List the running domains.
+
+    :return list: List of domains name in host.
+
+    """
     domain_list = []
-    for i in connection.listDomainsID():
-        dom = connection.lookupByID(i)
+    for i in Connection.get().listDomainsID():
+        dom = Connection.get().lookupByID(i)
         domain_list.append(dom.name())
     return domain_list
 
@@ -172,18 +214,19 @@ def list_domains():
 @req_connection
 @wrap_libvirtError
 def lookupByName(name):
-    '''Return with the requested Domain
-    '''
-    return connection.lookupByName(name)
+    """ Return with the requested Domain. """
+    return Connection.get().lookupByName(name)
 
 
 @celery.task
 @req_connection
 @wrap_libvirtError
 def undefine(name):
-    '''Undefine an already defined virtual machine.
-    If it's running it becomes transient (lsot on reboot)
-    '''
+    """ Undefine an already defined virtual machine.
+
+    If it's running it becomes transient (lost on reboot)
+
+    """
     domain = lookupByName(name)
     domain.undefine()
 
@@ -192,8 +235,8 @@ def undefine(name):
 @req_connection
 @wrap_libvirtError
 def start(name):
-    '''Start an already defined virtual machine.
-    '''
+    """ Start an already defined virtual machine."""
+
     domain = lookupByName(name)
     domain.create()
 
@@ -202,8 +245,12 @@ def start(name):
 @req_connection
 @wrap_libvirtError
 def suspend(name):
-    '''Stop virtual machine and keep memory in RAM.
-    '''
+    """ Stop virtual machine and keep memory in RAM.
+
+    Return the domain info dict.
+
+    """
+
     domain = lookupByName(name)
     domain.suspend()
     return _parse_info(domain.info())
@@ -213,8 +260,8 @@ def suspend(name):
 @req_connection
 @wrap_libvirtError
 def save(name, path):
-    '''Stop virtual machine and save its memory to path.
-    '''
+    """ Stop virtual machine and save its memory to path. """
+
     domain = lookupByName(name)
     domain.save(path)
 
@@ -223,9 +270,14 @@ def save(name, path):
 @req_connection
 @wrap_libvirtError
 def restore(name, path):
-    '''Restore a saved virtual machine
-    from the memory image stored at path.'''
-    connection.restore(path)
+    """ Restore a saved virtual machine.
+
+    Restores the virtual machine from the memory image
+    stored at path.
+    Return the domain info dict.
+
+    """
+    Connection.get().restore(path)
     return domain_info(name)
 
 
@@ -233,8 +285,12 @@ def restore(name, path):
 @req_connection
 @wrap_libvirtError
 def resume(name):
-    '''Resume stopped virtual machines.
-    '''
+    """ Resume stopped virtual machines.
+
+    Return the domain info dict.
+
+    """
+
     domain = lookupByName(name)
     domain.resume()
     return _parse_info(domain.info())
@@ -244,8 +300,12 @@ def resume(name):
 @req_connection
 @wrap_libvirtError
 def reset(name):
-    '''Reset (power reset) virtual machine.
-    '''
+    """ Reset (power reset) virtual machine.
+
+    Return the domain info dict.
+
+    """
+
     domain = lookupByName(name)
     domain.reset()
     return _parse_info(domain.info())
@@ -255,8 +315,11 @@ def reset(name):
 @req_connection
 @wrap_libvirtError
 def reboot(name):
-    '''Reboot (with guest acpi support) virtual machine.
-    '''
+    """ Reboot (with guest acpi support) virtual machine.
+
+    Return the domain info dict.
+
+    """
     domain = lookupByName(name)
     domain.reboot()
     return _parse_info(domain.info())
@@ -266,7 +329,10 @@ def reboot(name):
 @req_connection
 @wrap_libvirtError
 def node_info():
-    ''' Get info from Host as dict:
+    """ Get info from Host as dict.
+
+    Return dict:
+
     model   string indicating the CPU model
     memory  memory size in kilobytes
     cpus    the number of active CPUs
@@ -279,15 +345,22 @@ def node_info():
     cores    number of cores per socket, total number of
              processors in case of unusual NUMA topolog
     threads  number of threads per core, 1 in case of unusual numa topology
-    '''
+
+    """
+
     keys = ['model', 'memory', 'cpus', 'mhz',
             'nodes', 'sockets', 'cores', 'threads']
-    values = connection.getInfo()
+    values = Connection.get().getInfo()
     return dict(zip(keys, values))
 
 
 def _parse_info(values):
-    '''Parse libvirt domain info into dict'''
+    """ Parse libvirt domain info into dict.
+
+    Return the info dict.
+
+    """
+
     keys = ['state', 'maxmem', 'memory', 'virtcpunum', 'cputime']
     info = dict(zip(keys, values))
     # Change state to proper ENUM
@@ -299,13 +372,16 @@ def _parse_info(values):
 @req_connection
 @wrap_libvirtError
 def domain_info(name):
-    '''
+    """ Get the domain info from libvirt.
+
+    Return the domain info dict:
     state   the running state, one of virDomainState
     maxmem  the maximum memory in KBytes allowed
     memory  the memory in KBytes used by the domain
     virtcpunum    the number of virtual CPUs for the domain
     cputime    the CPU time used in nanoseconds
-    '''
+
+    """
     dom = lookupByName(name)
     return _parse_info(dom.info())
 
@@ -314,7 +390,8 @@ def domain_info(name):
 @req_connection
 @wrap_libvirtError
 def network_info(name, network):
-    '''
+    """ Return the network info dict.
+
     rx_bytes
     rx_packets
     rx_errs
@@ -323,7 +400,8 @@ def network_info(name, network):
     tx_packets
     tx_errs
     tx_drop
-    '''
+
+    """
     keys = ['rx_bytes', 'rx_packets', 'rx_errs', 'rx_drop',
             'tx_bytes', 'tx_packets', 'tx_errs', 'tx_drop']
     dom = lookupByName(name)
@@ -336,10 +414,12 @@ def network_info(name, network):
 @req_connection
 @wrap_libvirtError
 def send_key(name, key_code):
-    ''' Sending linux key_code to the name vm
+    """ Sending linux key_code to the name vm.
+
     key_code can be optained from linux_keys.py
     e.x: linuxkeys.KEY_RIGHTCTRL
-    '''
+
+    """
     domain = lookupByName(name)
     domain.sendKey(libvirt.VIR_KEYCODE_SET_LINUX, 100, [key_code], 1, 0)
 
@@ -353,19 +433,20 @@ def _stream_handler(stream, buf, opaque):
 @req_connection
 @wrap_libvirtError
 def screenshot(name, path):
-    """Save screenshot of virtual machine
-        to the path as name-screenshot.ppm
+    """Save screenshot of virtual machine.
+
+    Image is saved to the path as name-screenshot.ppm
+
     """
     # Import linuxkeys to get defines
     import linuxkeys
     # Connection need for the stream object
-    global connection
     domain = lookupByName(name)
     # Send key to wake up console
     domain.sendKey(libvirt.VIR_KEYCODE_SET_LINUX,
                    100, [linuxkeys.KEY_RIGHTCTRL], 1, 0)
     # Create Stream to get data
-    stream = connection.newStream(0)
+    stream = Connection.get().newStream(0)
     # Take screenshot accessible by stream (return mimetype)
     domain.screenshot(stream, 0, 0)
     # Get file to save data (TODO: send on AMQP?)
@@ -383,7 +464,7 @@ def screenshot(name, path):
 @req_connection
 @wrap_libvirtError
 def migrate(name, host, live=False):
-    '''Migrate domain to host'''
+    """ Migrate domain to host. """
     flags = libvirt.VIR_MIGRATE_PEER2PEER
     if live:
         flags = flags | libvirt.VIR_MIGRATE_LIVE
@@ -393,4 +474,4 @@ def migrate(name, host, live=False):
         flags=flags,
         dname=name,
         bandwidth=0)
-    #return _parse_info(domain.info())
+    # return _parse_info(domain.info())