[format] Add CGroup Manager in form of optional "plugin"

-  Move all Computer attribute initialization into Computer constructor
-  Rename 'construct' to 'format' because we are in slap.format
-  Introduce Manager base class
-  Implement CGroupManager to take care of cgroup's cpuset

slapos/README.format.txt

-format
+Format
 ======
 
-slapformat is an application to prepare SlapOS ready node (machine).
+slapformat is an application to prepare SlapOS-ready node to be used inside SlapGrid Cloud.
 
 It "formats" the machine by:
 
@@ -10,9 +10,21 @@ It "formats" the machine by:
  - creating needed tap interfaces
  - creating TUN interfaces
  - creating needed directories with proper ownership and permissions
+ - (optional-manager) creating cgroup resource tree for slapos
 
-In the end special report is generated and information are posted to
-configured SlapOS server.
+It reads configuration from /etc/opt/slapos/slapos.cfg and formats computer
+accordingly. The variables are number of partitions, IP addresses, storages
+and network interfaces.
+
+Format uploads a into configured SlapOS Master server.
+
+Format dumps allocated resources for the partition into a JSON file per 
+partition ~/.slapos-resource. This file contains network interfaces, 
+IP address ranges and port ranges. The resource constraints can be 
+recursively folded. 
+
+Pluggable parts for formatting are available too. They are called Managers
+and can be turned on/off via configuration property manager_list.
 
 This program shall be only run by root.
 

slapos/format.py

@@ -64,6 +64,10 @@ from slapos import version
 
 logger = logging.getLogger("slapos.format")
 
+# dict[str: ManagerClass] used in configuration and XML dump of computer
+# this dictionary is intended to be filled after each definition of a Manager
+available_manager_list = {}
+
 
 def prettify_xml(xml):
   root = lxml.etree.fromstring(xml)
@@ -235,39 +239,239 @@ def _getDict(obj):
     key: _getDict(value) \
     for key, value in dikt.iteritems() \
     # do not attempt to serialize logger: it is both useless and recursive.
-    if not isinstance(value, logging.Logger)
+    # do not serialize attributes starting with "_", let the classes have some privacy
+    if not key.startswith("_")
   }
 
 
+class Manager(object):
+  short_name = None
+
+  def format(self):
+    raise NotImplementedError("Implement function to format underlaying OS")
+
+  def update(self):
+    raise NotImplementedError("Implement function to format underlaying OS")
+
+
+class CGroupManager(Manager):
+  """Manage cgroups in terms on initializing and runtime operations.
+
+  This class takes advantage of slapformat being run periodically thus
+  it can act as a "daemon" performing runtime tasks.
+  """
+  short_name = 'cgroup'
+  cpu_exclusive_file = ".slapos-cpu-exclusive"
+  cpuset_path = "/sys/fs/cgroup/cpuset/"
+  task_write_mode = "at"
+
+  def __init__(self, computer):
+    """Extract necessary information from the ``computer``.
+
+    :param computer: slapos.format.Computer, extract necessary attributes
+    """
+    self.instance_root = computer.instance_root
+    self.software_gid = computer.software_gid
+    logger.info("Allowing " + self.__class__.__name__)
+
+  def __str__(self):
+    """Manager representation when dumped to string."""
+    return self.short_name
+
+  def is_allowed(self):
+    return os.path.exists("/sys/fs/cgroup/cpuset/cpuset.cpus")
+
+  def format(self):
+    """Build CGROUP tree to fit SlapOS needs.
+
+    - Create hierarchy of CPU sets so that every partition can have exclusive
+      hold of one of the CPUs.
+    """
+    self.prepare_cpuset()
+    self.prepare_cpu_space()
+
+  def update(self):
+    """Control runtime state of the computer."""
+    cpu0_path = os.path.join(self.cpuset_path, "cpu0")
+    if os.path.exists(cpu0_path):
+      # proceed only whe CPUSETs were formatted by this manager
+      self.prepare_cpu_space()
+      self.ensure_exlusive_cpu()
+    else:
+      logger.warning("Computer was not formatted by {} because {} doesn't exist!".format(
+        self.__class__.__name__, cpu0_path))
+
+  def prepare_cpuset(self):
+    """Create cgroup folder per-CPU with exclusive access to the CPU.
+
+    Those folders are "/sys/fs/cgroup/cpuset/cpu<N>".
+    """
+    for cpu in self._cpu_list():
+      cpu_path = self._prepare_folder(
+        os.path.join(self.cpuset_path, "cpu" + str(cpu)))
+      with open(cpu_path + "/cpuset.cpus", "wt") as fx:
+        fx.write(str(cpu))  # this cgroup manages only this cpu
+      with open(cpu_path + "/cpuset.cpu_exclusive", "wt") as fx:
+        fx.write("1")  # manages it exclusively
+      with open(cpu_path + "/cpuset.mems", "wt") as fx:
+        fx.write("0")  # it doesn't work without that
+      os.chown(cpu_path + "/tasks", -1, self.software_gid)
+      os.chmod(cpu_path + "/tasks", 0o664)
+
+  def ensure_exlusive_cpu(self):
+    """Move processes among exclusive CPUSets based on software release demands.
+
+    We expect PIDs which require own CPU to be found in ~instance/.slapos-cpu-exclusive
+    """
+    cpu_list = self._cpu_list()
+    generic_cpu = cpu_list[0]
+    exclusive_cpu_list = cpu_list[1:]
+
+    # gather all running PIDs for filtering out stale PIDs
+    running_pid_set = set()
+    with open(os.path.join(self.cpuset_path, "tasks"), "rt") as fi:
+      running_pid_set.update(map(int, fi.read().split()))
+    with open(os.path.join(self.cpuset_path, "cpu" + str(generic_cpu), "tasks"), "rt") as fi:
+      running_pid_set.update(map(int, fi.read().split()))
+
+    # gather already exclusively running PIDs
+    exclusive_pid_set = set()
+    for exclusive_cpu in exclusive_cpu_list:
+      with open(os.path.join(self.cpuset_path, "cpu" + str(exclusive_cpu), "tasks"), "rt") as fi:
+        exclusive_pid_set.update(map(int, fi.read().split()))
+
+    for request_file in glob.iglob(os.path.join(self.instance_root, '*', CGroupManager.cpu_exclusive_file)):
+      with open(request_file, "rt") as fi:
+        # take such PIDs which are either really running or are not already exclusive
+        request_pid_list = [int(pid) for pid in fi.read().split()
+                            if int(pid) in running_pid_set or int(pid) not in exclusive_pid_set]
+      with open(request_file, "wt") as fo:
+        fo.write("")  # empty file (we will write back only PIDs which weren't moved)
+      for request_pid in request_pid_list:
+        assigned_cpu = self._move_to_exclusive_cpu(request_pid)
+        if assigned_cpu < 0:
+          # if no exclusive CPU was assigned - write the PID back and try other time
+          with open(request_file, "at") as fo:
+            fo.write(str(request_pid) + "\n")
+
+  def prepare_cpu_space(self):
+    """Move all PIDs from the pool of all CPUs into the first exclusive CPU."""
+    with open(os.path.join(self.cpuset_path, "tasks"), "rt") as fi:
+      running_list = sorted(list(map(int, fi.read().split())), reverse=True)
+    first_cpu = self._cpu_list()[0]
+    success_set = set()
+    refused_set = set()
+    for pid in running_list:
+      try:
+        self._move_task(pid, first_cpu)
+        success_set.add(pid)
+        time.sleep(0.01)
+      except IOError as e:
+        refused_set.add(pid)
+    logger.debug("Refused to move {:d} PIDs: {!s}\n"
+                 "Suceeded in moving {:d} PIDs {!s}\n".format(
+      len(refused_set), refused_set, len(success_set), success_set)
+    )
+
+  def _cpu_list(self):
+    """Extract IDs of available CPUs and return them as a list.
+
+    The first one will be always used for all non-exclusive processes.
+    :return: list[int]
+    """
+    cpu_list = []  # types: list[int]
+    with open(self.cpuset_path + "cpuset.cpus", "rt") as cpu_def:
+      for cpu_def_split in cpu_def.read().strip().split(","):
+        # IDs can be in form "0-4" or "0,1,2,3,4"
+        if "-" in cpu_def_split:
+          a, b = map(int, cpu_def_split.split("-"))
+          cpu_list.extend(range(a, b + 1)) # because cgroup's range is inclusive
+          continue
+        cpu_list.append(int(cpu_def_split))
+    return cpu_list
+
+  def _move_to_exclusive_cpu(self, pid):
+    """Try all exclusive CPUs and place the ``pid`` to the first available one.
+
+    :return: int, cpu_id of used CPU, -1 if placement was not possible
+    """
+    exclusive_cpu_list = self._cpu_list()[1:]
+    for exclusive_cpu in exclusive_cpu_list:
+      # gather tasks assigned to current exclusive CPU
+      task_path = os.path.join(self.cpuset_path, "cpu" + str(exclusive_cpu), "tasks")
+      with open(task_path, "rt") as fi:
+        task_list = fi.read().split()
+      if len(task_list) > 0:
+        continue  # skip occupied CPUs
+      return self._move_task(pid, exclusive_cpu)[1]
+    return -1
+
+  def _move_task(self, pid, cpu_id):
+    """Move ``pid`` to ``cpu_id``."""
+    with open(os.path.join(self.cpuset_path, "cpu" + str(cpu_id), "tasks"), self.task_write_mode) as fo:
+      fo.write(str(pid) + "\n")
+    return pid, cpu_id
+
+  def _prepare_folder(self, folder):
+    """If-Create folder and set group write permission."""
+    if not os.path.exists(folder):
+      os.mkdir(folder)
+      os.chown(folder, -1, self.software_gid)
+      # make your life and testing easier and create mandatory files if they don't exist
+      mandatory_file_list = ("tasks", "cpuset.cpus")
+      for mandatory_file in mandatory_file_list:
+        file_path = os.path.join(folder, mandatory_file)
+        if not os.path.exists(file_path):
+          with open(file_path, "wb"):
+            pass  # touche
+    return folder
+
+# mark manager available
+available_manager_list[CGroupManager.short_name] = CGroupManager
+
+
 class Computer(object):
-  "Object representing the computer"
-  instance_root = None
-  software_root = None
-  instance_storage_home = None
+  """Object representing the computer"""
 
   def __init__(self, reference, interface=None, addr=None, netmask=None,
                ipv6_interface=None, software_user='slapsoft',
-               tap_gateway_interface=None):
+               tap_gateway_interface=None,
+               instance_root=None, software_root=None, instance_storage_home=None,
+               partition_list=None, manager_list=None):
     """
     Attributes:
-      reference: String, the reference of the computer.
-      interface: String, the name of the computer's used interface.
+      reference: str, the reference of the computer.
+      interface: str, the name of the computer's used interface.
     """
     self.reference = str(reference)
     self.interface = interface
-    self.partition_list = []
+    self.partition_list = partition_list or []
     self.address = addr
     self.netmask = netmask
     self.ipv6_interface = ipv6_interface
     self.software_user = software_user
     self.tap_gateway_interface = tap_gateway_interface
 
-    # The follow properties are updated on update() method
+    # Used to be static attributes of the class object - didn't make sense (Marco again)
+    assert instance_root is not None and software_root is not None, \
+           "Computer's instance_root and software_root must not be empty!"
+    self.software_root = software_root
+    self.instance_root = instance_root
+    self.instance_storage_home = instance_storage_home
+
+    # The following properties are updated on update() method
     self.public_ipv4_address = None
     self.os_type = None
     self.python_version = None
     self.slapos_version = None
 
+    # HASA relation to managers (could turn into plugins with `format` and `update` methods)
+    self.manager_list = manager_list  # for serialization
+    # hide list[Manager] from serializer by prepending "_"
+    self._manager_list = tuple(filter(lambda manager: manager.is_allowed(),
+                                    (available_manager_list[manager_str](self) for manager_str in manager_list))) \
+                        if manager_list else tuple()
+
   def __getinitargs__(self):
     return (self.reference, self.interface)
 
@@ -304,9 +508,12 @@ class Computer(object):
     raise NoAddressOnInterface('No valid IPv6 found on %s.' % self.interface.name)
 
   def update(self):
-    """
-      Collect environmental hardware/network information.
-    """
+    """Update computer runtime info and state."""
+    for manager in self._manager_list:
+      logger.info("Updating computer with " + manager.__class__.__name__)
+      manager.update()
+
+    # Collect environmental hardware/network information.
     self.public_ipv4_address = getPublicIPv4Address()
     self.slapos_version = version.version
     self.python_version = platform.python_version()
@@ -392,7 +599,8 @@ class Computer(object):
       archive.writestr(saved_filename, xml_content, zipfile.ZIP_DEFLATED)
 
   @classmethod
-  def load(cls, path_to_xml, reference, ipv6_interface, tap_gateway_interface):
+  def load(cls, path_to_xml, reference, ipv6_interface, tap_gateway_interface,
+           instance_root=None, software_root=None, manager_list=None):
     """
     Create a computer object from a valid xml file.
 
@@ -414,6 +622,9 @@ class Computer(object):
         ipv6_interface=ipv6_interface,
         software_user=dumped_dict.get('software_user', 'slapsoft'),
         tap_gateway_interface=tap_gateway_interface,
+        software_root=dumped_dict.get('software_root', software_root),
+        instance_root=dumped_dict.get('instance_root', instance_root),
+        manager_list=dumped_dict.get('manager_list', manager_list),
     )
 
     for partition_index, partition_dict in enumerate(dumped_dict['partition_list']):
@@ -492,9 +703,22 @@ class Computer(object):
     command = 'ip address add dev %s fd00::1/64' % interface_name
     callAndRead(command.split())
 
-  def construct(self, alter_user=True, alter_network=True, create_tap=True, use_unique_local_address_block=False):
+  @property
+  def software_gid(self):
+    """Return GID for self.software_user.
+
+    Has to be dynamic because __init__ happens before ``format`` where we 
+    effectively create the user and group."""
+    return pwd.getpwnam(self.software_user)[3]
+
+  def format(self, alter_user=True, alter_network=True, create_tap=True, use_unique_local_address_block=False):
     """
-    Construct the computer object as it is.
+    Setup underlaying OS so it reflects this instance (``self``).
+
+    - setup interfaces and addresses
+    - setup TAP and TUN interfaces
+    - add groups and users
+    - construct partitions inside slapgrid
     """
     if alter_network and self.address is not None:
       self.interface.addAddr(self.address, self.netmask)
@@ -521,6 +745,11 @@ class Computer(object):
       os.chown(slapsoft.path, slapsoft_pw.pw_uid, slapsoft_pw.pw_gid)
     os.chmod(self.software_root, 0o755)
 
+    # Iterate over all managers and let them `format` the computer too
+    for manager in self._manager_list:
+      logger.info("Formatting computer with " + manager.__class__.__name__)
+      manager.format()
+
     # get list of instance external storage if exist
     instance_external_list = []
     if self.instance_storage_home:
@@ -954,7 +1183,7 @@ class Interface(object):
         name: String, the name of the interface
     """
 
-    self.logger = logger
+    self._logger = logger
     self.name = str(name)
     self.ipv4_local_network = ipv4_local_network
     self.ipv6_interface = ipv6_interface
@@ -1138,7 +1367,7 @@ class Interface(object):
       if self._addSystemAddress(addr, netmask, False):
         return dict(addr=addr, netmask=netmask)
       else:
-        self.logger.warning('Impossible to add old local IPv4 %s. Generating '
+        self._logger.warning('Impossible to add old local IPv4 %s. Generating '
             'new IPv4 address.' % addr)
         return self._generateRandomIPv4Address(netmask)
     else:
@@ -1196,7 +1425,7 @@ class Interface(object):
             # succeed, return it
             return dict(addr=addr, netmask=netmask)
           else:
-            self.logger.warning('Impossible to add old public IPv6 %s. '
+            self._logger.warning('Impossible to add old public IPv6 %s. '
                 'Generating new IPv6 address.' % addr)
 
     # Try 10 times to add address, raise in case if not possible
@@ -1276,7 +1505,10 @@ def parse_computer_xml(conf, xml_path):
     computer = Computer.load(xml_path,
                              reference=conf.computer_id,
                              ipv6_interface=conf.ipv6_interface,
-                             tap_gateway_interface=conf.tap_gateway_interface)
+                             tap_gateway_interface=conf.tap_gateway_interface,
+                             software_root=conf.software_root,
+                             instance_root=conf.instance_root,
+                             manager_list=conf.manager_list)
     # Connect to the interface defined by the configuration
     computer.interface = interface
   else:
@@ -1284,12 +1516,15 @@ def parse_computer_xml(conf, xml_path):
     conf.logger.warning('Creating new computer data with id %r', conf.computer_id)
     computer = Computer(
       reference=conf.computer_id,
+      software_root=conf.software_root,
+      instance_root=conf.software_root,
       interface=interface,
       addr=None,
       netmask=None,
       ipv6_interface=conf.ipv6_interface,
       software_user=conf.software_user,
       tap_gateway_interface=conf.tap_gateway_interface,
+      manager_list=conf.manager_list,
     )
 
   partition_amount = int(conf.partition_amount)
@@ -1360,8 +1595,6 @@ def do_format(conf):
     # no definition file, figure out computer
     computer = parse_computer_xml(conf, conf.computer_xml)
 
-  computer.instance_root = conf.instance_root
-  computer.software_root = conf.software_root
   computer.instance_storage_home = conf.instance_storage_home
   conf.logger.info('Updating computer')
   address = computer.getAddress(conf.create_tap)
@@ -1371,7 +1604,7 @@ def do_format(conf):
   if conf.output_definition_file:
     write_computer_definition(conf, computer)
 
-  computer.construct(alter_user=conf.alter_user,
+  computer.format(alter_user=conf.alter_user,
                      alter_network=conf.alter_network,
                      create_tap=conf.create_tap,
                      use_unique_local_address_block=conf.use_unique_local_address_block)
@@ -1406,6 +1639,7 @@ class FormatConfig(object):
   tap_gateway_interface = None
   use_unique_local_address_block = None
   instance_storage_home = None
+  manager_list = None
 
   def __init__(self, logger):
     self.logger = logger
@@ -1493,6 +1727,16 @@ class FormatConfig(object):
           self.logger.error(message)
           raise UsageError(message)
 
+    # Split str into list[str] and check availability of every manager
+    # Config value is expected to be strings separated by spaces or commas
+    manager_list = []
+    for manager in self.manager_list.replace(",", " ").split():
+      if manager not in available_manager_list:
+        raise ValueError("Unknown manager \"{}\"! Known are: {!s}".format(
+          manager, list(available_manager_list.keys())))
+      manager_list.append(manager)
+    self.manager_list = manager_list  # replace original str with list[str] of known managers
+
     if not self.dry_run:
       if self.alter_user:
         self.checkRequiredBinary(['groupadd', 'useradd', 'usermod', ['passwd', '-h']])

slapos/tests/slapformat.py

@@ -26,15 +26,15 @@
 # Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 #
 ##############################################################################
-
+import glob
 import logging
 import slapos.format
 import slapos.util
 import unittest
 
 import netaddr
+import shutil
 import socket
-
 # for mocking
 import grp
 import netifaces
@@ -47,6 +47,20 @@ GROUP_LIST = []
 INTERFACE_DICT = {}
 
 
+def file_content(file_path):
+  """Read file(s) content."""
+  if isinstance(file_path, (list, tuple)):
+    return [file_content(fx) for fx in file_path]
+  with open(file_path, "rt") as fi:
+    return fi.read().strip()
+
+
+def file_write(stuff, file_path):
+  """Write stuff into file_path."""
+  with open(file_path, "wt") as fo:
+    fo.write(stuff)
+
+
 class FakeConfig:
   pass
 
@@ -138,11 +152,16 @@ class PwdMock:
   def getpwnam(self, name):
     global USER_LIST
     if name in USER_LIST:
-      class result:
+      class PwdResult:
         pw_uid = 0
         pw_gid = 0
-      return result
-    raise KeyError
+        def __getitem__(self, index):
+          if index == 2:
+            return self.pw_uid
+          if index == 3:
+            return self.pw_gid
+      return PwdResult()
+    raise KeyError("User \"{}\" not in global USER_LIST {!s}".format(name, USER_LIST))
 
 
 class NetifacesMock:
@@ -151,7 +170,8 @@ class NetifacesMock:
     global INTERFACE_DICT
     if name in INTERFACE_DICT:
       return INTERFACE_DICT[name]
-    raise ValueError
+    raise ValueError("Interface \"{}\" not in INTERFACE_DICT {!s}".format(
+      name, INTERFACE_DICT))
 
   @classmethod
   def interfaces(self):
@@ -163,6 +183,21 @@ class SlaposUtilMock:
   def chownDirectory(*args, **kw):
     pass
 
+
+class CGroupManagerMock(slapos.format.CGroupManager):
+
+  short_name = 'cgroup_mock'
+  cpuset_path = "/tmp/cpuset/"
+  task_write_mode = "at"  # append insted of write tasks PIDs for the tests
+
+  def is_allowed(self):
+    """Always allowed."""
+    return True
+
+# update available managers with our partially-mocked version
+slapos.format.available_manager_list[CGroupManagerMock.short_name] = CGroupManagerMock
+
+
 class SlapformatMixin(unittest.TestCase):
   # keep big diffs
   maxDiff = None
@@ -220,6 +255,8 @@ class SlapformatMixin(unittest.TestCase):
       setattr(os, fake, f)
 
   def restoreOs(self):
+    if not hasattr(self, 'saved_os'):
+      return  # os was never patched or already restored
     for name, original_value in self.saved_os.items():
       setattr(os, name, original_value)
     del self.saved_os
@@ -278,23 +315,23 @@ class SlapformatMixin(unittest.TestCase):
 
 class TestComputer(SlapformatMixin):
   def test_getAddress_empty_computer(self):
-    computer = slapos.format.Computer('computer')
+    computer = slapos.format.Computer('computer', instance_root='/instance_root', software_root='software_root')
     self.assertEqual(computer.getAddress(), {'netmask': None, 'addr': None})
 
   @unittest.skip("Not implemented")
   def test_construct_empty(self):
-    computer = slapos.format.Computer('computer')
-    computer.construct()
+    computer = slapos.format.Computer('computer', instance_root='/instance_root', software_root='software_root')
+    computer.format()
 
   @unittest.skip("Not implemented")
   def test_construct_empty_prepared(self):
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.logger,
-                                        name='bridge',
-                                        ipv4_local_network='127.0.0.1/16'))
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    computer.construct()
+      instance_root='/instance_root',
+      software_root='/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='bridge', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[])
+    computer.format()
     self.assertEqual([
       "makedirs('/instance_root', 493)",
       "makedirs('/software_root', 493)",
@@ -310,29 +347,31 @@ class TestComputer(SlapformatMixin):
 
   def test_construct_empty_prepared_no_alter_user(self):
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.logger,
-                                        name='bridge',
-                                        ipv4_local_network='127.0.0.1/16'))
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    computer.construct(alter_user=False)
+      instance_root='/instance_root',
+      software_root='/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='bridge', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[])
+    computer.format(alter_user=False)
     self.assertEqual([
       "makedirs('/instance_root', 493)",
       "makedirs('/software_root', 493)",
       "chmod('/software_root', 493)"],
       self.test_result.bucket)
-    self.assertEqual(['ip addr list bridge'],
-                     self.fakeCallAndRead.external_command_list)
+    self.assertEqual([
+        'ip addr list bridge',
+        'brctl show',
+      ],
+      self.fakeCallAndRead.external_command_list)
 
   @unittest.skip("Not implemented")
   def test_construct_empty_prepared_no_alter_network(self):
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.logger,
-                                        name='bridge',
-                                        ipv4_local_network='127.0.0.1/16'))
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    computer.construct(alter_network=False)
+      instance_root='/instance_root',
+      software_root='/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='bridge', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[])
     self.assertEqual([
       "makedirs('/instance_root', 493)",
       "makedirs('/software_root', 493)",
@@ -348,34 +387,34 @@ class TestComputer(SlapformatMixin):
 
   def test_construct_empty_prepared_no_alter_network_user(self):
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.logger,
-                                        name='bridge',
-                                        ipv4_local_network='127.0.0.1/16'))
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    computer.construct(alter_network=False, alter_user=False)
+      instance_root='/instance_root',
+      software_root='/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='bridge', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[])
+    computer.format(alter_network=False, alter_user=False)
     self.assertEqual([
       "makedirs('/instance_root', 493)",
       "makedirs('/software_root', 493)",
       "chmod('/software_root', 493)"],
       self.test_result.bucket)
     self.assertEqual([
-      'ip addr list bridge'
+        'ip addr list bridge',
+        'brctl show',
       ],
       self.fakeCallAndRead.external_command_list)
 
   @unittest.skip("Not implemented")
   def test_construct_prepared(self):
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.logger,
-                                        name='bridge',
-                                        ipv4_local_network='127.0.0.1/16'))
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    partition = slapos.format.Partition('partition', '/part_path',
-      slapos.format.User('testuser'), [], None)
-    partition.tap = slapos.format.Tap('tap')
-    computer.partition_list = [partition]
+      instance_root='/instance_root',
+      software_root='/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='bridge', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[
+          slapos.format.Partition(
+            'partition', '/part_path', slapos.format.User('testuser'), [], tap=slapos.format.Tap('tap')),
+        ])
     global INTERFACE_DICT
     INTERFACE_DICT['bridge'] = {
       socket.AF_INET: [{'addr': '192.168.242.77', 'broadcast': '127.0.0.1',
@@ -383,7 +422,7 @@ class TestComputer(SlapformatMixin):
       socket.AF_INET6: [{'addr': '2a01:e35:2e27::e59c', 'netmask': 'ffff:ffff:ffff:ffff::'}]
     }
 
-    computer.construct()
+    computer.format()
     self.assertEqual([
       "makedirs('/instance_root', 493)",
       "makedirs('/software_root', 493)",
@@ -400,7 +439,8 @@ class TestComputer(SlapformatMixin):
       'useradd -d /software_root -g slapsoft slapsoft -r',
       'groupadd testuser',
       'useradd -d /instance_root/partition -g testuser -G slapsoft testuser -r',
-      'tunctl -t tap -u testuser',
+      'brctl show',
+      'ip tuntap add dev tap mode tap user testuser',
       'ip link set tap up',
       'brctl show',
       'brctl addif bridge tap',
@@ -413,17 +453,16 @@ class TestComputer(SlapformatMixin):
 
   def test_construct_prepared_no_alter_user(self):
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.logger,
-                                        name='bridge',
-                                        ipv4_local_network='127.0.0.1/16'))
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    partition = slapos.format.Partition('partition', '/part_path',
-      slapos.format.User('testuser'), [], None)
+      instance_root='/instance_root',
+      software_root='/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='bridge', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[
+          slapos.format.Partition(
+            'partition', '/part_path', slapos.format.User('testuser'), [], tap=slapos.format.Tap('tap')),
+        ])
     global USER_LIST
     USER_LIST = ['testuser']
-    partition.tap = slapos.format.Tap('tap')
-    computer.partition_list = [partition]
     global INTERFACE_DICT
     INTERFACE_DICT['bridge'] = {
       socket.AF_INET: [{'addr': '192.168.242.77', 'broadcast': '127.0.0.1',
@@ -431,7 +470,7 @@ class TestComputer(SlapformatMixin):
       socket.AF_INET6: [{'addr': '2a01:e35:2e27::e59c', 'netmask': 'ffff:ffff:ffff:ffff::'}]
     }
 
-    computer.construct(alter_user=False)
+    computer.format(alter_user=False)
     self.assertEqual([
       "makedirs('/instance_root', 493)",
       "makedirs('/software_root', 493)",
@@ -441,33 +480,34 @@ class TestComputer(SlapformatMixin):
     ],
       self.test_result.bucket)
     self.assertEqual([
-      'ip addr list bridge',
-      'tunctl -t tap -u testuser',
-      'ip link set tap up',
-      'brctl show',  # we check bridges at Interface initialization
-      'brctl show',
-      'brctl addif bridge tap',
-      'ip addr add ip/255.255.255.255 dev bridge',
-      # 'ip addr list bridge',
-      'ip addr add ip/ffff:ffff:ffff:ffff:: dev bridge',
-      'ip -6 addr list bridge',
-    ],
+        'ip addr list bridge',
+        'brctl show',
+        'ip tuntap add dev tap mode tap user testuser',
+        'ip link set tap up',
+        'brctl show',
+        'brctl show',
+        'brctl addif bridge tap',
+        'ip addr add ip/255.255.255.255 dev bridge',
+        # 'ip addr list bridge',
+        'ip addr add ip/ffff:ffff:ffff:ffff:: dev bridge',
+        'ip -6 addr list bridge',
+      ],
       self.fakeCallAndRead.external_command_list)
 
   def test_construct_prepared_tap_no_alter_user(self):
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.test_result,
-                                        name='iface',
-                                        ipv4_local_network='127.0.0.1/16'),
-                                        tap_gateway_interface='eth1')
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    partition = slapos.format.Partition('partition', '/part_path',
-      slapos.format.User('testuser'), [], None)
+      instance_root='/instance_root',
+      software_root='/software_root',
+      tap_gateway_interface='eth1',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='iface', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[
+          slapos.format.Partition(
+            'partition', '/part_path', slapos.format.User('testuser'), [], 
+            tap=slapos.format.Tap('tap')),
+        ])
     global USER_LIST
     USER_LIST = ['testuser']
-    partition.tap = slapos.format.Tap('tap')
-    computer.partition_list = [partition]
     global INTERFACE_DICT
     INTERFACE_DICT['iface'] = {
       socket.AF_INET: [{'addr': '192.168.242.77', 'broadcast': '127.0.0.1',
@@ -479,7 +519,7 @@ class TestComputer(SlapformatMixin):
         'netmask': '255.255.255.0'}]
     }
 
-    computer.construct(alter_user=False)
+    computer.format(alter_user=False)
     self.assertEqual([
       "makedirs('/instance_root', 493)",
       "makedirs('/software_root', 493)",
@@ -490,15 +530,17 @@ class TestComputer(SlapformatMixin):
       self.test_result.bucket)
     self.assertEqual([
         'ip addr list iface',
-        'tunctl -t tap -u testuser',
+        'brctl show',
+        'ip tuntap add dev tap mode tap user testuser',
         'ip link set tap up',
         'ip route show 10.8.0.2',
-        'route add -host 10.8.0.2 dev tap',
+        'ip route add 10.8.0.2 dev tap',
         'ip addr add ip/255.255.255.255 dev iface',
         'ip addr add ip/ffff:ffff:ffff:ffff:: dev iface',
         'ip -6 addr list iface'
       ],
       self.fakeCallAndRead.external_command_list)
+    partition = computer.partition_list[0]
     self.assertEqual(partition.tap.ipv4_addr, '10.8.0.2')
     self.assertEqual(partition.tap.ipv4_netmask, '255.255.255.0')
     self.assertEqual(partition.tap.ipv4_gateway, '10.8.0.1')
@@ -507,23 +549,22 @@ class TestComputer(SlapformatMixin):
   @unittest.skip("Not implemented")
   def test_construct_prepared_no_alter_network(self):
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.logger,
-                                        name='bridge',
-                                        ipv4_local_network='127.0.0.1/16'))
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    partition = slapos.format.Partition('partition', '/part_path',
-      slapos.format.User('testuser'), [], None)
-    partition.tap = slapos.format.Tap('tap')
-    computer.partition_list = [partition]
+      instance_root='/instance_root',
+      software_root='/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='bridge', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[
+          slapos.format.Partition(
+            'partition', '/part_path', slapos.format.User('testuser'), [],
+            tap=slapos.format.Tap('tap')),
+        ])
     global INTERFACE_DICT
     INTERFACE_DICT['bridge'] = {
       socket.AF_INET: [{'addr': '192.168.242.77', 'broadcast': '127.0.0.1',
         'netmask': '255.255.255.0'}],
       socket.AF_INET6: [{'addr': '2a01:e35:2e27::e59c', 'netmask': 'ffff:ffff:ffff:ffff::'}]
     }
-
-    computer.construct(alter_network=False)
+    computer.format(alter_network=False)
     self.assertEqual([
       "makedirs('/instance_root', 493)",
       "makedirs('/software_root', 493)",
@@ -549,15 +590,15 @@ class TestComputer(SlapformatMixin):
 
   def test_construct_prepared_no_alter_network_user(self):
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.logger,
-                                        name='bridge',
-                                        ipv4_local_network='127.0.0.1/16'))
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    partition = slapos.format.Partition('partition', '/part_path',
-      slapos.format.User('testuser'), [], None)
-    partition.tap = slapos.format.Tap('tap')
-    computer.partition_list = [partition]
+      instance_root='/instance_root',
+      software_root='/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='bridge', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[
+          slapos.format.Partition(
+            'partition', '/part_path', slapos.format.User('testuser'), [],
+            tap=slapos.format.Tap('tap')),
+        ])
     global INTERFACE_DICT
     INTERFACE_DICT['bridge'] = {
       socket.AF_INET: [{'addr': '192.168.242.77', 'broadcast': '127.0.0.1',
@@ -565,22 +606,23 @@ class TestComputer(SlapformatMixin):
       socket.AF_INET6: [{'addr': '2a01:e35:2e27::e59c', 'netmask': 'ffff:ffff:ffff:ffff::'}]
     }
 
-    computer.construct(alter_network=False, alter_user=False)
+    computer.format(alter_network=False, alter_user=False)
     self.assertEqual([
-      "makedirs('/instance_root', 493)",
-      "makedirs('/software_root', 493)",
-      "chmod('/software_root', 493)",
-      "mkdir('/instance_root/partition', 488)",
-      "chmod('/instance_root/partition', 488)"
-    ],
+        "makedirs('/instance_root', 493)",
+        "makedirs('/software_root', 493)",
+        "chmod('/software_root', 493)",
+        "mkdir('/instance_root/partition', 488)",
+        "chmod('/instance_root/partition', 488)"
+      ],
       self.test_result.bucket)
     self.assertEqual([
-      'ip addr list bridge',
-      'ip addr add ip/255.255.255.255 dev bridge',
-      # 'ip addr list bridge',
-      'ip addr add ip/ffff:ffff:ffff:ffff:: dev bridge',
-      'ip -6 addr list bridge',
-    ],
+        'ip addr list bridge',
+        'brctl show',
+        'ip addr add ip/255.255.255.255 dev bridge',
+        # 'ip addr list bridge',
+        'ip addr add ip/ffff:ffff:ffff:ffff:: dev bridge',
+        'ip -6 addr list bridge',
+      ],
       self.fakeCallAndRead.external_command_list)
 
   def test_construct_use_unique_local_address_block(self):
@@ -590,15 +632,15 @@ class TestComputer(SlapformatMixin):
     global USER_LIST
     USER_LIST = ['root']
     computer = slapos.format.Computer('computer',
-      interface=slapos.format.Interface(logger=self.logger,
-                                        name='myinterface',
-                                        ipv4_local_network='127.0.0.1/16'))
-    computer.instance_root = '/instance_root'
-    computer.software_root = '/software_root'
-    partition = slapos.format.Partition('partition', '/part_path',
-      slapos.format.User('testuser'), [], None)
-    partition.tap = slapos.format.Tap('tap')
-    computer.partition_list = [partition]
+      instance_root='/instance_root',
+      software_root='/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='myinterface', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[
+          slapos.format.Partition(
+            'partition', '/part_path', slapos.format.User('testuser'), [],
+            tap=slapos.format.Tap('tap')),
+        ])
     global INTERFACE_DICT
     INTERFACE_DICT['myinterface'] = {
       socket.AF_INET: [{'addr': '192.168.242.77', 'broadcast': '127.0.0.1',
@@ -606,24 +648,108 @@ class TestComputer(SlapformatMixin):
       socket.AF_INET6: [{'addr': '2a01:e35:2e27::e59c', 'netmask': 'ffff:ffff:ffff:ffff::'}]
     }
 
-    computer.construct(use_unique_local_address_block=True, alter_user=False, create_tap=False)
+    computer.format(use_unique_local_address_block=True, alter_user=False, create_tap=False)
     self.assertEqual([
-      "makedirs('/instance_root', 493)",
-      "makedirs('/software_root', 493)",
-      "chmod('/software_root', 493)",
-      "mkdir('/instance_root/partition', 488)",
-      "chmod('/instance_root/partition', 488)"
-    ],
+        "makedirs('/instance_root', 493)",
+        "makedirs('/software_root', 493)",
+        "chmod('/software_root', 493)",
+        "mkdir('/instance_root/partition', 488)",
+        "chmod('/instance_root/partition', 488)"
+      ],
       self.test_result.bucket)
     self.assertEqual([
-      'ip addr list myinterface',
-      'ip address add dev myinterface fd00::1/64',
-      'ip addr add ip/255.255.255.255 dev myinterface',
-      'ip addr add ip/ffff:ffff:ffff:ffff:: dev myinterface',
-      'ip -6 addr list myinterface'
-    ],
+        'ip addr list myinterface',
+        'brctl show',
+        'ip address add dev myinterface fd00::1/64',
+        'ip addr add ip/255.255.255.255 dev myinterface',
+        'ip addr add ip/ffff:ffff:ffff:ffff:: dev myinterface',
+        'ip -6 addr list myinterface'
+      ],
       self.fakeCallAndRead.external_command_list)
 
+
+class TestComputerWithCGroup(SlapformatMixin):
+
+  def setUp(self):
+    super(TestComputerWithCGroup, self).setUp()
+    self.restoreOs()
+
+    if os.path.isdir("/tmp/slapgrid/"):
+      shutil.rmtree("/tmp/slapgrid/")
+    os.mkdir("/tmp/slapgrid/")
+
+    if os.path.isdir(CGroupManagerMock.cpuset_path):
+      shutil.rmtree(CGroupManagerMock.cpuset_path)
+    os.mkdir(CGroupManagerMock.cpuset_path)
+    file_write("0,1-3",
+               os.path.join(CGroupManagerMock.cpuset_path, "cpuset.cpus"))
+    file_write("\n".join(("1000", "1001", "1002", "")),
+               os.path.join(CGroupManagerMock.cpuset_path, "tasks"))
+    self.cpu_list = [0, 1, 2, 3]
+
+    global USER_LIST, INTERFACE_DICT
+    USER_LIST = ['testuser']
+    INTERFACE_DICT['bridge'] = {
+      socket.AF_INET: [
+        {'addr': '127.0.0.1', 'broadcast': '127.0.255.255', 'netmask': '255.255.0.0'}],
+      socket.AF_INET6: [
+        {'addr': '2a01:e35:2e27::e59c', 'netmask': 'ffff:ffff:ffff:ffff::'}]
+    }
+    self.computer = slapos.format.Computer('computer',
+      software_user='testuser',
+      instance_root='/tmp/slapgrid/instance_root',
+      software_root='/tmp/slapgrid/software_root',
+      interface=slapos.format.Interface(
+        logger=self.logger, name='bridge', ipv4_local_network='127.0.0.1/16'),
+      partition_list=[
+          slapos.format.Partition(
+            'partition', '/tmp/slapgrid/instance_root/part1', slapos.format.User('testuser'), [], tap=None),
+        ],
+      manager_list=(CGroupManagerMock.short_name, )
+    )
+    # self.patchOs(self.logger)
+
+  def tearDown(self):
+    """Cleanup temporary test folders."""
+    super(TestComputerWithCGroup, self).tearDown()
+    shutil.rmtree("/tmp/slapgrid/")
+    if CGroupManagerMock.cpuset_path.startswith("/tmp"):
+      shutil.rmtree(CGroupManagerMock.cpuset_path)
+
+  def test_positive_cgroups(self):
+    """Positive test of cgroups."""
+    # Test parsing "cpuset.cpus" file
+    self.assertEqual(self.computer._manager_list[0]._cpu_list(), self.cpu_list)
+    # This should created per-cpu groups and move all tasks in CPU pool into cpu0
+    self.computer.format(alter_network=False, alter_user=False)
+    # Test files creation for exclusive CPUs
+    for cpu_id in self.cpu_list:
+      cpu_n_path = os.path.join(CGroupManagerMock.cpuset_path, "cpu" + str(cpu_id))
+      self.assertEqual(str(cpu_id), file_content(os.path.join(cpu_n_path, "cpuset.cpus")))
+      self.assertEqual("1", file_content(os.path.join(cpu_n_path, "cpuset.cpu_exclusive")))
+      if cpu_id > 0:
+        self.assertEqual("", file_content(os.path.join(cpu_n_path, "tasks")))
+    # Test that format moved all PIDs from CPU pool into CPU0
+    tasks_at_cpu0 = file_content(os.path.join(CGroupManagerMock.cpuset_path, "cpu0", "tasks")).split()
+    self.assertIn("1000", tasks_at_cpu0)
+    self.assertIn("1001", tasks_at_cpu0)
+    self.assertIn("1002", tasks_at_cpu0)
+    # Simulate cgroup behaviour - empty tasks in the pool
+    file_write("", os.path.join(CGroupManagerMock.cpuset_path, "tasks"))
+    # test moving tasks from generic core to private core
+    # request PID 1001 to be moved to its private CPU
+    request_file_path = os.path.join(self.computer.partition_list[0].path,
+                                     CGroupManagerMock.cpu_exclusive_file)
+    file_write("1001\n", request_file_path)
+    # let format do the moving
+    self.computer.update()
+    # test if the moving suceeded into any provate CPUS (id>0)
+    self.assertTrue(any("1001" in file_content(exclusive_task)
+                        for exclusive_task in glob.glob(os.path.join(CGroupManagerMock.cpuset_path, "cpu[1-9]", "tasks"))))
+    # slapformat should remove successfully moved PIDs from the .slapos-cpu-exclusive file
+    self.assertEqual("", file_content(request_file_path).strip())
+
+
 class TestPartition(SlapformatMixin):
 
   def test_createPath_no_alter_user(self):