scheduler.py 3.85 KB
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# Copyright 2014 Budapest University of Technology and Economics (BME IK)
#
# This file is part of CIRCLE Cloud.
#
# CIRCLE 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 3 of the License, or (at your option)
# any later version.
#
# CIRCLE 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 CIRCLE.  If not, see <http://www.gnu.org/licenses/>.

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from logging import getLogger

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from django.db.models import Sum

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logger = getLogger(__name__)

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class NotEnoughMemoryException(Exception):
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    def __init__(self, message=None):
        if message is None:
            message = "No node has enough memory to accomodate the guest."

        Exception.__init__(self, message)


class TraitsUnsatisfiableException(Exception):
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    def __init__(self, message=None):
        if message is None:
            message = "No node can satisfy all required traits of the guest."

        Exception.__init__(self, message)


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def select_node(instance, nodes):
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    ''' Select a node for hosting an instance based on its requirements.
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    '''
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    # check required traits
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    nodes = [n for n in nodes
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             if n.enabled and n.online
             and has_traits(instance.req_traits.all(), n)]
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    if not nodes:
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        logger.warning('select_node: no usable node for %s', unicode(instance))
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        raise TraitsUnsatisfiableException()

    # check required RAM
    nodes = [n for n in nodes if has_enough_ram(instance.ram_size, n)]
    if not nodes:
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        logger.warning('select_node: no enough RAM for %s', unicode(instance))
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        raise NotEnoughMemoryException()

    # sort nodes first by processor usage, then priority
    nodes.sort(key=lambda n: n.priority, reverse=True)
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    nodes.sort(key=free_cpu_time, reverse=True)
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    result = nodes[0]
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    logger.info('select_node: %s for %s', unicode(result), unicode(instance))
    return result
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def has_traits(traits, node):
    """True, if the node has all specified traits; otherwise, false.
    """
    traits = set(traits)
    return traits.issubset(node.traits.all())


def has_enough_ram(ram_size, node):
    """True, if the node has enough memory to accomodate a guest requiring
       ram_size mebibytes of memory; otherwise, false.
    """
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    ram_size = ram_size * 1024 * 1024
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    try:
        total = node.ram_size
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        used = node.byte_ram_usage
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        unused = total - used
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        overcommit = node.ram_size_with_overcommit
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        reserved = (node.instance_set.aggregate(
            r=Sum('ram_size'))['r'] or 0) * 1024 * 1024
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        free = overcommit - reserved
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        retval = ram_size < unused and ram_size < free

        logger.debug('has_enough_ram(%d, %s)=%s (total=%s unused=%s'
                     ' overcommit=%s free=%s free_ok=%s overcommit_ok=%s)',
                     ram_size, node, retval, total, unused, overcommit, free,
                     ram_size < unused, ram_size < free)
        return retval
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    except TypeError as e:
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        logger.exception('Got incorrect monitoring data for node %s. %s',
                         unicode(node), unicode(e))
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        return False
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def free_cpu_time(node):
    """Get an indicator number for idle processor time on the node.
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    Higher values indicate more idle time.
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    """
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    try:
        activity = node.cpu_usage / 100
        inactivity = 1 - activity
        cores = node.num_cores
        return cores * inactivity
    except TypeError as e:
        logger.warning('Got incorrect monitoring data for node %s. %s',
                       unicode(node), unicode(e))
        return False  # monitoring data is incorrect