Statistics
| Branch: | Tag: | Revision:

root / snf-cyclades-app / synnefo / logic / allocators / default_allocator.py @ f96f60fd

History | View | Annotate | Download (2.8 kB)

1
# Copyright 2011 GRNET S.A. All rights reserved.
2
#
3
# Redistribution and use in source and binary forms, with or
4
# without modification, are permitted provided that the following
5
# conditions are met:
6
#
7
#   1. Redistributions of source code must retain the above
8
#      copyright notice, this list of conditions and the following
9
#      disclaimer.
10
#
11
#   2. Redistributions in binary form must reproduce the above
12
#      copyright notice, this list of conditions and the following
13
#      disclaimer in the documentation and/or other materials
14
#      provided with the distribution.
15
#
16
# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
17
# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19
# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
20
# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
23
# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
24
# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
26
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27
# POSSIBILITY OF SUCH DAMAGE.
28
#
29
# The views and conclusions contained in the software and
30
# documentation are those of the authors and should not be
31
# interpreted as representing official policies, either expressed
32
# or implied, of GRNET S.A.
33

    
34
from __future__ import division
35
import logging
36

    
37

    
38
log = logging.getLogger(__name__)
39

    
40

    
41
def allocate(backends, vm):
42
    if len(backends) == 1:
43
        return backends[0]
44

    
45
    # Filter those that can not host the vm
46
    capable_backends = [backend for backend in backends
47
                        if vm_fits_in_backend(backend, vm)]
48

    
49
    log.debug("Capable backends for VM %s: %s", vm, capable_backends)
50

    
51
    # Since we are conservatively updating backend resources on each
52
    # allocation, a backend may actually be able to host a vm (despite
53
    # the state of the backend in db)
54
    if not capable_backends:
55
        capable_backends = backends
56

    
57
    # Compute the scores for each backend
58
    backend_scores = [(backend, backend_score(backend, vm))
59
                      for backend in capable_backends]
60

    
61
    log.debug("Backend scores %s", backend_scores)
62

    
63
    # Pick out the best
64
    result = min(backend_scores, key=lambda (b, b_score): b_score)
65
    backend = result[0]
66

    
67
    return backend
68

    
69

    
70
def vm_fits_in_backend(backend, vm):
71
    return backend.dfree > vm['disk'] and backend.mfree > vm['ram']
72

    
73

    
74
def backend_score(backend, flavor):
75
    mratio = 1 - (backend.mfree / backend.mtotal)
76
    dratio = 1 - (backend.dfree / backend.dtotal)
77
    cratio = (backend.pinst_cnt + 1) / (backend.ctotal * 4)
78
    return 0.7 * (mratio + dratio) * 0.3 * cratio