root / snf-cyclades-app / synnefo / logic / allocators / default_allocator.py @ adf766e9
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# Copyright 2011 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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# 1. Redistributions of source code must retain the above
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# copyright notice, this list of conditions and the following
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# disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following
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# disclaimer in the documentation and/or other materials
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# provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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from __future__ import division |
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import logging |
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log = logging.getLogger(__name__) |
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def allocate(backends, vm): |
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if len(backends) == 1: |
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return backends[0] |
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# Filter those that cannot host the vm
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capable_backends = [backend for backend in backends |
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if vm_fits_in_backend(backend, vm)]
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log.debug("Capable backends for VM %s: %s", vm, capable_backends)
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# Since we are conservatively updating backend resources on each
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# allocation, a backend may actually be able to host a vm (despite
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# the state of the backend in db)
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if not capable_backends: |
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capable_backends = backends |
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# Compute the scores for each backend
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backend_scores = [(backend, backend_score(backend, vm)) |
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for backend in capable_backends] |
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log.debug("Backend scores %s", backend_scores)
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# Pick out the best
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result = min(backend_scores, key=lambda (b, b_score): b_score) |
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backend = result[0]
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return backend
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def vm_fits_in_backend(backend, vm): |
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has_disk = backend.dfree > vm['disk']
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has_mem = backend.mfree > vm['ram']
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# Consider each VM having 4 Virtual CPUs
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vcpu_ratio = ((backend.pinst_cnt + 1) * 4) / backend.ctotal |
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# Consider max vcpu/cpu ratio 3
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has_cpu = vcpu_ratio < 3
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return has_cpu and has_disk and has_mem |
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def backend_score(backend, flavor): |
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mem_ratio = 1 - (backend.mfree / backend.mtotal) if backend.mtotal else 0 |
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disk_ratio = 1 - (backend.dfree / backend.dtotal) if backend.dtotal else 0 |
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cpu_ratio = ((backend.pinst_cnt + 1) * 4) / (backend.ctotal * 3) |
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return 0.5 * cpu_ratio + 0.5 * (mem_ratio + disk_ratio) |