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#!/usr/bin/python
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#
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# Copyright (C) 2008 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Simple first-fit allocator for ganeti instance allocation framework.
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This allocator just iterates over the nodes and selects the first one
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that fits in both memory and disk space, without any consideration for
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equal spread or VCPU oversubscription.
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"""
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import simplejson
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import sys
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def SelectNode(nodes, request, to_skip):
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  """Select a node for the given instance
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  """
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  disk_size = request["disk_space_total"]
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  selected = None
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  for nname, ninfo in nodes.iteritems():
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    if nname in to_skip:
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      continue
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    if request["memory"] > ninfo["free_memory"]:
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      continue
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    if disk_size > ninfo["free_disk"]:
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      continue
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    selected = nname
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    break
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  return selected
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def OutputError(text, exit_code=1):
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  """Builds an error response with a given info message.
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  """
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  error = {
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    "success": False,
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    "info": text,
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    "nodes": [],
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    }
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  print simplejson.dumps(error, indent=2)
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  return exit_code
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def main():
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  """Main function.
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  """
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  if len(sys.argv) < 2:
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    print >> sys.stderr, "Usage: %s cluster.json" % (sys.argv[0])
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    return 1
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  data = simplejson.load(open(sys.argv[1]))
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  nodes =  data["nodes"]
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  request = data["request"]
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  req_type = request["type"]
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  offline_nodes = [name for name in nodes if nodes[name]["offline"]]
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  drained_nodes = [name for name in nodes if nodes[name]["offline"]]
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  if req_type == "allocate":
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    forbidden_nodes = offline_nodes + drained_nodes
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    inst_data = request
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  elif req_type == "relocate":
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    idict = data["instances"][request["name"]]
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    forbidden_nodes = idict["nodes"] + offline_nodes + drained_nodes
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    inst_data = idict
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    inst_data["disk_space_total"] = request["disk_space_total"]
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  else:
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    return OutputError("Unsupported allocator mode '%s'" % req_type)
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  result_nodes = []
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  while len(result_nodes) < request["required_nodes"]:
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    new_selection = SelectNode(nodes, inst_data, result_nodes+forbidden_nodes)
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    if new_selection is None:
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      return OutputError("Can't find a suitable node for position %s"
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                         " (already selected: %s)" %
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                         (len(result_nodes) + 1, ", ".join(result_nodes)),
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                         exit_code=0)
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    result_nodes.append(new_selection)
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  result = {
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    "success": True,
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    "info": "Allocation successful",
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    "nodes": result_nodes,
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    }
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  print simplejson.dumps(result, indent=2)
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  return 0
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if __name__ == "__main__":
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    sys.exit(main())