Synnefo » snf-ganeti

#!/usr/bin/python

#

# Copyright (C) 2008 Google Inc.

#

# This program 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 2 of the License, or

# (at your option) any later version.

#

# This program 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 this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Simple first-fit allocator for ganeti instance allocation framework.

This allocator just iterates over the nodes and selects the first one

that fits in both memory and disk space, without any consideration for

equal spread or VCPU oversubscription.

"""

import simplejson

import sys

def SelectNode(nodes, request, to_skip):

  """Select a node for the given instance

  """

  disk_size = request["disk_space_total"]

  selected = None

  for nname, ninfo in nodes.iteritems():

    if nname in to_skip:

      continue

    if request["memory"] > ninfo["free_memory"]:

      continue

    if disk_size > ninfo["free_disk"]:

      continue

    selected = nname

    break

  return selected

def OutputError(text, exit_code=1):

  """Builds an error response with a given info message.

  """

  error = {

    "success": False,

    "info": text,

    "nodes": [],

    }

  print simplejson.dumps(error, indent=2)

  return exit_code

def main():

  """Main function.

  """

  if len(sys.argv) < 2:

    print >> sys.stderr, "Usage: %s cluster.json" % (sys.argv[0])

    return 1

  data = simplejson.load(open(sys.argv[1]))

  nodes =  data["nodes"]

  request = data["request"]

  req_type = request["type"]

  if req_type == "allocate":

    forbidden_nodes = []

    inst_data = request

  elif req_type == "relocate":

    idict = data["instances"][request["name"]]

    forbidden_nodes = idict["nodes"]

    inst_data = idict

    inst_data["disk_space_total"] = request["disk_space_total"]

  else:

    return OutputError("Unsupported allocator mode '%s'" % req_type)

  result_nodes = []

  while len(result_nodes) < request["required_nodes"]:

    new_selection = SelectNode(nodes, inst_data, result_nodes+forbidden_nodes)

    if new_selection is None:

      return OutputError("Can't find a suitable node for position %s"

                         " (already selected: %s)" %

                         (len(result_nodes) + 1, ", ".join(result_nodes)),

                         exit_code=0)

    result_nodes.append(new_selection)

  result = {

          "success": True,

          "info": "Allocation successful",

          "nodes": result_nodes,

          }

  print simplejson.dumps(result, indent=2)

  return 0

if __name__ == "__main__":

    sys.exit(main())