dataDistribution.py

import random

from xtreemfs_client import osd


class DataDistribution(object):
    """
    class to keep track of the osd (object storage device) locations of different folders, i.e.,
    their physical location.

    this class also allows to calculate several data distributions, e.g., mappings from folders to OSDs (each folder
    gets mapped to one OSD).
    """

    def __init__(self):
        self.OSDs = {}

    def add_new_osd(self, osd_uuid):
        """
        create a new empty osd and add it to the existing OSDs.
        """
        if osd_uuid in self.OSDs:
            print("key: " + osd_uuid + " is already present!")
            return
        new_osd = osd.OSD(osd_uuid)
        self.OSDs[osd_uuid] = new_osd

    def add_osd(self, new_osd):
        """
        add the given OSD (object) to the existing OSDs.
        """
        if new_osd.uuid in self.OSDs:
            print("key: " + new_osd.uuid + " is already present!")
            return
        self.OSDs[new_osd.uuid] = new_osd

    def add_osd_list(self, osd_list):
        """
        add the given list of OSDs (objects) to the existing OSDs.
        """
        for osd_uuid in osd_list:
            if osd_uuid not in self.OSDs:
                new_osd = osd.OSD(osd_uuid)
                self.OSDs[osd_uuid] = new_osd

    def get_osd_list(self):
        """
        get a list of all existing OSDs.
        """
        osd_list = []
        for osd_name in self.OSDs.keys():
            osd_list.append(osd_name)
        return osd_list

    def get_containing_osd(self, folder_id):
        """
        get the OSD containing the given folder_id, or None if the folder is not assigned to any OSD.
        """
        for checked_osd in self.OSDs.values():
            if checked_osd.contains_folder(folder_id):
                return checked_osd
        return None

    def get_average_folder_size(self):
        """
        get the average folder size of all folders of all OSDs.
        """
        total_size = 0
        total_number_of_folders = 0
        for one_osd in self.OSDs.values():
            total_size += one_osd.total_folder_size
            total_number_of_folders += len(one_osd.folders)
        if total_number_of_folders == 0:
            return 0
        return total_size / total_number_of_folders

    def assign_new_osd(self, folder_id, new_osd):
        """
        assign folder_id to new_osd. if folder_id already is assigned to an OSD, this old assignment is deleted.
        """
        old_osd = self.get_containing_osd(folder_id)
        if old_osd is None:
            self.OSDs[new_osd].add_folder(folder_id, self.get_average_folder_size())
        else:
            self.OSDs[new_osd].add_folder(folder_id, self.OSDs[old_osd.uuid].folders[folder_id])
            self.OSDs[old_osd.uuid].remove_folder(folder_id)

    def add_folders(self, folders, osd_information=None, ratio_parameter='', random_osd_assignment=False):
        """
        adds a list of folders to the data distribution.
        if not specified otherwise, the assignments are calculated using the LPT algorithm.
        returns a list of assignments from folders to OSDs, for which (folders) there was previously no assignment.

        if the optional arguments are given, OSDs are assigned data proportionally to their ratio_parameter.
        """
        new_folders = []
        for folder in folders:
            containing_osd = self.get_containing_osd(folder.id)
            if containing_osd is not None:
                containing_osd.add_folder(folder.id, folder.size)
            else:
                new_folders.append(folder)

        print("dataDistribution: random_osd_assignment: " + str(random_osd_assignment))

        osds_for_new_folders = []

        # totally random OSD assignment, even ignoring OSD capacities
        # (might lead to I/O errors when too many groups are assigned to an OSD)
        if random_osd_assignment:
            print("using random osd assignment")
            for folder in new_folders:
                random_osd = random.choice(list(self.OSDs.values()))
                random_osd.add_folder(folder.id, folder.size)
                osds_for_new_folders.append((folder.id,
                                             random_osd.uuid))
            return osds_for_new_folders

        # balanced deterministic OSD assignment
        # (following largest processing time first or post-greedy approach)
        list.sort(new_folders, key=lambda x: x.size, reverse=True)

        osd_ratios = {}
        if osd_information is not None and ratio_parameter != '':
            total_osd_size = 0
            for osd_size in osd_information.values():
                total_osd_size += osd_size[ratio_parameter]
            for osd_uuid, osd_size in osd_information.items():
                osd_ratios[osd_uuid] = float(osd_size[ratio_parameter]) / float(total_osd_size)

        else:
            for osd_uuid in self.OSDs.keys():
                osd_ratios[osd_uuid] = float(1)

        for folder in new_folders:
            least_used_osd = None
            for one_osd in self.OSDs.values():
                if (least_used_osd is None) or \
                                one_osd.total_folder_size / osd_ratios[one_osd.uuid] \
                                <= least_used_osd.total_folder_size / osd_ratios[least_used_osd.uuid]:
                    least_used_osd = one_osd
            least_used_osd.add_folder(folder.id, folder.size)
            osds_for_new_folders.append((folder.id,
                                         least_used_osd.uuid))

        return osds_for_new_folders

    def update_folder(self, folder, size):
        """
        updates the size of a given folder
        """
        for one_osd in self.OSDs.values():
            if folder in one_osd.folders.keys():
                one_osd.update_folder(folder, size)

    def description(self):
        """
        generates a string describing this data distribution
        """
        string = ""
        for one_osd in self.OSDs.values():
            string += str(one_osd)
            string += "\n"
            string += "folders : " + str(one_osd.folders)
            string += "\n"
        string += "average folder size: " + str(self.get_average_folder_size())
        return string

    def __str__(self):
        string_representation = "DataDistribution has " + str(len(self.OSDs)) \
                                + " osds: \n"
        for key, value in self.OSDs.items():
            string_representation += str(value) + " \n"
        return string_representation