swift/test/unit/common/ring/test_ring.py

# Copyright (c) 2010-2012 OpenStack, LLC.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import array
import cPickle as pickle
import os
import sys
import unittest
from gzip import GzipFile
from shutil import rmtree
from time import sleep, time

from swift.common import ring, utils


class TestRingData(unittest.TestCase):

    def setUp(self):
        self.testdir = os.path.join(os.path.dirname(__file__), 'ring_data')
        rmtree(self.testdir, ignore_errors=1)
        os.mkdir(self.testdir)

    def tearDown(self):
        rmtree(self.testdir, ignore_errors=1)

    def assert_ring_data_equal(self, rd_expected, rd_got):
        self.assertEquals(rd_expected._replica2part2dev_id,
                          rd_got._replica2part2dev_id)
        self.assertEquals(rd_expected.devs, rd_got.devs)
        self.assertEquals(rd_expected._part_shift, rd_got._part_shift)

    def test_attrs(self):
        r2p2d = [[0, 1, 0, 1], [0, 1, 0, 1]]
        d = [{'id': 0, 'zone': 0}, {'id': 1, 'zone': 1}]
        s = 30
        rd = ring.RingData(r2p2d, d, s)
        self.assertEquals(rd._replica2part2dev_id, r2p2d)
        self.assertEquals(rd.devs, d)
        self.assertEquals(rd._part_shift, s)

    def test_can_load_pickled_ring_data(self):
        rd = ring.RingData([[0, 1, 0, 1], [0, 1, 0, 1]],
                [{'id': 0, 'zone': 0}, {'id': 1, 'zone': 1}], 30)
        ring_fname = os.path.join(self.testdir, 'foo.ring.gz')
        for p in xrange(pickle.HIGHEST_PROTOCOL):
            pickle.dump(rd, GzipFile(ring_fname, 'wb'), protocol=p)
            ring_data = ring.RingData.load(ring_fname)
            self.assert_ring_data_equal(rd, ring_data)

    def test_roundtrip_serialization(self):
        ring_fname = os.path.join(self.testdir, 'foo.ring.gz')
        rd = ring.RingData(
            [array.array('H', [0, 1, 0, 1]), array.array('H',[0, 1, 0, 1])],
            [{'id': 0, 'zone': 0}, {'id': 1, 'zone': 1}], 30)
        rd.save(ring_fname)
        rd2 = ring.RingData.load(ring_fname)
        self.assert_ring_data_equal(rd, rd2)

    def test_deterministic_serialization(self):
        """
        Two identical rings should produce identical .gz files on disk.

        Only true on Python 2.7 or greater.
        """
        if sys.version_info[0] == 2 and sys.version_info[1] < 7:
            return
        os.mkdir(os.path.join(self.testdir, '1'))
        os.mkdir(os.path.join(self.testdir, '2'))
        # These have to have the same filename (not full path,
        # obviously) since the filename gets encoded in the gzip data.
        ring_fname1 = os.path.join(self.testdir, '1', 'the.ring.gz')
        ring_fname2 = os.path.join(self.testdir, '2', 'the.ring.gz')
        rd = ring.RingData(
            [array.array('H', [0, 1, 0, 1]), array.array('H',[0, 1, 0, 1])],
            [{'id': 0, 'zone': 0}, {'id': 1, 'zone': 1}], 30)
        rd.save(ring_fname1)
        rd.save(ring_fname2)
        with open(ring_fname1) as ring1:
            with open(ring_fname2) as ring2:
                self.assertEqual(ring1.read(), ring2.read())


class TestRing(unittest.TestCase):

    def setUp(self):
        utils.HASH_PATH_SUFFIX = 'endcap'
        self.testdir = os.path.join(os.path.dirname(__file__), 'ring')
        rmtree(self.testdir, ignore_errors=1)
        os.mkdir(self.testdir)
        self.testgz = os.path.join(self.testdir, 'whatever.ring.gz')
        self.intended_replica2part2dev_id = [
            array.array('H', [0, 1, 0, 1]),
            array.array('H', [0, 1, 0, 1]),
            array.array('H', [3, 4, 3, 4])]
        self.intended_devs = [{'id': 0, 'zone': 0, 'weight': 1.0,
                               'ip': '10.1.1.1', 'port': 6000},
                              {'id': 1, 'zone': 0, 'weight': 1.0,
                               'ip': '10.1.1.1', 'port': 6000},
                              None,
                              {'id': 3, 'zone': 2, 'weight': 1.0,
                               'ip': '10.1.2.1', 'port': 6000},
                              {'id': 4, 'zone': 2, 'weight': 1.0,
                               'ip': '10.1.2.2', 'port': 6000}]
        self.intended_part_shift = 30
        self.intended_reload_time = 15
        ring.RingData(self.intended_replica2part2dev_id,
            self.intended_devs, self.intended_part_shift).save(self.testgz)
        self.ring = ring.Ring(self.testdir,
            reload_time=self.intended_reload_time, ring_name='whatever')

    def tearDown(self):
        rmtree(self.testdir, ignore_errors=1)

    def test_creation(self):
        self.assertEquals(self.ring._replica2part2dev_id,
                          self.intended_replica2part2dev_id)
        self.assertEquals(self.ring._part_shift, self.intended_part_shift)
        self.assertEquals(self.ring.devs, self.intended_devs)
        self.assertEquals(self.ring.reload_time, self.intended_reload_time)
        self.assertEquals(self.ring.serialized_path, self.testgz)
        # test invalid endcap
        _orig_hash_path_suffix = utils.HASH_PATH_SUFFIX
        try:
            utils.HASH_PATH_SUFFIX = ''
            self.assertRaises(SystemExit, ring.Ring, self.testdir, 'whatever')
        finally:
            utils.HASH_PATH_SUFFIX = _orig_hash_path_suffix

    def test_has_changed(self):
        self.assertEquals(self.ring.has_changed(), False)
        os.utime(self.testgz, (time() + 60, time() + 60))
        self.assertEquals(self.ring.has_changed(), True)

    def test_reload(self):
        os.utime(self.testgz, (time() - 300, time() - 300))
        self.ring = ring.Ring(self.testdir, reload_time=0.001,
                    ring_name='whatever')
        orig_mtime = self.ring._mtime
        self.assertEquals(len(self.ring.devs), 5)
        self.intended_devs.append({'id': 3, 'zone': 3, 'weight': 1.0})
        ring.RingData(self.intended_replica2part2dev_id,
            self.intended_devs, self.intended_part_shift).save(self.testgz)
        sleep(0.1)
        self.ring.get_nodes('a')
        self.assertEquals(len(self.ring.devs), 6)
        self.assertNotEquals(self.ring._mtime, orig_mtime)

        os.utime(self.testgz, (time() - 300, time() - 300))
        self.ring = ring.Ring(self.testdir, reload_time=0.001,
                    ring_name='whatever')
        orig_mtime = self.ring._mtime
        self.assertEquals(len(self.ring.devs), 6)
        self.intended_devs.append({'id': 5, 'zone': 4, 'weight': 1.0})
        ring.RingData(self.intended_replica2part2dev_id,
            self.intended_devs, self.intended_part_shift).save(self.testgz)
        sleep(0.1)
        self.ring.get_part_nodes(0)
        self.assertEquals(len(self.ring.devs), 7)
        self.assertNotEquals(self.ring._mtime, orig_mtime)

        os.utime(self.testgz, (time() - 300, time() - 300))
        self.ring = ring.Ring(self.testdir, reload_time=0.001,
                    ring_name='whatever')
        orig_mtime = self.ring._mtime
        part, nodes = self.ring.get_nodes('a')
        self.assertEquals(len(self.ring.devs), 7)
        self.intended_devs.append({'id': 6, 'zone': 5, 'weight': 1.0})
        ring.RingData(self.intended_replica2part2dev_id,
            self.intended_devs, self.intended_part_shift).save(self.testgz)
        sleep(0.1)
        self.ring.get_more_nodes(part).next()
        self.assertEquals(len(self.ring.devs), 8)
        self.assertNotEquals(self.ring._mtime, orig_mtime)

        os.utime(self.testgz, (time() - 300, time() - 300))
        self.ring = ring.Ring(self.testdir, reload_time=0.001,
                    ring_name='whatever')
        orig_mtime = self.ring._mtime
        self.assertEquals(len(self.ring.devs), 8)
        self.intended_devs.append({'id': 5, 'zone': 4, 'weight': 1.0})
        ring.RingData(self.intended_replica2part2dev_id,
            self.intended_devs, self.intended_part_shift).save(self.testgz)
        sleep(0.1)
        self.assertEquals(len(self.ring.devs), 9)
        self.assertNotEquals(self.ring._mtime, orig_mtime)

    def test_get_part_nodes(self):
        part, nodes = self.ring.get_nodes('a')
        self.assertEquals(nodes, self.ring.get_part_nodes(part))

    def test_get_nodes(self):
        # Yes, these tests are deliberately very fragile. We want to make sure
        # that if someones changes the results the ring produces, they know it.
        self.assertRaises(TypeError, self.ring.get_nodes)
        part, nodes = self.ring.get_nodes('a')
        self.assertEquals(part, 0)
        self.assertEquals(nodes, [self.intended_devs[0],
                                  self.intended_devs[3]])

        part, nodes = self.ring.get_nodes('a1')
        self.assertEquals(part, 0)
        self.assertEquals(nodes, [self.intended_devs[0],
                                  self.intended_devs[3]])

        part, nodes = self.ring.get_nodes('a4')
        self.assertEquals(part, 1)
        self.assertEquals(nodes, [self.intended_devs[1],
                                  self.intended_devs[4]])

        part, nodes = self.ring.get_nodes('aa')
        self.assertEquals(part, 1)
        self.assertEquals(nodes, [self.intended_devs[1],
                                  self.intended_devs[4]])

        part, nodes = self.ring.get_nodes('a', 'c1')
        self.assertEquals(part, 0)
        self.assertEquals(nodes, [self.intended_devs[0],
                                  self.intended_devs[3]])

        part, nodes = self.ring.get_nodes('a', 'c0')
        self.assertEquals(part, 3)
        self.assertEquals(nodes, [self.intended_devs[1],
                                  self.intended_devs[4]])

        part, nodes = self.ring.get_nodes('a', 'c3')
        self.assertEquals(part, 2)
        self.assertEquals(nodes, [self.intended_devs[0],
                                  self.intended_devs[3]])

        part, nodes = self.ring.get_nodes('a', 'c2')
        self.assertEquals(part, 2)
        self.assertEquals(nodes, [self.intended_devs[0],
                                  self.intended_devs[3]])

        part, nodes = self.ring.get_nodes('a', 'c', 'o1')
        self.assertEquals(part, 1)
        self.assertEquals(nodes, [self.intended_devs[1],
                                  self.intended_devs[4]])

        part, nodes = self.ring.get_nodes('a', 'c', 'o5')
        self.assertEquals(part, 0)
        self.assertEquals(nodes, [self.intended_devs[0],
                                  self.intended_devs[3]])

        part, nodes = self.ring.get_nodes('a', 'c', 'o0')
        self.assertEquals(part, 0)
        self.assertEquals(nodes, [self.intended_devs[0],
                                  self.intended_devs[3]])

        part, nodes = self.ring.get_nodes('a', 'c', 'o2')
        self.assertEquals(part, 2)
        self.assertEquals(nodes, [self.intended_devs[0],
                                  self.intended_devs[3]])

    def add_dev_to_ring(self, new_dev):
        self.ring.devs.append(new_dev)
        self.ring._rebuild_tier_data()

    def test_get_more_nodes(self):
        # Yes, these tests are deliberately very fragile. We want to make sure
        # that if someone changes the results the ring produces, they know it.
        exp_part = 6
        exp_devs = [48, 93, 96]
        exp_zones = set([5, 8, 9])
        exp_handoffs = [11, 47, 25, 76, 69, 23, 64, 43, 34, 3, 30, 83, 31, 16,
                        27, 39, 32, 60, 77, 24, 0, 42, 8, 72, 19, 71, 26, 9,
                        20, 35, 13, 5, 38, 14, 28, 41, 18, 66, 61, 21, 81, 1,
                        78, 74, 46, 4, 68, 40, 80, 75, 45, 79, 44, 62, 29, 7,
                        15, 70, 65, 12, 82, 17, 22, 6, 2, 67, 37, 63, 33, 73,
                        36, 10, 99, 59, 106, 107, 50, 88, 57, 103, 100, 56, 91,
                        84, 94, 102, 52, 101, 95, 105, 58, 90, 86, 54, 49, 87,
                        104, 97, 55, 89, 53, 92, 85, 51, 98]
        exp_first_handoffs = [1, 37, 48, 68, 84, 75, 11, 101, 14, 73, 100, 75,
                              29, 19, 18, 101, 15, 99, 95, 24, 46, 82, 73, 62,
                              24, 89, 9, 22, 107, 74, 54, 63, 40, 106, 99, 83,
                              64, 73, 73, 106, 106, 80, 6, 25, 20, 33, 6, 79,
                              59, 42, 62, 24, 14, 107, 28, 0, 85, 5, 4, 12, 58,
                              11, 92, 18, 36, 56, 86, 1, 21, 33, 80, 97, 4, 81,
                              79, 76, 89, 50, 75, 27, 7, 96, 47, 55, 81, 104,
                              12, 5, 18, 106, 27, 93, 39, 92, 42, 30, 20, 88,
                              58, 105, 65, 29, 17, 52, 11, 106, 7, 24, 21, 91,
                              62, 52, 50, 31, 77, 102, 19, 11, 8, 58, 53, 20,
                              26, 8, 18, 82, 48, 68, 82, 89, 101, 50, 3, 52,
                              46, 11, 2, 30, 79, 66, 4, 61, 3, 56, 45, 102, 73,
                              84, 36, 19, 34, 84, 49, 40, 103, 66, 31, 33, 93,
                              33, 4, 52, 26, 58, 30, 47, 100, 57, 40, 79, 33,
                              107, 24, 20, 44, 4, 7, 59, 83, 101, 1, 56, 20,
                              61, 33, 16, 5, 74, 98, 4, 80, 15, 104, 52, 73,
                              18, 67, 75, 98, 73, 79, 68, 75, 27, 91, 36, 100,
                              52, 95, 37, 46, 70, 14, 47, 3, 70, 23, 40, 105,
                              62, 86, 48, 22, 54, 4, 72, 81, 13, 0, 18, 98,
                              101, 36, 29, 24, 39, 79, 97, 105, 28, 107, 47,
                              52, 101, 20, 22, 29, 65, 27, 7, 33, 64, 101, 60,
                              19, 55]
        rb = ring.RingBuilder(8, 3, 1)
        next_dev_id = 0
        for zone in xrange(1, 10):
            for server in xrange(1, 5):
                for device in xrange(1, 4):
                    rb.add_dev({'id': next_dev_id,
                                'ip': '1.2.%d.%d' % (zone, server),
                                'port': 1234, 'zone': zone, 'weight': 1.0})
                    next_dev_id += 1
        rb.rebalance(seed=1)
        rb.get_ring().save(self.testgz)
        r = ring.Ring(self.testdir, ring_name='whatever')
        part, devs = r.get_nodes('a', 'c', 'o')
        primary_zones = set(d['zone'] for d in devs)
        self.assertEquals(part, exp_part)
        self.assertEquals([d['id'] for d in devs], exp_devs)
        self.assertEquals(primary_zones, exp_zones)
        devs = list(r.get_more_nodes(part))
        self.assertEquals([d['id'] for d in devs], exp_handoffs)
        seen_shared_zone = False
        for dev in devs:
            if dev['zone'] in primary_zones:
                seen_shared_zone = True
            else:
                self.assertFalse(seen_shared_zone)
        devs = []
        for part in xrange(r.partition_count):
            devs.append(r.get_more_nodes(part).next()['id'])
        self.assertEquals(devs, exp_first_handoffs)

        # Add a new device we can handoff to.
        zone = 5
        server = 0
        rb.add_dev({'id': next_dev_id,
                    'ip': '1.2.%d.%d' % (zone, server),
                    'port': 1234, 'zone': zone, 'weight': 1.0})
        next_dev_id += 1
        rb.rebalance(seed=1)
        rb.get_ring().save(self.testgz)
        r = ring.Ring(self.testdir, ring_name='whatever')
        # We would change expectations here, but in this test no handoffs
        # changed at all.
        part, devs = r.get_nodes('a', 'c', 'o')
        primary_zones = set(d['zone'] for d in devs)
        self.assertEquals(part, exp_part)
        self.assertEquals([d['id'] for d in devs], exp_devs)
        self.assertEquals(primary_zones, exp_zones)
        devs = list(r.get_more_nodes(part))
        dev_ids = [d['id'] for d in devs]
        self.assertEquals(len(dev_ids), len(exp_handoffs))
        for index, dev in enumerate(dev_ids):
            self.assertEquals(
                dev, exp_handoffs[index],
                'handoff differs at position %d\n%s\n%s' % (
                    index, dev_ids[index:], exp_handoffs[index:]))
        seen_shared_zone = False
        for dev in devs:
            if dev['zone'] in primary_zones:
                seen_shared_zone = True
            else:
                self.assertFalse(seen_shared_zone)
        devs = []
        for part in xrange(r.partition_count):
            devs.append(r.get_more_nodes(part).next()['id'])
        for part in xrange(r.partition_count):
            self.assertEquals(
                devs[part], exp_first_handoffs[part],
                'handoff for partitition %d is now device id %d' % (
                    part, devs[part]))


        # Remove a device.
        rb.remove_dev(0)
        rb.rebalance(seed=1)
        rb.get_ring().save(self.testgz)
        r = ring.Ring(self.testdir, ring_name='whatever')
        # Change expectations
        # The long string of handoff nodes for the partition were the same for
        # the first 20, which is pretty good.
        exp_handoffs[20:] = [42, 8, 72, 19, 71, 26, 9, 20, 35, 13, 5, 38, 14,
                             28, 41, 18, 66, 61, 21, 81, 1, 78, 74, 46, 4, 68,
                             40, 80, 75, 45, 79, 44, 62, 29, 7, 15, 70, 65, 12,
                             82, 17, 22, 6, 2, 67, 37, 63, 33, 73, 36, 10, 99,
                             59, 106, 107, 50, 88, 57, 103, 108, 100, 56, 91,
                             84, 94, 102, 52, 101, 95, 105, 58, 90, 86, 54, 49,
                             87, 104, 97, 55, 89, 53, 92, 85, 51, 98]
        # Just 4 of the first handoffs changed
        exp_first_handoffs[55] = 104
        exp_first_handoffs[116] = 6
        exp_first_handoffs[181] = 15
        exp_first_handoffs[228] = 38
        # Test
        part, devs = r.get_nodes('a', 'c', 'o')
        primary_zones = set(d['zone'] for d in devs)
        self.assertEquals(part, exp_part)
        self.assertEquals([d['id'] for d in devs], exp_devs)
        self.assertEquals(primary_zones, exp_zones)
        devs = list(r.get_more_nodes(part))
        dev_ids = [d['id'] for d in devs]
        self.assertEquals(len(dev_ids), len(exp_handoffs))
        for index, dev in enumerate(dev_ids):
            self.assertEquals(
                dev, exp_handoffs[index],
                'handoff differs at position %d\n%s\n%s' % (
                    index, dev_ids[index:], exp_handoffs[index:]))
        seen_shared_zone = False
        for dev in devs:
            if dev['zone'] in primary_zones:
                seen_shared_zone = True
            else:
                self.assertFalse(seen_shared_zone)
        devs = []
        for part in xrange(r.partition_count):
            devs.append(r.get_more_nodes(part).next()['id'])
        for part in xrange(r.partition_count):
            self.assertEquals(
                devs[part], exp_first_handoffs[part],
                'handoff for partitition %d is now device id %d' % (
                    part, devs[part]))

        # Add a partial replica
        rb.set_replicas(3.5)
        rb.rebalance(seed=1)
        rb.get_ring().save(self.testgz)
        r = ring.Ring(self.testdir, ring_name='whatever')
        # Change expectations
        # We have another replica now
        exp_devs.append(47)
        exp_zones.add(4)
        # Caused some major changes in the sequence of handoffs for our test
        # partition, but at least the first stayed the same.
        exp_handoffs[1:] = [81, 25, 76, 3, 69, 23, 64, 13, 34, 30, 16, 83, 31,
                            27, 74, 32, 60, 77, 24, 63, 8, 72, 19, 71, 7, 26,
                            9, 20, 35, 5, 14, 62, 28, 18, 66, 82, 22, 61, 21,
                            1, 67, 78, 4, 79, 68, 80, 75, 6, 29, 15, 70, 65,
                            12, 17, 2, 33, 73, 10, 99, 59, 106, 45, 107, 43,
                            50, 88, 57, 46, 103, 39, 108, 42, 100, 56, 91, 52,
                            84, 87, 38, 94, 41, 90, 102, 101, 85, 95, 98, 105,
                            58, 86, 40, 54, 44, 49, 104, 97, 55, 89, 37, 53,
                            92, 51, 36]
        # Lots of first handoffs changed, but 30 of 256 is still just 11.72%.
        exp_first_handoffs[1] = 6
        exp_first_handoffs[4] = 104
        exp_first_handoffs[11] = 106
        exp_first_handoffs[17] = 13
        exp_first_handoffs[21] = 77
        exp_first_handoffs[22] = 95
        exp_first_handoffs[27] = 46
        exp_first_handoffs[29] = 65
        exp_first_handoffs[30] = 3
        exp_first_handoffs[31] = 20
        exp_first_handoffs[51] = 50
        exp_first_handoffs[53] = 8
        exp_first_handoffs[54] = 2
        exp_first_handoffs[72] = 107
        exp_first_handoffs[79] = 72
        exp_first_handoffs[85] = 71
        exp_first_handoffs[88] = 66
        exp_first_handoffs[92] = 29
        exp_first_handoffs[93] = 46
        exp_first_handoffs[96] = 38
        exp_first_handoffs[101] = 57
        exp_first_handoffs[103] = 87
        exp_first_handoffs[104] = 28
        exp_first_handoffs[107] = 1
        exp_first_handoffs[109] = 69
        exp_first_handoffs[110] = 50
        exp_first_handoffs[111] = 76
        exp_first_handoffs[115] = 47
        exp_first_handoffs[117] = 48
        exp_first_handoffs[119] = 7
        # Test
        part, devs = r.get_nodes('a', 'c', 'o')
        primary_zones = set(d['zone'] for d in devs)
        self.assertEquals(part, exp_part)
        self.assertEquals([d['id'] for d in devs], exp_devs)
        self.assertEquals(primary_zones, exp_zones)
        devs = list(r.get_more_nodes(part))
        dev_ids = [d['id'] for d in devs]
        self.assertEquals(len(dev_ids), len(exp_handoffs))
        for index, dev in enumerate(dev_ids):
            self.assertEquals(
                dev, exp_handoffs[index],
                'handoff differs at position %d\n%s\n%s' % (
                    index, dev_ids[index:], exp_handoffs[index:]))
        seen_shared_zone = False
        for dev in devs:
            if dev['zone'] in primary_zones:
                seen_shared_zone = True
            else:
                self.assertFalse(seen_shared_zone)
        devs = []
        for part in xrange(r.partition_count):
            devs.append(r.get_more_nodes(part).next()['id'])
        for part in xrange(r.partition_count):
            self.assertEquals(
                devs[part], exp_first_handoffs[part],
                'handoff for partitition %d is now device id %d' % (
                    part, devs[part]))

        # One last test of a partial replica partition
        exp_part2 = 136
        exp_devs2 = [52, 76, 97]
        exp_zones2 = set([9, 5, 7])
        exp_handoffs2 = [2, 67, 37, 63, 44, 92, 33, 23, 85, 42, 35, 36, 10, 89,
                         84, 43, 4, 17, 32, 12, 41, 31, 65, 20, 25, 61, 1, 40,
                         9, 94, 47, 69, 95, 45, 5, 71, 86, 30, 93, 28, 91, 15,
                         88, 39, 18, 70, 27, 16, 24, 21, 14, 11, 8, 62, 6, 26,
                         29, 60, 34, 13, 87, 38, 3, 66, 7, 46, 64, 22, 68, 19,
                         90, 107, 96, 53, 103, 108, 73, 51, 98, 80, 49, 104,
                         58, 56, 74, 101, 78, 48, 57, 83, 72, 54, 77, 50, 105,
                         55, 59, 99, 75, 106, 82, 79, 81, 102, 100]
        part2, devs2 = r.get_nodes('a', 'c', 'o2')
        primary_zones2 = set(d['zone'] for d in devs2)
        self.assertEquals(part2, exp_part2)
        self.assertEquals([d['id'] for d in devs2], exp_devs2)
        self.assertEquals(primary_zones2, exp_zones2)
        devs2 = list(r.get_more_nodes(part2))
        dev_ids2 = [d['id'] for d in devs2]
        self.assertEquals(len(dev_ids2), len(exp_handoffs2))
        for index, dev in enumerate(dev_ids2):
            self.assertEquals(
                dev, exp_handoffs2[index],
                'handoff differs at position %d\n%s\n%s' % (
                    index, dev_ids2[index:], exp_handoffs2[index:]))
        seen_shared_zone = False
        for dev in devs2:
            if dev['zone'] in primary_zones2:
                seen_shared_zone = True
            else:
                self.assertFalse(seen_shared_zone)


if __name__ == '__main__':
    unittest.main()