def test_avl_is_balancing_correctly(self):
"""
Test that it is balancing correctly
"""
avl = AVLTree()
point = VirtualPoint("10.128.20.1", 20)
avl.insert(20, point)
point = VirtualPoint("10.128.20.2", 4)
avl.insert(4, point)
point = VirtualPoint("10.128.20.3", 3)
avl.insert(3, point)
point = VirtualPoint("10.128.20.4", 9)
avl.insert(9, point)
point = VirtualPoint("10.128.20.5", 10)
avl.insert(10, point)
point = VirtualPoint("10.128.20.6", 15)
avl.insert(15, point)
bal = avl.is_balanced()
self.assertEqual(bal, True)
def test_avl_is_removing_and_balancing_correctly(self):
"""
Test that it is balancing correctly after removal of a node
"""
avl = AVLTree()
point = VirtualPoint("10.128.20.1", 20)
avl.insert(20, point)
point = VirtualPoint("10.128.20.2", 4)
avl.insert(4, point)
point = VirtualPoint("10.128.20.3", 3)
avl.insert(3, point)
point = VirtualPoint("10.128.20.4", 9)
avl.insert(9, point)
point = VirtualPoint("10.128.20.5", 10)
avl.insert(10, point)
point = VirtualPoint("10.128.20.6", 15)
avl.insert(15, point)
avl.remove(20) # Will cause tree to rebalance
bal = avl.is_balanced()
self.assertEqual(bal, True)
def test_avl_postorder_traversal(self):
"""
Test that it traverses tree in post-order correctly
"""
avl = AVLTree()
point = VirtualPoint("10.128.20.1", 20)
avl.insert(20, point)
point = VirtualPoint("10.128.20.2", 4)
avl.insert(4, point)
point = VirtualPoint("10.128.20.3", 3)
avl.insert(3, point)
point = VirtualPoint("10.128.20.4", 9)
avl.insert(9, point)
point = VirtualPoint("10.128.20.5", 10)
avl.insert(10, point)
point = VirtualPoint("10.128.20.6", 15)
avl.insert(15, point)
keys = avl.postorder_traverse()
# Expected order of keys when post-order traversal applied
expected_key_order = [3, 9, 4, 15, 20, 10]
self.assertEqual(keys, expected_key_order)
class Ring():
"""
The `Ring` object represents the consistent hashing ring.
The `node_config` parameter defaults to `None`, however it
should be provided by the `Cache` object
The `replicas` parameter adds replicas for a virtual point
in the tree. This defaults to `1` and it is not recommended
to change this.
"""
def __init__(self, node_config=None, replicas=1):
self.replicas = replicas
self.ring = AVLTree()
if node_config:
with open(node_config, 'r') as nodes:
for node in nodes.readlines():
node = node.strip()
self.add(node)
def __len__(self):
return len(self.ring.get_nodes())
def __str__(self):
return self.ring.__str__()
def add(self, node):
"""
The `add()` method adds a GhostDB node to the
consistent hashing ring.
"""
for i in range(self.replicas):
key = self.key_hash(node, i)
vp = VirtualPoint(node, key)
self.ring.insert(key, vp)
def delete(self, node):
"""
The `delete()` method removes a GhostDB node from the
consistent hashing ring. This is typically performed
if the GhostDB node is unreachable.
"""
for i in range(self.replicas):
key = self.key_hash(node, i)
self.ring.remove(key)
def get_point_for(self, key):
"""
The `get_point_for()` method returns the correct
GhostDB node to send a request to for a given key.
"""
if len(self) == 0:
return None
key = self.key_hash(key)
node_key, node_value = self.ring.next_gte_pair(key)
if not node_value:
node_key, node_value = self.ring.minimum_pair()
return node_value
def get_points(self):
"""
The `get_points()` method returns all GhostDB nodes
in the consistent hashing ring.
"""
return self.ring.get_nodes()
def key_hash(self, key, index=None):
"""
The `key_hash()` method generates and returns
the unsigned CRC32 hash for a provided key in
hexidecimal form.
"""
if index:
key = "{:s}:{:d}".format(key, index)
s = binascii.crc32(bytes(key, 'utf-8'))
return hex(s)