Rotating bloom (#44)

barrust · web-flow · commit d313ebc672ce · 2018-11-12T13:48:55.000-05:00
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # PyProbables Changelog
 
+### Version 0.2.6
+* Bloom Filters:
+    * Addition of a Rotating Bloom Filter
+
+### Version 0.2.5
+* Bloom Filters:
+    * Addition of an Expanding Bloom Filter
+
 ### Version 0.2.0
 * Use __slots__
 
diff --git a/docs/source/code.rst b/docs/source/code.rst
@@ -46,6 +46,13 @@ ExpandingBloomFilter
 .. autoclass:: probables.ExpandingBloomFilter
     :members:
 
+RotatingBloomFilter
++++++++++++++++++++++++++++++++
+
+.. autoclass:: probables.RotatingBloomFilter
+    :members:
+    :inherited-members:
+
 CountingBloomFilter
 +++++++++++++++++++++++++++++++
 
diff --git a/docs/source/quickstart.rst b/docs/source/quickstart.rst
@@ -93,6 +93,17 @@ determine the number of elements that will be added.
 At this time, it is not possible to import or export an **Expanding Bloom
 Filter** but that is a planned feature.
 
+Rotating Bloom Filter
+"""""""""""""""""""""""""""""""""""""""""""""""
+
+The **Rotating Bloom Filter** is a specialized version of the standard
+Bloom Filter that rolls of earlier entries into the filter as they become more
+stale. The popping of the queue can be done either programmatically or
+automatically.
+
+At this time, it is not possible to import or export an **Expanding Bloom
+Filter** but that is a planned feature.
+
 
 Counting Bloom Filter
 """""""""""""""""""""""""""""""""""""""""""""""
diff --git a/probables/__init__.py b/probables/__init__.py
@@ -1,7 +1,7 @@
 ''' pyprobables module '''
 from __future__ import (unicode_literals, absolute_import, print_function)
 from . blooms import (BloomFilter, BloomFilterOnDisk, CountingBloomFilter,
-                      ExpandingBloomFilter)
+                      ExpandingBloomFilter, RotatingBloomFilter)
 from . countminsketch import (CountMinSketch, HeavyHitters, StreamThreshold,
                               CountMeanSketch, CountMeanMinSketch)
 from . cuckoo import (CuckooFilter, CountingCuckooFilter)
@@ -12,7 +12,7 @@
 __maintainer__ = 'Tyler Barrus'
 __email__ = 'barrust@gmail.com'
 __license__ = 'MIT'
-__version__ = '0.2.5'
+__version__ = '0.2.6'
 __credits__ = []
 __url__ = 'https://github.com/barrust/pyprobables'
 __bugtrack_url__ = 'https://github.com/barrust/pyprobables/issues'
@@ -22,4 +22,4 @@
            'HeavyHitters', 'StreamThreshold', 'CuckooFilter',
            'CountingCuckooFilter', 'InitializationError', 'NotSupportedError',
            'ProbablesBaseException', 'CuckooFilterFullError',
-           'ExpandingBloomFilter']
+           'ExpandingBloomFilter', 'RotatingBloomFilter']
diff --git a/probables/blooms/__init__.py b/probables/blooms/__init__.py
@@ -3,7 +3,7 @@
 
 from . bloom import (BloomFilter, BloomFilterOnDisk)
 from . countingbloom import (CountingBloomFilter)
-from . expandingbloom import (ExpandingBloomFilter)
+from . expandingbloom import (ExpandingBloomFilter, RotatingBloomFilter)
 
 __all__ = ['BloomFilter', 'BloomFilterOnDisk', 'CountingBloomFilter',
-           'ExpandingBloomFilter']
+           'ExpandingBloomFilter', 'RotatingBloomFilter']
diff --git a/probables/blooms/expandingbloom.py b/probables/blooms/expandingbloom.py
@@ -25,6 +25,9 @@ class ExpandingBloomFilter(object):
             At this point, the expanding Bloom Filter does not support \
             `export` or `import` '''
 
+    __slots__ = ['_blooms', '__fpr', '__est_elements', '__hash_func',
+                 '__added_elements']
+
     def __init__(self, est_elements=None, false_positive_rate=None,
                  hash_function=None):
         ''' initialize '''
@@ -62,16 +65,6 @@ def elements_added(self):
         ''' int: The total number of elements added '''
         return self.__added_elements
 
-    def __add_bloom_filter(self):
-        ''' build a new bloom and add it on! '''
-        blm = BloomFilter(self.__est_elements, self.__fpr, self.__hash_func)
-        self._blooms.append(blm)
-
-    def __check_for_growth(self):
-        ''' detereming if the bloom filter should automatically grow '''
-        if self._blooms[-1].elements_added >= self.__est_elements:
-            self.__add_bloom_filter()
-
     def check(self, key):
         ''' Check to see if the key is in the Bloom Filter
 
@@ -103,8 +96,8 @@ def add(self, key, force=False):
             Args:
                 key (str): The element to be inserted
                 force (bool): `True` will force it to be inserted, even if it \
-                              likely has been inserted before \
-                `False` will only insert if not found in the Bloom Filter '''
+                              likely has been inserted before `False` will \
+                              only insert if not found in the Bloom Filter '''
         hashes = self._blooms[0].hashes(key)
         self.add_alt(hashes, force)
 
@@ -115,8 +108,101 @@ def add_alt(self, hashes, force=False):
                 hashes (list): A list of integers representing the key to insert
                 force (bool): `True` will force it to be inserted, even if \
                               it likely has been inserted before \
-                `False` will only insert if not found in the Bloom Filter '''
+                              `False` will only insert if not found in the \
+                              Bloom Filter '''
         self.__added_elements += 1
         if force or not self.check_alt(hashes):
             self.__check_for_growth()
             self._blooms[-1].add_alt(hashes)
+
+    def __add_bloom_filter(self):
+        ''' build a new bloom and add it on! '''
+        blm = BloomFilter(est_elements=self.__est_elements,
+                          false_positive_rate=self.__fpr,
+                          hash_function=self.__hash_func)
+        self._blooms.append(blm)
+
+    def __check_for_growth(self):
+        ''' detereming if the bloom filter should automatically grow '''
+        if self._blooms[-1].elements_added >= self.__est_elements:
+            self.__add_bloom_filter()
+
+
+class RotatingBloomFilter(ExpandingBloomFilter):
+    ''' Simple Rotating Bloom Filter implementation that allows for the "older"
+        elements added to be removed, in chunks. As the queue fills up, those
+        elements inserted earlier will be bulk removed. This also provides the
+        user with the oportunity to force the removal instead of it being time
+        based.
+
+        Args:
+            est_elements (int): The number of estimated elements to be added
+            false_positive_rate (float): The desired false positive rate
+            max_queue_size (int): This is the number is used to determine the \
+            maximum number of Bloom Filters. Total elements added is based on \
+            `max_queue_size * est_elements`
+            hash_function (function): Hashing strategy function to use \
+            `hf(key, number)`
+    '''
+    __slots__ = ['_blooms', '__fpr', '__est_elements', '__hash_func',
+                 '__added_elements', '_queue_size']
+
+    def __init__(self, est_elements=None, false_positive_rate=None,
+                 max_queue_size=10, hash_function=None):
+        ''' initialize '''
+        super(RotatingBloomFilter,
+              self).__init__(est_elements=est_elements,
+                             false_positive_rate=false_positive_rate,
+                             hash_function=hash_function)
+        self.__fpr = false_positive_rate
+        self.__est_elements = est_elements
+        self.__hash_func = hash_function
+        self._queue_size = max_queue_size
+        self.__added_elements = 0
+
+    @property
+    def max_queue_size(self):
+        ''' int: The maximum size for the queue '''
+        return self._queue_size
+
+    @property
+    def current_queue_size(self):
+        ''' int: The current size of the queue '''
+        return len(self._blooms)
+
+    def add_alt(self, hashes, force=False):
+        ''' Add the element represented by hashes into the Bloom Filter
+
+            Args:
+                hashes (list): A list of integers representing the key to insert
+                force (bool): `True` will force it to be inserted, even if \
+                              it likely has been inserted before \
+                              `False` will only insert if not found in the \
+                              Bloom Filter '''
+        self.__added_elements += 1
+        if force or not self.check_alt(hashes):
+            self.__rotate_bloom_filter()
+            self._blooms[-1].add_alt(hashes)
+
+    def pop(self):
+        ''' Pop an element off of the queue '''
+        self.__rotate_bloom_filter(force=True)
+
+    def __rotate_bloom_filter(self, force=False):
+        ''' handle determining if/when the Bloom Filter queue needs to be
+            rotated '''
+        blm = self._blooms[-1]
+        ready_to_rotate = blm.elements_added == blm.estimated_elements
+        neeeds_to_pop = self.current_queue_size < self._queue_size
+        if force or (ready_to_rotate and neeeds_to_pop):
+            self.__add_bloom_filter()
+        elif force or ready_to_rotate:
+            blm = self._blooms.pop(0)
+            self.__add_bloom_filter()
+
+    def __add_bloom_filter(self):
+        ''' build a new bloom and add it on! '''
+        blm = BloomFilter(est_elements=self.__est_elements,
+                          false_positive_rate=self.__fpr,
+                          hash_function=self.__hash_func)
+        self._blooms.append(blm)
diff --git a/tests/cuckoo_test.py b/tests/cuckoo_test.py
@@ -114,23 +114,23 @@ def test_cuckoo_filter_fing_size(self):
         ''' test bad fingerprint size < 1 '''
         def runner():
             ''' runner '''
-            cko = CuckooFilter(capacity=100, bucket_size=2, finger_size=0)
+            CuckooFilter(capacity=100, bucket_size=2, finger_size=0)
 
         self.assertRaises(ValueError, runner)
 
     def test_cuckoo_filter_fing_size_2(self):
         ''' test bad fingerprint size > 4 '''
         def runner():
             ''' runner '''
-            cko = CuckooFilter(capacity=100, bucket_size=2, finger_size=5)
+            CuckooFilter(capacity=100, bucket_size=2, finger_size=5)
 
         self.assertRaises(ValueError, runner)
 
     def test_cuckoo_filter_fing_size_3(self):
         ''' test valid fingerprint size '''
         try:
-            cko = CuckooFilter(capacity=100, bucket_size=2, finger_size=1)
-        except:
+            CuckooFilter(capacity=100, bucket_size=2, finger_size=1)
+        except ValueError:
             self.assertEqual(True, False)
         self.assertEqual(True, True)
 
diff --git a/tests/expandingbloom_test.py b/tests/expandingbloom_test.py
@@ -2,7 +2,7 @@
 ''' Unittest class '''
 from __future__ import (unicode_literals, absolute_import, print_function)
 import unittest
-from probables import (ExpandingBloomFilter)
+from probables import (ExpandingBloomFilter, RotatingBloomFilter)
 
 class TestExpandingBloomFilter(unittest.TestCase):
 
@@ -54,3 +54,46 @@ def test_ebf_contains(self):
         self.assertEqual('this is another test' in blm, True)
         self.assertEqual('this is yet another test' in blm, False)
         self.assertEqual('this is not another test' in blm, False)
+
+
+class TestRotatingBloomFilter(unittest.TestCase):
+
+    def test_rbf_init(self):
+        ''' test the initialization of an rotating bloom filter '''
+        blm = RotatingBloomFilter(est_elements=10, false_positive_rate=0.05,
+                                  max_queue_size=10)
+        self.assertEqual(blm.expansions, 0)
+        self.assertEqual(blm.max_queue_size, 10)
+
+    def test_rfb_rotate(self):
+        ''' test that the bloom filter rotates the first bloom off the stack '''
+        blm = RotatingBloomFilter(est_elements=10, false_positive_rate=0.05,
+                                  max_queue_size=5)
+        self.assertEqual(blm.expansions, 0)
+        blm.add('test')
+        self.assertEqual(blm.expansions, 0)
+        for i in range(10):
+            blm.add('{}'.format(i), force=True)
+        self.assertEqual(blm.expansions, 1)
+        self.assertEqual(blm.current_queue_size, 2)
+        self.assertEqual(blm.check('test'), True)
+
+        for i in range(10, 20):
+            blm.add('{}'.format(i), force=True)
+        self.assertEqual(blm.check('test'), True)
+        self.assertEqual(blm.current_queue_size, 3)
+
+        for i in range(20, 30):
+            blm.add('{}'.format(i), force=True)
+        self.assertEqual(blm.check('test'), True)
+        self.assertEqual(blm.current_queue_size, 4)
+
+        for i in range(30, 40):
+            blm.add('{}'.format(i), force=True)
+        self.assertEqual(blm.check('test'), True)
+        self.assertEqual(blm.current_queue_size, 5)
+
+        for i in range(40, 50):
+            blm.add('{}'.format(i), force=True)
+        self.assertEqual(blm.check('test'), False)  # it should roll off
+        self.assertEqual(blm.current_queue_size, 5)
