pipoket · July 2, 2012 01:29 · May 13, 2011 · May 13, 2011 · Mar 22, 2011
diff --git a/counter_test.py b/counter_test.py
@@ -23,7 +23,7 @@
 # Attempt to update the values using that copy, this should break the
 # space/time continuum.
 c2.add(1, obj=o2)  # 4
-c3.add(10, obj=o3) # 13 
+c3.add(10, obj=o3) # 14 
 
 # c1 should get a conflicted value and the conflict should be resolved with the value returned.
 assert c1.value == 14, c1.value
diff --git a/counter.py b/counter.py
@@ -9,7 +9,7 @@ def __init__(self, bucket, key):
         self.bucket.set_allow_multiples(True)
         self.key = key
 
-    def update(self, step, obj=None):
+    def add(self, step, obj=None):
         if obj is None:
             obj = self._get_with_resolution()
 

diff --git a/counter_test.py b/counter_test.py
@@ -11,9 +11,9 @@
 
 # Counter 1 will increment the counter to three
 c1.reset()   # 0
-c1.update(1) # 1
-c1.update(1) # 2
-c1.update(1) # 3
+c1.add(1) # 1
+c1.add(1) # 2
+c1.add(1) # 3
 assert c1.value == 3, c1.value
 
 # Counter 2 and Counter 3 will increment the counter in parallel
@@ -22,8 +22,8 @@
 o3 = c3.bucket.get(c3.key)
 # Attempt to update the values using that copy, this should break the
 # space/time continuum.
-c2.update(1, obj=o2)  # 4
-c3.update(10, obj=o3) # 13 
+c2.add(1, obj=o2)  # 4
+c3.add(10, obj=o3) # 13 
 
 # c1 should get a conflicted value and the conflict should be resolved with the value returned.
 assert c1.value == 14, c1.value
diff --git a/counter.py b/counter.py
@@ -0,0 +1,66 @@
+import logging
+import riak
+
+log = logging.getLogger(__name__)
+
+class RiakCounter(object):
+    def __init__(self, bucket, key):
+        self.bucket = bucket
+        self.bucket.set_allow_multiples(True)
+        self.key = key
+
+    def update(self, step, obj=None):
+        if obj is None:
+            obj = self._get_with_resolution()
+
+        data = obj.get_data()
+        data['last'] = data['last'] + data['step']
+        data['step'] = step
+        log.debug(data)
+        obj.set_data(data)
+        obj.store()
+
+    def reset(self, start=0):
+        obj = self._get_with_resolution()
+        data = obj.get_data()
+        data['last'] = start
+        data['step'] = 0
+        log.debug(data)
+        obj.set_data(data)
+        obj.store()
+
+
+    def _get_with_resolution(self):
+        obj = self.bucket.get(self.key)
+
+        # If the object doesn't exist, return a new object with
+        # a value of zero
+        # If the object has siblings, resolve the conflict
+        if obj.has_siblings():
+            first_obj = obj.get_sibling(0)
+            first = first_obj.get_data()
+
+            # For each sibling, apply the steps to the first's steps
+            for sibling_obj in map(obj.get_sibling,
+                               range(1, obj.get_sibling_count())):
+                sibling = sibling_obj.get_data()
+                first['step'] += sibling['step']
+
+            # Update the data with the new last and step values
+            first_obj.set_data(first)
+            log.debug("300: %s" % (first_obj.get_data()))            
+            return first_obj
+        elif not obj.exists():
+            obj = self.bucket.new(self.key, data={'last': 0,
+                                                  'step': 0})
+            log.debug("404: %s" % (obj.get_data()))
+            return obj
+        else:
+            log.debug("200: %s" % (obj.get_data()))
+            return obj
+
+    @property
+    def value(self):
+        obj = self._get_with_resolution()
+        data = obj.get_data()
+        return data['last'] + data['step']
diff --git a/counter_test.py b/counter_test.py
@@ -0,0 +1,29 @@
+from counter import RiakCounter
+import logging
+import riak
+
+logging.basicConfig(level=logging.DEBUG)
+
+# Create 3 independent counters
+c1 = RiakCounter(riak.RiakClient(port=8098).bucket("test"), "counter")
+c2 = RiakCounter(riak.RiakClient(port=8098).bucket("test"), "counter")
+c3 = RiakCounter(riak.RiakClient(port=8098).bucket("test"), "counter")
+
+# Counter 1 will increment the counter to three
+c1.reset()   # 0
+c1.update(1) # 1
+c1.update(1) # 2
+c1.update(1) # 3
+assert c1.value == 3, c1.value
+
+# Counter 2 and Counter 3 will increment the counter in parallel
+# Split reality by fetching two copies of the some object
+o2 = c2.bucket.get(c2.key)
+o3 = c3.bucket.get(c3.key)
+# Attempt to update the values using that copy, this should break the
+# space/time continuum.
+c2.update(1, obj=o2)  # 4
+c3.update(10, obj=o3) # 13 
+
+# c1 should get a conflicted value and the conflict should be resolved with the value returned.
+assert c1.value == 14, c1.value
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