Add median and percentile graphite methods

README.md

@@ -158,7 +158,7 @@ The default options are:
         // Default loglevel
         "logging": "info",
 
-        // Default method (average, last_value, sum, minimum, maximum).
+        // Default method (average, last_value, sum, minimum, maximum, median, percentile k [eg. percentile 25]).
         // Can be redefined for each alert.
         "method": "average",
 
@@ -225,7 +225,7 @@ Currently two types of alerts are supported:
       // (optional) Default values format (none, bytes, s, ms, short)
       "format": "bytes",
 
-      // (optional) Alert method (average, last_value, sum, minimum, maximum)
+      // (optional) Alert method (average, last_value, sum, minimum, maximum, median, percentile k [eg. percentile 25])
       "method": "average",
 
       // (optional) Alert interval [eg. 15second, 30minute, 2hour, 1day, 3month, 1year]

graphite_beacon/alerts.py

@@ -18,7 +18,7 @@
 
 
 LOGGER = log.gen_log
-METHODS = "average", "last_value", "sum", "minimum", "maximum"
+METHODS = "average", "last_value", "sum", "minimum", "maximum", "median", "percentile"
 LEVELS = {
     'critical': 0,
     'warning': 10,
@@ -241,7 +241,14 @@ def configure(self, **options):
         self.default_nan_value = options.get(
             'default_nan_value', self.reactor.options['default_nan_value'])
         self.ignore_nan = options.get('ignore_nan', self.reactor.options['ignore_nan'])
-        assert self.method in METHODS, "Method is invalid"
+        method_tokens = self.method.split(' ', 1)
+        assert method_tokens[0] in METHODS, "Method is invalid"
+        if method_tokens[0] == 'percentile':
+            try:
+                rank = float(method_tokens[1])
+            except ValueError:
+                raise ValueError('Invalid percentile: %s' % method_tokens[1])
+            assert 0 <= rank <= 100, 'Percentile must be in the range [0,100]'
 
         self.auth_username = self.reactor.options.get('auth_username')
         self.auth_password = self.reactor.options.get('auth_password')
@@ -267,7 +274,7 @@ def load(self):
                     GraphiteRecord(line.decode('utf-8'), self.default_nan_value, self.ignore_nan)
                     for line in response.buffer)
                 data = [
-                    (None if record.empty else getattr(record, self.method), record.target)
+                    (None if record.empty else self._get_record_attr(record), record.target)
                     for record in records]
                 if len(data) == 0:
                     raise ValueError('No data')
@@ -293,6 +300,13 @@ def _graphite_url(self, query, raw_data=False, graphite_url=None):
             url = "{0}&rawData=true".format(url)
         return url
 
+    def _get_record_attr(self, record):
+        method_tokens = self.method.split(' ', 1)
+        if method_tokens[0] == 'percentile':
+            return record.percentile(float(method_tokens[1]))
+        else:
+            return getattr(record, self.method)
+
 
 class URLAlert(BaseAlert):
 

graphite_beacon/graphite.py

@@ -42,3 +42,15 @@ def minimum(self):
     @property
     def maximum(self):
         return max(self.values)
+
+    @property
+    def median(self):
+        return self.percentile(50)
+
+    def percentile(self, rank):
+        values = sorted(self.values)
+        if rank == 100 or len(self.values) == 1:
+            return values[-1]
+        k = int(len(values) * rank / 100.0)
+        return values[k]
+

tests.py

@@ -303,3 +303,38 @@ def test_html_template(reactor):
     assert message
 
     assert len(message._payload) == 2
+
+
+def test_graphite_record():
+    from random import choice, randint
+    from graphite_beacon.graphite import GraphiteRecord
+
+    def record(data):
+        meta = ','.join('0' * 4)
+        data = ','.join(map(str, data))
+        return GraphiteRecord('|'.join([meta, data]))
+
+    cases = [
+        ([0], 0, 0),
+        ([0], 50, 0),
+        ([0], 100, 0),
+        ([1, 0], 0, 0),
+        ([1, 0], 49.9, 0),
+        ([1, 0], 50, 1),
+        ([1, 0], 99.9, 1),
+        ([1, 0], 100, 1),
+        ([2, 1, 0], 0, 0),
+        ([2, 1, 0], 33.3, 0),
+        ([2, 1, 0], 33.4, 1),
+        ([2, 1, 0], 66.6, 1),
+        ([2, 1, 0], 66.7, 2),
+        ([2, 1, 0], 99.9, 2),
+        ([2, 1, 0], 100, 2),
+    ]
+
+    for (data, rank, result) in cases:
+        assert record(data).percentile(rank) == result
+
+    for _ in range(100):
+        data = [choice(range(100)) for _ in range(randint(50, 150))]
+        assert record(data).median == sorted(data)[int(len(data) / 2.0)]