Handle negative absolute gauges.

- For negative absolute gauge values, zero out the gauge first, since
  StatsD can't distinguish it from a delta.
- Add tests.
- Patch via Ben Gilbert (https://github.com/bgilbert)
- Fixes #40.

2 files changed, 37 insertions, 2 deletions

diff --git a/statsd/client.py b/statsd/client.py
index 1e3f80f..8b4f8e0 100644
--- a/statsd/client.py
+++ b/statsd/client.py
@@ -87,8 +87,16 @@ class StatsClient(object):
 
     def gauge(self, stat, value, rate=1, delta=False):
         """Set a gauge value."""
-        prefix = '+' if delta and value >= 0 else ''
-        self._send_stat(stat, '%s%s|g' % (prefix, value), rate)
+        if value < 0 and not delta:
+            if rate < 1:
+                if random.random() > rate:
+                    return
+            with self.pipeline() as pipe:
+                pipe._send_stat(stat, '0|g', 1)
+                pipe._send_stat(stat, '%s|g' % value, 1)
+        else:
+            prefix = '+' if delta and value >= 0 else ''
+            self._send_stat(stat, '%s%s|g' % (prefix, value), rate)
 
     def set(self, stat, value, rate=1):
         """Set a set value."""
diff --git a/statsd/tests.py b/statsd/tests.py
index 54a3773..c5d9ce9 100644
--- a/statsd/tests.py
+++ b/statsd/tests.py
@@ -146,6 +146,24 @@ def test_gauge_delta():
         yield _check, num, result
 
 
+def test_gauge_absolute_negative():
+    sc = _client()
+    sc.gauge('foo', -5, delta=False)
+    _sock_check(sc, 1, 'foo:0|g\nfoo:-5|g')
+
+
+@mock.patch.object(random, 'random')
+def test_gauge_absolute_negative_rate(mock_random):
+    sc = _client()
+    mock_random.return_value = -1
+    sc.gauge('foo', -1, rate=0.5, delta=False)
+    _sock_check(sc, 1, 'foo:0|g\nfoo:-1|g')
+    
+    mock_random.return_value = 2
+    sc.gauge('foo', -2, rate=0.5, delta=False)
+    _sock_check(sc, 1, 'foo:0|g\nfoo:-1|g')  # Should not have changed.
+
+
 @mock.patch.object(random, 'random', lambda: -1)
 def test_set():
     sc = _client()
@@ -412,6 +430,15 @@ def test_pipeline_packet_size():
     assert len(sc._sock.sendto.call_args_list[1][0][0]) <= 512
 
 
+def test_pipeline_negative_absolute_gauge():
+    """Negative absolute gauges use an internal pipeline."""
+    sc = _client()
+    with sc.pipeline() as pipe:
+        pipe.gauge('foo', -10, delta=False)
+        pipe.incr('bar')
+    _sock_check(sc, 1, 'foo:0|g\nfoo:-10|g\nbar:1|c')
+
+
 def test_big_numbers():
     num = 1234568901234
     result = 'foo:1234568901234|%s'