Merge pull request #116 from prometheus/beorn7/fingerprint

Fingerprinting fixes in client_golang

Author: beorn7

model/metric.go

@@ -26,14 +26,68 @@ var separator = []byte{0}
 // a singleton and refers to one and only one stream of samples.
 type Metric map[LabelName]LabelValue
 
-// Equal compares the fingerprints of both metrics.
+// Equal compares the metrics.
 func (m Metric) Equal(o Metric) bool {
-	return m.Fingerprint().Equal(o.Fingerprint())
+	if len(m) != len(o) {
+		return false
+	}
+	for ln, lv := range m {
+		olv, ok := o[ln]
+		if !ok {
+			return false
+		}
+		if olv != lv {
+			return false
+		}
+	}
+	return true
 }
 
-// Before compares the fingerprints of both metrics.
+// Before compares the metrics, using the following criteria:
+//
+// If m has fewer labels than o, it is before o. If it has more, it is not.
+//
+// If the number of labels is the same, the superset of all label names is
+// sorted alphanumerically. The first differing label pair found in that order
+// determines the outcome: If the label does not exist at all in m, then m is
+// before o, and vice versa. Otherwise the label value is compared
+// alphanumerically.
+//
+// If m and o are equal, the method returns false.
 func (m Metric) Before(o Metric) bool {
-	return m.Fingerprint().Less(o.Fingerprint())
+	if len(m) < len(o) {
+		return true
+	}
+	if len(m) > len(o) {
+		return false
+	}
+
+	lns := make(LabelNames, 0, len(m)+len(o))
+	for ln := range m {
+		lns = append(lns, ln)
+	}
+	for ln := range o {
+		lns = append(lns, ln)
+	}
+	// It's probably not worth it to de-dup lns.
+	sort.Sort(lns)
+	for _, ln := range lns {
+		mlv, ok := m[ln]
+		if !ok {
+			return true
+		}
+		olv, ok := o[ln]
+		if !ok {
+			return false
+		}
+		if mlv < olv {
+			return true
+		}
+		if mlv > olv {
+			return false
+		}
+	}
+	return false
 }
 
 // String implements Stringer.
@@ -67,6 +121,12 @@ func (m Metric) Fingerprint() Fingerprint {
 	return metricToFingerprint(m)
 }
 
+// Fingerprint returns a Metric's Fingerprint calculated by a faster hashing
+// algorithm, which is, however, more susceptible to hash collisions.
+func (m Metric) FastFingerprint() Fingerprint {
+	return metricToFastFingerprint(m)
+}
+
 // Clone returns a copy of the Metric.
 func (m Metric) Clone() Metric {
 	clone := Metric{}

model/metric_test.go

@@ -17,47 +17,56 @@ import "testing"
 
 func testMetric(t testing.TB) {
 	var scenarios = []struct {
-		input       Metric
-		fingerprint Fingerprint
+		input           Metric
+		fingerprint     Fingerprint
+		fastFingerprint Fingerprint
 	}{
 		{
-			input:       Metric{},
-			fingerprint: 14695981039346656037,
+			input:           Metric{},
+			fingerprint:     14695981039346656037,
+			fastFingerprint: 14695981039346656037,
 		},
 		{
 			input: Metric{
 				"first_name":   "electro",
 				"occupation":   "robot",
 				"manufacturer": "westinghouse",
 			},
-			fingerprint: 11310079640881077873,
+			fingerprint:     5911716720268894962,
+			fastFingerprint: 11310079640881077873,
 		},
 		{
 			input: Metric{
 				"x": "y",
 			},
-			fingerprint: 13948396922932177635,
+			fingerprint:     8241431561484471700,
+			fastFingerprint: 13948396922932177635,
 		},
 		{
 			input: Metric{
 				"a": "bb",
 				"b": "c",
 			},
-			fingerprint: 3198632812309449502,
+			fingerprint:     3016285359649981711,
+			fastFingerprint: 3198632812309449502,
 		},
 		{
 			input: Metric{
 				"a":  "b",
 				"bb": "c",
 			},
-			fingerprint: 5774953389407657638,
+			fingerprint:     7122421792099404749,
+			fastFingerprint: 5774953389407657638,
 		},
 	}
 
 	for i, scenario := range scenarios {
 		if scenario.fingerprint != scenario.input.Fingerprint() {
 			t.Errorf("%d. expected %d, got %d", i, scenario.fingerprint, scenario.input.Fingerprint())
 		}
+		if scenario.fastFingerprint != scenario.input.FastFingerprint() {
+			t.Errorf("%d. expected %d, got %d", i, scenario.fastFingerprint, scenario.input.FastFingerprint())
+		}
 	}
 }
 

model/sample_test.go

@@ -21,42 +21,36 @@ import (
 func TestSamplesSort(t *testing.T) {
 	input := Samples{
 		&Sample{
-			// Fingerprint: 81f9c9ed24563f8f.
 			Metric: Metric{
 				MetricNameLabel: "A",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 81f9c9ed24563f8f.
 			Metric: Metric{
 				MetricNameLabel: "A",
 			},
 			Timestamp: 2,
 		},
 		&Sample{
-			// Fingerprint: 1bf6c9ed24543f8f.
 			Metric: Metric{
 				MetricNameLabel: "C",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 1bf6c9ed24543f8f.
 			Metric: Metric{
 				MetricNameLabel: "C",
 			},
 			Timestamp: 2,
 		},
 		&Sample{
-			// Fingerprint: 68f4c9ed24533f8f.
 			Metric: Metric{
 				MetricNameLabel: "B",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 68f4c9ed24533f8f.
 			Metric: Metric{
 				MetricNameLabel: "B",
 			},
@@ -66,44 +60,38 @@ func TestSamplesSort(t *testing.T) {
 
 	expected := Samples{
 		&Sample{
-			// Fingerprint: 1bf6c9ed24543f8f.
 			Metric: Metric{
-				MetricNameLabel: "C",
+				MetricNameLabel: "A",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 1bf6c9ed24543f8f.
 			Metric: Metric{
-				MetricNameLabel: "C",
+				MetricNameLabel: "A",
 			},
 			Timestamp: 2,
 		},
 		&Sample{
-			// Fingerprint: 68f4c9ed24533f8f.
 			Metric: Metric{
 				MetricNameLabel: "B",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 68f4c9ed24533f8f.
 			Metric: Metric{
 				MetricNameLabel: "B",
 			},
 			Timestamp: 2,
 		},
 		&Sample{
-			// Fingerprint: 81f9c9ed24563f8f.
 			Metric: Metric{
-				MetricNameLabel: "A",
+				MetricNameLabel: "C",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 81f9c9ed24563f8f.
 			Metric: Metric{
-				MetricNameLabel: "A",
+				MetricNameLabel: "C",
 			},
 			Timestamp: 2,
 		},