Implement deletion based on partially matching labels (#1013)

* WIP partial match

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Cleanup

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Comments

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Tests and comments

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Handle properly deleting multiple metrics, update tests

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Comments

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Try using curry values

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Skip curry value to demo

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Fix curry deletion, remove outdated comment.

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Fix logic for deletion of metrics from prior to currying

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Don't match curried values. Update tests.

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Remove unneccesasry helper and todo comments

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Comment about partial matching curried labels

Signed-off-by: Zach Stone <zach@giantswarm.io>

* Simplify curried value check

Signed-off-by: Zach Stone <zach@giantswarm.io>

prometheus/vec.go

@@ -99,6 +99,16 @@ func (m *MetricVec) Delete(labels Labels) bool {
 	return m.metricMap.deleteByHashWithLabels(h, labels, m.curry)
 }
 
+// DeletePartialMatch deletes all metrics where the variable labels contain all of those
+// passed in as labels. The order of the labels does not matter.
+// It returns the number of metrics deleted.
+//
+// Note that curried labels will never be matched if deleting from the curried vector.
+// To match curried labels with DeletePartialMatch, it must be called on the base vector.
+func (m *MetricVec) DeletePartialMatch(labels Labels) int {
+	return m.metricMap.deleteByLabels(labels, m.curry)
+}
+
 // Without explicit forwarding of Describe, Collect, Reset, those methods won't
 // show up in GoDoc.
 
@@ -381,6 +391,82 @@ func (m *metricMap) deleteByHashWithLabels(
 	return true
 }
 
+// deleteByLabels deletes a metric if the given labels are present in the metric.
+func (m *metricMap) deleteByLabels(labels Labels, curry []curriedLabelValue) int {
+	m.mtx.Lock()
+	defer m.mtx.Unlock()
+
+	var numDeleted int
+
+	for h, metrics := range m.metrics {
+		i := findMetricWithPartialLabels(m.desc, metrics, labels, curry)
+		if i >= len(metrics) {
+			// Didn't find matching labels in this metric slice.
+			continue
+		}
+		delete(m.metrics, h)
+		numDeleted++
+	}
+
+	return numDeleted
+}
+
+// findMetricWithPartialLabel returns the index of the matching metric or
+// len(metrics) if not found.
+func findMetricWithPartialLabels(
+	desc *Desc, metrics []metricWithLabelValues, labels Labels, curry []curriedLabelValue,
+) int {
+	for i, metric := range metrics {
+		if matchPartialLabels(desc, metric.values, labels, curry) {
+			return i
+		}
+	}
+	return len(metrics)
+}
+
+// indexOf searches the given slice of strings for the target string and returns
+// the index or len(items) as well as a boolean whether the search succeeded.
+func indexOf(target string, items []string) (int, bool) {
+	for i, l := range items {
+		if l == target {
+			return i, true
+		}
+	}
+	return len(items), false
+}
+
+// valueMatchesVariableOrCurriedValue determines if a value was previously curried,
+// and returns whether it matches either the "base" value or the curried value accordingly.
+// It also indicates whether the match is against a curried or uncurried value.
+func valueMatchesVariableOrCurriedValue(targetValue string, index int, values []string, curry []curriedLabelValue) (bool, bool) {
+	for _, curriedValue := range curry {
+		if curriedValue.index == index {
+			// This label was curried. See if the curried value matches our target.
+			return curriedValue.value == targetValue, true
+		}
+	}
+	// This label was not curried. See if the current value matches our target label.
+	return values[index] == targetValue, false
+}
+
+// matchPartialLabels searches the current metric and returns whether all of the target label:value pairs are present.
+func matchPartialLabels(desc *Desc, values []string, labels Labels, curry []curriedLabelValue) bool {
+	for l, v := range labels {
+		// Check if the target label exists in our metrics and get the index.
+		varLabelIndex, validLabel := indexOf(l, desc.variableLabels)
+		if validLabel {
+			// Check the value of that label against the target value.
+			// We don't consider curried values in partial matches.
+			matches, curried := valueMatchesVariableOrCurriedValue(v, varLabelIndex, values, curry)
+			if matches && !curried {
+				continue
+			}
+		}
+		return false
+	}
+	return true
+}
+
 // getOrCreateMetricWithLabelValues retrieves the metric by hash and label value
 // or creates it and returns the new one.
 //

prometheus/vec_test.go

@@ -125,6 +125,93 @@ func testDeleteLabelValues(t *testing.T, vec *GaugeVec) {
 	}
 }
 
+func TestDeletePartialMatch(t *testing.T) {
+	baseVec := NewGaugeVec(
+		GaugeOpts{
+			Name: "test",
+			Help: "helpless",
+		},
+		[]string{"l1", "l2", "l3"},
+	)
+
+	assertNoMetric := func(t *testing.T) {
+		if n := len(baseVec.metricMap.metrics); n != 0 {
+			t.Error("expected no metrics, got", n)
+		}
+	}
+
+	// No metric value is set.
+	if got, want := baseVec.DeletePartialMatch(Labels{"l1": "v1", "l2": "v2"}), 0; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	baseVec.With(Labels{"l1": "baseValue1", "l2": "baseValue2", "l3": "baseValue3"}).Inc()
+	baseVec.With(Labels{"l1": "multiDeleteV1", "l2": "diff1BaseValue2", "l3": "v3"}).(Gauge).Set(42)
+	baseVec.With(Labels{"l1": "multiDeleteV1", "l2": "diff2BaseValue2", "l3": "v3"}).(Gauge).Set(84)
+	baseVec.With(Labels{"l1": "multiDeleteV1", "l2": "diff3BaseValue2", "l3": "v3"}).(Gauge).Set(168)
+
+	curriedVec := baseVec.MustCurryWith(Labels{"l2": "curriedValue2"})
+	curriedVec.WithLabelValues("curriedValue1", "curriedValue3").Inc()
+	curriedVec.WithLabelValues("curriedValue1", "differentCurriedValue3").Inc()
+	curriedVec.WithLabelValues("differentCurriedValue1", "differentCurriedValue3").Inc()
+
+	// Try to delete nonexistent label with existent value from curried vector.
+	if got, want := curriedVec.DeletePartialMatch(Labels{"lx": "curriedValue1"}), 0; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// Try to delete valid label with nonexistent value from curried vector.
+	if got, want := curriedVec.DeletePartialMatch(Labels{"l1": "badValue1"}), 0; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// Try to delete from a curried vector based on labels which were curried.
+	// This operation succeeds when run against the base vector below.
+	if got, want := curriedVec.DeletePartialMatch(Labels{"l2": "curriedValue2"}), 0; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// Try to delete from a curried vector based on labels which were curried,
+	// but the value actually exists in the base vector.
+	if got, want := curriedVec.DeletePartialMatch(Labels{"l2": "baseValue2"}), 0; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// Delete multiple matching metrics from a curried vector based on partial values.
+	if got, want := curriedVec.DeletePartialMatch(Labels{"l1": "curriedValue1"}), 2; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// Try to delete nonexistent label with existent value from base vector.
+	if got, want := baseVec.DeletePartialMatch(Labels{"lx": "curriedValue1"}), 0; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// Try to delete partially invalid labels from base vector.
+	if got, want := baseVec.DeletePartialMatch(Labels{"l1": "baseValue1", "l2": "badValue2"}), 0; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// Delete from the base vector based on values which were curried.
+	// This operation fails when run against a curried vector above.
+	if got, want := baseVec.DeletePartialMatch(Labels{"l2": "curriedValue2"}), 1; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// Delete multiple metrics from the base vector based on a single valid label.
+	if got, want := baseVec.DeletePartialMatch(Labels{"l1": "multiDeleteV1"}), 3; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// Delete from the base vector based on values which were not curried.
+	if got, want := baseVec.DeletePartialMatch(Labels{"l3": "baseValue3"}), 1; got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	// All metrics should have been deleted now.
+	assertNoMetric(t)
+}
+
 func TestMetricVec(t *testing.T) {
 	vec := NewGaugeVec(
 		GaugeOpts{