Remove servergroup added labels from matcher selectors for LabelValue…

…s to downstream

If a label was only added by promxy *and* a matcher we'd still pass that
matcher downstream. This is a problem as promxy is the one who added it
-- so it doesn't matter if downstream knows about it (usually it
doesn't).

Fixes #665

pkg/promclient/label.go

@@ -57,6 +57,34 @@ func (c *AddLabelClient) Key() model.LabelSet {
 	return c.Labels
 }
 
+func (c *AddLabelClient) filterMatchers(matchers []string) ([]string, bool, error) {
+	ret := make([]string, 0, len(matchers))
+	for i, matcher := range matchers {
+		selectors, err := parser.ParseMetricSelector(matcher)
+		if err != nil {
+			return nil, true, err
+		}
+
+		// If the selector matches our value -- remove the selector
+		// if the selector doesn't match, return empty
+		for sI, s := range selectors {
+			if v, ok := c.Labels[model.LabelName(s.Name)]; ok {
+				if s.Matches(string(v)) {
+					selectors = append(selectors[:sI], selectors[i+1:]...)
+				} else {
+					return nil, false, nil
+				}
+			}
+		}
+		newMatcher, err := promhttputil.MatcherToString(selectors)
+		if err != nil {
+			return nil, false, err
+		}
+		ret = append(ret, newMatcher)
+	}
+	return ret, true, nil
+}
+
 // LabelNames returns all the unique label names present in the block in sorted order.
 func (c *AddLabelClient) LabelNames(ctx context.Context, matchers []string, startTime time.Time, endTime time.Time) ([]string, v1.Warnings, error) {
 	l, w, err := c.API.LabelNames(ctx, matchers, startTime, endTime)
@@ -81,6 +109,14 @@ func (c *AddLabelClient) LabelNames(ctx context.Context, matchers []string, star
 
 // LabelValues performs a query for the values of the given label.
 func (c *AddLabelClient) LabelValues(ctx context.Context, label string, matchers []string, startTime time.Time, endTime time.Time) (model.LabelValues, v1.Warnings, error) {
+	matchers, ok, err := c.filterMatchers(matchers)
+	if err != nil {
+		return nil, nil, err
+	}
+	if !ok {
+		return nil, nil, nil
+	}
+
 	val, w, err := c.API.LabelValues(ctx, label, matchers, startTime, endTime)
 	if err != nil {
 		return nil, w, err

pkg/promclient/label_test.go

@@ -1,11 +1,18 @@
 package promclient
 
 import (
+	"context"
+	"fmt"
 	"reflect"
 	"strconv"
+	"strings"
 	"testing"
+	"time"
 
+	v1 "github.com/prometheus/client_golang/api/prometheus/v1"
 	model "github.com/prometheus/common/model"
+	"github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/promql/parser"
 )
 
 func TestMergeLabelValues(t *testing.T) {
@@ -85,3 +92,121 @@ func TestMergeLabelSets(t *testing.T) {
 		})
 	}
 }
+
+type labelStubAPI struct {
+	series []model.LabelSet
+}
+
+func (a *labelStubAPI) LabelNames(ctx context.Context, matchers []string, startTime time.Time, endTime time.Time) ([]string, v1.Warnings, error) {
+	return nil, nil, fmt.Errorf("not implemented")
+}
+
+func (a *labelStubAPI) LabelValues(ctx context.Context, label string, matchers []string, startTime time.Time, endTime time.Time) (model.LabelValues, v1.Warnings, error) {
+	series := append([]model.LabelSet{}, a.series...)
+	for _, m := range matchers {
+		selectors, err := parser.ParseMetricSelector(m)
+		if err != nil {
+			return nil, nil, err
+		}
+		for _, selector := range selectors {
+			for i, s := range series {
+				v, ok := s[model.LabelName(selector.Name)]
+				if !ok || !selector.Matches(string(v)) {
+					series = append(series[:i], series[i+1:]...)
+				}
+			}
+		}
+	}
+	values := make(map[string]struct{})
+	for _, s := range series {
+		for k, v := range s {
+			if strings.HasPrefix(string(k), model.ReservedLabelPrefix) {
+				continue
+			}
+			values[string(v)] = struct{}{}
+		}
+	}
+	ret := make(model.LabelValues, 0, len(values))
+	for k := range values {
+		ret = append(ret, model.LabelValue(k))
+	}
+	return ret, nil, nil
+}
+
+// Query performs a query for the given time.
+func (a *labelStubAPI) Query(ctx context.Context, query string, ts time.Time) (model.Value, v1.Warnings, error) {
+	return nil, nil, fmt.Errorf("not implemented")
+
+}
+
+// QueryRange performs a query for the given range.
+func (a *labelStubAPI) QueryRange(ctx context.Context, query string, r v1.Range) (model.Value, v1.Warnings, error) {
+	return nil, nil, fmt.Errorf("not implemented")
+}
+
+// Series finds series by label matchers.
+func (a *labelStubAPI) Series(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]model.LabelSet, v1.Warnings, error) {
+	return nil, nil, fmt.Errorf("not implemented")
+
+}
+
+// GetValue loads the raw data for a given set of matchers in the time range
+func (a *labelStubAPI) GetValue(ctx context.Context, start, end time.Time, matchers []*labels.Matcher) (model.Value, v1.Warnings, error) {
+	return nil, nil, fmt.Errorf("not implemented")
+
+}
+
+// Metadata returns metadata about metrics currently scraped by the metric name.
+func (a *labelStubAPI) Metadata(ctx context.Context, metric, limit string) (map[string][]v1.Metadata, error) {
+	return nil, fmt.Errorf("not implemented")
+}
+func TestAddLabelClient(t *testing.T) {
+
+	stub := &labelStubAPI{
+		series: []model.LabelSet{{model.MetricNameLabel: "testmetric", "a": "1"}},
+	}
+
+	tests := []struct {
+		labelSet    model.LabelSet
+		err         bool
+		matchers    []string
+		labelValues []string
+	}{
+		{
+			labelSet:    model.LabelSet{"b": "1"},
+			labelValues: []string{"1"},
+		},
+		{
+			labelSet:    model.LabelSet{"b": "1"},
+			labelValues: []string{"1"},
+			matchers:    []string{`{b="1"}`},
+		},
+	}
+
+	for i, test := range tests {
+		a := &AddLabelClient{stub, test.labelSet}
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			t.Run("LabelNames", func(t *testing.T) {
+				v, _, err := a.LabelValues(context.TODO(), "a", test.matchers, time.Time{}, time.Time{})
+				if err != nil != test.err {
+					if test.err {
+						t.Fatalf("missing expected err")
+					} else {
+						t.Fatalf("Unexpected Err: %v", err)
+					}
+				}
+				if err == nil {
+					if len(v) != len(test.labelValues) {
+						t.Fatalf("mismatch in len: \nexpected=%v\nactual=%v", test.labelValues, v)
+					}
+
+					for i, actualV := range v {
+						if actualV != model.LabelValue(test.labelValues[i]) {
+							t.Fatalf("mismatch in value: \nexpected=%v\nactual=%v", test.labelValues, v)
+						}
+					}
+				}
+			})
+		})
+	}
+}