prometheus: improve flatten key performance.

The flattenKey function is called whenever a gauge, counter, or
sample is set when using the Prometheus sink. The change most
notably uses a replacer rather than a regex. The hash formatting
also now uses + for concatenation rather than fmt.Sprintf for an
addition perf improvement.

prometheus/prometheus.go

@@ -6,7 +6,6 @@ package prometheus
 import (
  "fmt"
  "log"
- "regexp"
  "strings"
  "sync"
  "time"
@@ -248,15 +247,15 @@ func initCounters(m *sync.Map, counters []CounterDefinition, help map[string]str
  return
 }
 
-var forbiddenChars = regexp.MustCompile("[ .=\\-/]")
+var forbiddenCharsReplacer = strings.NewReplacer(" ", "_", ".", "_", "=", "_", "-", "_", "/", "_")
 
 func flattenKey(parts []string, labels []metrics.Label) (string, string) {
  key := strings.Join(parts, "_")
- key = forbiddenChars.ReplaceAllString(key, "_")
+ key = forbiddenCharsReplacer.Replace(key)
 
  hash := key
  for _, label := range labels {
- hash += fmt.Sprintf(";%s=%s", label.Name, label.Value)
+ hash += ";" + label.Name + "=" + label.Value
  }
 
  return key, hash

prometheus/prometheus_test.go

@@ -367,3 +367,86 @@ func TestMetricSinkInterface(t *testing.T) {
  var pps *PrometheusPushSink
  _ = metrics.MetricSink(pps)
 }
+
+func Test_flattenKey(t *testing.T) {
+ testCases := []struct {
+ name string
+ inputParts []string
+ inputLabels []metrics.Label
+ expectedOutputKey string
+ expectedOutputHash string
+ }{
+ {
+ name: "no replacement needed",
+ inputParts: []string{"my", "example", "metric"},
+ inputLabels: []metrics.Label{
+ {Name: "foo", Value: "bar"},
+ {Name: "baz", Value: "buz"},
+ },
+ expectedOutputKey: "my_example_metric",
+ expectedOutputHash: "my_example_metric;foo=bar;baz=buz",
+ },
+ {
+ name: "key with whitespace",
+ inputParts: []string{" my ", " example ", " metric "},
+ inputLabels: []metrics.Label{
+ {Name: "foo", Value: "bar"},
+ {Name: "baz", Value: "buz"},
+ },
+ expectedOutputKey: "_my___example___metric_",
+ expectedOutputHash: "_my___example___metric_;foo=bar;baz=buz",
+ },
+ {
+ name: "key with dot",
+ inputParts: []string{".my.", ".example.", ".metric."},
+ inputLabels: []metrics.Label{
+ {Name: "foo", Value: "bar"},
+ {Name: "baz", Value: "buz"},
+ },
+ expectedOutputKey: "_my___example___metric_",
+ expectedOutputHash: "_my___example___metric_;foo=bar;baz=buz",
+ },
+ {
+ name: "key with dash",
+ inputParts: []string{"-my-", "-example-", "-metric-"},
+ inputLabels: []metrics.Label{
+ {Name: "foo", Value: "bar"},
+ {Name: "baz", Value: "buz"},
+ },
+ expectedOutputKey: "_my___example___metric_",
+ expectedOutputHash: "_my___example___metric_;foo=bar;baz=buz",
+ },
+ {
+ name: "key with forward slash",
+ inputParts: []string{"/my/", "/example/", "/metric/"},
+ inputLabels: []metrics.Label{
+ {Name: "foo", Value: "bar"},
+ {Name: "baz", Value: "buz"},
+ },
+ expectedOutputKey: "_my___example___metric_",
+ expectedOutputHash: "_my___example___metric_;foo=bar;baz=buz",
+ },
+ {
+ name: "key with all restricted",
+ inputParts: []string{"/my-", ".example ", "metric"},
+ inputLabels: []metrics.Label{
+ {Name: "foo", Value: "bar"},
+ {Name: "baz", Value: "buz"},
+ },
+ expectedOutputKey: "_my___example__metric",
+ expectedOutputHash: "_my___example__metric;foo=bar;baz=buz",
+ },
+ }
+
+ for _, tc := range testCases {
+ t.Run(tc.name, func(b *testing.T) {
+ actualKey, actualHash := flattenKey(tc.inputParts, tc.inputLabels)
+ if actualKey != tc.expectedOutputKey {
+ t.Fatalf("expected key %s, got %s", tc.expectedOutputKey, actualKey)
+ }
+ if actualHash != tc.expectedOutputHash {
+ t.Fatalf("expected hash %s, got %s", tc.expectedOutputHash, actualHash)
+ }
+ })
+ }
+}