hw/vendor/mcquay.me/metrics/metrics.go

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2018-03-08 13:58:15 -08:00
package metrics
import (
"fmt"
"net/http"
"time"
"github.com/pkg/errors"
"github.com/prometheus/client_golang/prometheus"
)
// Metrics provides a simple way to track latency and http status
type Metrics struct {
latency *prometheus.SummaryVec
status *prometheus.CounterVec
}
func New(prefix string) (*Metrics, error) {
m := &Metrics{
latency: prometheus.NewSummaryVec(prometheus.SummaryOpts{
Namespace: prefix,
Subsystem: "http",
Name: "request_latency_ms",
Help: "Latency in ms of http requests grouped by req path",
}, []string{"path"}),
status: prometheus.NewCounterVec(prometheus.CounterOpts{
Namespace: prefix,
Subsystem: "http",
Name: "status_count",
Help: "The count of http responses issued classified by status and api endpoint",
}, []string{"path", "code"}),
}
if err := m.registerPromMetrics(); err != nil {
return nil, errors.Wrap(err, "registration")
}
return m, nil
}
// registerPromMetrics registers all the metrics that eventmanger uses.
func (m *Metrics) registerPromMetrics() error {
if err := prometheus.Register(m.latency); err != nil {
return errors.Wrap(err, "http request latency")
}
if err := prometheus.Register(m.status); err != nil {
return errors.Wrap(err, "http response counter")
}
return nil
}
// Wrap calls a http.Handler and tracks status code and latency.
func (m *Metrics) Wrap(prefix string, h http.Handler) http.HandlerFunc {
return m.WrapFunc(prefix, h.ServeHTTP)
}
// WrapFunc calls a http.Handler and tracks status code and latency.
func (m *Metrics) WrapFunc(prefix string, h http.HandlerFunc) http.HandlerFunc {
return func(w http.ResponseWriter, req *http.Request) {
start := time.Now()
defer func() {
m.HTTPLatency(prefix, start)
}()
lw := NewStatusRecorder(w)
h(lw, req)
m.HTTPStatus(prefix, lw.Status())
}
}
// HTTPLatency records a request latency for a given url path.
func (m *Metrics) HTTPLatency(path string, start time.Time) {
m.latency.WithLabelValues(path).Observe(msSince(start))
}
// HTTPStatus records counts of http statuses, bucketed according to status types.
func (m *Metrics) HTTPStatus(path string, status int) {
m.status.WithLabelValues(path, fmt.Sprintf("%d", bucketHTTPStatus(status))).Inc()
}
// bucketHTTPStatus rounds down to the nearest hundred to facilitate categorizing http statuses.
func bucketHTTPStatus(i int) int {
return i - i%100
}
// msSince returns milliseconds since start.
func msSince(start time.Time) float64 {
return float64(time.Since(start)) / float64(time.Millisecond)
}
// buckets returns the default prometheus buckets scaled to milliseconds.
func buckets() []float64 {
r := []float64{}
for _, v := range prometheus.DefBuckets {
r = append(r, v*float64(time.Second/time.Millisecond))
}
return r
}