130 lines
3.6 KiB
Go
130 lines
3.6 KiB
Go
package servertiming
|
|
|
|
import (
|
|
"fmt"
|
|
"net/http"
|
|
"regexp"
|
|
"strings"
|
|
"sync"
|
|
"time"
|
|
|
|
"github.com/golang/gddo/httputil/header"
|
|
)
|
|
|
|
// HeaderKey is the specified key for the Server-Timing header.
|
|
const HeaderKey = "Server-Timing"
|
|
|
|
// Header represents a collection of metrics that can be encoded as
|
|
// a Server-Timing header value.
|
|
//
|
|
// The functions for working with metrics are concurrency-safe to make
|
|
// it easy to record metrics from goroutines. If you want to avoid the
|
|
// lock overhead, you can access the Metrics field directly.
|
|
//
|
|
// The functions for working with metrics are also usable on a nil
|
|
// Header pointer. This allows functions that use FromContext to get the
|
|
// *Header value to skip nil-checking and use it as normal. On a nil
|
|
// *Header, Metrics are not recorded.
|
|
type Header struct {
|
|
// Metrics is the list of metrics in the header.
|
|
Metrics []*Metric
|
|
|
|
// The lock that is held when Metrics is being modified. This
|
|
// ONLY NEEDS TO BE SET WHEN working with Metrics directly. If using
|
|
// the functions on the struct, the lock is managed automatically.
|
|
sync.Mutex
|
|
}
|
|
|
|
// ParseHeader parses a Server-Timing header value.
|
|
func ParseHeader(input string) (*Header, error) {
|
|
// Split the comma-separated list of metrics
|
|
rawMetrics := header.ParseList(headerParams(input))
|
|
|
|
// Parse the list of metrics. We can pre-allocate the length of the
|
|
// comma-separated list of metrics since at most it will be that and
|
|
// most likely it will be that length.
|
|
metrics := make([]*Metric, 0, len(rawMetrics))
|
|
for _, raw := range rawMetrics {
|
|
var m Metric
|
|
m.Name, m.Extra = header.ParseValueAndParams(headerParams(raw))
|
|
|
|
// Description
|
|
if v, ok := m.Extra[paramNameDesc]; ok {
|
|
m.Desc = v
|
|
delete(m.Extra, paramNameDesc)
|
|
}
|
|
|
|
// Duration. This is treated as a millisecond value since that
|
|
// is what modern browsers are treating it as. If the parsing of
|
|
// an integer fails, the set value remains in the Extra field.
|
|
if v, ok := m.Extra[paramNameDur]; ok {
|
|
m.Duration, _ = time.ParseDuration(v + "ms")
|
|
delete(m.Extra, paramNameDur)
|
|
}
|
|
|
|
metrics = append(metrics, &m)
|
|
}
|
|
|
|
return &Header{Metrics: metrics}, nil
|
|
}
|
|
|
|
// NewMetric creates a new Metric and adds it to this header.
|
|
func (h *Header) NewMetric(name string) *Metric {
|
|
return h.Add(&Metric{Name: name})
|
|
}
|
|
|
|
// Add adds the given metric to the header.
|
|
//
|
|
// This function is safe to call concurrently.
|
|
func (h *Header) Add(m *Metric) *Metric {
|
|
if h == nil {
|
|
return m
|
|
}
|
|
|
|
h.Lock()
|
|
defer h.Unlock()
|
|
h.Metrics = append(h.Metrics, m)
|
|
return m
|
|
}
|
|
|
|
// String returns the valid Server-Timing header value that can be
|
|
// sent in an HTTP response.
|
|
func (h *Header) String() string {
|
|
parts := make([]string, 0, len(h.Metrics))
|
|
for _, m := range h.Metrics {
|
|
parts = append(parts, m.String())
|
|
}
|
|
|
|
return strings.Join(parts, ",")
|
|
}
|
|
|
|
// Specified server-timing-param-name values.
|
|
const (
|
|
paramNameDesc = "desc"
|
|
paramNameDur = "dur"
|
|
)
|
|
|
|
// headerParams is a helper function that takes a header value and turns
|
|
// it into the expected argument format for the httputil/header library
|
|
// functions..
|
|
func headerParams(s string) (http.Header, string) {
|
|
const key = "Key"
|
|
return http.Header(map[string][]string{
|
|
key: {s},
|
|
}), key
|
|
}
|
|
|
|
var reNumber = regexp.MustCompile(`^\d+\.?\d*$`)
|
|
|
|
// headerEncodeParam encodes a key/value pair as a proper `key=value`
|
|
// syntax, using double-quotes if necessary.
|
|
func headerEncodeParam(key, value string) string {
|
|
// The only case we currently don't quote is numbers. We can make this
|
|
// smarter in the future.
|
|
if reNumber.MatchString(value) {
|
|
return fmt.Sprintf(`%s=%s`, key, value)
|
|
}
|
|
|
|
return fmt.Sprintf(`%s=%q`, key, value)
|
|
}
|