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package caddy
import (
"net/http"
"strconv"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/collectors"
"github.com/prometheus/client_golang/prometheus/promauto"
)
// define and register the metrics used in this package.
func init() {
prometheus.MustRegister(collectors.NewBuildInfoCollector())
const ns, sub = "caddy", "admin"
adminMetrics.requestCount = promauto.NewCounterVec(prometheus.CounterOpts{
Namespace: ns,
Subsystem: sub,
Name: "http_requests_total",
Help: "Counter of requests made to the Admin API's HTTP endpoints.",
}, []string{"handler", "path", "code", "method"})
adminMetrics.requestErrors = promauto.NewCounterVec(prometheus.CounterOpts{
Namespace: ns,
Subsystem: sub,
Name: "http_request_errors_total",
Help: "Number of requests resulting in middleware errors.",
}, []string{"handler", "path", "method"})
}
// adminMetrics is a collection of metrics that can be tracked for the admin API.
var adminMetrics = struct {
requestCount *prometheus.CounterVec
requestErrors *prometheus.CounterVec
}{}
// Similar to promhttp.InstrumentHandlerCounter, but upper-cases method names
// instead of lower-casing them.
//
// Unlike promhttp.InstrumentHandlerCounter, this assumes a "code" and "method"
// label is present, and will panic otherwise.
func instrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler) http.HandlerFunc {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
d := newDelegator(w)
next.ServeHTTP(d, r)
counter.With(prometheus.Labels{
"code": sanitizeCode(d.status),
"method": sanitizeMethod(r.Method),
}).Inc()
})
}
func newDelegator(w http.ResponseWriter) *delegator {
return &delegator{
ResponseWriter: w,
}
}
type delegator struct {
http.ResponseWriter
status int
}
func (d *delegator) WriteHeader(code int) {
d.status = code
d.ResponseWriter.WriteHeader(code)
}
func sanitizeCode(s int) string {
switch s {
case 0, 200:
return "200"
default:
return strconv.Itoa(s)
}
}
// Only support the list of "regular" HTTP methods, see
// https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods
var methodMap = map[string]string{
"GET": http.MethodGet, "get": http.MethodGet,
"HEAD": http.MethodHead, "head": http.MethodHead,
"PUT": http.MethodPut, "put": http.MethodPut,
"POST": http.MethodPost, "post": http.MethodPost,
"DELETE": http.MethodDelete, "delete": http.MethodDelete,
"CONNECT": http.MethodConnect, "connect": http.MethodConnect,
"OPTIONS": http.MethodOptions, "options": http.MethodOptions,
"TRACE": http.MethodTrace, "trace": http.MethodTrace,
"PATCH": http.MethodPatch, "patch": http.MethodPatch,
}
// sanitizeMethod sanitizes the method for use as a metric label. This helps
// prevent high cardinality on the method label. The name is always upper case.
func sanitizeMethod(m string) string {
if m, ok := methodMap[m]; ok {
return m
}
return "OTHER"
}
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