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127 lines
3.6 KiB
Go
127 lines
3.6 KiB
Go
package middleware
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import (
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"bufio"
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"fmt"
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"net"
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"net/http"
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"regexp"
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"strconv"
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"strings"
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"time"
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"github.com/gorilla/mux"
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"github.com/prometheus/client_golang/prometheus"
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)
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// RouteMatcher matches routes
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type RouteMatcher interface {
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Match(*http.Request, *mux.RouteMatch) bool
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}
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// Instrument is a Middleware which records timings for every HTTP request
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type Instrument struct {
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RouteMatcher RouteMatcher
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Duration *prometheus.HistogramVec
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}
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// IsWSHandshakeRequest returns true if the given request is a websocket handshake request.
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func IsWSHandshakeRequest(req *http.Request) bool {
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if strings.ToLower(req.Header.Get("Upgrade")) == "websocket" {
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// Connection header values can be of form "foo, bar, ..."
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parts := strings.Split(strings.ToLower(req.Header.Get("Connection")), ",")
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for _, part := range parts {
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if strings.TrimSpace(part) == "upgrade" {
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return true
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}
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}
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}
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return false
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}
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// Wrap implements middleware.Interface
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func (i Instrument) Wrap(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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begin := time.Now()
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isWS := strconv.FormatBool(IsWSHandshakeRequest(r))
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interceptor := &interceptor{ResponseWriter: w, statusCode: http.StatusOK}
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route := i.getRouteName(r)
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next.ServeHTTP(interceptor, r)
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var (
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status = strconv.Itoa(interceptor.statusCode)
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took = time.Since(begin)
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)
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i.Duration.WithLabelValues(r.Method, route, status, isWS).Observe(took.Seconds())
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})
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}
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// Return a name identifier for ths request. There are three options:
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// 1. The request matches a gorilla mux route, with a name. Use that.
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// 2. The request matches an unamed gorilla mux router. Munge the path
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// template such that templates like '/api/{org}/foo' come out as
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// 'api_org_foo'.
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// 3. The request doesn't match a mux route. Return "other"
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// We do all this as we do not wish to emit high cardinality labels to
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// prometheus.
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func (i Instrument) getRouteName(r *http.Request) string {
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var routeMatch mux.RouteMatch
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if i.RouteMatcher != nil && i.RouteMatcher.Match(r, &routeMatch) {
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if name := routeMatch.Route.GetName(); name != "" {
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return name
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}
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if tmpl, err := routeMatch.Route.GetPathTemplate(); err == nil {
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return MakeLabelValue(tmpl)
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}
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}
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return "other"
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}
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var invalidChars = regexp.MustCompile(`[^a-zA-Z0-9]+`)
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// MakeLabelValue converts a Gorilla mux path to a string suitable for use in
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// a Prometheus label value.
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func MakeLabelValue(path string) string {
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// Convert non-alnums to underscores.
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result := invalidChars.ReplaceAllString(path, "_")
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// Trim leading and trailing underscores.
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result = strings.Trim(result, "_")
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// Make it all lowercase
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result = strings.ToLower(result)
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// Special case.
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if result == "" {
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result = "root"
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}
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return result
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}
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// interceptor implements WriteHeader to intercept status codes. WriteHeader
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// may not be called on success, so initialize statusCode with the status you
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// want to report on success, i.e. http.StatusOK.
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//
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// interceptor also implements net.Hijacker, to let the downstream Handler
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// hijack the connection. This is needed, for example, for working with websockets.
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type interceptor struct {
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http.ResponseWriter
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statusCode int
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recorded bool
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}
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func (i *interceptor) WriteHeader(code int) {
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if !i.recorded {
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i.statusCode = code
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i.recorded = true
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}
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i.ResponseWriter.WriteHeader(code)
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}
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func (i *interceptor) Hijack() (net.Conn, *bufio.ReadWriter, error) {
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hj, ok := i.ResponseWriter.(http.Hijacker)
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if !ok {
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return nil, nil, fmt.Errorf("interceptor: can't cast parent ResponseWriter to Hijacker")
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}
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return hj.Hijack()
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}
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