86 lines
2.4 KiB
Go
86 lines
2.4 KiB
Go
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package main
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import (
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"net/http"
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"sync"
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"time"
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)
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// StatsRecorder is an optional middleware that records more details statistics
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// about requests and how they are processed. This currently consists of recent
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// requests that have caused errors (4xx and 5xx status codes), making it easy
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// to pinpoint problems.
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type StatsRecorder struct {
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mutex sync.RWMutex
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numRecentErrors int
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recentErrors []*statsError
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}
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// Stats includes all of the stats gathered by the recorder.
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type Stats struct {
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RecentErrors []*statsError `json:"recent_errors"`
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}
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// statsError represents an error that has occurred during request processing.
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type statsError struct {
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StatusCode int `json:"status_code"`
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Status string `json:"status"`
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Method string `json:"method"`
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Host string `json:"host"`
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Path string `json:"path"`
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Time time.Time `json:"time"`
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}
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// responseRecorder captures information from the response and preserves it for
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// later analysis.
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type responseRecorder struct {
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http.ResponseWriter
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statusCode int
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}
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// WriteHeader captures the status code for later retrieval.
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func (r *responseRecorder) WriteHeader(status int) {
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r.ResponseWriter.WriteHeader(status)
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r.statusCode = status
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}
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// ServeHTTP silently extracts information from the request and response as it
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// is processed. If the response is 4xx or 5xx, add it to the list of 10 most
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// recent errors.
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func (s *StatsRecorder) ServeHTTP(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
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recorder := &responseRecorder{w, http.StatusOK}
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next(recorder, r)
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if recorder.statusCode >= 400 {
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s.mutex.Lock()
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defer s.mutex.Unlock()
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s.recentErrors = append([]*statsError{
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{
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StatusCode: recorder.statusCode,
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Status: http.StatusText(recorder.statusCode),
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Method: r.Method,
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Host: r.Host,
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Path: r.URL.Path,
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Time: time.Now(),
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},
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}, s.recentErrors...)
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// Limit the size of the list to numRecentErrors
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if len(s.recentErrors) > s.numRecentErrors {
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s.recentErrors = s.recentErrors[:s.numRecentErrors]
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}
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}
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}
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// Data returns a copy of the statistics that have been gathered.
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func (s *StatsRecorder) Data() *Stats {
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s.mutex.RLock()
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defer s.mutex.RUnlock()
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// We can't return the slice directly or a race condition might develop
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recentErrors := make([]*statsError, len(s.recentErrors))
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copy(recentErrors, s.recentErrors)
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return &Stats{
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RecentErrors: recentErrors,
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}
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}
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