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logger.go
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logger.go
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package main
import (
"bytes"
"encoding/json"
"fmt"
"net/http"
"time"
)
type LogLevel int
const (
Metadata LogLevel = iota
Headers
Body
)
var (
maxBodyBytesDefault = 10 * 1024 * 1024
)
type LoggerSettings struct {
Handler string
Level LogLevel
MaxBodyBytes *int
}
type LogMessage struct {
Date string `json:"date"`
DurationNs int `json:"durationNs"`
Method string `json:"method"`
URL string `json:"url"`
Handler string `json:"handler"`
ResponseCode int `json:"responseCode"`
RequestHeaders string `json:"requestHeaders,omitempty"`
RequestBody string `json:"requestBody,omitempty"`
ResponseHeaders string `json:"responseHeaders,omitempty"`
ResponseBody string `json:"responseBody,omitempty"`
}
func LoggerHandler(settings LoggerSettings, next http.Handler) http.Handler {
if settings.MaxBodyBytes == nil {
settings.MaxBodyBytes = &maxBodyBytesDefault
}
handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
rw := newResponseWriter(w, *settings.MaxBodyBytes)
start := time.Now()
next.ServeHTTP(rw, r)
duration := time.Now().Sub(start)
log := LogMessage{
Date: start.Format(time.RFC3339Nano),
DurationNs: int(duration.Nanoseconds()),
Method: r.Method,
URL: r.URL.String(),
Handler: settings.Handler,
ResponseCode: rw.code,
}
bytes, err := json.Marshal(log)
if err != nil {
fmt.Printf("Failed to marshal log message: %+v\n", err)
}
fmt.Println(string(bytes))
})
return handler
}
type responseWriter struct {
w http.ResponseWriter
maxBodyBytes int
body *bytes.Buffer
code int
headers http.Header
}
func newResponseWriter(w http.ResponseWriter, maxBodyBytes int) *responseWriter {
return &responseWriter{
w: w,
maxBodyBytes: maxBodyBytes,
body: &bytes.Buffer{},
headers: map[string][]string{},
}
}
func (rw *responseWriter) Header() http.Header {
return rw.headers
}
func (rw *responseWriter) Write(b []byte) (int, error) {
maxWrite := len(b)
if rw.body.Len()+len(b) > rw.maxBodyBytes {
maxWrite = rw.maxBodyBytes - rw.body.Len()
}
_, err := rw.body.Write(b[:maxWrite])
if err != nil {
return 0, err
}
return rw.w.Write(b)
}
func (rw *responseWriter) WriteHeader(code int) {
rw.code = code
rw.w.WriteHeader(code)
}