middleware/logger/logger.go

package logger

import (
	"io"
	"log"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// DefaultOptions represents default logger middleware options
var DefaultOptions = Options(
	WithBody(),
	SetMaxBodySize(1*1024*1024),
	SetIPFn(defaultIPFn),
	SetLogHandler(DefaultLogHandler),
)

// Options turns a list of option instances into an option
func Options(opts ...Option) Option {
	return func(l *logger) {
		for _, opt := range opts {
			opt(l)
		}
	}
}

// Option configures logger middleware
type Option func(l *logger)

// WithBody enables request body logging
func WithBody() Option {
	return func(l *logger) {
		l.logBody = true
	}
}

// WithoutBody disables request body logging
func WithoutBody() Option {
	return func(l *logger) {
		l.logBody = false
	}
}

// SetMaxBodySize sets maximum request body size
func SetMaxBodySize(size int) Option {
	return func(l *logger) {
		l.maxBodySize = size
	}
}

// SetIPFn sets function that extracts ip from request
func SetIPFn(fn func(r *http.Request) string) Option {
	return func(l *logger) {
		l.ipFn = fn
	}
}

// SetUserFn sets function that extracts user from request
func SetUserFn(fn func(r *http.Request) string) Option {
	return func(l *logger) {
		l.userFn = fn
	}
}

// SetSanitizeFn sets function that sanitizes request query or body
func SetSanitizeFn(fn func(input string) string) Option {
	return func(l *logger) {
		l.sanitizeFn = fn
	}
}

// SetLogHandler sets log handler
func SetLogHandler(fn func(entry LogEntry)) Option {
	return func(l *logger) {
		l.logHandler = fn
	}
}

// LogEntry is a http log entry
type LogEntry struct {
	Method     string
	RawURL     string
	Body       string
	RemoteIP   string
	StatusCode int
	Written    int
	Duration   time.Duration
	User       string
	TraceID    string
}

type logger struct {
	logBody     bool
	maxBodySize int
	ipFn        func(r *http.Request) string
	userFn      func(r *http.Request) string
	sanitizeFn  func(input string) string
	logHandler  func(entry LogEntry)
}

func (s *logger) body(r *http.Request) string {
	if !s.logBody {
		return ""
	}

	rdr, body, hasMore, err := peek(r.Body, int64(s.maxBodySize))
	if err != nil {
		return ""
	}

	r.Body = io.NopCloser(rdr)

	if len(body) > 0 {
		body = strings.ReplaceAll(body, "\n", " ")
		body = regexpMultiWhitespace.ReplaceAllString(body, " ")
	}

	if hasMore {
		body += "..."
	}

	return body
}

// Middleware is a http logger middleware
func Middleware(opts ...Option) func(http.Handler) http.Handler {
	l := &logger{}
	opts = append([]Option{DefaultOptions}, opts...)

	for _, opt := range opts {
		opt(l)
	}

	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			ww := newTrackingResponseWriter(w)

			body := l.body(r)
			if l.sanitizeFn != nil {
				body = l.sanitizeFn(body)
			}

			startTS := time.Now()
			defer func() {
				stopTS := time.Now()

				query := r.URL.String()
				if qun, err := url.QueryUnescape(query); err == nil {
					query = qun
				}

				if l.sanitizeFn != nil {
					query = l.sanitizeFn(query)
				}

				var ip string
				if l.ipFn != nil {
					ip = l.ipFn(r)
				}

				var user string
				if l.userFn != nil {
					user = l.userFn(r)
				}

				entry := LogEntry{
					Method:     r.Method,
					RawURL:     query,
					RemoteIP:   ip,
					Body:       body,
					StatusCode: ww.status,
					Written:    ww.size,
					Duration:   stopTS.Sub(startTS),
					User:       user,
					TraceID:    r.Header.Get("X-Request-ID"),
				}

				l.logHandler(entry)
			}()

			next.ServeHTTP(ww, r)
		})
	}
}

// DefaultLogHandler is a default log handler
func DefaultLogHandler(entry LogEntry) { // nolint:gocritic // For backwards compatibility
	log.Printf(
		"%s - %s - %s - %d (%d) - %v",
		entry.Method,
		entry.RawURL,
		entry.RemoteIP,
		entry.StatusCode,
		entry.Written,
		entry.Duration,
	)
}

func defaultIPFn(r *http.Request) string {
	return strings.Split(r.RemoteAddr, ":")[0]
}