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replacer.go
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replacer.go
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package httpserver
import (
"bytes"
"io"
"io/ioutil"
"net"
"net/http"
"net/http/httputil"
"net/url"
"os"
"path"
"strconv"
"strings"
"time"
)
// requestReplacer is a strings.Replacer which is used to
// encode literal \r and \n characters and keep everything
// on one line
var requestReplacer = strings.NewReplacer(
"\r", "\\r",
"\n", "\\n",
)
// Replacer is a type which can replace placeholder
// substrings in a string with actual values from a
// http.Request and ResponseRecorder. Always use
// NewReplacer to get one of these. Any placeholders
// made with Set() should overwrite existing values if
// the key is already used.
type Replacer interface {
Replace(string) string
Set(key, value string)
}
// replacer implements Replacer. customReplacements
// is used to store custom replacements created with
// Set() until the time of replacement, at which point
// they will be used to overwrite other replacements
// if there is a name conflict.
type replacer struct {
customReplacements map[string]string
emptyValue string
responseRecorder *ResponseRecorder
request *http.Request
requestBody *limitWriter
}
type limitWriter struct {
w bytes.Buffer
remain int
}
func newLimitWriter(max int) *limitWriter {
return &limitWriter{
w: bytes.Buffer{},
remain: max,
}
}
func (lw *limitWriter) Write(p []byte) (int, error) {
// skip if we are full
if lw.remain <= 0 {
return len(p), nil
}
if n := len(p); n > lw.remain {
p = p[:lw.remain]
}
n, err := lw.w.Write(p)
lw.remain -= n
return n, err
}
func (lw *limitWriter) String() string {
return lw.w.String()
}
// NewReplacer makes a new replacer based on r and rr which
// are used for request and response placeholders, respectively.
// Request placeholders are created immediately, whereas
// response placeholders are not created until Replace()
// is invoked. rr may be nil if it is not available.
// emptyValue should be the string that is used in place
// of empty string (can still be empty string).
func NewReplacer(r *http.Request, rr *ResponseRecorder, emptyValue string) Replacer {
rb := newLimitWriter(MaxLogBodySize)
if r.Body != nil {
r.Body = struct {
io.Reader
io.Closer
}{io.TeeReader(r.Body, rb), io.Closer(r.Body)}
}
return &replacer{
request: r,
requestBody: rb,
responseRecorder: rr,
customReplacements: make(map[string]string),
emptyValue: emptyValue,
}
}
func canLogRequest(r *http.Request) bool {
if r.Method == "POST" || r.Method == "PUT" {
for _, cType := range r.Header[headerContentType] {
// the cType could have charset and other info
if strings.Contains(cType, contentTypeJSON) || strings.Contains(cType, contentTypeXML) {
return true
}
}
}
return false
}
// Replace performs a replacement of values on s and returns
// the string with the replaced values.
func (r *replacer) Replace(s string) string {
// Do not attempt replacements if no placeholder is found.
if !strings.ContainsAny(s, "{}") {
return s
}
result := ""
for {
idxStart := strings.Index(s, "{")
if idxStart == -1 {
// no placeholder anymore
break
}
idxEnd := strings.Index(s[idxStart:], "}")
if idxEnd == -1 {
// unpaired placeholder
break
}
idxEnd += idxStart
// get a replacement
placeholder := s[idxStart : idxEnd+1]
replacement := r.getSubstitution(placeholder)
// append prefix + replacement
result += s[:idxStart] + replacement
// strip out scanned parts
s = s[idxEnd+1:]
}
// append unscanned parts
return result + s
}
func roundDuration(d time.Duration) time.Duration {
if d >= time.Millisecond {
return round(d, time.Millisecond)
} else if d >= time.Microsecond {
return round(d, time.Microsecond)
}
return d
}
// round rounds d to the nearest r
func round(d, r time.Duration) time.Duration {
if r <= 0 {
return d
}
neg := d < 0
if neg {
d = -d
}
if m := d % r; m+m < r {
d = d - m
} else {
d = d + r - m
}
if neg {
return -d
}
return d
}
// getSubstitution retrieves value from corresponding key
func (r *replacer) getSubstitution(key string) string {
// search custom replacements first
if value, ok := r.customReplacements[key]; ok {
return value
}
// search request headers then
if key[1] == '>' {
want := key[2 : len(key)-1]
for key, values := range r.request.Header {
// Header placeholders (case-insensitive)
if strings.EqualFold(key, want) {
return strings.Join(values, ",")
}
}
}
// search default replacements in the end
switch key {
case "{method}":
return r.request.Method
case "{scheme}":
if r.request.TLS != nil {
return "https"
}
return "http"
case "{hostname}":
name, err := os.Hostname()
if err != nil {
return r.emptyValue
}
return name
case "{host}":
return r.request.Host
case "{hostonly}":
host, _, err := net.SplitHostPort(r.request.Host)
if err != nil {
return r.request.Host
}
return host
case "{path}":
return r.request.URL.Path
case "{path_escaped}":
return url.QueryEscape(r.request.URL.Path)
case "{query}":
return r.request.URL.RawQuery
case "{query_escaped}":
return url.QueryEscape(r.request.URL.RawQuery)
case "{fragment}":
return r.request.URL.Fragment
case "{proto}":
return r.request.Proto
case "{remote}":
host, _, err := net.SplitHostPort(r.request.RemoteAddr)
if err != nil {
return r.request.RemoteAddr
}
return host
case "{port}":
_, port, err := net.SplitHostPort(r.request.RemoteAddr)
if err != nil {
return r.emptyValue
}
return port
case "{uri}":
return r.request.URL.RequestURI()
case "{uri_escaped}":
return url.QueryEscape(r.request.URL.RequestURI())
case "{when}":
return time.Now().Format(timeFormat)
case "{file}":
_, file := path.Split(r.request.URL.Path)
return file
case "{dir}":
dir, _ := path.Split(r.request.URL.Path)
return dir
case "{request}":
dump, err := httputil.DumpRequest(r.request, false)
if err != nil {
return r.emptyValue
}
return requestReplacer.Replace(string(dump))
case "{request_body}":
if !canLogRequest(r.request) {
return r.emptyValue
}
_, err := ioutil.ReadAll(r.request.Body)
if err != nil {
return r.emptyValue
}
return requestReplacer.Replace(r.requestBody.String())
case "{status}":
if r.responseRecorder == nil {
return r.emptyValue
}
return strconv.Itoa(r.responseRecorder.status)
case "{size}":
if r.responseRecorder == nil {
return r.emptyValue
}
return strconv.Itoa(r.responseRecorder.size)
case "{latency}":
if r.responseRecorder == nil {
return r.emptyValue
}
return roundDuration(time.Since(r.responseRecorder.start)).String()
}
return r.emptyValue
}
// Set sets key to value in the r.customReplacements map.
func (r *replacer) Set(key, value string) {
r.customReplacements["{"+key+"}"] = value
}
const (
timeFormat = "02/Jan/2006:15:04:05 -0700"
headerContentType = "Content-Type"
contentTypeJSON = "application/json"
contentTypeXML = "application/xml"
// MaxLogBodySize limits the size of logged request's body
MaxLogBodySize = 100 * 1024
)