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request_log.go
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request_log.go
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/*
Copyright 2019 The Knative Authors
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package http
import (
"fmt"
"io"
"net/http"
"strings"
"sync"
"text/template"
"time"
)
// RequestLogHandler implements an http.Handler that writes request logs
// and calls the next handler.
type RequestLogHandler struct {
handler http.Handler
inputGetter RequestLogTemplateInputGetter
writer io.Writer
templateMux sync.RWMutex
templateStr string
template *template.Template
}
// RequestLogRevision provides revision related static information
// for the template execution.
type RequestLogRevision struct {
Name string
Namespace string
Service string
Configuration string
PodName string
PodIP string
}
// RequestLogResponse provided response related information for the template execution.
type RequestLogResponse struct {
Code int
Size int
Latency float64
}
// RequestLogTemplateInput is the wrapper struct that provides all
// necessary information for the template execution.
type RequestLogTemplateInput struct {
Request *http.Request
Response *RequestLogResponse
Revision *RequestLogRevision
}
// RequestLogTemplateInputGetter defines a function returning the input to pass to a request log writer.
type RequestLogTemplateInputGetter func(req *http.Request, resp *RequestLogResponse) *RequestLogTemplateInput
// RequestLogTemplateInputGetterFromRevision returns a func that forms a template input using a static
// revision information.
func RequestLogTemplateInputGetterFromRevision(rev *RequestLogRevision) RequestLogTemplateInputGetter {
return func(req *http.Request, resp *RequestLogResponse) *RequestLogTemplateInput {
return &RequestLogTemplateInput{
Request: req,
Response: resp,
Revision: rev,
}
}
}
// NewRequestLogHandler creates an http.Handler that logs request logs to an io.Writer.
func NewRequestLogHandler(h http.Handler, w io.Writer, templateStr string,
inputGetter RequestLogTemplateInputGetter) (*RequestLogHandler, error) {
reqHandler := &RequestLogHandler{
handler: h,
writer: w,
inputGetter: inputGetter,
}
if err := reqHandler.SetTemplate(templateStr); err != nil {
return nil, err
}
return reqHandler, nil
}
// SetTemplate sets the template to use for formatting request logs.
// Setting the template to an empty string turns of writing request logs.
func (h *RequestLogHandler) SetTemplate(templateStr string) error {
var t *template.Template
// If templateStr is empty, we will set the template to nil
// and effectively disable request logs.
if templateStr != "" {
// Make sure that the template ends with a newline. Otherwise,
// logging backends will not be able to parse entries separately.
if !strings.HasSuffix(templateStr, "\n") {
templateStr = templateStr + "\n"
}
var err error
t, err = template.New("requestLog").Parse(templateStr)
if err != nil {
return err
}
}
h.templateMux.Lock()
defer h.templateMux.Unlock()
h.templateStr = templateStr
h.template = t
return nil
}
func (h *RequestLogHandler) getTemplate() *template.Template {
h.templateMux.RLock()
defer h.templateMux.RUnlock()
return h.template
}
func (h *RequestLogHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
t := h.getTemplate()
if t == nil {
h.handler.ServeHTTP(w, r)
return
}
rr := NewResponseRecorder(w, http.StatusOK)
startTime := time.Now()
defer func() {
// If ServeHTTP panics, recover, record the failure and panic again.
err := recover()
latency := time.Since(startTime).Seconds()
if err != nil {
h.write(t, h.inputGetter(r, &RequestLogResponse{
Code: http.StatusInternalServerError,
Latency: latency,
Size: 0,
}))
panic(err)
} else {
h.write(t, h.inputGetter(r, &RequestLogResponse{
Code: rr.ResponseCode,
Latency: latency,
Size: (int)(rr.ResponseSize),
}))
}
}()
h.handler.ServeHTTP(rr, r)
}
func (h *RequestLogHandler) write(t *template.Template, in *RequestLogTemplateInput) {
if err := t.Execute(h.writer, in); err != nil {
// Template execution failed. Write an error message with some basic information about the request.
fmt.Fprintf(h.writer, "Invalid request log template: method: %v, response code: %v, latency: %v, url: %v\n",
in.Request.Method, in.Response.Code, in.Response.Latency, in.Request.URL)
}
}