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// Copyright 2015 Light Code Labs, LLC
//
// 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 errors implements an HTTP error handling middleware.
package errors
import (
"fmt"
"io"
"mime"
"net/http"
"os"
"path/filepath"
"runtime"
"strings"
"github.com/caddyserver/caddy"
"github.com/caddyserver/caddy/caddyhttp/httpserver"
)
func init() {
caddy.RegisterPlugin("errors", caddy.Plugin{
ServerType: "http",
Action: setup,
})
}
// ErrorHandler handles HTTP errors (and errors from other middleware).
type ErrorHandler struct {
Next httpserver.Handler
GenericErrorPage string // default error page filename
ErrorPages map[int]string // map of status code to filename
Log *httpserver.Logger
Debug bool // if true, errors are written out to client rather than to a log
}
func (h ErrorHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
defer h.recovery(w, r)
status, err := h.Next.ServeHTTP(w, r)
if err != nil {
errMsg := fmt.Sprintf("[ERROR %d %s] %v", status, r.URL.Path, err)
if h.Debug {
// Write error to response instead of to log
w.Header().Set("Content-Type", "text/plain; charset=utf-8")
w.WriteHeader(status)
fmt.Fprintln(w, errMsg)
return 0, err // returning 0 signals that a response has been written
}
h.Log.Println(errMsg)
}
if status >= 400 {
h.errorPage(w, r, status)
return 0, err
}
return status, err
}
// errorPage serves a static error page to w according to the status
// code. If there is an error serving the error page, a plaintext error
// message is written instead, and the extra error is logged.
func (h ErrorHandler) errorPage(w http.ResponseWriter, r *http.Request, code int) {
// See if an error page for this status code was specified
if pagePath, ok := h.findErrorPage(code); ok {
// Try to open it
errorPage, err := os.Open(pagePath)
if err != nil {
// An additional error handling an error... <insert grumpy cat here>
h.Log.Printf("[NOTICE %d %s] could not load error page: %v", code, r.URL.String(), err)
httpserver.DefaultErrorFunc(w, r, code)
return
}
defer errorPage.Close()
// Get content type by extension
contentType := mime.TypeByExtension(filepath.Ext(pagePath))
if contentType == "" {
contentType = "text/html; charset=utf-8"
}
// Copy the page body into the response
w.Header().Set("Content-Type", contentType)
w.WriteHeader(code)
_, err = io.Copy(w, errorPage)
if err != nil {
// Epic fail... sigh.
h.Log.Printf("[NOTICE %d %s] could not respond with %s: %v", code, r.URL.String(), pagePath, err)
httpserver.DefaultErrorFunc(w, r, code)
}
return
}
// Default error response
httpserver.DefaultErrorFunc(w, r, code)
}
func (h ErrorHandler) findErrorPage(code int) (string, bool) {
if pagePath, ok := h.ErrorPages[code]; ok {
return pagePath, true
}
if h.GenericErrorPage != "" {
return h.GenericErrorPage, true
}
return "", false
}
func (h ErrorHandler) recovery(w http.ResponseWriter, r *http.Request) {
rec := recover()
if rec == nil {
return
}
// Obtain source of panic
// From: https://gist.github.com/swdunlop/9629168
var name, file string // function name, file name
var line int
var pc [16]uintptr
n := runtime.Callers(3, pc[:])
for _, pc := range pc[:n] {
fn := runtime.FuncForPC(pc)
if fn == nil {
continue
}
file, line = fn.FileLine(pc)
name = fn.Name()
if !strings.HasPrefix(name, "runtime.") {
break
}
}
// Trim file path
delim := "/github.com/caddyserver/caddy/"
pkgPathPos := strings.Index(file, delim)
if pkgPathPos > -1 && len(file) > pkgPathPos+len(delim) {
file = file[pkgPathPos+len(delim):]
}
panicMsg := fmt.Sprintf("[PANIC %s] %s:%d - %v", r.URL.String(), file, line, rec)
if h.Debug {
// Write error and stack trace to the response rather than to a log
var stackBuf [4096]byte
stack := stackBuf[:runtime.Stack(stackBuf[:], false)]
httpserver.WriteTextResponse(w, http.StatusInternalServerError, fmt.Sprintf("%s\n\n%s", panicMsg, stack))
} else {
// Currently we don't use the function name, since file:line is more conventional
h.Log.Printf(panicMsg)
h.errorPage(w, r, http.StatusInternalServerError)
}
}
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