package middleware // The original work was derived from Goji's middleware, source: // https://github.com/zenazn/goji/tree/master/web/middleware import ( "bytes" "errors" "fmt" "net/http" "os" "runtime/debug" "strings" ) // Recoverer is a middleware that recovers from panics, logs the panic (and a // backtrace), and returns a HTTP 500 (Internal Server Error) status if // possible. Recoverer prints a request ID if one is provided. // // Alternatively, look at https://github.com/pressly/lg middleware pkgs. func Recoverer(next http.Handler) http.Handler { fn := func(w http.ResponseWriter, r *http.Request) { defer func() { if rvr := recover(); rvr != nil && rvr != http.ErrAbortHandler { logEntry := GetLogEntry(r) if logEntry != nil { logEntry.Panic(rvr, debug.Stack()) } else { PrintPrettyStack(rvr) } w.WriteHeader(http.StatusInternalServerError) } }() next.ServeHTTP(w, r) } return http.HandlerFunc(fn) } func PrintPrettyStack(rvr interface{}) { debugStack := debug.Stack() s := prettyStack{} out, err := s.parse(debugStack, rvr) if err == nil { os.Stderr.Write(out) } else { // print stdlib output as a fallback os.Stderr.Write(debugStack) } } type prettyStack struct { } func (s prettyStack) parse(debugStack []byte, rvr interface{}) ([]byte, error) { var err error useColor := true buf := &bytes.Buffer{} cW(buf, false, bRed, "\n") cW(buf, useColor, bCyan, " panic: ") cW(buf, useColor, bBlue, "%v", rvr) cW(buf, false, bWhite, "\n \n") // process debug stack info stack := strings.Split(string(debugStack), "\n") lines := []string{} // locate panic line, as we may have nested panics for i := len(stack) - 1; i > 0; i-- { lines = append(lines, stack[i]) if strings.HasPrefix(stack[i], "panic(0x") { lines = lines[0 : len(lines)-2] // remove boilerplate break } } // reverse for i := len(lines)/2 - 1; i >= 0; i-- { opp := len(lines) - 1 - i lines[i], lines[opp] = lines[opp], lines[i] } // decorate for i, line := range lines { lines[i], err = s.decorateLine(line, useColor, i) if err != nil { return nil, err } } for _, l := range lines { fmt.Fprintf(buf, "%s", l) } return buf.Bytes(), nil } func (s prettyStack) decorateLine(line string, useColor bool, num int) (string, error) { line = strings.TrimSpace(line) if strings.HasPrefix(line, "\t") || strings.Contains(line, ".go:") { return s.decorateSourceLine(line, useColor, num) } else if strings.HasSuffix(line, ")") { return s.decorateFuncCallLine(line, useColor, num) } else { if strings.HasPrefix(line, "\t") { return strings.Replace(line, "\t", " ", 1), nil } else { return fmt.Sprintf(" %s\n", line), nil } } } func (s prettyStack) decorateFuncCallLine(line string, useColor bool, num int) (string, error) { idx := strings.LastIndex(line, "(") if idx < 0 { return "", errors.New("not a func call line") } buf := &bytes.Buffer{} pkg := line[0:idx] // addr := line[idx:] method := "" idx = strings.LastIndex(pkg, string(os.PathSeparator)) if idx < 0 { idx = strings.Index(pkg, ".") method = pkg[idx:] pkg = pkg[0:idx] } else { method = pkg[idx+1:] pkg = pkg[0 : idx+1] idx = strings.Index(method, ".") pkg += method[0:idx] method = method[idx:] } pkgColor := nYellow methodColor := bGreen if num == 0 { cW(buf, useColor, bRed, " -> ") pkgColor = bMagenta methodColor = bRed } else { cW(buf, useColor, bWhite, " ") } cW(buf, useColor, pkgColor, "%s", pkg) cW(buf, useColor, methodColor, "%s\n", method) // cW(buf, useColor, nBlack, "%s", addr) return buf.String(), nil } func (s prettyStack) decorateSourceLine(line string, useColor bool, num int) (string, error) { idx := strings.LastIndex(line, ".go:") if idx < 0 { return "", errors.New("not a source line") } buf := &bytes.Buffer{} path := line[0 : idx+3] lineno := line[idx+3:] idx = strings.LastIndex(path, string(os.PathSeparator)) dir := path[0 : idx+1] file := path[idx+1:] idx = strings.Index(lineno, " ") if idx > 0 { lineno = lineno[0:idx] } fileColor := bCyan lineColor := bGreen if num == 1 { cW(buf, useColor, bRed, " -> ") fileColor = bRed lineColor = bMagenta } else { cW(buf, false, bWhite, " ") } cW(buf, useColor, bWhite, "%s", dir) cW(buf, useColor, fileColor, "%s", file) cW(buf, useColor, lineColor, "%s", lineno) if num == 1 { cW(buf, false, bWhite, "\n") } cW(buf, false, bWhite, "\n") return buf.String(), nil }