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package handlers
import (
"log"
"net/http"
"runtime/debug"
)
// RecoveryHandlerLogger is an interface used by the recovering handler to print logs.
type RecoveryHandlerLogger interface {
Println(...interface{})
}
type recoveryHandler struct {
handler http.Handler
logger RecoveryHandlerLogger
printStack bool
}
// RecoveryOption provides a functional approach to define
// configuration for a handler; such as setting the logging
// whether or not to print strack traces on panic.
type RecoveryOption func(http.Handler)
func parseRecoveryOptions(h http.Handler, opts ...RecoveryOption) http.Handler {
for _, option := range opts {
option(h)
}
return h
}
// RecoveryHandler is HTTP middleware that recovers from a panic,
// logs the panic, writes http.StatusInternalServerError, and
// continues to the next handler.
//
// Example:
//
// r := mux.NewRouter()
// r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
// panic("Unexpected error!")
// })
//
// http.ListenAndServe(":1123", handlers.RecoveryHandler()(r))
func RecoveryHandler(opts ...RecoveryOption) func(h http.Handler) http.Handler {
return func(h http.Handler) http.Handler {
r := &recoveryHandler{handler: h}
return parseRecoveryOptions(r, opts...)
}
}
// RecoveryLogger is a functional option to override
// the default logger
func RecoveryLogger(logger RecoveryHandlerLogger) RecoveryOption {
return func(h http.Handler) {
r := h.(*recoveryHandler)
r.logger = logger
}
}
// PrintRecoveryStack is a functional option to enable
// or disable printing stack traces on panic.
func PrintRecoveryStack(print bool) RecoveryOption {
return func(h http.Handler) {
r := h.(*recoveryHandler)
r.printStack = print
}
}
func (h recoveryHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
defer func() {
if err := recover(); err != nil {
w.WriteHeader(http.StatusInternalServerError)
h.log(err)
}
}()
h.handler.ServeHTTP(w, req)
}
func (h recoveryHandler) log(v ...interface{}) {
if h.logger != nil {
h.logger.Println(v...)
} else {
log.Println(v...)
}
if h.printStack {
debug.PrintStack()
}
}