error.go

// Copyright 2017 CoreOS, Inc.
//
// 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 client

import (
	"encoding/xml"
	"errors"
	"io"
	"net"
	"net/http"
	"time"

	"github.com/coreos/go-omaha/omaha"
)

var (
	bodySizeError = &omahaError{
		Err:  errors.New("http response exceeded 1MB"),
		Code: ExitCodeOmahaResponseInvalid,
	}
	bodyEmptyError = &omahaError{
		Err:  errors.New("http response was empty"),
		Code: ExitCodeOmahaRequestEmptyResponseError,
	}

	// default parameters for expNetBackoff
	backoffStart = time.Second
	backoffTries = 7
)

// retries and exponentially backs off for temporary network errors
func expNetBackoff(f func() error) error {
	var (
		backoff = backoffStart
		tries   = backoffTries
	)
	for {
		err := f()
		tries--
		if tries <= 0 {
			return err
		}
		if neterr, ok := err.(net.Error); !ok || !neterr.Temporary() {
			return err
		}
		FuzzySleep(backoff, backoff)
		backoff *= 2
	}
}

// xml doesn't return the standard io.ErrUnexpectedEOF so check for both.
func isUnexpectedEOF(err error) bool {
	if xerr, ok := err.(*xml.SyntaxError); ok {
		return xerr.Msg == "unexpected EOF"
	}
	return err == io.ErrUnexpectedEOF
}

// omahaError implements error and ErrorEvent for omaha requests/responses.
type omahaError struct {
	Err  error
	Code ExitCode
}

func (oe *omahaError) Error() string {
	return "omaha: request failed: " + oe.Err.Error()
}

func (oe *omahaError) ErrorEvent() *omaha.EventRequest {
	return NewErrorEvent(oe.Code)
}

// httpError implements error, net.Error, and ErrorEvent for http responses.
type httpError struct {
	*http.Response
}

func (he *httpError) Error() string {
	return "http error: " + he.Status
}

func (he *httpError) ErrorEvent() *omaha.EventRequest {
	code := ExitCodeOmahaRequestError
	if he.StatusCode > 0 && he.StatusCode < 1000 {
		code = ExitCodeOmahaRequestHTTPResponseBase + ExitCode(he.StatusCode)
	}
	return NewErrorEvent(code)
}

func (he *httpError) Timeout() bool {
	switch he.StatusCode {
	case http.StatusRequestTimeout: // 408
		return true
	case http.StatusGatewayTimeout: // 504
		return true
	default:
		return false
	}
}

func (he *httpError) Temporary() bool {
	if he.Timeout() {
		return true
	}
	switch he.StatusCode {
	case http.StatusTooManyRequests: // 429
		return true
	case http.StatusInternalServerError: // 500
		return true
	case http.StatusBadGateway: // 502
		return true
	case http.StatusServiceUnavailable: // 503
		return true
	default:
		return false
	}
}