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error.go
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error.go
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// Package fserrors provides errors and error handling
package fserrors
import (
"fmt"
"io"
"net/http"
"reflect"
"strings"
"github.com/pkg/errors"
)
// Retrier is an optional interface for error as to whether the
// operation should be retried at a high level.
//
// This should be returned from Update or Put methods as required
type Retrier interface {
error
Retry() bool
}
// retryError is a type of error
type retryError string
// Error interface
func (r retryError) Error() string {
return string(r)
}
// Retry interface
func (r retryError) Retry() bool {
return true
}
// Check interface
var _ Retrier = retryError("")
// RetryErrorf makes an error which indicates it would like to be retried
func RetryErrorf(format string, a ...interface{}) error {
return retryError(fmt.Sprintf(format, a...))
}
// wrappedRetryError is an error wrapped so it will satisfy the
// Retrier interface and return true
type wrappedRetryError struct {
error
}
// Retry interface
func (err wrappedRetryError) Retry() bool {
return true
}
// Check interface
var _ Retrier = wrappedRetryError{error(nil)}
// RetryError makes an error which indicates it would like to be retried
func RetryError(err error) error {
if err == nil {
err = errors.New("needs retry")
}
return wrappedRetryError{err}
}
// IsRetryError returns true if err conforms to the Retry interface
// and calling the Retry method returns true.
func IsRetryError(err error) bool {
if err == nil {
return false
}
_, err = Cause(err)
if r, ok := err.(Retrier); ok {
return r.Retry()
}
return false
}
// Fataler is an optional interface for error as to whether the
// operation should cause the entire operation to finish immediately.
//
// This should be returned from Update or Put methods as required
type Fataler interface {
error
Fatal() bool
}
// wrappedFatalError is an error wrapped so it will satisfy the
// Retrier interface and return true
type wrappedFatalError struct {
error
}
// Fatal interface
func (err wrappedFatalError) Fatal() bool {
return true
}
// Check interface
var _ Fataler = wrappedFatalError{error(nil)}
// FatalError makes an error which indicates it is a fatal error and
// the sync should stop.
func FatalError(err error) error {
if err == nil {
err = errors.New("fatal error")
}
return wrappedFatalError{err}
}
// IsFatalError returns true if err conforms to the Fatal interface
// and calling the Fatal method returns true.
func IsFatalError(err error) bool {
if err == nil {
return false
}
_, err = Cause(err)
if r, ok := err.(Fataler); ok {
return r.Fatal()
}
return false
}
// NoRetrier is an optional interface for error as to whether the
// operation should not be retried at a high level.
//
// If only NoRetry errors are returned in a sync then the sync won't
// be retried.
//
// This should be returned from Update or Put methods as required
type NoRetrier interface {
error
NoRetry() bool
}
// wrappedNoRetryError is an error wrapped so it will satisfy the
// Retrier interface and return true
type wrappedNoRetryError struct {
error
}
// NoRetry interface
func (err wrappedNoRetryError) NoRetry() bool {
return true
}
// Check interface
var _ NoRetrier = wrappedNoRetryError{error(nil)}
// NoRetryError makes an error which indicates the sync shouldn't be
// retried.
func NoRetryError(err error) error {
return wrappedNoRetryError{err}
}
// IsNoRetryError returns true if err conforms to the NoRetry
// interface and calling the NoRetry method returns true.
func IsNoRetryError(err error) bool {
if err == nil {
return false
}
_, err = Cause(err)
if r, ok := err.(NoRetrier); ok {
return r.NoRetry()
}
return false
}
// Cause is a souped up errors.Cause which can unwrap some standard
// library errors too. It returns true if any of the intermediate
// errors had a Timeout() or Temporary() method which returned true.
func Cause(cause error) (retriable bool, err error) {
err = cause
for prev := err; err != nil; prev = err {
// Check for net error Timeout()
if x, ok := err.(interface {
Timeout() bool
}); ok && x.Timeout() {
retriable = true
}
// Check for net error Temporary()
if x, ok := err.(interface {
Temporary() bool
}); ok && x.Temporary() {
retriable = true
}
// Unwrap 1 level if possible
err = errors.Cause(err)
if err == nil {
// errors.Cause can return nil which isn't
// desirable so pick the previous error in
// this case.
err = prev
}
if err == prev {
// Unpack any struct or *struct with a field
// of name Err which satisfies the error
// interface. This includes *url.Error,
// *net.OpError, *os.SyscallError and many
// others in the stdlib
errType := reflect.TypeOf(err)
errValue := reflect.ValueOf(err)
if errValue.IsValid() && errType.Kind() == reflect.Ptr {
errType = errType.Elem()
errValue = errValue.Elem()
}
if errValue.IsValid() && errType.Kind() == reflect.Struct {
if errField := errValue.FieldByName("Err"); errField.IsValid() {
errFieldValue := errField.Interface()
if newErr, ok := errFieldValue.(error); ok {
err = newErr
}
}
}
}
if err == prev {
break
}
}
return retriable, err
}
// retriableErrorStrings is a list of phrases which when we find it
// in an an error, we know it is a networking error which should be
// retried.
//
// This is incredibly ugly - if only errors.Cause worked for all
// errors and all errors were exported from the stdlib.
var retriableErrorStrings = []string{
"use of closed network connection", // internal/poll/fd.go
"unexpected EOF reading trailer", // net/http/transfer.go
"transport connection broken", // net/http/transport.go
"http: ContentLength=", // net/http/transfer.go
"server closed idle connection", // net/http/transport.go
}
// Errors which indicate networking errors which should be retried
//
// These are added to in retriable_errors*.go
var retriableErrors = []error{
io.EOF,
io.ErrUnexpectedEOF,
}
// ShouldRetry looks at an error and tries to work out if retrying the
// operation that caused it would be a good idea. It returns true if
// the error implements Timeout() or Temporary() or if the error
// indicates a premature closing of the connection.
func ShouldRetry(err error) bool {
if err == nil {
return false
}
// Find root cause if available
retriable, err := Cause(err)
if retriable {
return true
}
// Check if it is a retriable error
for _, retriableErr := range retriableErrors {
if err == retriableErr {
return true
}
}
// Check error strings (yuch!) too
errString := err.Error()
for _, phrase := range retriableErrorStrings {
if strings.Contains(errString, phrase) {
return true
}
}
return false
}
// ShouldRetryHTTP returns a boolean as to whether this resp deserves.
// It checks to see if the HTTP response code is in the slice
// retryErrorCodes.
func ShouldRetryHTTP(resp *http.Response, retryErrorCodes []int) bool {
if resp == nil {
return false
}
for _, e := range retryErrorCodes {
if resp.StatusCode == e {
return true
}
}
return false
}