fs: improve retriable error detection

This commit is contained in:
Nick Craig-Wood 2017-09-15 17:09:20 +01:00
parent 7f8d306c9c
commit 6df12b3f00
5 changed files with 142 additions and 96 deletions

View File

@ -1,46 +0,0 @@
// +build !plan9
package fs
import (
"net"
"os"
"syscall"
)
// closedConnErrors indicate a connection is closed or broken and
// should be retried
//
// These are added to in closed_conn_win.go
var closedConnErrors = []syscall.Errno{
syscall.EPIPE,
syscall.ETIMEDOUT,
syscall.ECONNREFUSED,
syscall.EHOSTDOWN,
syscall.EHOSTUNREACH,
syscall.ECONNABORTED,
syscall.EAGAIN,
syscall.EWOULDBLOCK,
syscall.ECONNRESET,
}
// isClosedConnErrorPlatform reports whether err is an error from use
// of a closed network connection using platform specific error codes.
func isClosedConnErrorPlatform(err error) bool {
// now check whether err is an error from use of a closed
// network connection using platform specific error codes.
//
// Code adapted from net/http
if oe, ok := err.(*net.OpError); ok {
if se, ok := oe.Err.(*os.SyscallError); ok {
if errno, ok := se.Err.(syscall.Errno); ok {
for _, retriableErrno := range closedConnErrors {
if errno == retriableErrno {
return true
}
}
}
}
}
return false
}

View File

@ -6,7 +6,7 @@ import (
"fmt" "fmt"
"io" "io"
"net/http" "net/http"
"net/url" "reflect"
"strings" "strings"
"github.com/pkg/errors" "github.com/pkg/errors"
@ -167,34 +167,72 @@ func IsNoRetryError(err error) bool {
return false return false
} }
// closedConnErrorStrings is a list of phrases which when we find it // 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 == 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 errType.Kind() == reflect.Ptr {
errType = errType.Elem()
errValue = errValue.Elem()
}
if 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 // in an an error, we know it is a networking error which should be
// retried. // retried.
// //
// This is incredibly ugly - if only errors.Cause worked for all // This is incredibly ugly - if only errors.Cause worked for all
// errors and all errors were exported from the stdlib. // errors and all errors were exported from the stdlib.
var closedConnErrorStrings = []string{ var retriableErrorStrings = []string{
"use of closed network connection", // not exported :-( "use of closed network connection", // not exported :-(
} }
// isClosedConnError reports whether err is an error from use of a closed // Errors which indicate networking errors which should be retried
// network connection or prematurely closed connection
// //
// Code adapted from net/http // These are added to in retriable_errors*.go
func isClosedConnError(err error) bool { var retriableErrors = []error{
if err == nil { io.EOF,
return false io.ErrUnexpectedEOF,
}
errString := err.Error()
for _, phrase := range closedConnErrorStrings {
if strings.Contains(errString, phrase) {
return true
}
}
return isClosedConnErrorPlatform(err)
} }
// ShouldRetry looks at an error and tries to work out if retrying the // ShouldRetry looks at an error and tries to work out if retrying the
@ -207,30 +245,24 @@ func ShouldRetry(err error) bool {
} }
// Find root cause if available // Find root cause if available
err = errors.Cause(err) retriable, err := Cause(err)
if retriable {
// Unwrap url.Error
if urlErr, ok := err.(*url.Error); ok {
err = urlErr.Err
}
// Look for premature closing of connection
if err == io.EOF || err == io.ErrUnexpectedEOF || isClosedConnError(err) {
return true return true
} }
// Check for net error Timeout() // Check if it is a retriable error
if x, ok := err.(interface { for _, retriableErr := range retriableErrors {
Timeout() bool if err == retriableErr {
}); ok && x.Timeout() { return true
return true }
} }
// Check for net error Temporary() // Check error strings (yuch!) too
if x, ok := err.(interface { errString := err.Error()
Temporary() bool for _, phrase := range retriableErrorStrings {
}); ok && x.Temporary() { if strings.Contains(errString, phrase) {
return true return true
}
} }
return false return false

View File

@ -29,19 +29,56 @@ func makeNetErr(errno syscall.Errno) error {
} }
} }
func TestIsClosedConnError(t *testing.T) { type myError1 struct {
Err error
}
func (e myError1) Error() string { return e.Err.Error() }
type myError2 struct {
Err error
}
func (e *myError2) Error() string { return e.Err.Error() }
type myError3 struct {
Err int
}
func (e *myError3) Error() string { return "hello" }
type myError4 struct {
e error
}
func (e *myError4) Error() string { return e.e.Error() }
func TestCause(t *testing.T) {
e3 := &myError3{3}
e4 := &myError4{io.EOF}
errPotato := errors.New("potato")
for i, test := range []struct { for i, test := range []struct {
err error err error
want bool wantRetriable bool
wantErr error
}{ }{
{nil, false}, {nil, false, nil},
{errors.New("potato"), false}, {errPotato, false, errPotato},
{errUseOfClosedNetworkConnection, true}, {errors.Wrap(errPotato, "potato"), false, errPotato},
{makeNetErr(syscall.EAGAIN), true}, {errors.Wrap(errors.Wrap(errPotato, "potato2"), "potato"), false, errPotato},
{makeNetErr(syscall.Errno(123123123)), false}, {errUseOfClosedNetworkConnection, false, errUseOfClosedNetworkConnection},
{makeNetErr(syscall.EAGAIN), true, syscall.EAGAIN},
{makeNetErr(syscall.Errno(123123123)), false, syscall.Errno(123123123)},
{myError1{io.EOF}, false, io.EOF},
{&myError2{io.EOF}, false, io.EOF},
{e3, false, e3},
{e4, false, e4},
} { } {
got := isClosedConnError(test.err) gotRetriable, gotErr := Cause(test.err)
assert.Equal(t, test.want, got, fmt.Sprintf("test #%d: %v", i, test.err)) what := fmt.Sprintf("test #%d: %v", i, test.err)
assert.Equal(t, test.wantErr, gotErr, what)
assert.Equal(t, test.wantRetriable, gotRetriable, what)
} }
} }
@ -55,6 +92,8 @@ func TestShouldRetry(t *testing.T) {
{errors.Wrap(errUseOfClosedNetworkConnection, "connection"), true}, {errors.Wrap(errUseOfClosedNetworkConnection, "connection"), true},
{io.EOF, true}, {io.EOF, true},
{io.ErrUnexpectedEOF, true}, {io.ErrUnexpectedEOF, true},
{makeNetErr(syscall.EAGAIN), true},
{makeNetErr(syscall.Errno(123123123)), false},
{&url.Error{Op: "post", URL: "/", Err: io.EOF}, true}, {&url.Error{Op: "post", URL: "/", Err: io.EOF}, true},
{&url.Error{Op: "post", URL: "/", Err: errUseOfClosedNetworkConnection}, true}, {&url.Error{Op: "post", URL: "/", Err: errUseOfClosedNetworkConnection}, true},
{ {

21
fs/retriable_errors.go Normal file
View File

@ -0,0 +1,21 @@
// +build !plan9
package fs
import (
"syscall"
)
func init() {
retriableErrors = append(retriableErrors,
syscall.EPIPE,
syscall.ETIMEDOUT,
syscall.ECONNREFUSED,
syscall.EHOSTDOWN,
syscall.EHOSTUNREACH,
syscall.ECONNABORTED,
syscall.EAGAIN,
syscall.EWOULDBLOCK,
syscall.ECONNRESET,
)
}

View File

@ -17,7 +17,7 @@ const (
func init() { func init() {
// append some lower level errors since the standardized ones // append some lower level errors since the standardized ones
// don't seem to happen // don't seem to happen
closedConnErrors = append(closedConnErrors, retriableErrors = append(retriableErrors,
syscall.WSAECONNRESET, syscall.WSAECONNRESET,
WSAECONNABORTED, WSAECONNABORTED,
WSAHOST_NOT_FOUND, WSAHOST_NOT_FOUND,