added temp-err-catcher

Godeps/Godeps.json

@@ -150,6 +150,10 @@
 			"ImportPath": "github.com/jbenet/go-random",
 			"Rev": "2e83344e7dc7898f94501665af34edd4aa95a013"
 		},
+		{
+			"ImportPath": "github.com/jbenet/go-temp-err-catcher",
+			"Rev": "c531232018e678b2a702cfb86b5c3f68d1c8beb8"
+		},
 		{
 			"ImportPath": "github.com/jbenet/goprocess",
 			"Rev": "162148a58668ca38b0b8f0459ccc6ca88e32f1f4"

Godeps/_workspace/src/github.com/jbenet/go-temp-err-catcher/.travis.yml

+language: go
+
+go:
+  - 1.3
+  - release
+  - tip
+
+script:
+  - go test -v

Godeps/_workspace/src/github.com/jbenet/go-temp-err-catcher/README.md

+# go-temp-err-catcher
+
+This is a little package to use with your net.Listeners.
+
+Docs: https://godoc.org/github.com/jbenet/go-temp-err-catcher
+
+Get:
+
+  go get github.com/jbenet/go-temp-err-catcher
+
+## Examples
+
+It is meant to be used with things like net.Lister.Accept:
+
+```go
+import (
+  tec "github.com/jbenet/go-temp-err-catcher"
+)
+
+func listen(listener net.Listener) {
+  var c tec.TempErrCatcher
+
+  for {
+    conn, err := listener.Accept()
+    if err != nil && c.IsTemporary(c) {
+      continue
+    }
+    return conn, err
+  }
+}
+```
+
+You can make your errors implement `Temporary`:
+
+```go
+type errTemp struct {
+  e error
+}
+
+func (e errTemp) Temporary() bool {
+  return true
+}
+
+func (e errTemp) Error() string {
+  return e.e.Error()
+}
+
+err := errors.New("beep boop")
+var c tec.TempErrCatcher
+c.IsTemporary(err)              // false
+c.IsTemporary(errTemp{err}) // true
+```
+
+Or just use `ErrTemp`:
+
+```go
+err := errors.New("beep boop")
+var c tec.TempErrCatcher
+c.IsTemporary(err)              // false
+c.IsTemporary(tec.ErrTemp{err}) // true
+```
+
+
+You can also define an `IsTemp` function to classify errors:
+
+```go
+var ErrSkip = errors.New("this should be skipped")
+var ErrNotSkip = errors.New("this should not be skipped")
+
+var c tec.TempErrCatcher
+c.IsTemp = func(e error) bool {
+  return e == ErrSkip
+}
+
+c.IsTemporary(ErrSkip) // true
+c.IsTemporary(ErrNotSkip) // false
+c.IsTemporary(ErrTemp) // false! no longer accepts Temporary()
+```

Godeps/_workspace/src/github.com/jbenet/go-temp-err-catcher/doc.go

+// Package temperrcatcher provides a TempErrCatcher object,
+// which implements simple error-retrying functionality.
+// It is meant to be used with things like net.Lister.Accept:
+//
+//   import (
+//     tec "github.com/jbenet/go-temp-err-catcher"
+//   )
+//
+//   func listen(listener net.Listener) {
+//     var c tec.TempErrCatcher
+//
+//     for {
+//       conn, err := listener.Accept()
+//       if err != nil && c.IsTemporary(c) {
+//         continue
+//       }
+//       return conn, err
+//     }
+//   }
+//
+// You can make your errors implement `Temporary`:
+//
+//   type errTemp struct {
+//     e error
+//   }
+//
+//   func (e errTemp) Temporary() bool {
+//     return true
+//   }
+//
+//   func (e errTemp) Error() string {
+//     return e.e.Error()
+//   }
+//
+//   err := errors.New("beep boop")
+//   var c tec.TempErrCatcher
+//   c.IsTemporary(err)              // false
+//   c.IsTemporary(errTemp{err}) // true
+//
+// Or just use `ErrTemp`:
+//
+//   err := errors.New("beep boop")
+//   var c tec.TempErrCatcher
+//   c.IsTemporary(err)              // false
+//   c.IsTemporary(tec.ErrTemp{err}) // true
+//
+//
+// You can also define an `IsTemp` function to classify errors:
+//
+//   var ErrSkip = errors.New("this should be skipped")
+//   var ErrNotSkip = errors.New("this should not be skipped")
+//
+//   var c tec.TempErrCatcher
+//   c.IsTemp = func(e error) bool {
+//     return e == ErrSkip
+//   }
+//
+//   c.IsTemporary(ErrSkip) // true
+//   c.IsTemporary(ErrNotSkip) // false
+//   c.IsTemporary(ErrTemp) // false! no longer accepts Temporary()
+//
+package temperrcatcher

Godeps/_workspace/src/github.com/jbenet/go-temp-err-catcher/example/example.go

+package main
+
+import (
+	"fmt"
+
+	tec "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-temp-err-catcher"
+)
+
+var (
+	ErrTemp  = tec.ErrTemporary{fmt.Errorf("ErrTemp")}
+	ErrSkip  = fmt.Errorf("ErrSkip")
+	ErrOther = fmt.Errorf("ErrOther")
+)
+
+func main() {
+	var normal tec.TempErrCatcher
+	var skipper tec.TempErrCatcher
+	skipper.IsTemp = func(e error) bool {
+		return e == ErrSkip
+	}
+
+	fmt.Println("trying normal (uses Temporary interface)")
+	tryTec(normal)
+	fmt.Println("")
+	fmt.Println("trying skipper (uses our IsTemp function)")
+	tryTec(skipper)
+}
+
+func tryTec(c tec.TempErrCatcher) {
+	errs := []error{
+		ErrTemp,
+		ErrSkip,
+		ErrOther,
+		ErrTemp,
+		ErrSkip,
+		ErrOther,
+	}
+
+	for _, e := range errs {
+		if c.IsTemporary(e) {
+			fmt.Printf("\tIsTemporary: true  - skipped     %s\n", e)
+			continue
+		}
+
+		fmt.Printf("\tIsTemporary: false - not skipped %s\n", e)
+	}
+}

Godeps/_workspace/src/github.com/jbenet/go-temp-err-catcher/tec_test.go

+package temperrcatcher
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+var (
+	ErrTemp  = ErrTemporary{fmt.Errorf("ErrTemp")}
+	ErrSkip  = fmt.Errorf("ErrSkip")
+	ErrOther = fmt.Errorf("ErrOther")
+)
+
+func testTec(t *testing.T, c TempErrCatcher, errs map[error]bool) {
+	for e, expected := range errs {
+		if c.IsTemporary(e) != expected {
+			t.Error("expected %s to be %v", e, expected)
+		}
+	}
+}
+
+func TestNil(t *testing.T) {
+	var c TempErrCatcher
+	testTec(t, c, map[error]bool{
+		ErrTemp:  true,
+		ErrSkip:  false,
+		ErrOther: false,
+	})
+}
+
+func TestWait(t *testing.T) {
+	var c TempErrCatcher
+	worked := make(chan time.Duration, 3)
+	c.Wait = func(t time.Duration) {
+		worked <- t
+	}
+	testTec(t, c, map[error]bool{
+		ErrTemp:  true,
+		ErrSkip:  false,
+		ErrOther: false,
+	})
+
+	// should've called it once
+	select {
+	case <-worked:
+	default:
+		t.Error("did not call our Wait func")
+	}
+
+	// should've called it ONLY once
+	select {
+	case <-worked:
+		t.Error("called our Wait func more than once")
+	default:
+	}
+}
+
+func TestTemporary(t *testing.T) {
+	var c TempErrCatcher
+	testTec(t, c, map[error]bool{
+		ErrTemp:  true,
+		ErrSkip:  false,
+		ErrOther: false,
+	})
+}
+
+func TestDoubles(t *testing.T) {
+	last := time.Now()
+	diff := func() time.Duration {
+		now := time.Now()
+		diff := now.Sub(last)
+		last = now
+		return diff
+	}
+
+	testDiff := func(low, hi time.Duration) {
+		d := diff()
+		grace := time.Duration(time.Microsecond)
+		if (d + grace) < low {
+			t.Error("time difference is smaller than", low, d)
+		}
+		if (d - grace) > hi {
+			t.Error("time difference is greater than", hi, d)
+		}
+	}
+
+	var c TempErrCatcher
+	testDiff(0, c.Start)
+	c.IsTemporary(ErrTemp)
+	testDiff(c.Start, 2*c.Start) // first time.
+	c.IsTemporary(ErrTemp)
+	testDiff(2*c.Start, 4*c.Start) // second time.
+	c.IsTemporary(ErrTemp)
+	testDiff(4*c.Start, 8*c.Start) // third time.
+}
+
+func TestDifferentStart(t *testing.T) {
+	last := time.Now()
+	diff := func() time.Duration {
+		now := time.Now()
+		diff := now.Sub(last)
+		last = now
+		return diff
+	}
+
+	testDiff := func(low, hi time.Duration) {
+		d := diff()
+		grace := time.Duration(time.Microsecond)
+		if (d + grace) < low {
+			t.Error("time difference is smaller than", low, d)
+		}
+		if (d - grace) > hi {
+			t.Error("time difference is greater than", hi, d)
+		}
+	}
+
+	var c TempErrCatcher
+	f := time.Millisecond
+	testDiff(0, f)
+	c.IsTemporary(ErrTemp)
+	testDiff(f, 2*f) // first time.
+	c.IsTemporary(ErrTemp)
+	testDiff(2*f, 4*f) // second time.
+	c.IsTemporary(ErrTemp)
+	testDiff(4*f, 8*f) // third time.
+
+	c.Reset()
+	c.Start = 10 * time.Millisecond
+	f = c.Start
+	testDiff(0, f)
+	c.IsTemporary(ErrTemp)
+	testDiff(f, 2*f) // first time.
+	c.IsTemporary(ErrTemp)
+	testDiff(2*f, 4*f) // second time.
+	c.IsTemporary(ErrTemp)
+	testDiff(4*f, 8*f) // third time.
+}
+
+func TestDifferentStreaks(t *testing.T) {
+	var c TempErrCatcher
+	// one streak
+	c.IsTemporary(ErrTemp) // 1
+	c.IsTemporary(ErrTemp) // 2
+	c.IsTemporary(ErrTemp) // 4
+	expect := 4 * time.Millisecond
+	if c.delay != expect {
+		t.Error("delay should be:", expect, c.delay)
+	}
+
+	<-time.After(c.delay * 10)
+
+	// a different streak
+	c.IsTemporary(ErrTemp) // 1
+	c.IsTemporary(ErrTemp) // 2
+	c.IsTemporary(ErrTemp) // 4
+	if c.delay != expect {
+		t.Error("delay should be:", expect, c.delay)
+	}
+}
+
+func TestFunc(t *testing.T) {
+	var c TempErrCatcher
+	c.IsTemp = func(e error) bool {
+		return e == ErrSkip
+	}
+	testTec(t, c, map[error]bool{
+		ErrTemp:  false,
+		ErrSkip:  true,
+		ErrOther: false,
+	})
+}

Godeps/_workspace/src/github.com/jbenet/go-temp-err-catcher/temp_err_catcher.go

+// Package temperrcatcher provides a TempErrCatcher object,
+// which implements simple error-retrying functionality.
+package temperrcatcher
+
+import (
+	"time"
+)
+
+// InitialDelay governs how long to wait the first time.
+// This is defaulted to time.Millisecond, which makes sense
+// for network listener failures. You may want a much smaller
+// delay. You can configure this package wide, or in each
+// TempErrCatcher
+var InitialDelay = time.Millisecond
+
+// Temporary is an interface errors can implement to
+// ensure they are correctly classified by the default
+// TempErrCatcher classifier
+type Temporary interface {
+	Temporary() bool
+}
+
+// ErrIsTemporary returns whether an error is Temporary(),
+// iff it implements the Temporary interface.
+func ErrIsTemporary(e error) bool {
+	te, ok := e.(Temporary)
+	return ok && te.Temporary()
+}
+
+// TempErrCatcher catches temporary errors for you. It then sleeps
+// for a bit before returning (you should then try again). This may
+// seem odd, but it's exactly what net/http does:
+// http://golang.org/src/net/http/server.go?s=51504:51550#L1728
+//
+// You can set a few options in TempErrCatcher. They all have defaults
+// so a zero TempErrCatcher is ready to be used:
+//
+//  var c tec.TempErrCatcher
+//  c.IsTemporary(tempErr)
+//
+type TempErrCatcher struct {
+	IsTemp func(error) bool    // the classifier to use. default: ErrIsTemporary
+	Wait   func(time.Duration) // the wait func to call. default: time.Sleep
+	Max    time.Duration       // the maximum time to wait. default: time.Second
+	Start  time.Duration       // the delay to start with. default: InitialDelay
+	delay  time.Duration
+	last   time.Time
+}
+
+func (tec *TempErrCatcher) init() {
+	if tec.Max == 0 {
+		tec.Max = time.Second
+	}
+	if tec.IsTemp == nil {
+		tec.IsTemp = ErrIsTemporary
+	}
+	if tec.Wait == nil {
+		tec.Wait = time.Sleep
+	}
+	if tec.Start == 0 {
+		tec.Start = InitialDelay
+	}
+}
+
+// IsTemporary checks whether an error is temporary. It will call
+// tec.Wait before returning, with a delay. The delay is also
+// doubled, so we do not constantly spin. This is the strategy
+// net.Listener uses.
+//
+// Note: you will want to call Reset() if you get a success,
+// so that the stored delay is brough back to 0.
+func (tec *TempErrCatcher) IsTemporary(e error) bool {
+	tec.init()
+	if tec.IsTemp(e) {
+		now := time.Now()
+		if now.Sub(tec.last) > (tec.delay * 5) {
+			// this is a "new streak" of temp failures. reset.
+			tec.Reset()
+		}
+
+		if tec.delay == 0 { // init case.
+			tec.delay = tec.Start
+		} else {
+			tec.delay *= 2
+		}
+
+		if tec.delay > tec.Max {
+			tec.delay = tec.Max
+		}
+		tec.Wait(tec.delay)
+		tec.last = now
+		return true
+	}
+	tec.Reset() // different failure. call reset
+	return false
+}
+
+// Reset sets the internal delay counter to 0
+func (tec *TempErrCatcher) Reset() {
+	tec.delay = 0
+}
+
+// ErrTemporary wraps any error and implements Temporary function.
+//
+//   err := errors.New("beep boop")
+//   var c tec.TempErrCatcher
+//   c.IsTemporary(err)              // false
+//   c.IsTemporary(tec.ErrTemp{err}) // true
+//
+type ErrTemporary struct {
+	Err error
+}
+
+func (e ErrTemporary) Temporary() bool {
+	return true
+}
+
+func (e ErrTemporary) Error() string {
+	return e.Err.Error()
+}
+
+func (e ErrTemporary) String() string {
+	return e.Error()
+}