Merge pull request #554 from jbenet/feat/reprovide

basic reprovider implementation

Godeps/Godeps.json

@@ -60,6 +60,10 @@
 			"ImportPath": "github.com/camlistore/lock",
 			"Rev": "ae27720f340952636b826119b58130b9c1a847a0"
 		},
+		{
+			"ImportPath": "github.com/cenkalti/backoff",
+			"Rev": "9831e1e25c874e0a0601b6dc43641071414eec7a"
+		},
 		{
 			"ImportPath": "github.com/coreos/go-semver/semver",
 			"Rev": "6fe83ccda8fb9b7549c9ab4ba47f47858bc950aa"
@@ -118,7 +122,7 @@
 		},
 		{
 			"ImportPath": "github.com/jbenet/go-fuse-version",
-			"Rev": "ff72c39433f95ada15f116fa493a51eeec2bd52e"
+			"Rev": "c723f93ceeb1d1e21eb7fe6fd39aa21a9fe7db99"
 		},
 		{
 			"ImportPath": "github.com/jbenet/go-is-domain",

Godeps/_workspace/src/github.com/cenkalti/backoff/.gitignore

@@ -0,0 +1,22 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe

Godeps/_workspace/src/github.com/cenkalti/backoff/.travis.yml

@@ -0,0 +1,2 @@
+language: go
+go: 1.3.3

Godeps/_workspace/src/github.com/cenkalti/backoff/LICENSE

@@ -0,0 +1,20 @@
+The MIT License (MIT)
+
+Copyright (c) 2014 Cenk Altı
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Godeps/_workspace/src/github.com/cenkalti/backoff/README.md

@@ -0,0 +1,69 @@
+# backoff
+
+[![GoDoc](https://godoc.org/github.com/cenkalti/backoff?status.png)](https://godoc.org/github.com/cenkalti/backoff)
+[![Build Status](https://travis-ci.org/cenkalti/backoff.png)](https://travis-ci.org/cenkalti/backoff)
+
+This is a Go port of the exponential backoff algorithm from
+[google-http-java-client](https://code.google.com/p/google-http-java-client/wiki/ExponentialBackoff).
+
+[Exponential backoff](http://en.wikipedia.org/wiki/Exponential_backoff)
+is an algorithm that uses feedback to multiplicatively decrease the rate of some process,
+in order to gradually find an acceptable rate.
+The retries exponentially increase and stop increasing when a certain threshold is met.
+
+
+
+
+## Install
+
+```bash
+go get github.com/cenkalti/backoff
+```
+
+## Example
+
+Simple retry helper that uses exponential back-off algorithm:
+
+```go
+operation := func() error {
+    // An operation that might fail
+}
+
+err := backoff.Retry(operation, backoff.NewExponentialBackOff())
+if err != nil {
+    // handle error
+}
+
+// operation is successfull
+```
+
+Ticker example:
+
+```go
+operation := func() error {
+    // An operation that may fail
+}
+
+b := backoff.NewExponentialBackOff()
+ticker := backoff.NewTicker(b)
+
+var err error
+
+// Ticks will continue to arrive when the previous operation is still running,
+// so operations that take a while to fail could run in quick succession.
+for t = range ticker.C {
+    if err = operation(); err != nil {
+        log.Println(err, "will retry...")
+        continue
+    }
+
+    ticker.Stop()
+    break
+}
+
+if err != nil {
+    // Operation has failed.
+}
+
+// Operation is successfull.
+```

Godeps/_workspace/src/github.com/cenkalti/backoff/backoff.go

@@ -0,0 +1,56 @@
+// Package backoff implements backoff algorithms for retrying operations.
+//
+// Also has a Retry() helper for retrying operations that may fail.
+package backoff
+
+import "time"
+
+// Back-off policy when retrying an operation.
+type BackOff interface {
+	// Gets the duration to wait before retrying the operation or
+	// backoff.Stop to indicate that no retries should be made.
+	//
+	// Example usage:
+	//
+	// 	duration := backoff.NextBackOff();
+	// 	if (duration == backoff.Stop) {
+	// 		// do not retry operation
+	// 	} else {
+	// 		// sleep for duration and retry operation
+	// 	}
+	//
+	NextBackOff() time.Duration
+
+	// Reset to initial state.
+	Reset()
+}
+
+// Indicates that no more retries should be made for use in NextBackOff().
+const Stop time.Duration = -1
+
+// ZeroBackOff is a fixed back-off policy whose back-off time is always zero,
+// meaning that the operation is retried immediately without waiting.
+type ZeroBackOff struct{}
+
+func (b *ZeroBackOff) Reset() {}
+
+func (b *ZeroBackOff) NextBackOff() time.Duration { return 0 }
+
+// StopBackOff is a fixed back-off policy that always returns backoff.Stop for
+// NextBackOff(), meaning that the operation should not be retried.
+type StopBackOff struct{}
+
+func (b *StopBackOff) Reset() {}
+
+func (b *StopBackOff) NextBackOff() time.Duration { return Stop }
+
+type ConstantBackOff struct {
+	Interval time.Duration
+}
+
+func (b *ConstantBackOff) Reset()                     {}
+func (b *ConstantBackOff) NextBackOff() time.Duration { return b.Interval }
+
+func NewConstantBackOff(d time.Duration) *ConstantBackOff {
+	return &ConstantBackOff{Interval: d}
+}

Godeps/_workspace/src/github.com/cenkalti/backoff/backoff_test.go

@@ -0,0 +1,28 @@
+package backoff
+
+import (
+	"time"
+
+	"testing"
+)
+
+func TestNextBackOffMillis(t *testing.T) {
+	subtestNextBackOff(t, 0, new(ZeroBackOff))
+	subtestNextBackOff(t, Stop, new(StopBackOff))
+}
+
+func subtestNextBackOff(t *testing.T, expectedValue time.Duration, backOffPolicy BackOff) {
+	for i := 0; i < 10; i++ {
+		next := backOffPolicy.NextBackOff()
+		if next != expectedValue {
+			t.Errorf("got: %d expected: %d", next, expectedValue)
+		}
+	}
+}
+
+func TestConstantBackOff(t *testing.T) {
+	backoff := NewConstantBackOff(time.Second)
+	if backoff.NextBackOff() != time.Second {
+		t.Error("invalid interval")
+	}
+}

Godeps/_workspace/src/github.com/cenkalti/backoff/exponential.go

@@ -0,0 +1,141 @@
+package backoff
+
+import (
+	"math/rand"
+	"time"
+)
+
+/*
+ExponentialBackOff is an implementation of BackOff that increases the back off
+period for each retry attempt using a randomization function that grows exponentially.
+
+NextBackOff() is calculated using the following formula:
+
+	randomized_interval =
+	    retry_interval * (random value in range [1 - randomization_factor, 1 + randomization_factor])
+
+In other words NextBackOff() will range between the randomization factor
+percentage below and above the retry interval. For example, using 2 seconds as the base retry
+interval and 0.5 as the randomization factor, the actual back off period used in the next retry
+attempt will be between 1 and 3 seconds.
+
+Note: max_interval caps the retry_interval and not the randomized_interval.
+
+If the time elapsed since an ExponentialBackOff instance is created goes past the
+max_elapsed_time then the method NextBackOff() starts returning backoff.Stop.
+The elapsed time can be reset by calling Reset().
+
+Example: The default retry_interval is .5 seconds, default randomization_factor is 0.5, default
+multiplier is 1.5 and the default max_interval is 1 minute. For 10 tries the sequence will be
+(values in seconds) and assuming we go over the max_elapsed_time on the 10th try:
+
+	request#     retry_interval     randomized_interval
+
+	1             0.5                [0.25,   0.75]
+	2             0.75               [0.375,  1.125]
+	3             1.125              [0.562,  1.687]
+	4             1.687              [0.8435, 2.53]
+	5             2.53               [1.265,  3.795]
+	6             3.795              [1.897,  5.692]
+	7             5.692              [2.846,  8.538]
+	8             8.538              [4.269, 12.807]
+	9            12.807              [6.403, 19.210]
+	10           19.210              backoff.Stop
+
+Implementation is not thread-safe.
+*/
+type ExponentialBackOff struct {
+	InitialInterval     time.Duration
+	RandomizationFactor float64
+	Multiplier          float64
+	MaxInterval         time.Duration
+	// After MaxElapsedTime the ExponentialBackOff stops.
+	// It never stops if MaxElapsedTime == 0.
+	MaxElapsedTime time.Duration
+	Clock          Clock
+
+	currentInterval time.Duration
+	startTime       time.Time
+}
+
+// Clock is an interface that returns current time for BackOff.
+type Clock interface {
+	Now() time.Time
+}
+
+// Default values for ExponentialBackOff.
+const (
+	DefaultInitialInterval     = 500 * time.Millisecond
+	DefaultRandomizationFactor = 0.5
+	DefaultMultiplier          = 1.5
+	DefaultMaxInterval         = 60 * time.Second
+	DefaultMaxElapsedTime      = 15 * time.Minute
+)
+
+// NewExponentialBackOff creates an instance of ExponentialBackOff using default values.
+func NewExponentialBackOff() *ExponentialBackOff {
+	return &ExponentialBackOff{
+		InitialInterval:     DefaultInitialInterval,
+		RandomizationFactor: DefaultRandomizationFactor,
+		Multiplier:          DefaultMultiplier,
+		MaxInterval:         DefaultMaxInterval,
+		MaxElapsedTime:      DefaultMaxElapsedTime,
+		Clock:               SystemClock,
+	}
+}
+
+type systemClock struct{}
+
+func (t systemClock) Now() time.Time {
+	return time.Now()
+}
+
+// SystemClock implements Clock interface that uses time.Now().
+var SystemClock = systemClock{}
+
+// Reset the interval back to the initial retry interval and restarts the timer.
+func (b *ExponentialBackOff) Reset() {
+	b.currentInterval = b.InitialInterval
+	b.startTime = b.Clock.Now()
+}
+
+// NextBackOff calculates the next back off interval using the formula:
+// 	randomized_interval = retry_interval +/- (randomization_factor * retry_interval)
+func (b *ExponentialBackOff) NextBackOff() time.Duration {
+	// Make sure we have not gone over the maximum elapsed time.
+	if b.MaxElapsedTime != 0 && b.GetElapsedTime() > b.MaxElapsedTime {
+		return Stop
+	}
+	defer b.incrementCurrentInterval()
+	return getRandomValueFromInterval(b.RandomizationFactor, rand.Float64(), b.currentInterval)
+}
+
+// GetElapsedTime returns the elapsed time since an ExponentialBackOff instance
+// is created and is reset when Reset() is called.
+//
+// The elapsed time is computed using time.Now().UnixNano().
+func (b *ExponentialBackOff) GetElapsedTime() time.Duration {
+	return b.Clock.Now().Sub(b.startTime)
+}
+
+// Increments the current interval by multiplying it with the multiplier.
+func (b *ExponentialBackOff) incrementCurrentInterval() {
+	// Check for overflow, if overflow is detected set the current interval to the max interval.
+	if float64(b.currentInterval) >= float64(b.MaxInterval)/b.Multiplier {
+		b.currentInterval = b.MaxInterval
+	} else {
+		b.currentInterval = time.Duration(float64(b.currentInterval) * b.Multiplier)
+	}
+}
+
+// Returns a random value from the interval:
+// 	[randomizationFactor * currentInterval, randomizationFactor * currentInterval].
+func getRandomValueFromInterval(randomizationFactor, random float64, currentInterval time.Duration) time.Duration {
+	var delta = randomizationFactor * float64(currentInterval)
+	var minInterval = float64(currentInterval) - delta
+	var maxInterval = float64(currentInterval) + delta
+	// Get a random value from the range [minInterval, maxInterval].
+	// The formula used below has a +1 because if the minInterval is 1 and the maxInterval is 3 then
+	// we want a 33% chance for selecting either 1, 2 or 3.
+	return time.Duration(minInterval + (random * (maxInterval - minInterval + 1)))
+}

Godeps/_workspace/src/github.com/cenkalti/backoff/exponential_test.go

@@ -0,0 +1,111 @@
+package backoff
+
+import (
+	"math"
+	"testing"
+	"time"
+)
+
+func TestBackOff(t *testing.T) {
+	var (
+		testInitialInterval     = 500 * time.Millisecond
+		testRandomizationFactor = 0.1
+		testMultiplier          = 2.0
+		testMaxInterval         = 5 * time.Second
+		testMaxElapsedTime      = 15 * time.Minute
+	)
+
+	exp := NewExponentialBackOff()
+	exp.InitialInterval = testInitialInterval
+	exp.RandomizationFactor = testRandomizationFactor
+	exp.Multiplier = testMultiplier
+	exp.MaxInterval = testMaxInterval
+	exp.MaxElapsedTime = testMaxElapsedTime
+	exp.Reset()
+
+	var expectedResults = []time.Duration{500, 1000, 2000, 4000, 5000, 5000, 5000, 5000, 5000, 5000}
+	for i, d := range expectedResults {
+		expectedResults[i] = d * time.Millisecond
+	}
+
+	for _, expected := range expectedResults {
+		assertEquals(t, expected, exp.currentInterval)
+		// Assert that the next back off falls in the expected range.
+		var minInterval = expected - time.Duration(testRandomizationFactor*float64(expected))
+		var maxInterval = expected + time.Duration(testRandomizationFactor*float64(expected))
+		var actualInterval = exp.NextBackOff()
+		if !(minInterval <= actualInterval && actualInterval <= maxInterval) {
+			t.Error("error")
+		}
+	}
+}
+
+func TestGetRandomizedInterval(t *testing.T) {
+	// 33% chance of being 1.
+	assertEquals(t, 1, getRandomValueFromInterval(0.5, 0, 2))
+	assertEquals(t, 1, getRandomValueFromInterval(0.5, 0.33, 2))
+	// 33% chance of being 2.
+	assertEquals(t, 2, getRandomValueFromInterval(0.5, 0.34, 2))
+	assertEquals(t, 2, getRandomValueFromInterval(0.5, 0.66, 2))
+	// 33% chance of being 3.
+	assertEquals(t, 3, getRandomValueFromInterval(0.5, 0.67, 2))
+	assertEquals(t, 3, getRandomValueFromInterval(0.5, 0.99, 2))
+}
+
+type TestClock struct {
+	i     time.Duration
+	start time.Time
+}
+
+func (c *TestClock) Now() time.Time {
+	t := c.start.Add(c.i)
+	c.i += time.Second
+	return t
+}
+
+func TestGetElapsedTime(t *testing.T) {
+	var exp = NewExponentialBackOff()
+	exp.Clock = &TestClock{}
+	exp.Reset()
+
+	var elapsedTime = exp.GetElapsedTime()
+	if elapsedTime != time.Second {
+		t.Errorf("elapsedTime=%d", elapsedTime)
+	}
+}
+
+func TestMaxElapsedTime(t *testing.T) {
+	var exp = NewExponentialBackOff()
+	exp.Clock = &TestClock{start: time.Time{}.Add(10000 * time.Second)}
+	if exp.NextBackOff() != Stop {
+		t.Error("error2")
+	}
+	// Change the currentElapsedTime to be 0 ensuring that the elapsed time will be greater
+	// than the max elapsed time.
+	exp.startTime = time.Time{}
+	assertEquals(t, Stop, exp.NextBackOff())
+}
+
+func TestBackOffOverflow(t *testing.T) {
+	var (
+		testInitialInterval time.Duration = math.MaxInt64 / 2
+		testMaxInterval     time.Duration = math.MaxInt64
+		testMultiplier      float64       = 2.1
+	)
+
+	exp := NewExponentialBackOff()
+	exp.InitialInterval = testInitialInterval
+	exp.Multiplier = testMultiplier
+	exp.MaxInterval = testMaxInterval
+	exp.Reset()
+
+	exp.NextBackOff()
+	// Assert that when an overflow is possible the current varerval   time.Duration    is set to the max varerval   time.Duration   .
+	assertEquals(t, testMaxInterval, exp.currentInterval)
+}
+
+func assertEquals(t *testing.T, expected, value time.Duration) {
+	if expected != value {
+		t.Errorf("got: %d, expected: %d", value, expected)
+	}
+}

Godeps/_workspace/src/github.com/cenkalti/backoff/retry.go

@@ -0,0 +1,47 @@
+package backoff
+
+import "time"
+
+// Retry the function f until it does not return error or BackOff stops.
+// f is guaranteed to be run at least once.
+// It is the caller's responsibility to reset b after Retry returns.
+//
+// Retry sleeps the goroutine for the duration returned by BackOff after a
+// failed operation returns.
+//
+// Usage:
+// 	operation := func() error {
+// 		// An operation that may fail
+// 	}
+//
+// 	err := backoff.Retry(operation, backoff.NewExponentialBackOff())
+// 	if err != nil {
+// 		// Operation has failed.
+// 	}
+//
+// 	// Operation is successfull.
+//
+func Retry(f func() error, b BackOff) error { return RetryNotify(f, b, nil) }
+
+// RetryNotify calls notify function with the error and wait duration for each failed attempt before sleep.
+func RetryNotify(f func() error, b BackOff, notify func(err error, wait time.Duration)) error {
+	var err error
+	var next time.Duration
+
+	b.Reset()
+	for {
+		if err = f(); err == nil {
+			return nil
+		}
+
+		if next = b.NextBackOff(); next == Stop {
+			return err
+		}
+
+		if notify != nil {
+			notify(err, next)
+		}
+
+		time.Sleep(next)
+	}
+}

Godeps/_workspace/src/github.com/cenkalti/backoff/retry_test.go

@@ -0,0 +1,34 @@
+package backoff
+
+import (
+	"errors"
+	"log"
+	"testing"
+)
+
+func TestRetry(t *testing.T) {
+	const successOn = 3
+	var i = 0
+
+	// This function is successfull on "successOn" calls.
+	f := func() error {
+		i++
+		log.Printf("function is called %d. time\n", i)
+
+		if i == successOn {
+			log.Println("OK")
+			return nil
+		}
+
+		log.Println("error")
+		return errors.New("error")
+	}
+
+	err := Retry(f, NewExponentialBackOff())
+	if err != nil {
+		t.Errorf("unexpected error: %s", err.Error())
+	}
+	if i != successOn {
+		t.Errorf("invalid number of retries: %d", i)
+	}
+}

Godeps/_workspace/src/github.com/cenkalti/backoff/ticker.go

@@ -0,0 +1,105 @@
+package backoff
+
+import (
+	"runtime"
+	"sync"
+	"time"
+)
+
+// Ticker holds a channel that delivers `ticks' of a clock at times reported by a BackOff.
+//
+// Ticks will continue to arrive when the previous operation is still running,
+// so operations that take a while to fail could run in quick succession.
+//
+// Usage:
+// 	operation := func() error {
+// 		// An operation that may fail
+// 	}
+//
+//	b := backoff.NewExponentialBackOff()
+//	ticker := backoff.NewTicker(b)
+//
+// 	var err error
+//	for _ = range ticker.C {
+//		if err = operation(); err != nil {
+//			log.Println(err, "will retry...")
+//			continue
+//		}
+//
+//		ticker.Stop()
+//		break
+//	}
+//
+// 	if err != nil {
+// 		// Operation has failed.
+// 	}
+//
+// 	// Operation is successfull.
+//
+type Ticker struct {
+	C        <-chan time.Time
+	c        chan time.Time
+	b        BackOff
+	stop     chan struct{}
+	stopOnce sync.Once
+}
+
+// NewTicker returns a new Ticker containing a channel that will send the time at times
+// specified by the BackOff argument. Ticker is guaranteed to tick at least once.
+// The channel is closed when Stop method is called or BackOff stops.
+func NewTicker(b BackOff) *Ticker {
+	c := make(chan time.Time)
+	t := &Ticker{
+		C:    c,
+		c:    c,
+		b:    b,
+		stop: make(chan struct{}),
+	}
+	go t.run()
+	runtime.SetFinalizer(t, (*Ticker).Stop)
+	return t
+}
+
+// Stop turns off a ticker. After Stop, no more ticks will be sent.
+func (t *Ticker) Stop() {
+	t.stopOnce.Do(func() { close(t.stop) })
+}
+
+func (t *Ticker) run() {
+	c := t.c
+	defer close(c)
+	t.b.Reset()
+
+	// Ticker is guaranteed to tick at least once.
+	afterC := t.send(time.Now())
+
+	for {
+		if afterC == nil {
+			return
+		}
+
+		select {
+		case tick := <-afterC:
+			afterC = t.send(tick)
+		case <-t.stop:
+			t.c = nil // Prevent future ticks from being sent to the channel.
+			return
+		}
+	}
+}
+
+func (t *Ticker) send(tick time.Time) <-chan time.Time {
+	select {
+	case t.c <- tick:
+	case <-t.stop:
+		return nil
+	}
+
+	next := t.b.NextBackOff()
+	if next == Stop {
+		t.Stop()
+		return nil
+	}
+
+	return time.After(next)
+}

Godeps/_workspace/src/github.com/cenkalti/backoff/ticker_test.go

@@ -0,0 +1,45 @@
+package backoff
+
+import (
+	"errors"
+	"log"
+	"testing"
+)
+
+func TestTicker(t *testing.T) {
+	const successOn = 3
+	var i = 0
+
+	// This function is successfull on "successOn" calls.
+	f := func() error {
+		i++
+		log.Printf("function is called %d. time\n", i)
+
+		if i == successOn {
+			log.Println("OK")
+			return nil
+		}
+
+		log.Println("error")
+		return errors.New("error")
+	}
+
+	b := NewExponentialBackOff()
+	ticker := NewTicker(b)
+
+	var err error
+	for _ = range ticker.C {
+		if err = f(); err != nil {
+			t.Log(err)
+			continue
+		}
+
+		break
+	}
+	if err != nil {
+		t.Errorf("unexpected error: %s", err.Error())
+	}
+	if i != successOn {
+		t.Errorf("invalid number of retries: %d", i)
+	}
+}

Godeps/_workspace/src/github.com/jbenet/go-fuse-version/version_bsd.go

@@ -3,9 +3,10 @@
 package fuseversion
 
 import (
+	"fmt"
 	"runtime"
 )
 
 func getLocalFuseSystems() (*Systems, error) {
-	return nil, fmt.Sprintf(notImplYet, runtime.GOARCH())
+	return nil, fmt.Errorf(notImplYet, runtime.GOARCH)
 }

Godeps/_workspace/src/github.com/jbenet/go-fuse-version/version_linux.go

@@ -1,9 +1,10 @@
 package fuseversion
 
 import (
+	"fmt"
 	"runtime"
 )
 
 func getLocalFuseSystems() (*Systems, error) {
-	return nil, fmt.Sprintf(notImplYet, runtime.GOARCH())
+	return nil, fmt.Errorf(notImplYet, runtime.GOARCH)
 }

Godeps/_workspace/src/github.com/jbenet/go-fuse-version/version_windows.go

@@ -1,9 +1,10 @@
 package fuseversion
 
 import (
+	"fmt"
 	"runtime"
 )
 
 func getLocalFuseSystems() (*Systems, error) {
-	return nil, fmt.Sprintf(notImplYet, runtime.GOARCH())
+	return nil, fmt.Errorf(notImplYet, runtime.GOARCH)
 }

core/core.go

@@ -2,6 +2,7 @@ package core
 
 import (
 	"fmt"
+	"time"
 
 	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
 	b58 "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-base58"
@@ -16,6 +17,7 @@ import (
 	bitswap "github.com/jbenet/go-ipfs/exchange/bitswap"
 	bsnet "github.com/jbenet/go-ipfs/exchange/bitswap/network"
 	offline "github.com/jbenet/go-ipfs/exchange/offline"
+	rp "github.com/jbenet/go-ipfs/exchange/reprovide"
 	mount "github.com/jbenet/go-ipfs/fuse/mount"
 	merkledag "github.com/jbenet/go-ipfs/merkledag"
 	namesys "github.com/jbenet/go-ipfs/namesys"
@@ -79,6 +81,7 @@ type IpfsNode struct {
 	Exchange    exchange.Interface  // the block exchange + strategy (bitswap)
 	Namesys     namesys.NameSystem  // the name system, resolves paths to hashes
 	Diagnostics *diag.Diagnostics   // the diagnostics service
+	Reprovider  *rp.Reprovider      // the value reprovider system
 
 	ctxgroup.ContextGroup
 
@@ -247,6 +250,10 @@ func (n *IpfsNode) StartOnlineServices() error {
 		bootstrapPeers = append(bootstrapPeers, p)
 	}
 	go superviseConnections(ctx, n.PeerHost, n.DHT, n.Peerstore, bootstrapPeers)
+
+	// Start up reprovider system
+	n.Reprovider = rp.NewReprovider(n.Routing, n.Blockstore)
+	go n.Reprovider.ProvideEvery(ctx, time.Hour*12)
 	return nil
 }
 

exchange/reprovide/reprovide.go

@@ -0,0 +1,71 @@
+package reprovide
+
+import (
+	"time"
+
+	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
+	backoff "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/cenkalti/backoff"
+
+	blocks "github.com/jbenet/go-ipfs/blocks/blockstore"
+	routing "github.com/jbenet/go-ipfs/routing"
+	debugerror "github.com/jbenet/go-ipfs/util/debugerror"
+	eventlog "github.com/jbenet/go-ipfs/util/eventlog"
+)
+
+var log = eventlog.Logger("reprovider")
+
+type Reprovider struct {
+	// The routing system to provide values through
+	rsys routing.IpfsRouting
+
+	// The backing store for blocks to be provided
+	bstore blocks.Blockstore
+}
+
+func NewReprovider(rsys routing.IpfsRouting, bstore blocks.Blockstore) *Reprovider {
+	return &Reprovider{
+		rsys:   rsys,
+		bstore: bstore,
+	}
+}
+
+func (rp *Reprovider) ProvideEvery(ctx context.Context, tick time.Duration) {
+	after := time.After(0)
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-after:
+			err := rp.Reprovide(ctx)
+			if err != nil {
+				log.Error(err)
+			}
+			after = time.After(tick)
+		}
+	}
+}
+
+func (rp *Reprovider) Reprovide(ctx context.Context) error {
+	keychan, err := rp.bstore.AllKeysChan(ctx, 0, 1<<16)
+	if err != nil {
+		return debugerror.Errorf("Failed to get key chan from blockstore: %s", err)
+	}
+	for k := range keychan {
+		op := func() error {
+			err := rp.rsys.Provide(ctx, k)
+			if err != nil {
+				log.Warningf("Failed to provide key: %s", err)
+			}
+			return err
+		}
+
+		// TODO: this backoff library does not respect our context, we should
+		// eventually work contexts into it. low priority.
+		err := backoff.Retry(op, backoff.NewExponentialBackOff())
+		if err != nil {
+			log.Errorf("Providing failed after number of retries: %s", err)
+			return err
+		}
+	}
+	return nil
+}

exchange/reprovide/reprovide_test.go

@@ -0,0 +1,53 @@
+package reprovide_test
+
+import (
+	"testing"
+
+	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
+	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
+	dssync "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/sync"
+
+	blocks "github.com/jbenet/go-ipfs/blocks"
+	blockstore "github.com/jbenet/go-ipfs/blocks/blockstore"
+	mock "github.com/jbenet/go-ipfs/routing/mock"
+	testutil "github.com/jbenet/go-ipfs/util/testutil"
+
+	. "github.com/jbenet/go-ipfs/exchange/reprovide"
+)
+
+func TestReprovide(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	mrserv := mock.NewServer()
+
+	idA := testutil.RandIdentityOrFatal(t)
+	idB := testutil.RandIdentityOrFatal(t)
+
+	clA := mrserv.Client(idA)
+	clB := mrserv.Client(idB)
+
+	bstore := blockstore.NewBlockstore(dssync.MutexWrap(ds.NewMapDatastore()))
+
+	blk := blocks.NewBlock([]byte("this is a test"))
+	bstore.Put(blk)
+
+	reprov := NewReprovider(clA, bstore)
+	err := reprov.Reprovide(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	provs, err := clB.FindProviders(ctx, blk.Key())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(provs) == 0 {
+		t.Fatal("Should have gotten a provider")
+	}
+
+	if provs[0].ID != idA.ID() {
+		t.Fatal("Somehow got the wrong peer back as a provider.")
+	}
+}