From d8ac330589e46858857f4394e2760ed8b565aaab Mon Sep 17 00:00:00 2001
From: Tom Wilkie <tom@weave.works>
Date: Wed, 9 Sep 2015 09:56:39 +0000
Subject: [PATCH] Backoff on failed report pushes.

---
 xfer/publisher.go | 34 ++++++++++++++++++++++++++++++----
 1 file changed, 30 insertions(+), 4 deletions(-)

diff --git a/xfer/publisher.go b/xfer/publisher.go
index 015cd01057..1eb1fcdd26 100644
--- a/xfer/publisher.go
+++ b/xfer/publisher.go
@@ -10,10 +10,16 @@ import (
 	"net/url"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/weaveworks/scope/report"
 )
 
+const (
+	initialBackoff = 1 * time.Second
+	maxBackoff     = 60 * time.Second
+)
+
 // Publisher is something which can send a report to a remote collector.
 type Publisher interface {
 	Publish(report.Report) error
@@ -52,6 +58,10 @@ func NewHTTPPublisher(target, token, id string) (*HTTPPublisher, error) {
 	}, nil
 }
 
+func (p HTTPPublisher) String() string {
+	return p.url
+}
+
 // Publish publishes the report to the URL.
 func (p HTTPPublisher) Publish(rpt report.Report) error {
 	gzbuf := bytes.Buffer{}
@@ -99,6 +109,7 @@ func AuthorizationHeader(token string) string {
 type BackgroundPublisher struct {
 	publisher Publisher
 	reports   chan report.Report
+	quit      chan struct{}
 }
 
 // NewBackgroundPublisher creates a new BackgroundPublisher with the given publisher
@@ -106,15 +117,30 @@ func NewBackgroundPublisher(p Publisher) *BackgroundPublisher {
 	result := &BackgroundPublisher{
 		publisher: p,
 		reports:   make(chan report.Report),
+		quit:      make(chan struct{}),
 	}
 	go result.loop()
 	return result
 }
 
 func (b *BackgroundPublisher) loop() {
+	backoff := initialBackoff
+
 	for r := range b.reports {
-		if err := b.publisher.Publish(r); err != nil {
-			log.Printf("Error publishing: %v", err)
+		err := b.publisher.Publish(r)
+		if err == nil {
+			backoff = initialBackoff
+			continue
+		}
+
+		log.Printf("Error publishing to %s, backing off %s: %v", b.publisher, backoff, err)
+		select {
+		case <-time.After(backoff):
+		case <-b.quit:
+		}
+		backoff = backoff * 2
+		if backoff > maxBackoff {
+			backoff = maxBackoff
 		}
 	}
 }
@@ -123,15 +149,15 @@ func (b *BackgroundPublisher) loop() {
 func (b *BackgroundPublisher) Publish(r report.Report) error {
 	select {
 	case b.reports <- r:
-		return nil
 	default:
-		return fmt.Errorf("Dropping report - can't push fast enough")
 	}
+	return nil
 }
 
 // Stop implements Publisher
 func (b *BackgroundPublisher) Stop() {
 	close(b.reports)
+	close(b.quit)
 	b.publisher.Stop()
 }