From 832fe2f0b06e7d4fd8a8fd4b336acf40b9b4998b Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Thu, 30 Nov 2017 19:47:31 +0000
Subject: [PATCH] Update local copy of annotations even after error

e.g. if we get a clash because someone else has updated the data, it
returns the new data so we should work off that next time.

Also re-fetch the Annotations every time round the main loop for safety.
---
 prog/kube-peers/annotations.go | 38 ++++++++++++++--------------------
 prog/kube-peers/main.go        |  3 +++
 2 files changed, 19 insertions(+), 22 deletions(-)

diff --git a/prog/kube-peers/annotations.go b/prog/kube-peers/annotations.go
index dd8b2db8..86915618 100644
--- a/prog/kube-peers/annotations.go
+++ b/prog/kube-peers/annotations.go
@@ -130,46 +130,40 @@ func (cml *configMapAnnotations) UpdatePeerList(list peerList) error {
 	return cml.UpdateAnnotation(KubePeersAnnotationKey, string(recordBytes))
 }
 
-func (cml *configMapAnnotations) UpdateAnnotation(key, value string) error {
+func (cml *configMapAnnotations) UpdateAnnotation(key, value string) (err error) {
 	if cml.cm == nil {
 		return errors.New("endpoint not initialized, call Init first")
 	}
-	cm := cml.cm
-	cm.Annotations[key] = value
-	cm, err := cml.Client.ConfigMaps(cml.Namespace).Update(cml.cm)
-	if err == nil {
-		cml.cm = cm
-	}
+	// speculatively change the state, then replace with whatever comes back
+	// from Update(), which will be the latest on the server whatever happened
+	cml.cm.Annotations[key] = value
+	cml.cm, err = cml.Client.ConfigMaps(cml.Namespace).Update(cml.cm)
 	return err
 }
 
-func (cml *configMapAnnotations) RemoveAnnotation(key string) error {
+func (cml *configMapAnnotations) RemoveAnnotation(key string) (err error) {
 	if cml.cm == nil {
 		return errors.New("endpoint not initialized, call Init first")
 	}
-	cm := cml.cm
-	delete(cm.Annotations, key)
-	cm, err := cml.Client.ConfigMaps(cml.Namespace).Update(cml.cm)
-	if err == nil {
-		cml.cm = cm
-	}
+	// speculatively change the state, then replace with whatever comes back
+	// from Update(), which will be the latest on the server whatever happened
+	delete(cml.cm.Annotations, key)
+	cml.cm, err = cml.Client.ConfigMaps(cml.Namespace).Update(cml.cm)
 	return err
 }
 
-func (cml *configMapAnnotations) RemoveAnnotationsWithValue(valueToRemove string) error {
+func (cml *configMapAnnotations) RemoveAnnotationsWithValue(valueToRemove string) (err error) {
 	if cml.cm == nil {
 		return errors.New("endpoint not initialized, call Init first")
 	}
-	cm := cml.cm
-	for key, value := range cm.Annotations {
+	// speculatively change the state, then replace with whatever comes back
+	// from Update(), which will be the latest on the server whatever happened
+	for key, value := range cml.cm.Annotations {
 		if value == valueToRemove {
-			delete(cm.Annotations, key)
+			delete(cml.cm.Annotations, key)
 		}
 	}
-	cm, err := cml.Client.ConfigMaps(cml.Namespace).Update(cml.cm)
-	if err == nil {
-		cml.cm = cm
-	}
+	cml.cm, err = cml.Client.ConfigMaps(cml.Namespace).Update(cml.cm)
 	return err
 }
 
diff --git a/prog/kube-peers/main.go b/prog/kube-peers/main.go
index 03a15225..1961f70c 100644
--- a/prog/kube-peers/main.go
+++ b/prog/kube-peers/main.go
@@ -98,6 +98,9 @@ func checkIamInPeerList(cml *configMapAnnotations, c *kubernetes.Clientset, peer
 // Kubernetes, remove it from Weave IPAM
 func reclaimRemovedPeers(weave *weaveapi.Client, cml *configMapAnnotations, nodes []nodeInfo, myPeerName string) error {
 	for {
+		if err := cml.Init(); err != nil {
+			return err
+		}
 		// 1. Compare peers stored in the peerList against all peers reported by k8s now.
 		storedPeerList, err := cml.GetPeerList()
 		if err != nil {