From b3cda39b0bc4dcca88eafe172ed517f7c174b0aa Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Mon, 2 Nov 2015 18:01:40 +0000
Subject: [PATCH] Let IPAM pick any peer we know about to transfer ownership
 to, when shutting down

---
 ipam/allocator.go        | 16 ++++++++++++++--
 ipam/testutils_test.go   |  2 +-
 prog/weaver/main.go      |  3 ++-
 test/165_reset_2_test.sh | 22 ++++++++++++++++++++++
 4 files changed, 39 insertions(+), 4 deletions(-)
 create mode 100755 test/165_reset_2_test.sh

diff --git a/ipam/allocator.go b/ipam/allocator.go
index 04ad0cd9..958788cf 100644
--- a/ipam/allocator.go
+++ b/ipam/allocator.go
@@ -56,10 +56,11 @@ type Allocator struct {
 	paxosTicker      *time.Ticker
 	shuttingDown     bool // to avoid doing any requests while trying to shut down
 	now              func() time.Time
+	namesFunc        func() map[router.PeerName]struct{}
 }
 
 // NewAllocator creates and initialises a new Allocator
-func NewAllocator(ourName router.PeerName, ourUID router.PeerUID, ourNickname string, universe address.Range, quorum uint) *Allocator {
+func NewAllocator(ourName router.PeerName, ourUID router.PeerUID, ourNickname string, universe address.Range, quorum uint, names func() map[router.PeerName]struct{}) *Allocator {
 	return &Allocator{
 		ourName:   ourName,
 		universe:  universe,
@@ -68,6 +69,7 @@ func NewAllocator(ourName router.PeerName, ourUID router.PeerUID, ourNickname st
 		paxos:     paxos.NewNode(ourName, ourUID, quorum),
 		nicknames: map[router.PeerName]string{ourName: ourNickname},
 		now:       time.Now,
+		namesFunc: names,
 	}
 }
 
@@ -282,7 +284,17 @@ func (alloc *Allocator) Shutdown() {
 		alloc.shuttingDown = true
 		alloc.cancelOps(&alloc.pendingClaims)
 		alloc.cancelOps(&alloc.pendingAllocates)
-		if heir := alloc.ring.PickPeerForTransfer(); heir != router.UnknownPeerName {
+		heir := alloc.ring.PickPeerForTransfer()
+		if heir == router.UnknownPeerName && alloc.namesFunc != nil {
+			// No peers in the ring; pick one via the function we were given at init
+			for peerName := range alloc.namesFunc() {
+				if peerName != alloc.ourName {
+					heir = peerName
+					break
+				}
+			}
+		}
+		if heir != router.UnknownPeerName {
 			alloc.ring.Transfer(alloc.ourName, heir)
 			alloc.space.Clear()
 			alloc.gossip.GossipBroadcast(alloc.Gossip())
diff --git a/ipam/testutils_test.go b/ipam/testutils_test.go
index 95f6407a..ea954aa0 100644
--- a/ipam/testutils_test.go
+++ b/ipam/testutils_test.go
@@ -135,7 +135,7 @@ func makeAllocator(name string, cidrStr string, quorum uint) (*Allocator, addres
 	}
 
 	alloc := NewAllocator(peername, router.PeerUID(rand.Int63()),
-		"nick-"+name, cidr.Range(), quorum)
+		"nick-"+name, cidr.Range(), quorum, nil)
 
 	return alloc, cidr.HostRange()
 }
diff --git a/prog/weaver/main.go b/prog/weaver/main.go
index bf85b916..5444f2f4 100644
--- a/prog/weaver/main.go
+++ b/prog/weaver/main.go
@@ -368,7 +368,8 @@ func createAllocator(router *weave.Router, ipRangeStr string, defaultSubnetStr s
 			Log.Fatalf("IP address allocation default subnet %s does not overlap with allocation range %s", defaultSubnet, ipRange)
 		}
 	}
-	allocator := ipam.NewAllocator(router.Ourself.Peer.Name, router.Ourself.Peer.UID, router.Ourself.Peer.NickName, ipRange.Range(), quorum)
+	namesFunc := func() map[weave.PeerName]struct{} { return router.Peers.Names() }
+	allocator := ipam.NewAllocator(router.Ourself.Peer.Name, router.Ourself.Peer.UID, router.Ourself.Peer.NickName, ipRange.Range(), quorum, namesFunc)
 
 	allocator.SetInterfaces(router.NewGossip("IPallocation", allocator))
 	allocator.Start()
diff --git a/test/165_reset_2_test.sh b/test/165_reset_2_test.sh
new file mode 100755
index 00000000..cc4cdaed
--- /dev/null
+++ b/test/165_reset_2_test.sh
@@ -0,0 +1,22 @@
+#! /bin/bash
+
+. ./config.sh
+
+start_suite "Claiming addresses"
+
+weave_on $HOST1 launch-router
+weave_on $HOST2 launch-router $HOST1
+
+start_container $HOST1 --name=c1
+start_container $HOST2 --name=c2
+
+# Now reset the routers so they should give their space away, and restart
+weave_on $HOST1 reset
+weave_on $HOST1 launch-router $HOST2
+weave_on $HOST2 reset
+weave_on $HOST2 launch-router $HOST1
+
+# And try to start a container
+assert_raises "timeout 10 cat <( start_container $HOST1 )"
+
+end_suite