From 3d91faf85a81b369f219ca9694491bc44dde7627 Mon Sep 17 00:00:00 2001
From: Ben Darnell <bdarnell@squareup.com>
Date: Fri, 5 Dec 2014 15:35:39 -0500
Subject: [PATCH 1/2] Pre-apply the bootstrapping ConfChange entries.

This eliminates the need to fake an ApplyConfChange call before Campaign
in tests.

Fixes #1856.
---
 raft/node.go      | 12 ++++++++++++
 raft/node_test.go |  2 --
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/raft/node.go b/raft/node.go
index 83f788a44..b0d0ab6a5 100644
--- a/raft/node.go
+++ b/raft/node.go
@@ -150,6 +150,18 @@ func StartNode(id uint64, peers []Peer, election, heartbeat int, storage Storage
 	// TODO(bdarnell): These entries are still unstable; do we need to preserve
 	// the invariant that committed < unstable?
 	r.raftLog.committed = r.raftLog.lastIndex()
+	// Now apply them, mainly so that the application can call Campaign
+	// immediately after StartNode in tests. Note that these nodes will
+	// be added to raft twice: here and when the application's Ready
+	// loop calls ApplyConfChange. The calls to addNode must come after
+	// all calls to raftLog.append so progress.next is set after these
+	// bootstrapping entries (it is an error if we try to append these
+	// entries since they have already been committed).
+	// We do not set raftLog.applied so the application will be able
+	// to observe all conf changes via Ready.CommittedEntries.
+	for _, peer := range peers {
+		r.addNode(peer.ID)
+	}
 
 	go n.run(r)
 	return &n
diff --git a/raft/node_test.go b/raft/node_test.go
index 52fcfa15e..1617dc110 100644
--- a/raft/node_test.go
+++ b/raft/node_test.go
@@ -324,7 +324,6 @@ func TestNodeStart(t *testing.T) {
 	}
 	storage := NewMemoryStorage()
 	n := StartNode(1, []Peer{{ID: 1}}, 10, 1, storage)
-	n.ApplyConfChange(cc)
 	n.Campaign(ctx)
 	g := <-n.Ready()
 	if !reflect.DeepEqual(g, wants[0]) {
@@ -421,7 +420,6 @@ func TestNodeAdvance(t *testing.T) {
 
 	storage := NewMemoryStorage()
 	n := StartNode(1, []Peer{{ID: 1}}, 10, 1, storage)
-	n.ApplyConfChange(raftpb.ConfChange{Type: raftpb.ConfChangeAddNode, NodeID: 1})
 	n.Campaign(ctx)
 	<-n.Ready()
 	n.Propose(ctx, []byte("foo"))

From ea4d645a83b70979f1892199be1b4a5d6dd1f7fa Mon Sep 17 00:00:00 2001
From: Ben Darnell <bdarnell@squareup.com>
Date: Fri, 5 Dec 2014 17:15:50 -0500
Subject: [PATCH 2/2] raft: Ignore redundant addNode calls.

This avoids clobbering any state when bootstrapping entries are
applied twice.
---
 raft/raft.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/raft/raft.go b/raft/raft.go
index a6e93ece8..8531df47b 100644
--- a/raft/raft.go
+++ b/raft/raft.go
@@ -472,6 +472,12 @@ func (r *raft) handleSnapshot(m pb.Message) {
 func (r *raft) resetPendingConf() { r.pendingConf = false }
 
 func (r *raft) addNode(id uint64) {
+	if _, ok := r.prs[id]; ok {
+		// Ignore any redundant addNode calls (which can happen because the
+		// initial bootstrapping entries are applied twice).
+		return
+	}
+
 	r.setProgress(id, 0, r.raftLog.lastIndex()+1)
 	r.pendingConf = false
 }