From 405ec78f42abd6be630a1208ce6822d70458d442 Mon Sep 17 00:00:00 2001
From: Ben Johnson <benbjohnson@yahoo.com>
Date: Wed, 10 Jun 2015 23:40:20 -0600
Subject: [PATCH] Limit cluster to 3 nodes

This commit restricts the maximum number of nodes in a cluster to 3.

Fixes #2750
---
 CHANGELOG.md       |  1 +
 meta/errors.go     |  3 +++
 meta/store.go      |  6 ++++++
 meta/store_test.go | 11 +++++++++++
 4 files changed, 21 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 26e62161923..e7f43e192df 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
 - [#2886](https://github.com/influxdb/influxdb/issues/2886): Refactor backup & restore
 - [#2804](https://github.com/influxdb/influxdb/pull/2804): BREAKING: change time literals to be single quoted in InfluxQL. Thanks @nvcook42!
 - [#2906](https://github.com/influxdb/influxdb/pull/2906): Restrict replication factor to the cluster size
+- [#2905](https://github.com/influxdb/influxdb/pull/2905): Restrict clusters to 3 peers
 
 ## v0.9.0-rc33 [2015-06-09]
 
diff --git a/meta/errors.go b/meta/errors.go
index 1c4b7e7f8bd..b7698a51179 100644
--- a/meta/errors.go
+++ b/meta/errors.go
@@ -8,6 +8,9 @@ var (
 
 	// ErrStoreClosed is returned when closing an already closed store.
 	ErrStoreClosed = errors.New("raft store already closed")
+
+	// ErrTooManyPeers is returned when more than 3 peers are used.
+	ErrTooManyPeers = errors.New("too many peers; influxdb v0.9.0 is limited to 3 nodes in a cluster")
 )
 
 var (
diff --git a/meta/store.go b/meta/store.go
index 03a1f056820..8afed939e03 100644
--- a/meta/store.go
+++ b/meta/store.go
@@ -129,6 +129,12 @@ func (s *Store) IDPath() string { return filepath.Join(s.path, "id") }
 
 // Open opens and initializes the raft store.
 func (s *Store) Open() error {
+	// Verify that no more than 3 peers.
+	// https://github.com/influxdb/influxdb/issues/2750
+	if len(s.peers) > 3 {
+		return ErrTooManyPeers
+	}
+
 	// Verify listeners are set.
 	if s.RaftListener == nil {
 		panic("Store.RaftListener not set")
diff --git a/meta/store_test.go b/meta/store_test.go
index 99cc9da880d..6e17a55f219 100644
--- a/meta/store_test.go
+++ b/meta/store_test.go
@@ -36,6 +36,17 @@ func TestStore_Open_ErrStoreOpen(t *testing.T) {
 	}
 }
 
+// Ensure that opening a store with more than 3 peers returns an error.
+func TestStore_Open_ErrTooManyPeers(t *testing.T) {
+	t.Parallel()
+	config := NewConfig(MustTempFile())
+	config.Peers = []string{"localhost:9000", "localhost:9001", "localhost:9002", "localhost:9003"}
+	s := NewStore(config)
+	if err := s.Open(); err != meta.ErrTooManyPeers {
+		t.Fatalf("unexpected error: %s", err)
+	}
+}
+
 // Ensure the store can create a new node.
 func TestStore_CreateNode(t *testing.T) {
 	t.Parallel()