From eccb56ade0c856a7ce734ef8a38556aa3ac6db3a Mon Sep 17 00:00:00 2001
From: Pierre Souchay <p.souchay@criteo.com>
Date: Mon, 26 Mar 2018 16:44:13 +0200
Subject: [PATCH] Added support for renaming nodes when their IP does not
 change

---
 agent/consul/state/catalog.go      | 13 +++++++++++--
 agent/consul/state/catalog_test.go | 29 +++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/agent/consul/state/catalog.go b/agent/consul/state/catalog.go
index 38d59e810..819693484 100644
--- a/agent/consul/state/catalog.go
+++ b/agent/consul/state/catalog.go
@@ -355,9 +355,18 @@ func (s *Store) ensureNodeTxn(tx *memdb.Txn, idx uint64, node *structs.Node) err
 		if existing != nil {
 			n = existing.(*structs.Node)
 			if n.Node != node.Node {
-				return fmt.Errorf("node ID %q for node %q aliases existing node %q",
-					node.ID, node.Node, n.Node)
+				if n.Address != node.Address {
+					return fmt.Errorf("node ID %q for node %q (%s) aliases existing node %q (%s)",
+						node.ID, node.Node, node.Address, n.Node, n.Address)
+				}
+				fmt.Printf("Node renaming: %s VS %s -- idx=%d\n", node.Node, n.Node, idx)
+				err := s.deleteNodeTxn(tx, idx, n.Node)
+				if err != nil {
+					return fmt.Errorf("Error while renaming Node ID: %q from %s to %s",
+						node.ID, n.Node, node.Node)
+				}
 			}
+
 		}
 	}
 
diff --git a/agent/consul/state/catalog_test.go b/agent/consul/state/catalog_test.go
index 39cd81d60..03e0f1f48 100644
--- a/agent/consul/state/catalog_test.go
+++ b/agent/consul/state/catalog_test.go
@@ -476,6 +476,35 @@ func TestStateStore_EnsureNode(t *testing.T) {
 	if err == nil || !strings.Contains(err.Error(), "aliases existing node") {
 		t.Fatalf("err: %v", err)
 	}
+
+	// Renaming a node should work as long as IP did not change
+	in = &structs.Node{
+		Node:    "node1-renamed",
+		ID:      types.NodeID("cda916bc-a357-4a19-b886-59419fcee50c"),
+		Address: "1.1.1.2",
+	}
+	if err := s.EnsureNode(6, in); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Retrieve the node
+	idx, out, err = s.GetNode("node1")
+	if out != nil {
+		t.Fatalf("Node should not exist anymore: %q", out)
+	}
+
+	idx, out, err = s.GetNode("node1-renamed")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Node and indexes were updated
+	if out.CreateIndex != 1 || out.ModifyIndex != 6 || out.Address != "1.1.1.2" || out.Node != "node1-renamed" {
+		t.Fatalf("bad: %#v", out)
+	}
+	if idx != 6 {
+		t.Fatalf("bad index: %d", idx)
+	}
 }
 
 func TestStateStore_GetNodes(t *testing.T) {