From 9e2557c53c81a8f47baaebf9604754b6a61562e2 Mon Sep 17 00:00:00 2001
From: Sean Chittenden <sean@chittenden.org>
Date: Wed, 1 Feb 2017 10:27:04 -0800
Subject: [PATCH] Re-cherry-pick 71d807f607589f2eb4fea4e83e3876d122c8afc0 and
 e2320d69b6b155d8223758415aabafc60a0e9d3b.

---
 command/agent/agent.go | 46 +++++++++++++++++++++++++++++++++++++-----
 1 file changed, 41 insertions(+), 5 deletions(-)

diff --git a/command/agent/agent.go b/command/agent/agent.go
index 6f3171782..1d420e9ab 100644
--- a/command/agent/agent.go
+++ b/command/agent/agent.go
@@ -27,6 +27,7 @@ import (
 	"github.com/hashicorp/go-uuid"
 	"github.com/hashicorp/serf/coordinate"
 	"github.com/hashicorp/serf/serf"
+	"github.com/shirou/gopsutil/host"
 )
 
 const (
@@ -593,6 +594,43 @@ func (a *Agent) setupClient() error {
 	return nil
 }
 
+// makeRandomID will generate a random UUID for a node.
+func (a *Agent) makeRandomID() (string, error) {
+	id, err := uuid.GenerateUUID()
+	if err != nil {
+		return "", err
+	}
+
+	a.logger.Printf("[DEBUG] Using random ID %q as node ID", id)
+	return id, nil
+}
+
+// makeNodeID will try to find a host-specific ID, or else will generate a
+// random ID. The returned ID will always be formatted as a GUID. We don't tell
+// the caller whether this ID is random or stable since the consequences are
+// high for us if this changes, so we will persist it either way. This will let
+// gopsutil change implementations without affecting in-place upgrades of nodes.
+func (a *Agent) makeNodeID() (string, error) {
+	// Try to get a stable ID associated with the host itself.
+	info, err := host.Info()
+	if err != nil {
+		a.logger.Printf("[DEBUG] Couldn't get a unique ID from the host: %v", err)
+		return a.makeRandomID()
+	}
+
+	// Make sure the host ID parses as a UUID, since we don't have complete
+	// control over this process.
+	id := strings.ToLower(info.HostID)
+	if _, err := uuid.ParseUUID(id); err != nil {
+		a.logger.Printf("[DEBUG] Unique ID %q from host isn't formatted as a UUID: %v",
+			id, err)
+		return a.makeRandomID()
+	}
+
+	a.logger.Printf("[DEBUG] Using unique ID %q from host as node ID", id)
+	return id, nil
+}
+
 // setupNodeID will pull the persisted node ID, if any, or create a random one
 // and persist it.
 func (a *Agent) setupNodeID(config *Config) error {
@@ -606,15 +644,14 @@ func (a *Agent) setupNodeID(config *Config) error {
 		return nil
 	}
 
-	// For dev mode we have no filesystem access so just make a GUID.
+	// For dev mode we have no filesystem access so just make one.
 	if a.config.DevMode {
-		id, err := uuid.GenerateUUID()
+		id, err := a.makeNodeID()
 		if err != nil {
 			return err
 		}
 
 		config.NodeID = types.NodeID(id)
-		a.logger.Printf("[INFO] agent: Generated unique node ID %q for this agent (will not be persisted in dev mode)", config.NodeID)
 		return nil
 	}
 
@@ -637,7 +674,7 @@ func (a *Agent) setupNodeID(config *Config) error {
 
 	// If we still don't have a valid node ID, make one.
 	if config.NodeID == "" {
-		id, err := uuid.GenerateUUID()
+		id, err := a.makeNodeID()
 		if err != nil {
 			return err
 		}
@@ -649,7 +686,6 @@ func (a *Agent) setupNodeID(config *Config) error {
 		}
 
 		config.NodeID = types.NodeID(id)
-		a.logger.Printf("[INFO] agent: Generated unique node ID %q for this agent (persisted)", config.NodeID)
 	}
 	return nil
 }