Changes host-based node IDs from opt-out to opt-in. (#3187)

agent/agent.go

@@ -940,7 +940,7 @@ func (a *Agent) makeRandomID() (string, error) {
 // gopsutil change implementations without affecting in-place upgrades of nodes.
 func (a *Agent) makeNodeID() (string, error) {
 	// If they've disabled host-based IDs then just make a random one.
-	if a.config.DisableHostNodeID {
+	if *a.config.DisableHostNodeID {
 		return a.makeRandomID()
 	}
 

agent/agent_test.go

@@ -306,24 +306,34 @@ func TestAgent_makeNodeID(t *testing.T) {
 		t.Fatalf("err: %v", err)
 	}
 
-	// Calling again should yield the same ID since it's host-based.
+	// Calling again should yield a random ID by default.
 	another, err := a.makeNodeID()
 	if err != nil {
 		t.Fatalf("err: %v", err)
 	}
-	if id != another {
+	if id == another {
 		t.Fatalf("bad: %s vs %s", id, another)
 	}
 
-	// Turn off host-based IDs and try again. We should get a random ID.
-	a.Config.DisableHostNodeID = true
-	another, err = a.makeNodeID()
+	// Turn on host-based IDs and try again. We should get the same ID
+	// each time (and a different one from the random one above).
+	a.Config.DisableHostNodeID = Bool(false)
+	id, err = a.makeNodeID()
 	if err != nil {
 		t.Fatalf("err: %v", err)
 	}
 	if id == another {
 		t.Fatalf("bad: %s vs %s", id, another)
 	}
+
+	// Calling again should yield the host-based ID.
+	another, err = a.makeNodeID()
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if id != another {
+		t.Fatalf("bad: %s vs %s", id, another)
+	}
 }
 
 func TestAgent_AddService(t *testing.T) {

agent/config.go

@@ -402,7 +402,7 @@ type Config struct {
 	// DisableHostNodeID will prevent Consul from using information from the
 	// host to generate a node ID, and will cause Consul to generate a
 	// random ID instead.
-	DisableHostNodeID bool `mapstructure:"disable_host_node_id"`
+	DisableHostNodeID *bool `mapstructure:"disable_host_node_id"`
 
 	// Node name is the name we use to advertise. Defaults to hostname.
 	NodeName string `mapstructure:"node_name"`
@@ -959,6 +959,8 @@ func DefaultConfig() *Config {
 
 		EncryptVerifyIncoming: Bool(true),
 		EncryptVerifyOutgoing: Bool(true),
+
+		DisableHostNodeID: Bool(true),
 	}
 }
 
@@ -1616,7 +1618,7 @@ func MergeConfig(a, b *Config) *Config {
 	if b.NodeID != "" {
 		result.NodeID = b.NodeID
 	}
-	if b.DisableHostNodeID == true {
+	if b.DisableHostNodeID != nil {
 		result.DisableHostNodeID = b.DisableHostNodeID
 	}
 	if b.NodeName != "" {

agent/config_test.go

@@ -242,8 +242,8 @@ func TestDecodeConfig(t *testing.T) {
 			c:  &Config{DisableCoordinates: true},
 		},
 		{
-			in: `{"disable_host_node_id":true}`,
-			c:  &Config{DisableHostNodeID: true},
+			in: `{"disable_host_node_id":false}`,
+			c:  &Config{DisableHostNodeID: Bool(false)},
 		},
 		{
 			in: `{"dns_config":{"allow_stale":true}}`,
@@ -1305,7 +1305,7 @@ func TestMergeConfig(t *testing.T) {
 		Domain:            "other",
 		LogLevel:          "info",
 		NodeID:            "bar",
-		DisableHostNodeID: true,
+		DisableHostNodeID: Bool(false),
 		NodeName:          "baz",
 		ClientAddr:        "127.0.0.2",
 		BindAddr:          "127.0.0.2",

command/agent.go

@@ -79,10 +79,13 @@ func (cmd *AgentCommand) readConfig() *agent.Config {
 	f.StringVar((*string)(&cmdCfg.NodeID), "node-id", "",
 		"A unique ID for this node across space and time. Defaults to a randomly-generated ID"+
 			" that persists in the data-dir.")
-	f.BoolVar(&cmdCfg.DisableHostNodeID, "disable-host-node-id", false,
+
+	var disableHostNodeID configutil.BoolValue
+	f.Var(&disableHostNodeID, "disable-host-node-id",
 		"Setting this to true will prevent Consul from using information from the"+
 			" host to generate a node ID, and will cause Consul to generate a"+
 			" random node ID instead.")
+
 	f.StringVar(&cmdCfg.Datacenter, "datacenter", "", "Datacenter of the agent.")
 	f.StringVar(&cmdCfg.DataDir, "data-dir", "", "Path to a data directory to store agent state.")
 	f.BoolVar(&cmdCfg.EnableUI, "ui", false, "Enables the built-in static web UI server.")
@@ -238,6 +241,7 @@ func (cmd *AgentCommand) readConfig() *agent.Config {
 	cmdCfg.DNSRecursors = append(cmdCfg.DNSRecursors, dnsRecursors...)
 
 	cfg = agent.MergeConfig(cfg, &cmdCfg)
+	disableHostNodeID.Merge(cfg.DisableHostNodeID)
 
 	if cfg.NodeName == "" {
 		hostname, err := os.Hostname()

command/agent_test.go

@@ -291,6 +291,48 @@ func TestReadCliConfig(t *testing.T) {
 	}
 }
 
+func TestAgent_HostBasedIDs(t *testing.T) {
+	t.Parallel()
+	tmpDir := testutil.TempDir(t, "consul")
+	defer os.RemoveAll(tmpDir)
+
+	shutdownCh := make(chan struct{})
+	defer close(shutdownCh)
+
+	// Host-based IDs are disabled by default.
+	{
+		cmd := &AgentCommand{
+			args: []string{
+				"-data-dir", tmpDir,
+			},
+			ShutdownCh:  shutdownCh,
+			BaseCommand: baseCommand(cli.NewMockUi()),
+		}
+
+		config := cmd.readConfig()
+		if *config.DisableHostNodeID != true {
+			t.Fatalf("expected host-based node IDs to be disabled")
+		}
+	}
+
+	// Try enabling host-based IDs.
+	{
+		cmd := &AgentCommand{
+			args: []string{
+				"-data-dir", tmpDir,
+				"-disable-host-node-id=false",
+			},
+			ShutdownCh:  shutdownCh,
+			BaseCommand: baseCommand(cli.NewMockUi()),
+		}
+
+		config := cmd.readConfig()
+		if *config.DisableHostNodeID != false {
+			t.Fatalf("expected host-based node IDs to be enabled")
+		}
+	}
+}
+
 func TestRetryJoinFail(t *testing.T) {
 	t.Skip("fs: skipping tests that use cmd.Run until signal handling is fixed")
 	t.Parallel()

website/source/docs/agent/options.html.md

@@ -141,7 +141,11 @@ will exit with an error at startup.
 * <a name="_disable_host_node_id"></a><a href="#_disable_host_node_id">`-disable-host-node-id`</a> - Setting
   this to true will prevent Consul from using information from the host to generate a deterministic node ID,
   and will instead generate a random node ID which will be persisted in the data directory. This is useful
-  when running multiple Consul agents on the same host for testing. This defaults to false.
+  when running multiple Consul agents on the same host for testing. This defaults to false in Consul prior
+  to version 0.8.5 and in 0.8.5 and later defaults to true, so you must opt-in for host-based IDs. Host-based
+  IDs are generated using https://github.com/shirou/gopsutil/tree/master/host, which is shared with HashiCorp's
+  [Nomad](https://www.nomadproject.io/), so if you opt-in to host-based IDs then Consul and Nomad will use
+  information on the host to automatically assign the same ID in both systems.
 
 * <a name="_dns_port"></a><a href="#_dns_port">`-dns-port`</a> - the DNS port to listen on.
   This overrides the default port 8600. This is available in Consul 0.7 and later.