default raft protocol v2

command/agent/command.go

@@ -1203,7 +1203,7 @@ Server Options:
 
   -raft-protocol=<num>
     The Raft protocol version to use. Used for enabling certain Autopilot
-    features. Defaults to 3.
+    features. Defaults to 2.
 
   -retry-join=<address>
     Address of an agent to join at start time with retries enabled.

nomad/config.go

@@ -398,9 +398,8 @@ func DefaultConfig() *Config {
 	// Disable shutdown on removal
 	c.RaftConfig.ShutdownOnRemove = false
 
-	// Default to Raft v3 to enable new Raft and autopilot features.
-	// Compatible with v2 servers.
-	c.RaftConfig.ProtocolVersion = 3
+	// Default to Raft v2, update to v3 to enable new Raft and autopilot features.
+	c.RaftConfig.ProtocolVersion = 2
 
 	return c
 }

website/source/guides/operations/autopilot.html.md

@@ -14,7 +14,8 @@ servers, monitoring the state of the Raft cluster, and stable server introductio
 
 To enable Autopilot features (with the exception of dead server cleanup),
 the `raft_protocol` setting in the [server stanza](/docs/configuration/server.html)
-must be set to 3 on all servers. In Nomad 0.8 and 0.9 this setting defaults to 2; in Nomad 0.10 it will default to 3.
+must be set to 3 on all servers. This setting defaults to 2; a cluster configured with protocol 2 can be upgraded
+to protocol 3 with a rolling update, provided time for membership to stabilize following each server update.
 For more information, see the [Version Upgrade section](/guides/upgrade/upgrade-specific.html#raft-protocol-version-compatibility)
 on Raft Protocol versions.