consul: allow returning custom error for merge delegate

consul/client.go

@@ -139,7 +139,7 @@ func (c *Client) setupSerf(conf *serf.Config, ch chan serf.Event, path string) (
 	conf.SnapshotPath = filepath.Join(c.config.DataDir, path)
 	conf.ProtocolVersion = protocolVersionMap[c.config.ProtocolVersion]
 	conf.RejoinAfterLeave = c.config.RejoinAfterLeave
-	conf.Merge = &lanMergeDelegate{logger: c.logger, dc: c.config.Datacenter}
+	conf.Merge = &lanMergeDelegate{dc: c.config.Datacenter}
 	if err := ensurePath(conf.SnapshotPath, false); err != nil {
 		return nil, err
 	}

consul/merge.go

@@ -1,7 +1,7 @@
 package consul
 
 import (
-	"log"
+	"fmt"
 
 	"github.com/hashicorp/serf/serf"
 )
@@ -10,47 +10,41 @@ import (
 // ring. We check that the peers are in the same datacenter and abort the
 // merge if there is a mis-match.
 type lanMergeDelegate struct {
-	logger *log.Logger
 	dc string
 }
 
-func (md *lanMergeDelegate) NotifyMerge(members []*serf.Member) (cancel bool) {
+func (md *lanMergeDelegate) NotifyMerge(members []*serf.Member) error {
 	for _, m := range members {
 		ok, dc := isConsulNode(*m)
 		if ok {
 			if dc != md.dc {
-				md.logger.Printf("[WARN] consul: Canceling cluster merge, member '%s' part of wrong datacenter '%s'",
+				return fmt.Errorf("Member '%s' part of wrong datacenter '%s'",
 					m.Name, dc)
-				return true
 			}
 			continue
 		}
 
 		ok, parts := isConsulServer(*m)
 		if ok && parts.Datacenter != md.dc {
-			md.logger.Printf("[WARN] consul: Canceling cluster merge, member '%s' part of wrong datacenter '%s'",
+			return fmt.Errorf("Member '%s' part of wrong datacenter '%s'",
 				m.Name, parts.Datacenter)
-			return true
 		}
 	}
-	return false
+	return nil
 }
 
 // wanMergeDelegate is used to handle a cluster merge on the WAN gossip
 // ring. We check that the peers are server nodes and abort the merge
 // otherwise.
 type wanMergeDelegate struct {
-	logger *log.Logger
 }
 
-func (md *wanMergeDelegate) NotifyMerge(members []*serf.Member) (cancel bool) {
+func (md *wanMergeDelegate) NotifyMerge(members []*serf.Member) error {
 	for _, m := range members {
 		ok, _ := isConsulServer(*m)
 		if !ok {
-			md.logger.Printf("[WARN] consul: Canceling cluster merge, member '%s' is not a server",
-				m.Name)
-			return true
+			return fmt.Errorf("Member '%s' is not a server", m.Name)
 		}
 	}
-	return false
+	return nil
 }

consul/server.go

@@ -311,9 +311,9 @@ func (s *Server) setupSerf(conf *serf.Config, ch chan serf.Event, path string, w
 	conf.ProtocolVersion = protocolVersionMap[s.config.ProtocolVersion]
 	conf.RejoinAfterLeave = s.config.RejoinAfterLeave
 	if wan {
-		conf.Merge = &wanMergeDelegate{logger: s.logger}
+		conf.Merge = &wanMergeDelegate{}
 	} else {
-		conf.Merge = &lanMergeDelegate{logger: s.logger, dc: s.config.Datacenter}
+		conf.Merge = &lanMergeDelegate{dc: s.config.Datacenter}
 	}
 
 	// Until Consul supports this fully, we disable automatic resolution.