Add custom String() formatter to Membership

Close hashicorp#167: Make the stats into a real structure

api.go

@@ -960,7 +960,7 @@ func (s *Stats) Strings() []struct{ K, V string } {
 		{"fsm_pending", toString(uint64(s.FSMPending))},
 		{"last_snapshot_index", toString(uint64(s.LastSnapshotIndex))},
 		{"last_snapshot_term", toString(uint64(s.LastSnapshotTerm))},
-		{"latest_membership", fmt.Sprintf("%+v", s.LatestMembership.Servers)},
+		{"latest_membership", fmt.Sprintf("%v", s.LatestMembership)},
 		{"latest_membership_index", toString(uint64(s.LatestMembershipIndex))},
 		{"last_contact", lastContact},
 		{"num_peers", toString(uint64(s.NumPeers))},

api_test.go

@@ -1,9 +1,13 @@
 package raft
 
-import "testing"
+import (
+	"fmt"
+	"testing"
+)
 
 func TestAPI_Stats(t *testing.T) {
 	c := MakeCluster(1, t, nil)
+	defer c.Close()
 	future := c.rafts[0].Stats()
 	if err := future.Error(); err != nil {
 		c.FailNowf("Stats() returned err %v", err)
@@ -12,5 +16,34 @@ func TestAPI_Stats(t *testing.T) {
 	if s.LastLogTerm != 1 {
 		c.FailNowf("stats.LastLogTerm expected 1, got %v", s.LastLogTerm)
 	}
-	c.Close()
+}
+
+func TestAPI_Stats_membershipFormatting(t *testing.T) {
+	c := MakeCluster(1, t, nil)
+	defer c.Close()
+	c.GetInState(Leader)
+	addFuture := c.rafts[0].AddNonvoter("S2", "s2-addr", 0, 0)
+	err := addFuture.Error()
+	if err != nil {
+		c.FailNowf("AddNonvoter() returned err %v", err)
+	}
+
+	statsFuture := c.rafts[0].Stats()
+	err = statsFuture.Error()
+	if err != nil {
+		c.FailNowf("Stats() returned err %v", err)
+	}
+	s := statsFuture.Stats()
+	membership := "not found"
+	for _, kv := range s.Strings() {
+		if kv.K == "latest_membership" {
+			membership = kv.V
+		}
+	}
+	exp := fmt.Sprintf("[%v at %v (Voter), S2 at s2-addr (Nonvoter)]",
+		c.rafts[0].server.localID, c.rafts[0].server.localAddr)
+	if membership != exp {
+		c.Failf("membership not stringified correctly. Expected: '%s', got: '%s'",
+			exp, membership)
+	}
 }

membership.go

@@ -1,6 +1,9 @@
 package raft
 
-import "fmt"
+import (
+	"fmt"
+	"strings"
+)
 
 // Membership changes follow the single-server algorithm described in Diego
 // Ongaro's PhD dissertation. The Membership struct defines a cluster membership
@@ -85,6 +88,15 @@ type Membership struct {
 	Servers []Server
 }
 
+func (m Membership) String() string {
+	vec := make([]string, 0, len(m.Servers))
+	for _, server := range m.Servers {
+		vec = append(vec, fmt.Sprintf("%s at %s (%s)",
+			server.ID, server.Address, server.Suffrage))
+	}
+	return fmt.Sprintf("[%s]", strings.Join(vec, ", "))
+}
+
 // Clone makes a deep copy of a Membership.
 func (m *Membership) Clone() (copy Membership) {
 	copy.Servers = append(copy.Servers, m.Servers...)