Make some final tweaks to autopilot package

agent/consul/autopilot/autopilot.go

@@ -143,6 +143,14 @@ func NumPeers(raftConfig raft.Configuration) int {
 	return numPeers
 }
 
+// RemoveDeadServers triggers a pruning of dead servers in a non-blocking way.
+func (a *Autopilot) RemoveDeadServers() {
+	select {
+	case a.removeDeadCh <- struct{}{}:
+	default:
+	}
+}
+
 // pruneDeadServers removes up to numPeers/2 failed servers
 func (a *Autopilot) pruneDeadServers() error {
 	conf := a.delegate.AutopilotConfig()
@@ -223,14 +231,17 @@ func (a *Autopilot) pruneDeadServers() error {
 
 // MinRaftProtocol returns the lowest supported Raft protocol among alive servers
 func (a *Autopilot) MinRaftProtocol() (int, error) {
+	return minRaftProtocol(a.delegate.Serf().Members(), a.delegate.IsServer)
+}
+
+func minRaftProtocol(members []serf.Member, serverFunc func(serf.Member) (*ServerInfo, error)) (int, error) {
 	minVersion := -1
-	members := a.delegate.Serf().Members()
 	for _, m := range members {
 		if m.Status != serf.StatusAlive {
 			continue
 		}
 
-		server, err := a.delegate.IsServer(m)
+		server, err := serverFunc(m)
 		if err != nil {
 			return -1, err
 		}

agent/consul/autopilot/autopilot_test.go

@@ -0,0 +1,86 @@
+package autopilot
+
+import (
+	"errors"
+	"net"
+	"testing"
+
+	"github.com/hashicorp/serf/serf"
+)
+
+func TestMinRaftProtocol(t *testing.T) {
+	t.Parallel()
+	makeMember := func(version string) serf.Member {
+		return serf.Member{
+			Name: "foo",
+			Addr: net.IP([]byte{127, 0, 0, 1}),
+			Tags: map[string]string{
+				"role":     "consul",
+				"dc":       "dc1",
+				"port":     "10000",
+				"vsn":      "1",
+				"raft_vsn": version,
+			},
+			Status: serf.StatusAlive,
+		}
+	}
+
+	cases := []struct {
+		members  []serf.Member
+		expected int
+		err      error
+	}{
+		// No servers, error
+		{
+			members:  []serf.Member{},
+			expected: -1,
+			err:      errors.New("No servers found"),
+		},
+		// One server
+		{
+			members: []serf.Member{
+				makeMember("1"),
+			},
+			expected: 1,
+		},
+		// One server, bad version formatting
+		{
+			members: []serf.Member{
+				makeMember("asdf"),
+			},
+			expected: -1,
+			err:      errors.New(`strconv.Atoi: parsing "asdf": invalid syntax`),
+		},
+		// Multiple servers, different versions
+		{
+			members: []serf.Member{
+				makeMember("1"),
+				makeMember("2"),
+			},
+			expected: 1,
+		},
+		// Multiple servers, same version
+		{
+			members: []serf.Member{
+				makeMember("2"),
+				makeMember("2"),
+			},
+			expected: 2,
+		},
+	}
+
+	serverFunc := func(m serf.Member) (*ServerInfo, error) {
+		return &ServerInfo{}, nil
+	}
+	for _, tc := range cases {
+		result, err := minRaftProtocol(tc.members, serverFunc)
+		if result != tc.expected {
+			t.Fatalf("bad: %v, %v, %v", result, tc.expected, tc)
+		}
+		if tc.err != nil {
+			if err == nil || tc.err.Error() != err.Error() {
+				t.Fatalf("bad: %v, %v, %v", err, tc.err, tc)
+			}
+		}
+	}
+}

agent/consul/leader.go

@@ -738,10 +738,7 @@ func (s *Server) joinConsulServer(m serf.Member, parts *metadata.Server) error {
 	}
 
 	// Trigger a check to remove dead servers
-	select {
-	case s.autopilotRemoveDeadCh <- struct{}{}:
-	default:
-	}
+	s.autopilot.RemoveDeadServers()
 
 	return nil
 }

agent/consul/server.go

@@ -90,12 +90,6 @@ type Server struct {
 	// autopilot is the Autopilot instance for this server.
 	autopilot *autopilot.Autopilot
 
-	// autopilotRemoveDeadCh is used to trigger a check for dead server removals.
-	autopilotRemoveDeadCh chan struct{}
-
-	// autopilotShutdownCh is used to stop the Autopilot loop.
-	autopilotShutdownCh chan struct{}
-
 	// autopilotWaitGroup is used to block until Autopilot shuts down.
 	autopilotWaitGroup sync.WaitGroup
 
@@ -281,8 +275,6 @@ func NewServerLogger(config *Config, logger *log.Logger, tokens *token.Store) (*
 
 	// Create server.
 	s := &Server{
-		autopilotRemoveDeadCh: make(chan struct{}),
-		autopilotShutdownCh:   make(chan struct{}),
 		config:           config,
 		tokens:           tokens,
 		connPool:         connPool,