Provides a JSON format for recovery when using server IDs.

peersjson.go

@@ -44,3 +44,55 @@ func ReadPeersJSON(path string) (Configuration, error) {
 	}
 	return configuration, nil
 }
+
+// configEntry is used when decoding a new-style peers.json.
+type configEntry struct {
+	// ID is the ID of the server (a UUID, usually).
+	ID ServerID `json:"id"`
+
+	// Address is the host:port of the server.
+	Address ServerAddress `json:"address"`
+
+	// NonVoter controls the suffrage. We choose this sense so people
+	// can leave this out and get a Voter by default.
+	NonVoter bool `json:"non_voter"`
+}
+
+// ReadConfigJSON reads a new-style peers.json and returns a configuration
+// structure. This can be used to perform manual recovery when running protocol
+// versions that use server IDs.
+func ReadConfigJSON(path string) (Configuration, error) {
+	// Read in the file.
+	buf, err := ioutil.ReadFile(path)
+	if err != nil {
+		return Configuration{}, err
+	}
+
+	// Parse it as JSON.
+	var peers []configEntry
+	dec := json.NewDecoder(bytes.NewReader(buf))
+	if err := dec.Decode(&peers); err != nil {
+		return Configuration{}, err
+	}
+
+	// Map it into the new-style configuration structure.
+	var configuration Configuration
+	for _, peer := range peers {
+		suffrage := Voter
+		if peer.NonVoter {
+			suffrage = Nonvoter
+		}
+		server := Server{
+			Suffrage: suffrage,
+			ID:       peer.ID,
+			Address:  peer.Address,
+		}
+		configuration.Servers = append(configuration.Servers, server)
+	}
+
+	// We should only ingest valid configurations.
+	if err := checkConfiguration(configuration); err != nil {
+		return Configuration{}, err
+	}
+	return configuration, nil
+}

peersjson_test.go

@@ -27,14 +27,18 @@ func TestPeersJSON_BadConfiguration(t *testing.T) {
 	}
 }
 
-func Test_PeersJSON(t *testing.T) {
+func TestPeersJSON_ReadPeersJSON(t *testing.T) {
 	base, err := ioutil.TempDir("", "")
 	if err != nil {
 		t.Fatalf("err: %v", err)
 	}
 	defer os.RemoveAll(base)
 
-	content := []byte("[\"127.0.0.1:123\", \"127.0.0.2:123\", \"127.0.0.3:123\"]")
+	content := []byte(`
+["127.0.0.1:123",
+ "127.0.0.2:123",
+ "127.0.0.3:123"]
+`)
 	peers := filepath.Join(base, "peers.json")
 	if err := ioutil.WriteFile(peers, content, 0666); err != nil {
 		t.Fatalf("err: %v", err)
@@ -68,3 +72,62 @@ func Test_PeersJSON(t *testing.T) {
 		t.Fatalf("bad configuration: %+v != %+v", configuration, expected)
 	}
 }
+
+func TestPeersJSON_ReadConfigJSON(t *testing.T) {
+	base, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	defer os.RemoveAll(base)
+
+	content := []byte(`
+[
+  {
+    "id": "adf4238a-882b-9ddc-4a9d-5b6758e4159e",
+    "address": "127.0.0.1:123",
+    "non_voter": false
+  },
+  {
+    "id": "8b6dda82-3103-11e7-93ae-92361f002671",
+    "address": "127.0.0.2:123"
+  },
+  {
+    "id": "97e17742-3103-11e7-93ae-92361f002671",
+    "address": "127.0.0.3:123",
+    "non_voter": true
+  }
+]
+`)
+	peers := filepath.Join(base, "peers.json")
+	if err := ioutil.WriteFile(peers, content, 0666); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	configuration, err := ReadConfigJSON(peers)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	expected := Configuration{
+		Servers: []Server{
+			Server{
+				Suffrage: Voter,
+				ID:       ServerID("adf4238a-882b-9ddc-4a9d-5b6758e4159e"),
+				Address:  ServerAddress("127.0.0.1:123"),
+			},
+			Server{
+				Suffrage: Voter,
+				ID:       ServerID("8b6dda82-3103-11e7-93ae-92361f002671"),
+				Address:  ServerAddress("127.0.0.2:123"),
+			},
+			Server{
+				Suffrage: Nonvoter,
+				ID:       ServerID("97e17742-3103-11e7-93ae-92361f002671"),
+				Address:  ServerAddress("127.0.0.3:123"),
+			},
+		},
+	}
+	if !reflect.DeepEqual(configuration, expected) {
+		t.Fatalf("bad configuration: %+v != %+v", configuration, expected)
+	}
+}