Merge pull request #1 from fly-apps/only_primary_region_primary

Don't allow members outside primary region to become primary

Author: DAlperin

cmd/start/main.go

@@ -33,7 +33,7 @@ func main() {
 		for range t.C {
 
 			if err := node.PostInit(); err != nil {
-				fmt.Printf("failed post-init: %s", err)
+				fmt.Printf("failed post-init: %s. Retrying...", err)
 				continue
 			}
 

pkg/flypg/node.go

@@ -31,6 +31,7 @@ type Node struct {
 	AppName   string
 	PrivateIP string
 	DataDir   string
+	Region    string
 	PGPort    int
 
 	SUCredentials       Credentials
@@ -48,6 +49,7 @@ func NewNode() (*Node, error) {
 		DataDir:             "/data/postgresql",
 		ManagerDatabaseName: "repmgr",
 		ManagerConfigPath:   "/data/repmgr.conf",
+		Region:              os.Getenv("FLY_REGION"),
 	}
 
 	if appName := os.Getenv("FLY_APP_NAME"); appName != "" {
@@ -149,6 +151,13 @@ func (n *Node) Init() error {
 	return nil
 }
 
+func (n *Node) ValidPrimary() bool {
+	if n.Region == os.Getenv("PRIMARY_REGION") {
+		return true
+	}
+	return false
+}
+
 // PostInit are operations that should be executed against a running Postgres on boot.
 func (n *Node) PostInit() error {
 	client, err := state.NewConsulClient()
@@ -163,6 +172,11 @@ func (n *Node) PostInit() error {
 
 	switch primaryIP {
 	case "":
+		// Check if we can be a primary
+		if !n.ValidPrimary() {
+			return fmt.Errorf("no primary to follow and can't configure self as primary because primary region is '%s' and we are in '%s'", n.Region, os.Getenv("PRIMARY_REGION"))
+		}
+
 		// Initialize ourselves as the primary.
 		conn, err := n.NewLocalConnection(context.TODO())
 		if err != nil {

pkg/flypg/repmgr.go

@@ -99,6 +99,7 @@ func writeManagerConf(node Node) error {
 		"follow_command":             fmt.Sprintf("'repmgr standby follow -f %s --log-to-file --upstream-node-id=%%n'", node.ManagerConfigPath),
 		"event_notification_command": fmt.Sprintf("'/usr/local/bin/event_handler -node-id %%n -event %%e -success %%s -details \"%%d\"'"),
 		"event_notifications":        "'repmgrd_failover_promote,standby_promote'",
+		"location":                   node.Region,
 	}
 
 	for key, value := range conf {