switch node names to machine ID (#251)

* WIP switch node names to machine ID

* fix replica clone

* updates

* fixes

* TODO

* fix application_name on replica startup

* move to function

* reuse code

* upgrade primary

* clean up the diff

* fix tests

* silence warning

* missed a few

* fix deepsource callout

* make restart-repmgrd more resilient

* make pg_unregister work with new names

* Accept migration failures

* add missing panic

* update pg_unregister comment

* remove old comment

Author: benwaffle

Diff for: bin/restart-repmgrd

@@ -1,3 +1,10 @@
 #!/bin/bash
 
-kill `cat /tmp/repmgrd.pid`
+if [ -f /tmp/repmgrd.pid ]; then
+    PID=$(cat /tmp/repmgrd.pid)
+
+    # Check if the process is running
+    if ps -p $PID > /dev/null 2>&1; then
+        kill $PID
+    fi
+fi

Diff for: cmd/pg_unregister/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"log"
 	"os"
@@ -44,7 +45,15 @@ func processUnregistration(ctx context.Context) error {
 	defer func() { _ = conn.Close(ctx) }()
 
 	member, err := node.RepMgr.MemberByHostname(ctx, conn, string(hostnameBytes))
-	if err != nil {
+	if errors.Is(err, pgx.ErrNoRows) {
+		// for historical reasons, old versions of flyctl passes in the 6pn as the hostname
+		// most likely this won't work because the hostname does not resolve if the machine is stopped,
+		// but we try anyway
+		member, err = node.RepMgr.MemberBy6PN(ctx, conn, string(hostnameBytes))
+		if err != nil {
+			return fmt.Errorf("failed to resolve member by hostname and 6pn: %s", err)
+		}
+	} else if err != nil {
 		return fmt.Errorf("failed to resolve member: %s", err)
 	}
 

Diff for: go.mod

@@ -8,8 +8,10 @@ require (
 	github.com/hashicorp/consul/api v1.18.0
 	github.com/jackc/pgconn v1.14.3
 	github.com/jackc/pgx/v5 v5.5.4
+	github.com/olekukonko/tablewriter v0.0.5
 	github.com/pkg/errors v0.9.1
 	github.com/pkg/term v1.1.0
+	github.com/spf13/cobra v1.8.1
 	github.com/superfly/fly-checks v0.0.0-20230510154016-d189351293f2
 	golang.org/x/exp v0.0.0-20230105202349-8879d0199aa3
 	golang.org/x/sync v0.1.0
@@ -36,8 +38,6 @@ require (
 	github.com/mattn/go-runewidth v0.0.9 // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
 	github.com/mitchellh/mapstructure v1.4.1 // indirect
-	github.com/olekukonko/tablewriter v0.0.5 // indirect
-	github.com/spf13/cobra v1.8.1 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/stretchr/objx v0.5.0 // indirect
 	golang.org/x/crypto v0.20.0 // indirect

Diff for: internal/flypg/node.go

@@ -16,10 +16,12 @@ import (
 	"github.com/fly-apps/postgres-flex/internal/privnet"
 	"github.com/fly-apps/postgres-flex/internal/utils"
 	"github.com/jackc/pgx/v5"
+	"golang.org/x/exp/slices"
 )
 
 type Node struct {
 	AppName       string
+	MachineID     string
 	PrivateIP     string
 	PrimaryRegion string
 	DataDir       string
@@ -52,6 +54,8 @@ func NewNode() (*Node, error) {
 
 	node.PrivateIP = ipv6.String()
 
+	node.MachineID = os.Getenv("FLY_MACHINE_ID")
+
 	node.PrimaryRegion = os.Getenv("PRIMARY_REGION")
 	if node.PrimaryRegion == "" {
 		return nil, fmt.Errorf("PRIMARY_REGION environment variable must be set")
@@ -89,6 +93,7 @@ func NewNode() (*Node, error) {
 		PasswordConfigPath: "/data/.pgpass",
 		DataDir:            node.DataDir,
 		PrivateIP:          node.PrivateIP,
+		MachineID:          node.MachineID,
 		Port:               5433,
 		DatabaseName:       "repmgr",
 		Credentials:        node.ReplCredentials,
@@ -265,7 +270,7 @@ func (n *Node) PostInit(ctx context.Context) error {
 			return fmt.Errorf("failed to resolve member role: %s", err)
 		}
 
-		// Restart repmgrd in the event the IP changes for an already registered node.
+		// Restart repmgrd in the event the machine ID changes for an already registered node.
 		// This can happen if the underlying volume is moved to a different node.
 		daemonRestartRequired := n.RepMgr.daemonRestartRequired(member)
 
@@ -279,6 +284,8 @@ func (n *Node) PostInit(ctx context.Context) error {
 				if err := Quarantine(ctx, n, primary); err != nil {
 					return fmt.Errorf("failed to quarantine failed primary: %s", err)
 				}
+
+				panic(err)
 			} else if errors.Is(err, ErrZombieDiscovered) {
 				log.Printf("[ERROR] The majority of registered members agree that '%s' is the real primary.\n", primary)
 				// Turn member read-only
@@ -292,10 +299,10 @@ func (n *Node) PostInit(ctx context.Context) error {
 			}
 
 			// This should never happen
-			if primary != n.PrivateIP {
+			if primary != n.RepMgr.machineIdToDNS(n.MachineID) {
 				return fmt.Errorf("resolved primary '%s' does not match ourself '%s'. this should not happen",
 					primary,
-					n.PrivateIP,
+					n.RepMgr.machineIdToDNS(n.MachineID),
 				)
 			}
 
@@ -311,6 +318,11 @@ func (n *Node) PostInit(ctx context.Context) error {
 				}
 			}
 		case StandbyRoleName:
+			if err := n.migrateNodeNameIfNeeded(ctx, repConn); err != nil {
+				log.Printf("[ERROR] failed to migrate node name: %s", err)
+				// We try to bring the standby up anyway
+			}
+
 			// Register existing standby to apply any configuration changes.
 			if err := n.RepMgr.registerStandby(daemonRestartRequired); err != nil {
 				return fmt.Errorf("failed to register existing standby: %s", err)
@@ -527,3 +539,50 @@ func (n *Node) handleRemoteRestore(ctx context.Context, store *state.Store) erro
 
 	return nil
 }
+
+// migrate node name from 6pn to machine ID if needed
+func (n *Node) migrateNodeNameIfNeeded(ctx context.Context, repConn *pgx.Conn) error {
+	primary, err := n.RepMgr.PrimaryMember(ctx, repConn)
+	if err != nil {
+		return fmt.Errorf("failed to resolve primary member when updating standby: %s", err)
+	}
+
+	primaryConn, err := n.RepMgr.NewRemoteConnection(ctx, primary.Hostname)
+	if err != nil {
+		return fmt.Errorf("failed to establish connection to primary: %s", err)
+	}
+	defer func() { _ = primaryConn.Close(ctx) }()
+
+	rows, err := primaryConn.Query(ctx, "select application_name from pg_stat_replication")
+	if err != nil {
+		return fmt.Errorf("failed to query pg_stat_replication: %s", err)
+	}
+	defer rows.Close()
+
+	var applicationNames []string
+	for rows.Next() {
+		var applicationName string
+		if err := rows.Scan(&applicationName); err != nil {
+			return fmt.Errorf("failed to scan application_name: %s", err)
+		}
+		applicationNames = append(applicationNames, applicationName)
+	}
+	if err := rows.Err(); err != nil {
+		return fmt.Errorf("failed to iterate over rows: %s", err)
+	}
+
+	// if we find our 6pn as application_name, we need to regenerate postgresql.auto.conf and reload postgresql
+	if slices.Contains(applicationNames, n.PrivateIP) {
+		log.Printf("pg_stat_replication on the primary has our ipv6 address as application_name, converting to machine ID...")
+
+		if err := n.RepMgr.regenReplicationConf(ctx); err != nil {
+			return fmt.Errorf("failed to clone standby: %s", err)
+		}
+
+		if err := admin.ReloadPostgresConfig(ctx, repConn); err != nil {
+			return fmt.Errorf("failed to reload postgresql: %s", err)
+		}
+	}
+
+	return nil
+}

Diff for: internal/flypg/readonly.go

@@ -70,7 +70,7 @@ func BroadcastReadonlyChange(ctx context.Context, n *Node, enabled bool) error {
 
 	for _, member := range members {
 		if member.Role == PrimaryRoleName {
-			endpoint := fmt.Sprintf("http://[%s]:5500/%s", member.Hostname, target)
+			endpoint := fmt.Sprintf("http://%s:5500/%s", member.Hostname, target)
 			resp, err := http.Get(endpoint)
 			if err != nil {
 				log.Printf("[WARN] Failed to broadcast readonly state change to member %s: %s", member.Hostname, err)
@@ -85,7 +85,7 @@ func BroadcastReadonlyChange(ctx context.Context, n *Node, enabled bool) error {
 	}
 
 	for _, member := range members {
-		endpoint := fmt.Sprintf("http://[%s]:5500/%s", member.Hostname, RestartHaproxyEndpoint)
+		endpoint := fmt.Sprintf("http://%s:5500/%s", member.Hostname, RestartHaproxyEndpoint)
 		resp, err := http.Get(endpoint)
 		if err != nil {
 			log.Printf("[WARN] Failed to restart haproxy on member %s: %s", member.Hostname, err)

Diff for: internal/flypg/repmgr.go

@@ -34,6 +34,7 @@ type RepMgr struct {
 	PrimaryRegion      string
 	Region             string
 	PrivateIP          string
+	MachineID          string
 	DataDir            string
 	DatabaseName       string
 	Credentials        admin.Credential
@@ -161,10 +162,12 @@ func (r *RepMgr) setDefaults() error {
 		return err
 	}
 
+	hostname := r.machineIdToDNS(r.MachineID)
+
 	conf := ConfigMap{
 		"node_id":                      nodeID,
-		"node_name":                    fmt.Sprintf("'%s'", r.PrivateIP),
-		"conninfo":                     fmt.Sprintf("'host=%s port=%d user=%s dbname=%s connect_timeout=5'", r.PrivateIP, r.Port, r.Credentials.Username, r.DatabaseName),
+		"node_name":                    fmt.Sprintf("'%s'", hostname),
+		"conninfo":                     fmt.Sprintf("'host=%s port=%d user=%s dbname=%s connect_timeout=5'", hostname, r.Port, r.Credentials.Username, r.DatabaseName),
 		"data_directory":               fmt.Sprintf("'%s'", r.DataDir),
 		"failover":                     "'automatic'",
 		"use_replication_slots":        "yes",
@@ -276,7 +279,7 @@ func (*RepMgr) restartDaemon() error {
 }
 
 func (r *RepMgr) daemonRestartRequired(m *Member) bool {
-	return m.Hostname != r.PrivateIP
+	return m.Hostname != r.MachineID
 }
 
 func (r *RepMgr) unregisterWitness(id int) error {
@@ -301,14 +304,14 @@ func (r *RepMgr) rejoinCluster(hostname string) error {
 	return err
 }
 
-func (r *RepMgr) clonePrimary(ipStr string) error {
+func (r *RepMgr) clonePrimary(hostname string) error {
 	cmdStr := fmt.Sprintf("mkdir -p %s", r.DataDir)
 	if _, err := utils.RunCommand(cmdStr, "postgres"); err != nil {
 		return fmt.Errorf("failed to create pg directory: %s", err)
 	}
 
 	cmdStr = fmt.Sprintf("repmgr -h %s -p %d -d %s -U %s -f %s standby clone -c -F",
-		ipStr,
+		hostname,
 		r.Port,
 		r.DatabaseName,
 		r.Credentials.Username,
@@ -322,6 +325,21 @@ func (r *RepMgr) clonePrimary(ipStr string) error {
 	return nil
 }
 
+func (r *RepMgr) regenReplicationConf(ctx context.Context) error {
+	// TODO: do we need -c?
+	if _, err := utils.RunCmd(ctx, "postgres",
+		"repmgr", "--replication-conf-only",
+		"-h", "",
+		"-p", fmt.Sprint(r.Port),
+		"-d", r.DatabaseName,
+		"-U", r.Credentials.Username,
+		"-f", r.ConfigPath,
+		"standby", "clone", "-F"); err != nil {
+		return fmt.Errorf("failed to regenerate replication conf: %s", err)
+	}
+	return nil
+}
+
 type Member struct {
 	ID       int
 	Hostname string
@@ -431,26 +449,56 @@ func (*RepMgr) MemberByHostname(ctx context.Context, pg *pgx.Conn, hostname stri
 	return &member, nil
 }
 
+// MemberBy6PN returns a member by its 6PN address.
+func (r *RepMgr) MemberBy6PN(ctx context.Context, pg *pgx.Conn, ip string) (*Member, error) {
+	members, err := r.Members(ctx, pg)
+	if err != nil {
+		return nil, err
+	}
+
+	resolver := privnet.GetResolver()
+	var lastErr error
+	for _, member := range members {
+		ips, err := resolver.LookupIPAddr(ctx, member.Hostname)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+
+		for _, addr := range ips {
+			if addr.IP.String() == ip {
+				return &member, nil
+			}
+		}
+	}
+
+	if lastErr != nil {
+		return nil, fmt.Errorf("no matches found for %s, and error encountered: %s", ip, lastErr)
+	}
+
+	return nil, nil
+}
+
 func (r *RepMgr) ResolveMemberOverDNS(ctx context.Context) (*Member, error) {
-	ips, err := r.InRegionPeerIPs(ctx)
+	machineIds, err := r.InRegionPeerMachines(ctx)
 	if err != nil {
 		return nil, err
 	}
 
 	var target *Member
 
-	for _, ip := range ips {
-		if ip.String() == r.PrivateIP {
+	for _, machineId := range machineIds {
+		if machineId == r.MachineID {
 			continue
 		}
 
-		conn, err := r.NewRemoteConnection(ctx, ip.String())
+		conn, err := r.NewRemoteConnection(ctx, r.machineIdToDNS(machineId))
 		if err != nil {
 			continue
 		}
 		defer func() { _ = conn.Close(ctx) }()
 
-		member, err := r.MemberByHostname(ctx, conn, ip.String())
+		member, err := r.MemberByHostname(ctx, conn, r.machineIdToDNS(machineId))
 		if err != nil {
 			continue
 		}
@@ -477,6 +525,21 @@ func (r *RepMgr) InRegionPeerIPs(ctx context.Context) ([]net.IPAddr, error) {
 	return privnet.AllPeers(ctx, targets)
 }
 
+func (r *RepMgr) InRegionPeerMachines(ctx context.Context) ([]string, error) {
+	machines, err := privnet.AllMachines(ctx, r.AppName)
+	if err != nil {
+		return nil, err
+	}
+
+	var machineIDs []string
+	for _, machine := range machines {
+		if machine.Region == r.PrimaryRegion {
+			machineIDs = append(machineIDs, machine.Id)
+		}
+	}
+	return machineIDs, nil
+}
+
 func (r *RepMgr) HostInRegion(ctx context.Context, hostname string) (bool, error) {
 	ips, err := r.InRegionPeerIPs(ctx)
 	if err != nil {
@@ -514,3 +577,11 @@ func (r *RepMgr) UnregisterMember(member Member) error {
 func (r *RepMgr) eligiblePrimary() bool {
 	return r.Region == r.PrimaryRegion
 }
+
+func (r *RepMgr) machineIdToDNS(nodeName string) string {
+	if len(nodeName) != 14 {
+		panic("invalid machine id")
+	}
+
+	return fmt.Sprintf("%s.vm.%s.internal", nodeName, r.AppName)
+}

Diff for: internal/flypg/repmgr_test.go

@@ -33,6 +33,7 @@ func TestRepmgrInitialization(t *testing.T) {
 		UserConfigPath:     repgmrUserConfigFilePath,
 		PasswordConfigPath: repgmrPasswordConfigFilePath,
 		DataDir:            repmgrTestDirectory,
+		MachineID:          "abcdefg1234567",
 		PrivateIP:          "127.0.0.1",
 		Credentials: admin.Credential{
 			Username: "user",
@@ -91,8 +92,8 @@ func TestRepmgrInitialization(t *testing.T) {
 			t.Fatal(err)
 		}
 
-		if config["node_name"] != "'127.0.0.1'" {
-			t.Fatalf("expected node_name to be '127.0.0.1', got %v", config["node_name"])
+		if config["node_name"] != "'abcdefg1234567.vm.test-app.internal'" {
+			t.Fatalf("expected node_name to be 'abcdefg1234567.vm.test-app.internal', got %v", config["node_name"])
 		}
 
 		if config["location"] != "'dev'" {
@@ -122,6 +123,7 @@ func TestRepmgrNodeIDGeneration(t *testing.T) {
 
 		DataDir:      repmgrTestDirectory,
 		PrivateIP:    "127.0.0.1",
+		MachineID:    "abcdefg1234567",
 		Port:         5433,
 		DatabaseName: "repmgr",
 		Credentials: admin.Credential{