Ensure implementation is migration friendly

Author: Ben Iofel

.github/workflows/push.yml

@@ -18,7 +18,7 @@ jobs:
 
       - uses: actions/setup-go@v3
         with:
-          go-version: '1.20'
+          go-version: '1.23'
           go-version-file: 'go.mod'
           cache: true
 
@@ -36,7 +36,7 @@ jobs:
 
       - uses: actions/setup-go@v3
         with:
-          go-version: '1.20'
+          go-version: '1.23'
           go-version-file: 'go.mod'
           cache: true
 
@@ -52,7 +52,7 @@ jobs:
 
       - uses: actions/setup-go@v3
         with:
-          go-version: '1.20'
+          go-version: '1.23'
           go-version-file: 'go.mod'
           cache: true
 
@@ -68,7 +68,7 @@ jobs:
 
       - uses: actions/setup-go@v3
         with:
-          go-version: '1.20'
+          go-version: '1.23'
           go-version-file: 'go.mod'
           cache: true
 

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

cmd/pg_unregister/main.go

@@ -27,9 +27,9 @@ func main() {
 
 func processUnregistration(ctx context.Context) error {
 	encodedArg := os.Args[1]
-	hostnameBytes, err := base64.StdEncoding.DecodeString(encodedArg)
+	machineBytes, err := base64.StdEncoding.DecodeString(encodedArg)
 	if err != nil {
-		return fmt.Errorf("failed to decode hostname: %v", err)
+		return fmt.Errorf("failed to decode machine: %v", err)
 	}
 
 	node, err := flypg.NewNode()
@@ -43,21 +43,23 @@ func processUnregistration(ctx context.Context) error {
 	}
 	defer func() { _ = conn.Close(ctx) }()
 
-	member, err := node.RepMgr.MemberByHostname(ctx, conn, string(hostnameBytes))
+	machineID := string(machineBytes)
+
+	if len(machineID) != 14 {
+		return fmt.Errorf("invalid machine id: %s. (expected length 16, got %d)", machineID, len(machineBytes))
+	}
+
+	member, err := node.RepMgr.MemberByNodeName(ctx, conn, machineID)
 	if err != nil {
-		return fmt.Errorf("failed to resolve member: %s", err)
+		return fmt.Errorf("failed to resolve member using %s: %s", machineID, err)
 	}
 
 	if err := node.RepMgr.UnregisterMember(*member); err != nil {
 		return fmt.Errorf("failed to unregister member: %v", err)
 	}
 
 	slotName := fmt.Sprintf("repmgr_slot_%d", member.ID)
-	if err := removeReplicationSlot(ctx, conn, slotName); err != nil {
-		return err
-	}
-
-	return nil
+	return removeReplicationSlot(ctx, conn, slotName)
 }
 
 func removeReplicationSlot(ctx context.Context, conn *pgx.Conn, slotName string) error {

go.mod

@@ -1,15 +1,17 @@
 module github.com/fly-apps/postgres-flex
 
-go 1.20
+go 1.23
 
 require (
 	github.com/go-chi/chi/v5 v5.0.8
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
 	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

go.sum

@@ -69,6 +69,7 @@ github.com/jackc/pgconn v1.14.3/go.mod h1:RZbme4uasqzybK2RK5c65VsHxoyaml09lx3tXO
 github.com/jackc/pgio v1.0.0 h1:g12B9UwVnzGhueNavwioyEEpAmqMe1E/BN9ES+8ovkE=
 github.com/jackc/pgio v1.0.0/go.mod h1:oP+2QK2wFfUWgr+gxjoBH9KGBb31Eio69xUb0w5bYf8=
 github.com/jackc/pgmock v0.0.0-20210724152146-4ad1a8207f65 h1:DadwsjnMwFjfWc9y5Wi/+Zz7xoE5ALHsRQlOctkOiHc=
+github.com/jackc/pgmock v0.0.0-20210724152146-4ad1a8207f65/go.mod h1:5R2h2EEX+qri8jOWMbJCtaPWkrrNc7OHwsp2TCqp7ak=
 github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
 github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
 github.com/jackc/pgproto3/v2 v2.3.3 h1:1HLSx5H+tXR9pW3in3zaztoEwQYRC9SQaYUHjTSUOag=
@@ -78,6 +79,7 @@ github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a/go.mod h1:5TJZ
 github.com/jackc/pgx/v5 v5.5.4 h1:Xp2aQS8uXButQdnCMWNmvx6UysWQQC+u1EoizjguY+8=
 github.com/jackc/pgx/v5 v5.5.4/go.mod h1:ez9gk+OAat140fv9ErkZDYFWmXLfV+++K0uAOiwgm1A=
 github.com/jackc/puddle/v2 v2.2.1 h1:RhxXJtFG022u4ibrCSMSiu5aOq1i77R3OHKNJj77OAk=
+github.com/jackc/puddle/v2 v2.2.1/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
 github.com/kr/pretty v0.2.0/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
 github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
@@ -139,6 +141,7 @@ github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
+github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/superfly/fly-checks v0.0.0-20230510154016-d189351293f2 h1:mZNiJSrmbQA/3+Vy8GLL/Q9qdHxPzjcxKv+E14GZLFs=
 github.com/superfly/fly-checks v0.0.0-20230510154016-d189351293f2/go.mod h1:BbqpB4y6Z/cijQqKWJ3i8LMsAoC29gzX6vsSD3Qq7uw=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
@@ -154,6 +157,7 @@ golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v
 golang.org/x/net v0.0.0-20210410081132-afb366fc7cd1/go.mod h1:9tjilg8BloeKEkVJvy7fQ90B1CfIiPueXVOjqfkSzI8=
 golang.org/x/net v0.0.0-20211216030914-fe4d6282115f/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
 golang.org/x/net v0.21.0 h1:AQyQV4dYCvJ7vGmJyKki9+PBdyvhkSd8EIx/qb0AYv4=
+golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=

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")
@@ -88,7 +92,9 @@ func NewNode() (*Node, error) {
 		UserConfigPath:     "/data/repmgr.user.conf",
 		PasswordConfigPath: "/data/.pgpass",
 		DataDir:            node.DataDir,
+		HostName:           node.Hostname(),
 		PrivateIP:          node.PrivateIP,
+		MachineID:          node.MachineID,
 		Port:               5433,
 		DatabaseName:       "repmgr",
 		Credentials:        node.ReplCredentials,
@@ -182,7 +188,7 @@ func (n *Node) Init(ctx context.Context) error {
 				}
 			} else {
 				log.Println("Provisioning standby")
-				cloneTarget, err := n.RepMgr.ResolveMemberOverDNS(ctx)
+				cloneTarget, err := n.RepMgr.ResolvePrimaryOverDNS(ctx)
 				if err != nil {
 					return fmt.Errorf("failed to resolve member over dns: %s", err)
 				}
@@ -265,7 +271,7 @@ 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)
 
@@ -311,6 +317,10 @@ func (n *Node) PostInit(ctx context.Context) error {
 				}
 			}
 		case StandbyRoleName:
+			if err := n.migrateNodeNameIfNeeded(ctx, repConn); err != nil {
+				return fmt.Errorf("failed to migrate node name: %s", err)
+			}
+
 			// 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)
@@ -399,7 +409,7 @@ func (n *Node) PostInit(ctx context.Context) error {
 					return fmt.Errorf("failed to enable repmgr: %s", err)
 				}
 
-				primary, err := n.RepMgr.ResolveMemberOverDNS(ctx)
+				primary, err := n.RepMgr.ResolvePrimaryOverDNS(ctx)
 				if err != nil {
 					return fmt.Errorf("failed to resolve primary member: %s", err)
 				}
@@ -527,3 +537,55 @@ 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
+}
+
+// Hostname returns the hostname of the node.
+func (n *Node) Hostname() string {
+	return fmt.Sprintf("%s.vm.%s.internal", n.MachineID, n.AppName)
+}

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)