pgxpool: Don't use idle connections with stdlib when doing pooling (#…

…4137)

* manage idle connections in the pgx pool

* migrate: add verification for latest migration consistency

app/app.go

@@ -202,9 +202,6 @@ func NewApp(c Config, pool *pgxpool.Pool) (*App, error) {
 		}
 	}
 
-	app.db.SetMaxIdleConns(c.DBMaxIdle)
-	app.db.SetMaxOpenConns(c.DBMaxOpen)
-
 	app.mgr = lifecycle.NewManager(app._Run, app._Shutdown)
 	err = app.mgr.SetStartupFunc(app.startup)
 	if err != nil {

app/cmd.go

@@ -145,12 +145,24 @@ Available Flags:
 
 		var pool *pgxpool.Pool
 		if cfg.DBURLNext != "" {
+			err = migrate.VerifyIsLatest(ctx, cfg.DBURL)
+			if err != nil {
+				return errors.Wrap(err, "verify db")
+			}
+
 			err = doMigrations(cfg.DBURLNext)
 			if err != nil {
 				return errors.Wrap(err, "nextdb")
 			}
 
-			mgr, err := swo.NewManager(swo.Config{OldDBURL: cfg.DBURL, NewDBURL: cfg.DBURLNext, CanExec: !cfg.APIOnly, Logger: cfg.LegacyLogger})
+			mgr, err := swo.NewManager(swo.Config{
+				OldDBURL: cfg.DBURL,
+				NewDBURL: cfg.DBURLNext,
+				CanExec:  !cfg.APIOnly,
+				Logger:   cfg.LegacyLogger,
+				MaxOpen:  cfg.DBMaxOpen,
+				MaxIdle:  cfg.DBMaxIdle,
+			})
 			if err != nil {
 				return errors.Wrap(err, "init switchover handler")
 			}
@@ -162,13 +174,15 @@ Available Flags:
 				return errors.Wrap(err, "connect to postgres")
 			}
 
-			cfg, err := pgxpool.ParseConfig(appURL)
+			poolCfg, err := pgxpool.ParseConfig(appURL)
 			if err != nil {
 				return errors.Wrap(err, "parse db URL")
 			}
-			sqldrv.SetConfigRetries(cfg)
+			poolCfg.MaxConns = int32(cfg.DBMaxOpen)
+			poolCfg.MinConns = int32(cfg.DBMaxIdle)
+			sqldrv.SetConfigRetries(poolCfg)
 
-			pool, err = pgxpool.NewWithConfig(context.Background(), cfg)
+			pool, err = pgxpool.NewWithConfig(context.Background(), poolCfg)
 			if err != nil {
 				return errors.Wrap(err, "connect to postgres")
 			}

app/pause.go

@@ -2,7 +2,6 @@ package app
 
 import (
 	"context"
-	"time"
 )
 
 // LogBackgroundContext returns a context.Background with the application logger configured.
@@ -19,17 +18,11 @@ func (app *App) Resume(ctx context.Context) error {
 }
 
 func (app *App) _pause(ctx context.Context) error {
-	app.db.SetMaxIdleConns(0)
-	app.db.SetConnMaxLifetime(time.Second)
-	app.db.SetMaxOpenConns(3)
 	app.events.Stop()
 	return nil
 }
 
 func (app *App) _resume(ctx context.Context) error {
-	app.db.SetMaxOpenConns(app.cfg.DBMaxOpen)
-	app.db.SetMaxIdleConns(app.cfg.DBMaxIdle)
-	app.db.SetConnMaxLifetime(0)
 	app.events.Start()
 
 	return nil

migrate/migrate.go

@@ -39,6 +39,15 @@ func migrationIDs() []string {
 	return ids
 }
 
+// LatestID will return the ID of the latest migration.
+func LatestID() string {
+	ids := migrationIDs()
+	if len(ids) == 0 {
+		return ""
+	}
+	return ids[len(ids)-1]
+}
+
 // Names will return all AssetNames without the timestamps and extensions
 func Names() []string {
 	uniq := make(map[string]struct{})
@@ -74,6 +83,29 @@ func migrationID(name string) (int, string) {
 	return -1, ""
 }
 
+// VerifyIsLatest will verify the latest migration is the same as the latest available migration.
+//
+// This ensures the DB isn't newer than the currently running code.
+func VerifyIsLatest(ctx context.Context, url string) error {
+	conn, err := getConn(ctx, url)
+	if err != nil {
+		return err
+	}
+	defer conn.Close(ctx)
+
+	var dbLatest string
+	err = conn.QueryRow(ctx, `select id from gorp_migrations order by id desc limit 1`).Scan(&dbLatest)
+	if err != nil {
+		return fmt.Errorf("read latest migration from DB: %w", err)
+	}
+
+	if dbLatest != LatestID() {
+		return errors.Errorf("latest migration in DB is '%s' but expected '%s'; local GoAlert version is likely older than the DB's latest migration (not allowed in SWO-mode)", dbLatest, LatestID())
+	}
+
+	return nil
+}
+
 // VerifyAll will verify all migrations have already been applied.
 func VerifyAll(ctx context.Context, url string) error {
 	ids := migrationIDs()

swo/manager.go

@@ -57,6 +57,9 @@ type Config struct {
 	OldDBURL, NewDBURL string
 	CanExec            bool
 	Logger             *log.Logger
+
+	MaxOpen int
+	MaxIdle int
 }
 
 // NewManager will create a new Manager with the given configuration.
@@ -97,7 +100,7 @@ func NewManager(cfg Config) (*Manager, error) {
 		return nil, fmt.Errorf("connect to new db: %w", err)
 	}
 
-	appPgx, err := NewAppPGXPool(appMainURL, appNextURL)
+	appPgx, err := NewAppPGXPool(appMainURL, appNextURL, cfg.MaxOpen, cfg.MaxIdle)
 	if err != nil {
 		return nil, fmt.Errorf("create pool: %w", err)
 	}

swo/pgxpool.go

@@ -16,17 +16,22 @@ import (
 //
 // Until the switchover is complete, the old database will be protected with a
 // shared advisory lock (4369).
-func NewAppPGXPool(oldURL, nextURL string) (*pgxpool.Pool, error) {
+func NewAppPGXPool(oldURL, nextURL string, maxOpen, maxIdle int) (*pgxpool.Pool, error) {
 	cfg, err := pgxpool.ParseConfig(oldURL)
 	if err != nil {
 		return nil, fmt.Errorf("parse old URL: %w", err)
 	}
 	sqldrv.SetConfigRetries(cfg)
+	cfg.MaxConns = int32(maxOpen)
+	cfg.MinConns = int32(maxIdle)
+
 	nextCfg, err := pgxpool.ParseConfig(nextURL)
 	if err != nil {
 		return nil, fmt.Errorf("parse next URL: %w", err)
 	}
 	sqldrv.SetConfigRetries(nextCfg)
+	nextCfg.MaxConns = int32(maxOpen)
+	nextCfg.MinConns = int32(maxIdle)
 
 	var mx sync.Mutex
 	var isDone bool