[chore] set max open / idle conns + conn max lifetime for both postgres and sqlite (#1369)

* [chore] set max open / idle conns + conn max lifetime for both postgres and sqlite

* reduce cache size default to 8MiB, reduce connections to 2 * cpu

* introduce max open conns multiplier, tune sqlite and pg separately

* go fmt

5 files changed, 141 insertions, 102 deletions

diff --git a/internal/config/config.go b/internal/config/config.go
index 472e7b93d..7025ab63a 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -58,18 +58,19 @@ type Configuration struct {
 	TrustedProxies  []string `name:"trusted-proxies" usage:"Proxies to trust when parsing x-forwarded headers into real IPs."`
 	SoftwareVersion string   `name:"software-version" usage:""`
 
-	DbType              string        `name:"db-type" usage:"Database type: eg., postgres"`
-	DbAddress           string        `name:"db-address" usage:"Database ipv4 address, hostname, or filename"`
-	DbPort              int           `name:"db-port" usage:"Database port"`
-	DbUser              string        `name:"db-user" usage:"Database username"`
-	DbPassword          string        `name:"db-password" usage:"Database password"`
-	DbDatabase          string        `name:"db-database" usage:"Database name"`
-	DbTLSMode           string        `name:"db-tls-mode" usage:"Database tls mode"`
-	DbTLSCACert         string        `name:"db-tls-ca-cert" usage:"Path to CA cert for db tls connection"`
-	DbSqliteJournalMode string        `name:"db-sqlite-journal-mode" usage:"Sqlite only: see https://www.sqlite.org/pragma.html#pragma_journal_mode"`
-	DbSqliteSynchronous string        `name:"db-sqlite-synchronous" usage:"Sqlite only: see https://www.sqlite.org/pragma.html#pragma_synchronous"`
-	DbSqliteCacheSize   bytesize.Size `name:"db-sqlite-cache-size" usage:"Sqlite only: see https://www.sqlite.org/pragma.html#pragma_cache_size"`
-	DbSqliteBusyTimeout time.Duration `name:"db-sqlite-busy-timeout" usage:"Sqlite only: see https://www.sqlite.org/pragma.html#pragma_busy_timeout"`
+	DbType                   string        `name:"db-type" usage:"Database type: eg., postgres"`
+	DbAddress                string        `name:"db-address" usage:"Database ipv4 address, hostname, or filename"`
+	DbPort                   int           `name:"db-port" usage:"Database port"`
+	DbUser                   string        `name:"db-user" usage:"Database username"`
+	DbPassword               string        `name:"db-password" usage:"Database password"`
+	DbDatabase               string        `name:"db-database" usage:"Database name"`
+	DbTLSMode                string        `name:"db-tls-mode" usage:"Database tls mode"`
+	DbTLSCACert              string        `name:"db-tls-ca-cert" usage:"Path to CA cert for db tls connection"`
+	DbMaxOpenConnsMultiplier int           `name:"db-max-open-conns-multiplier" usage:"Multiplier to use per cpu for max open database connections. 0 or less is normalized to 1."`
+	DbSqliteJournalMode      string        `name:"db-sqlite-journal-mode" usage:"Sqlite only: see https://www.sqlite.org/pragma.html#pragma_journal_mode"`
+	DbSqliteSynchronous      string        `name:"db-sqlite-synchronous" usage:"Sqlite only: see https://www.sqlite.org/pragma.html#pragma_synchronous"`
+	DbSqliteCacheSize        bytesize.Size `name:"db-sqlite-cache-size" usage:"Sqlite only: see https://www.sqlite.org/pragma.html#pragma_cache_size"`
+	DbSqliteBusyTimeout      time.Duration `name:"db-sqlite-busy-timeout" usage:"Sqlite only: see https://www.sqlite.org/pragma.html#pragma_busy_timeout"`
 
 	WebTemplateBaseDir string `name:"web-template-base-dir" usage:"Basedir for html templating files for rendering pages and composing emails."`
 	WebAssetBaseDir    string `name:"web-asset-base-dir" usage:"Directory to serve static assets from, accessible at example.org/assets/"`
diff --git a/internal/config/defaults.go b/internal/config/defaults.go
index ecd32be2f..6b4c5db17 100644
--- a/internal/config/defaults.go
+++ b/internal/config/defaults.go
@@ -40,18 +40,19 @@ var Defaults = Configuration{
 	Port:            8080,
 	TrustedProxies:  []string{"127.0.0.1/32", "::1"}, // localhost
 
-	DbType:              "postgres",
-	DbAddress:           "",
-	DbPort:              5432,
-	DbUser:              "",
-	DbPassword:          "",
-	DbDatabase:          "gotosocial",
-	DbTLSMode:           "disable",
-	DbTLSCACert:         "",
-	DbSqliteJournalMode: "WAL",
-	DbSqliteSynchronous: "NORMAL",
-	DbSqliteCacheSize:   64 * bytesize.MiB,
-	DbSqliteBusyTimeout: time.Minute * 5,
+	DbType:                   "postgres",
+	DbAddress:                "",
+	DbPort:                   5432,
+	DbUser:                   "",
+	DbPassword:               "",
+	DbDatabase:               "gotosocial",
+	DbTLSMode:                "disable",
+	DbTLSCACert:              "",
+	DbMaxOpenConnsMultiplier: 8,
+	DbSqliteJournalMode:      "WAL",
+	DbSqliteSynchronous:      "NORMAL",
+	DbSqliteCacheSize:        8 * bytesize.MiB,
+	DbSqliteBusyTimeout:      time.Minute * 5,
 
 	WebTemplateBaseDir: "./web/template/",
 	WebAssetBaseDir:    "./web/assets/",
diff --git a/internal/config/flags.go b/internal/config/flags.go
index a21f17f53..e594615d1 100644
--- a/internal/config/flags.go
+++ b/internal/config/flags.go
@@ -51,6 +51,7 @@ func (s *ConfigState) AddGlobalFlags(cmd *cobra.Command) {
 		cmd.PersistentFlags().String(DbDatabaseFlag(), cfg.DbDatabase, fieldtag("DbDatabase", "usage"))
 		cmd.PersistentFlags().String(DbTLSModeFlag(), cfg.DbTLSMode, fieldtag("DbTLSMode", "usage"))
 		cmd.PersistentFlags().String(DbTLSCACertFlag(), cfg.DbTLSCACert, fieldtag("DbTLSCACert", "usage"))
+		cmd.PersistentFlags().Int(DbMaxOpenConnsMultiplierFlag(), cfg.DbMaxOpenConnsMultiplier, fieldtag("DbMaxOpenConnsMultiplier", "usage"))
 		cmd.PersistentFlags().String(DbSqliteJournalModeFlag(), cfg.DbSqliteJournalMode, fieldtag("DbSqliteJournalMode", "usage"))
 		cmd.PersistentFlags().String(DbSqliteSynchronousFlag(), cfg.DbSqliteSynchronous, fieldtag("DbSqliteSynchronous", "usage"))
 		cmd.PersistentFlags().Uint64(DbSqliteCacheSizeFlag(), uint64(cfg.DbSqliteCacheSize), fieldtag("DbSqliteCacheSize", "usage"))
diff --git a/internal/config/helpers.gen.go b/internal/config/helpers.gen.go
index 3560c566a..3bf62efc6 100644
--- a/internal/config/helpers.gen.go
+++ b/internal/config/helpers.gen.go
@@ -524,6 +524,31 @@ func GetDbTLSCACert() string { return global.GetDbTLSCACert() }
 // SetDbTLSCACert safely sets the value for global configuration 'DbTLSCACert' field
 func SetDbTLSCACert(v string) { global.SetDbTLSCACert(v) }
 
+// GetDbMaxOpenConnsMultiplier safely fetches the Configuration value for state's 'DbMaxOpenConnsMultiplier' field
+func (st *ConfigState) GetDbMaxOpenConnsMultiplier() (v int) {
+	st.mutex.Lock()
+	v = st.config.DbMaxOpenConnsMultiplier
+	st.mutex.Unlock()
+	return
+}
+
+// SetDbMaxOpenConnsMultiplier safely sets the Configuration value for state's 'DbMaxOpenConnsMultiplier' field
+func (st *ConfigState) SetDbMaxOpenConnsMultiplier(v int) {
+	st.mutex.Lock()
+	defer st.mutex.Unlock()
+	st.config.DbMaxOpenConnsMultiplier = v
+	st.reloadToViper()
+}
+
+// DbMaxOpenConnsMultiplierFlag returns the flag name for the 'DbMaxOpenConnsMultiplier' field
+func DbMaxOpenConnsMultiplierFlag() string { return "db-max-open-conns-multiplier" }
+
+// GetDbMaxOpenConnsMultiplier safely fetches the value for global configuration 'DbMaxOpenConnsMultiplier' field
+func GetDbMaxOpenConnsMultiplier() int { return global.GetDbMaxOpenConnsMultiplier() }
+
+// SetDbMaxOpenConnsMultiplier safely sets the value for global configuration 'DbMaxOpenConnsMultiplier' field
+func SetDbMaxOpenConnsMultiplier(v int) { global.SetDbMaxOpenConnsMultiplier(v) }
+
 // GetDbSqliteJournalMode safely fetches the Configuration value for state's 'DbSqliteJournalMode' field
 func (st *ConfigState) GetDbSqliteJournalMode() (v string) {
 	st.mutex.Lock()
diff --git a/internal/db/bundb/bundb.go b/internal/db/bundb/bundb.go
index b6a07bdc6..385b0ca1f 100644
--- a/internal/db/bundb/bundb.go
+++ b/internal/db/bundb/bundb.go
@@ -222,6 +222,32 @@ func NewBunDBService(ctx context.Context, state *state.State) (db.DB, error) {
 	return ps, nil
 }
 
+func pgConn(ctx context.Context) (*DBConn, error) {
+	opts, err := deriveBunDBPGOptions() //nolint:contextcheck
+	if err != nil {
+		return nil, fmt.Errorf("could not create bundb postgres options: %s", err)
+	}
+
+	sqldb := stdlib.OpenDB(*opts)
+
+	// Tune db connections for postgres, see:
+	// - https://bun.uptrace.dev/guide/running-bun-in-production.html#database-sql
+	// - https://www.alexedwards.net/blog/configuring-sqldb
+	sqldb.SetMaxOpenConns(maxOpenConns())     // x number of conns per CPU
+	sqldb.SetMaxIdleConns(2)                  // assume default 2; if max idle is less than max open, it will be automatically adjusted
+	sqldb.SetConnMaxLifetime(5 * time.Minute) // fine to kill old connections
+
+	conn := WrapDBConn(bun.NewDB(sqldb, pgdialect.New()))
+
+	// ping to check the db is there and listening
+	if err := conn.PingContext(ctx); err != nil {
+		return nil, fmt.Errorf("postgres ping: %s", err)
+	}
+
+	log.Info("connected to POSTGRES database")
+	return conn, nil
+}
+
 func sqliteConn(ctx context.Context) (*DBConn, error) {
 	// validate db address has actually been set
 	address := config.GetDbAddress()
@@ -236,13 +262,10 @@ func sqliteConn(ctx context.Context) (*DBConn, error) {
 	// Append our own SQLite preferences
 	address = "file:" + address
 
-	var inMem bool
-
 	if address == "file::memory:" {
 		address = fmt.Sprintf("file:%s?mode=memory&cache=shared", uuid.NewString())
 		log.Infof("using in-memory database address " + address)
 		log.Warn("sqlite in-memory database should only be used for debugging")
-		inMem = true
 	}
 
 	// Open new DB instance
@@ -254,12 +277,12 @@ func sqliteConn(ctx context.Context) (*DBConn, error) {
 		return nil, fmt.Errorf("could not open sqlite db: %s", err)
 	}
 
-	if inMem {
-		// don't close connections on disconnect -- otherwise
-		// the SQLite database will be deleted when there
-		// are no active connections
-		sqldb.SetConnMaxLifetime(0)
-	}
+	// Tune db connections for sqlite, see:
+	// - https://bun.uptrace.dev/guide/running-bun-in-production.html#database-sql
+	// - https://www.alexedwards.net/blog/configuring-sqldb
+	sqldb.SetMaxOpenConns(maxOpenConns()) // x number of conns per cpu
+	sqldb.SetMaxIdleConns(1)              // only keep max 1 idle connection around
+	sqldb.SetConnMaxLifetime(0)           // don't kill connections due to age
 
 	// Wrap Bun database conn in our own wrapper
 	conn := WrapDBConn(bun.NewDB(sqldb, sqlitedialect.New()))
@@ -276,79 +299,20 @@ func sqliteConn(ctx context.Context) (*DBConn, error) {
 	return conn, nil
 }
 
-func sqlitePragmas(ctx context.Context, conn *DBConn) error {
-	var pragmas [][]string
-	if mode := config.GetDbSqliteJournalMode(); mode != "" {
-		// Set the user provided SQLite journal mode
-		pragmas = append(pragmas, []string{"journal_mode", mode})
-	}
-
-	if mode := config.GetDbSqliteSynchronous(); mode != "" {
-		// Set the user provided SQLite synchronous mode
-		pragmas = append(pragmas, []string{"synchronous", mode})
-	}
-
-	if size := config.GetDbSqliteCacheSize(); size > 0 {
-		// Set the user provided SQLite cache size (in kibibytes)
-		// Prepend a '-' character to this to indicate to sqlite
-		// that we're giving kibibytes rather than num pages.
-		// https://www.sqlite.org/pragma.html#pragma_cache_size
-		s := "-" + strconv.FormatUint(uint64(size/bytesize.KiB), 10)
-		pragmas = append(pragmas, []string{"cache_size", s})
-	}
-
-	if timeout := config.GetDbSqliteBusyTimeout(); timeout > 0 {
-		t := strconv.FormatInt(timeout.Milliseconds(), 10)
-		pragmas = append(pragmas, []string{"busy_timeout", t})
-	}
-
-	for _, p := range pragmas {
-		pk := p[0]
-		pv := p[1]
-
-		if _, err := conn.DB.ExecContext(ctx, "PRAGMA ?=?", bun.Ident(pk), bun.Safe(pv)); err != nil {
-			return fmt.Errorf("error executing sqlite pragma %s: %w", pk, err)
-		}
-
-		var res string
-		if err := conn.DB.NewRaw("PRAGMA ?", bun.Ident(pk)).Scan(ctx, &res); err != nil {
-			return fmt.Errorf("error scanning sqlite pragma %s: %w", pv, err)
-		}
-
-		log.Infof("sqlite pragma %s set to %s", pk, res)
-	}
-
-	return nil
-}
-
-func pgConn(ctx context.Context) (*DBConn, error) {
-	opts, err := deriveBunDBPGOptions() //nolint:contextcheck
-	if err != nil {
-		return nil, fmt.Errorf("could not create bundb postgres options: %s", err)
-	}
-
-	sqldb := stdlib.OpenDB(*opts)
-
-	// https://bun.uptrace.dev/postgres/running-bun-in-production.html#database-sql
-	maxOpenConns := 4 * runtime.GOMAXPROCS(0)
-	sqldb.SetMaxOpenConns(maxOpenConns)
-	sqldb.SetMaxIdleConns(maxOpenConns)
-
-	conn := WrapDBConn(bun.NewDB(sqldb, pgdialect.New()))
-
-	// ping to check the db is there and listening
-	if err := conn.PingContext(ctx); err != nil {
-		return nil, fmt.Errorf("postgres ping: %s", err)
-	}
-
-	log.Info("connected to POSTGRES database")
-	return conn, nil
-}
-
 /*
 	HANDY STUFF
 */
 
+// maxOpenConns returns multiplier * GOMAXPROCS,
+// clamping multiplier to 1 if it was below 1.
+func maxOpenConns() int {
+	multiplier := config.GetDbMaxOpenConnsMultiplier()
+	if multiplier < 1 {
+		multiplier = 1
+	}
+	return multiplier * runtime.GOMAXPROCS(0)
+}
+
 // deriveBunDBPGOptions takes an application config and returns either a ready-to-use set of options
 // with sensible defaults, or an error if it's not satisfied by the provided config.
 func deriveBunDBPGOptions() (*pgx.ConnConfig, error) {
@@ -434,6 +398,53 @@ func deriveBunDBPGOptions() (*pgx.ConnConfig, error) {
 	return cfg, nil
 }
 
+// sqlitePragmas sets desired sqlite pragmas based on configured values, and
+// logs the results of the pragma queries. Errors if something goes wrong.
+func sqlitePragmas(ctx context.Context, conn *DBConn) error {
+	var pragmas [][]string
+	if mode := config.GetDbSqliteJournalMode(); mode != "" {
+		// Set the user provided SQLite journal mode
+		pragmas = append(pragmas, []string{"journal_mode", mode})
+	}
+
+	if mode := config.GetDbSqliteSynchronous(); mode != "" {
+		// Set the user provided SQLite synchronous mode
+		pragmas = append(pragmas, []string{"synchronous", mode})
+	}
+
+	if size := config.GetDbSqliteCacheSize(); size > 0 {
+		// Set the user provided SQLite cache size (in kibibytes)
+		// Prepend a '-' character to this to indicate to sqlite
+		// that we're giving kibibytes rather than num pages.
+		// https://www.sqlite.org/pragma.html#pragma_cache_size
+		s := "-" + strconv.FormatUint(uint64(size/bytesize.KiB), 10)
+		pragmas = append(pragmas, []string{"cache_size", s})
+	}
+
+	if timeout := config.GetDbSqliteBusyTimeout(); timeout > 0 {
+		t := strconv.FormatInt(timeout.Milliseconds(), 10)
+		pragmas = append(pragmas, []string{"busy_timeout", t})
+	}
+
+	for _, p := range pragmas {
+		pk := p[0]
+		pv := p[1]
+
+		if _, err := conn.DB.ExecContext(ctx, "PRAGMA ?=?", bun.Ident(pk), bun.Safe(pv)); err != nil {
+			return fmt.Errorf("error executing sqlite pragma %s: %w", pk, err)
+		}
+
+		var res string
+		if err := conn.DB.NewRaw("PRAGMA ?", bun.Ident(pk)).Scan(ctx, &res); err != nil {
+			return fmt.Errorf("error scanning sqlite pragma %s: %w", pv, err)
+		}
+
+		log.Infof("sqlite pragma %s set to %s", pk, res)
+	}
+
+	return nil
+}
+
 /*
 	CONVERSION FUNCTIONS
 */