Use a more general db client factory approach.

cmd/mtseeder/baselevel.go

@@ -56,7 +56,7 @@ func createTiles(
 }
 
 func createBaseLevel(
-	dbcc common.DBClientCreator,
+	dbcf common.DBClientFactory,
 	xMin, yMin, zMin, xMax, yMax, zMax int,
 	transparent bool, transparentDim float32,
 	colorsFile string, bg color.RGBA, outDir string,
@@ -81,7 +81,7 @@ func createBaseLevel(
 	for i := 0; i < numWorkers; i++ {
 		var client common.DBClient
 
-		if client, err = dbcc(); err != nil {
+		if client, err = dbcf.Create(); err != nil {
 			return
 		}
 		done.Add(1)

cmd/mtseeder/main.go

@@ -68,12 +68,16 @@ func main() {
 
 	bg := common.ParseColorDefault(bgColor, common.BackgroundColor)
 
-	dbcc := common.CreateDBClientCreator(host, port)
+	dbcf, err := common.CreateDBClientFactory(host, port)
+	if err != nil {
+		log.Fatalf("error: %s\n", err)
+	}
+	defer dbcf.Close()
 
 	if !skipBaseLevel {
 		td := common.Clamp32f(float32(transparentDim/100.0), 0.0, 1.0)
 		if err := createBaseLevel(
-			dbcc,
+			dbcf,
 			xMin, yMin, zMin, xMax, yMax, zMax,
 			transparent, td,
 			colorsFile, bg,

cmd/mttilemapper/main.go

@@ -83,7 +83,12 @@ func main() {
 	colors.TransparentDim = common.Clamp32f(
 		float32(transparentDim/100.0), 0.0, 100.0)
 
-	client, err := common.CreateDBClientCreator(host, port)()
+	cf, err := common.CreateDBClientFactory(host, port)
+	if err != nil {
+		log.Fatalf("error: %v\n", err)
+	}
+
+	client, err := cf.Create()
 	if err != nil {
 		log.Fatalf("Cannot connect to '%s:%d': %s", host, port, err)
 	}

cmd/mtwebmapper/main.go

@@ -118,7 +118,11 @@ func main() {
 		colors.TransparentDim = common.Clamp32f(
 			float32(transparentDim/100.0), 0.0, 100.0)
 
-		dbcc := common.CreateDBClientCreator(redisHost, redisPort)
+		dbcf, err := common.CreateDBClientFactory(redisHost, redisPort)
+		if err != nil {
+			log.Fatalf("error: %v\n", err)
+		}
+		defer dbcf.Close()
 
 		var allowedUpdateIps []net.IP
 		if allowedUpdateIps, err = ipsFromHosts(updateHosts); err != nil {
@@ -127,7 +131,7 @@ func main() {
 
 		tu := newTileUpdater(
 			mapDir,
-			dbcc,
+			dbcf,
 			allowedUpdateIps,
 			colors, bg,
 			yMin, yMax,

cmd/mtwebmapper/tilesupdater.go

@@ -38,7 +38,7 @@ type tileUpdater struct {
 	changes     map[xz]struct{}
 	btu         baseTilesUpdates
 	mapDir      string
-	dbcc        common.DBClientCreator
+	dbcf        common.DBClientFactory
 	ips         []net.IP
 	colors      *common.Colors
 	bg          color.RGBA
@@ -82,7 +82,7 @@ func (c xz) parent() xzm {
 
 func newTileUpdater(
 	mapDir string,
-	dbcc common.DBClientCreator,
+	dbcf common.DBClientFactory,
 	ips []net.IP,
 	colors *common.Colors,
 	bg color.RGBA,
@@ -94,7 +94,7 @@ func newTileUpdater(
 	tu := tileUpdater{
 		btu:         btu,
 		mapDir:      mapDir,
-		dbcc:        dbcc,
+		dbcf:        dbcf,
 		ips:         ips,
 		changes:     map[xz]struct{}{},
 		colors:      colors,
@@ -262,10 +262,11 @@ func (tu *tileUpdater) doUpdates() {
 		for i, n := 0, common.Min(tu.workers, len(changes)); i < n; i++ {
 			var client common.DBClient
 			var err error
-			if client, err = tu.dbcc(); err != nil {
+			if client, err = tu.dbcf.Create(); err != nil {
 				log.Printf("WARN: Cannot connect to redis server: %s\n", err)
 				continue
 			}
+
 			btc := common.NewBaseTileCreator(
 				client, tu.colors, tu.bg,
 				tu.yMin, tu.yMax,

common/clientfactory.go

@@ -5,11 +5,18 @@
 package common
 
 import (
-	"fmt"
 	"strings"
 )
 
-type DBClientCreator func() (DBClient, error)
+type DBClient interface {
+	QueryCuboid(cuboid Cuboid, fn func(*Block) *Block) (count int, err error)
+	Close() error
+}
+
+type DBClientFactory interface {
+	Create() (DBClient, error)
+	Close() error
+}
 
 func IsPostgreSQL(host string) (string, bool) {
 	if strings.HasPrefix(host, "postgres:") {
@@ -18,29 +25,11 @@ func IsPostgreSQL(host string) (string, bool) {
 	return "", false
 }
 
-func CreateDBClientCreator(host string, port int) DBClientCreator {
+func CreateDBClientFactory(host string, port int) (DBClientFactory, error) {
 
-	if host, ok := IsPostgreSQL(host); ok {
+	if connS, ok := IsPostgreSQL(host); ok {
-		return func() (DBClient, error) {
+		return NewPGClientFactory(connS)
-			return NewPGClient(host)
-		}
 	}
 
-	var address string
+	return NewRedisClientFactory(host, port)
-	if strings.ContainsRune(host, '/') {
-		address = host
-	} else {
-		address = fmt.Sprintf("%s:%d", host, port)
-	}
-
-	var proto string
-	if strings.ContainsRune(address, '/') {
-		proto = "unix"
-	} else {
-		proto = "tcp"
-	}
-
-	return func() (DBClient, error) {
-		return NewRedisClient(proto, address)
-	}
 }

common/dbclient.go

@@ -1,10 +0,0 @@
-// Copyright 2022 by Sascha L. Teichmann
-// Use of this source code is governed by the MIT license
-// that can be found in the LICENSE file.
-
-package common
-
-type DBClient interface {
-	QueryCuboid(cuboid Cuboid, fn func(*Block) *Block) (count int, err error)
-	Close() error
-}

common/pgclient.go

@@ -19,24 +19,43 @@ WHERE
   posz BETWEEN $5 AND $6`
 
 type PGClient struct {
-	db              *sql.DB
+	conn            *sql.Conn
 	queryCuboidStmt *sql.Stmt
 }
 
-func NewPGClient(connS string) (*PGClient, error) {
+type PGClientFactory struct {
+	db *sql.DB
+}
+
+func NewPGClientFactory(connS string) (*PGClientFactory, error) {
 	db, err := sql.Open("pgx", connS)
 	if err != nil {
 		return nil, err
 	}
-	stmt, err := db.Prepare(queryCuboidSQL)
+	return &PGClientFactory{db: db}, nil
+}
+
+func (pgcf *PGClientFactory) Close() error {
+	return pgcf.db.Close()
+}
+
+func (pgcf *PGClientFactory) Create() (DBClient, error) {
+
+	ctx := context.Background()
+
+	conn, err := pgcf.db.Conn(ctx)
 	if err != nil {
 		return nil, err
 	}
-	client := PGClient{
+	stmt, err := conn.PrepareContext(ctx, queryCuboidSQL)
-		db:              db,
+	if err != nil {
-		queryCuboidStmt: stmt,
+		conn.Close()
+		return nil, err
 	}
-	return &client, nil
+	return &PGClient{
+		conn:            conn,
+		queryCuboidStmt: stmt,
+	}, nil
 }
 
 func (pgc *PGClient) QueryCuboid(
@@ -94,5 +113,5 @@ func (pgc *PGClient) Close() error {
 	if pgc.queryCuboidStmt != nil {
 		pgc.queryCuboidStmt.Close()
 	}
-	return pgc.db.Close()
+	return pgc.conn.Close()
 }

common/redisclient.go

@@ -11,9 +11,43 @@ import (
 	"fmt"
 	"net"
 	"strconv"
+	"strings"
 	"unicode"
 )
 
+type RedisClientFactory struct {
+	proto   string
+	address string
+}
+
+func NewRedisClientFactory(host string, port int) (*RedisClientFactory, error) {
+	var address string
+	if strings.ContainsRune(host, '/') {
+		address = host
+	} else {
+		address = fmt.Sprintf("%s:%d", host, port)
+	}
+
+	var proto string
+	if strings.ContainsRune(address, '/') {
+		proto = "unix"
+	} else {
+		proto = "tcp"
+	}
+	return &RedisClientFactory{
+		proto:   proto,
+		address: address,
+	}, nil
+}
+
+func (rcf *RedisClientFactory) Close() error {
+	return nil
+}
+
+func (rcf *RedisClientFactory) Create() (DBClient, error) {
+	return NewRedisClient(rcf.proto, rcf.address)
+}
+
 type RedisClient struct {
 	conn    net.Conn
 	reader  *bufio.Reader