Use a more general db client factory approach.

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 {
-		return func() (DBClient, error) {
-			return NewPGClient(host)
-		}
+	if connS, ok := IsPostgreSQL(host); ok {
+		return NewPGClientFactory(connS)
 	}
 
-	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 func() (DBClient, error) {
-		return NewRedisClient(proto, address)
-	}
+	return NewRedisClientFactory(host, port)
 }

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{
-		db:              db,
-		queryCuboidStmt: stmt,
+	stmt, err := conn.PrepareContext(ctx, queryCuboidSQL)
+	if err != nil {
+		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