Add AfterConnect callback for ConnectionPool

connection_pool.go

@@ -1,27 +1,37 @@
 package pgx
 
+type ConnectionPoolOptions struct {
+	MaxConnections int // max simultaneous connections to use (currently all are immediately connected)
+	AfterConnect   func(*Connection) error
+}
+
 type ConnectionPool struct {
 	connectionChannel chan *Connection
-	parameters        ConnectionParameters // options used when establishing connection
-	MaxConnections    int
+	parameters        ConnectionParameters // parameters used when establishing connection
+	options           ConnectionPoolOptions
 }
 
-// NewConnectionPool creates a new ConnectionPool. options are passed through to
-// Connect directly. MaxConnections is max simultaneous connections to use
-// (currently all are immediately connected).
-func NewConnectionPool(parameters ConnectionParameters, MaxConnections int) (p *ConnectionPool, err error) {
+// NewConnectionPool creates a new ConnectionPool. parameters are passed through to
+// Connect directly.
+func NewConnectionPool(parameters ConnectionParameters, options ConnectionPoolOptions) (p *ConnectionPool, err error) {
 	p = new(ConnectionPool)
-	p.connectionChannel = make(chan *Connection, MaxConnections)
-	p.MaxConnections = MaxConnections
+	p.connectionChannel = make(chan *Connection, options.MaxConnections)
 
 	p.parameters = parameters
+	p.options = options
 
-	for i := 0; i < p.MaxConnections; i++ {
+	for i := 0; i < p.options.MaxConnections; i++ {
 		var c *Connection
 		c, err = Connect(p.parameters)
 		if err != nil {
 			return
 		}
+		if p.options.AfterConnect != nil {
+			err = p.options.AfterConnect(c)
+			if err != nil {
+				return
+			}
+		}
 		p.connectionChannel <- c
 	}
 
@@ -44,7 +54,7 @@ func (p *ConnectionPool) Release(c *Connection) {
 
 // Close ends the use of a connection by closing all underlying connections.
 func (p *ConnectionPool) Close() {
-	for i := 0; i < p.MaxConnections; i++ {
+	for i := 0; i < p.options.MaxConnections; i++ {
 		c := <-p.connectionChannel
 		_ = c.Close()
 	}

connection_pool_test.go

@@ -1,13 +1,15 @@
 package pgx_test
 
 import (
+	"errors"
 	"fmt"
 	"github.com/JackC/pgx"
 	"testing"
 )
 
 func createConnectionPool(t *testing.T, maxConnections int) *pgx.ConnectionPool {
-	pool, err := pgx.NewConnectionPool(*defaultConnectionParameters, maxConnections)
+	options := pgx.ConnectionPoolOptions{MaxConnections: maxConnections}
+	pool, err := pgx.NewConnectionPool(*defaultConnectionParameters, options)
 	if err != nil {
 		t.Fatalf("Unable to create connection pool: %v", err)
 	}
@@ -15,14 +17,33 @@ func createConnectionPool(t *testing.T, maxConnections int) *pgx.ConnectionPool
 }
 
 func TestNewConnectionPool(t *testing.T) {
-	pool, err := pgx.NewConnectionPool(*defaultConnectionParameters, 5)
+	var numCallbacks int
+	afterConnect := func(c *pgx.Connection) error {
+		numCallbacks++
+		return nil
+	}
+
+	options := pgx.ConnectionPoolOptions{MaxConnections: 2, AfterConnect: afterConnect}
+	pool, err := pgx.NewConnectionPool(*defaultConnectionParameters, options)
 	if err != nil {
 		t.Fatal("Unable to establish connection pool")
 	}
 	defer pool.Close()
 
-	if pool.MaxConnections != 5 {
-		t.Error("Wrong maxConnections")
+	if numCallbacks != 2 {
+		t.Errorf("Expected AfterConnect callback to fire %v times but only fired %v times", numCallbacks, numCallbacks)
+	}
+
+	// Pool creation returns an error if any AfterConnect callback does
+	errAfterConnect := errors.New("Some error")
+	afterConnect = func(c *pgx.Connection) error {
+		return errAfterConnect
+	}
+
+	options = pgx.ConnectionPoolOptions{MaxConnections: 2, AfterConnect: afterConnect}
+	pool, err = pgx.NewConnectionPool(*defaultConnectionParameters, options)
+	if err != errAfterConnect {
+		t.Errorf("Expected errAfterConnect but received unexpected: %v", err)
 	}
 }