Merge pull request #709 from georgysavva/flexible-pool-init

Add ability to skip network operations on pool initialization.

pgxpool/pool.go

@@ -112,6 +112,11 @@ type Config struct {
 	// HealthCheckPeriod is the duration between checks of the health of idle connections.
 	HealthCheckPeriod time.Duration
 
+	// If set to true, pool doesn't do any I/O operation on initialization.
+	// And connects to the server only when the pool starts to be used.
+	// The default is false.
+	LazyConnect bool
+
 	createdByParseConfig bool // Used to enforce created by ParseConfig rule.
 }
 
@@ -180,13 +185,15 @@ func ConnectConfig(ctx context.Context, config *Config) (*Pool, error) {
 
 	go p.backgroundHealthCheck()
 
-	// Initially establish one connection
-	res, err := p.p.Acquire(ctx)
-	if err != nil {
-		p.p.Close()
-		return nil, err
+	if !config.LazyConnect {
+		// Initially establish one connection
+		res, err := p.p.Acquire(ctx)
+		if err != nil {
+			p.p.Close()
+			return nil, err
+		}
+		res.Release()
 	}
-	res.Release()
 
 	return p, nil
 }

pgxpool/pool_test.go

@@ -41,6 +41,23 @@ func TestConnectCancel(t *testing.T) {
 	assert.Equal(t, context.Canceled, err)
 }
 
+func TestLazyConnect(t *testing.T) {
+	t.Parallel()
+
+	config, err := pgxpool.ParseConfig(os.Getenv("PGX_TEST_DATABASE"))
+	assert.NoError(t, err)
+	config.LazyConnect = true
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	pool, err := pgxpool.ConnectConfig(ctx, config)
+	assert.NoError(t, err)
+
+	_, err = pool.Exec(ctx, "SELECT 1")
+	assert.Equal(t, context.Canceled, err)
+}
+
 func TestConnectConfigRequiresConnConfigFromParseConfig(t *testing.T) {
 	t.Parallel()