feat: expose Dialer and add DialerOptions (#7)

dial.go

@@ -17,95 +17,31 @@ package cloudsqlconn
 
 import (
 	"context"
-	"crypto/rand"
-	"crypto/rsa"
-	"fmt"
 	"net"
 	"sync"
-
-	"cloud.google.com/cloudsqlconn/internal/cloudsql"
-	sqladmin "google.golang.org/api/sqladmin/v1beta4"
 )
 
 var (
-	once sync.Once
-	dm   *dialManager
-	dErr error
+	once          sync.Once
+	defaultDialer *Dialer
+	dErr          error
 )
 
 // Dial returns a net.Conn connected to the specified Cloud SQL instance. The instance argument must be the
 // instance's connection name, which is in the format "project-name:region:instance-name".
 func Dial(ctx context.Context, instance string) (net.Conn, error) {
-	d, err := defaultDialer()
+	d, err := getDefaultDialer()
 	if err != nil {
 		return nil, err
 	}
-	return d.dial(ctx, instance)
+	return d.Dial(ctx, instance)
 }
 
-// defaultDialer provides the singleton dialer as a default for dial functions.
-func defaultDialer() (*dialManager, error) {
+// getDefaultDialer provides the singleton dialer as a default for dial functions.
+func getDefaultDialer() (*Dialer, error) {
 	// TODO: Provide functionality for customizing/setting the default dialer
 	once.Do(func() {
-		dm, dErr = newDialManager()
+		defaultDialer, dErr = NewDialer(context.Background())
 	})
-	return dm, dErr
-}
-
-type dialManager struct {
-	lock      sync.RWMutex
-	instances map[string]*cloudsql.Instance
-
-	sqladmin *sqladmin.Service
-	key      *rsa.PrivateKey
-}
-
-func newDialManager() (*dialManager, error) {
-	// TODO: Add ability to customize keys / clients
-	key, err := rsa.GenerateKey(rand.Reader, 2048)
-	if err != nil {
-		return nil, fmt.Errorf("failed to generate rsa keys: %v", err)
-	}
-	client, err := sqladmin.NewService(context.Background())
-	if err != nil {
-		return nil, fmt.Errorf("failed to create sqladmin client: %v", err)
-	}
-	d := &dialManager{
-		instances: make(map[string]*cloudsql.Instance),
-		sqladmin:  client,
-		key:       key,
-	}
-	return d, nil
-}
-
-func (d *dialManager) instance(connName string) (*cloudsql.Instance, error) {
-	// Check instance cache
-	d.lock.RLock()
-	i, ok := d.instances[connName]
-	d.lock.RUnlock()
-	if !ok {
-		d.lock.Lock()
-		// Recheck to ensure instance wasn't created between locks
-		i, ok = d.instances[connName]
-		if !ok {
-			// Create a new instance
-			var err error
-			i, err = cloudsql.NewInstance(connName, d.sqladmin, d.key)
-			if err != nil {
-				d.lock.Unlock()
-				return nil, err
-			}
-			d.instances[connName] = i
-		}
-		d.lock.Unlock()
-	}
-	return i, nil
-}
-
-func (d *dialManager) dial(ctx context.Context, instance string) (net.Conn, error) {
-	i, err := d.instance(instance)
-	if err != nil {
-		return nil, err
-	}
-	return i.Connect(ctx)
+	return defaultDialer, dErr
 }

dialer.go

@@ -0,0 +1,99 @@
+// Copyright 2020 Google LLC
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cloudsqlconn
+
+import (
+	"context"
+	"crypto/rand"
+	"crypto/rsa"
+	"fmt"
+	"net"
+	"sync"
+
+	"cloud.google.com/cloudsqlconn/internal/cloudsql"
+	apiopt "google.golang.org/api/option"
+	sqladmin "google.golang.org/api/sqladmin/v1beta4"
+)
+
+type dialerConfig struct {
+	sqladminOpts []apiopt.ClientOption
+}
+
+// A Dialer is used to create connections to Cloud SQL instances.
+type Dialer struct {
+	lock      sync.RWMutex
+	instances map[string]*cloudsql.Instance
+	key       *rsa.PrivateKey
+
+	sqladmin *sqladmin.Service
+}
+
+// NewDialer creates a new Dialer.
+func NewDialer(ctx context.Context, opts ...DialerOption) (*Dialer, error) {
+	// TODO: Add shared / async key generation
+	key, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate rsa keys: %v", err)
+	}
+
+	cfg := &dialerConfig{}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+
+	client, err := sqladmin.NewService(context.Background(), cfg.sqladminOpts...)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create sqladmin client: %v", err)
+	}
+	d := &Dialer{
+		instances: make(map[string]*cloudsql.Instance),
+		sqladmin:  client,
+		key:       key,
+	}
+	return d, nil
+}
+
+// Dial creates an authorized connection to a Cloud SQL instance specified by it's instance connection name.
+func (d *Dialer) Dial(ctx context.Context, instance string) (net.Conn, error) {
+	i, err := d.instance(instance)
+	if err != nil {
+		return nil, err
+	}
+	return i.Connect(ctx)
+}
+
+func (d *Dialer) instance(connName string) (*cloudsql.Instance, error) {
+	// Check instance cache
+	d.lock.RLock()
+	i, ok := d.instances[connName]
+	d.lock.RUnlock()
+	if !ok {
+		d.lock.Lock()
+		// Recheck to ensure instance wasn't created between locks
+		i, ok = d.instances[connName]
+		if !ok {
+			// Create a new instance
+			var err error
+			i, err = cloudsql.NewInstance(connName, d.sqladmin, d.key)
+			if err != nil {
+				d.lock.Unlock()
+				return nil, err
+			}
+			d.instances[connName] = i
+		}
+		d.lock.Unlock()
+	}
+	return i, nil
+}

go.mod

@@ -5,7 +5,7 @@ go 1.14
 require (
 	github.com/jackc/pgx/v4 v4.10.1
 	golang.org/x/net v0.0.0-20200904194848-62affa334b73
-	golang.org/x/oauth2 v0.0.0-20200902213428-5d25da1a8d43 // indirect
+	golang.org/x/oauth2 v0.0.0-20200902213428-5d25da1a8d43
 	golang.org/x/sys v0.0.0-20200909081042-eff7692f9009 // indirect
 	google.golang.org/api v0.31.0
 	google.golang.org/genproto v0.0.0-20200911024640-645f7a48b24f // indirect

options.go

@@ -0,0 +1,53 @@
+// Copyright 2020 Google LLC
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cloudsqlconn
+
+import (
+	"golang.org/x/oauth2"
+	apiopt "google.golang.org/api/option"
+)
+
+// A DialerOption is an option for configuring a Dialer.
+type DialerOption func(d *dialerConfig)
+
+// DialerOptions turns a list of DialerOption instances into a DialerOption.
+func DialerOptions(opts ...DialerOption) DialerOption {
+	return func(d *dialerConfig) {
+		for _, opt := range opts {
+			opt(d)
+		}
+	}
+}
+
+// WithCredentialsFile returns a DialerOption that specifies a service account or refresh token JSON credentials file to be used as the basis for authentication.
+func WithCredentialsFile(filename string) DialerOption {
+	return func(d *dialerConfig) {
+		d.sqladminOpts = append(d.sqladminOpts, apiopt.WithCredentialsFile(filename))
+	}
+}
+
+// WithCredentialsJSON returns a DialerOption that specifies a service account or refresh token JSON credentials to be used as the basis for authentication.
+func WithCredentialsJSON(p []byte) DialerOption {
+	return func(d *dialerConfig) {
+		d.sqladminOpts = append(d.sqladminOpts, apiopt.WithCredentialsJSON(p))
+	}
+}
+
+// WithTokenSource returns a DialerOption that specifies an OAuth2 token source to be used as the basis for authentication.
+func WithTokenSource(s oauth2.TokenSource) DialerOption {
+	return func(d *dialerConfig) {
+		d.sqladminOpts = append(d.sqladminOpts, apiopt.WithTokenSource(s))
+	}
+}