storage/sql/postgres: expose stdlib tunables, set them for tests

- adapted TestUnmarshalConfig to ensure the fields are read in
- added a test to see that at least MaxOpenConns works:
  - this is only exposed through (*db).Stats() in go 1.11, so this test
    has a build tag
  - the other two configurables can't be read back, so we've got to
    trust that the mechanism works given the one instance that's tested..

Signed-off-by: Stephan Renatus <srenatus@chef.io>

cmd/dex/config_test.go

@@ -18,10 +18,14 @@ func TestUnmarshalConfig(t *testing.T) {
 	rawConfig := []byte(`
 issuer: http://127.0.0.1:5556/dex
 storage:
-  type: sqlite3
+  type: postgres
   config:
-    file: examples/dex.db
+    host: 10.0.0.1
-
+    port: 65432
+    maxOpenConns: 5
+    maxIdleConns: 3
+    connMaxLifetime: 30
+    connectionTimeout: 3
 web:
   http: 127.0.0.1:5556
 staticClients:
@@ -69,9 +73,14 @@ logger:
 	want := Config{
 		Issuer: "http://127.0.0.1:5556/dex",
 		Storage: Storage{
-			Type: "sqlite3",
+			Type: "postgres",
-			Config: &sql.SQLite3{
+			Config: &sql.Postgres{
-				File: "examples/dex.db",
+				Host:              "10.0.0.1",
+				Port:              65432,
+				MaxOpenConns:      5,
+				MaxIdleConns:      3,
+				ConnMaxLifetime:   30,
+				ConnectionTimeout: 3,
 			},
 		},
 		Web: Web{

storage/sql/config.go

@@ -7,6 +7,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/lib/pq"
 	sqlite3 "github.com/mattn/go-sqlite3"
@@ -88,6 +89,13 @@ type Postgres struct {
 	SSL PostgresSSL `json:"ssl" yaml:"ssl"`
 
 	ConnectionTimeout int // Seconds
+
+	// database/sql tunables, see
+	// https://golang.org/pkg/database/sql/#DB.SetConnMaxLifetime and below
+	// Note: defaults will be set if these are 0
+	MaxOpenConns    int // default: 5
+	MaxIdleConns    int // default: 5
+	ConnMaxLifetime int // Seconds, default: not set
 }
 
 // Open creates a new storage implementation backed by Postgres.
@@ -177,6 +185,23 @@ func (p *Postgres) open(logger logrus.FieldLogger, dataSourceName string) (*conn
 		return nil, err
 	}
 
+	// set database/sql tunables if configured
+	if p.ConnMaxLifetime != 0 {
+		db.SetConnMaxLifetime(time.Duration(p.ConnMaxLifetime) * time.Second)
+	}
+
+	if p.MaxIdleConns == 0 {
+		db.SetMaxIdleConns(5)
+	} else {
+		db.SetMaxIdleConns(p.MaxIdleConns)
+	}
+
+	if p.MaxOpenConns == 0 {
+		db.SetMaxOpenConns(5)
+	} else {
+		db.SetMaxOpenConns(p.MaxOpenConns)
+	}
+
 	errCheck := func(err error) bool {
 		sqlErr, ok := err.(*pq.Error)
 		if !ok {

storage/sql/postgres_test.go

@@ -0,0 +1,48 @@
+// +build go1.11
+
+package sql
+
+import (
+	"os"
+	"testing"
+)
+
+func TestPostgresTunables(t *testing.T) {
+	host := os.Getenv(testPostgresEnv)
+	if host == "" {
+		t.Skipf("test environment variable %q not set, skipping", testPostgresEnv)
+	}
+	baseCfg := &Postgres{
+		Database: getenv("DEX_POSTGRES_DATABASE", "postgres"),
+		User:     getenv("DEX_POSTGRES_USER", "postgres"),
+		Password: getenv("DEX_POSTGRES_PASSWORD", "postgres"),
+		Host:     host,
+		SSL: PostgresSSL{
+			Mode: sslDisable, // Postgres container doesn't support SSL.
+		}}
+
+	t.Run("with nothing set, uses defaults", func(t *testing.T) {
+		cfg := *baseCfg
+		c, err := cfg.open(logger, cfg.createDataSourceName())
+		if err != nil {
+			t.Fatalf("error opening connector: %s", err.Error())
+		}
+		defer c.db.Close()
+		if m := c.db.Stats().MaxOpenConnections; m != 5 {
+			t.Errorf("expected MaxOpenConnections to have its default (5), got %d", m)
+		}
+	})
+
+	t.Run("with something set, uses that", func(t *testing.T) {
+		cfg := *baseCfg
+		cfg.MaxOpenConns = 101
+		c, err := cfg.open(logger, cfg.createDataSourceName())
+		if err != nil {
+			t.Fatalf("error opening connector: %s", err.Error())
+		}
+		defer c.db.Close()
+		if m := c.db.Stats().MaxOpenConnections; m != 101 {
+			t.Errorf("expected MaxOpenConnections to be set to 101, got %d", m)
+		}
+	})
+}