database: Allow specifying datastore driver by config

Fixes #145

clair.go

@@ -26,7 +26,7 @@ import (
 	"github.com/coreos/clair/api"
 	"github.com/coreos/clair/api/context"
 	"github.com/coreos/clair/config"
-	"github.com/coreos/clair/database/pgsql"
+	"github.com/coreos/clair/database"
 	"github.com/coreos/clair/notifier"
 	"github.com/coreos/clair/updater"
 	"github.com/coreos/clair/utils"
@@ -42,7 +42,7 @@ func Boot(config *config.Config) {
 	st := utils.NewStopper()
 
 	// Open database
-	db, err := pgsql.Open(config.Database)
+	db, err := database.Open(config.Database)
 	if err != nil {
 		log.Fatal(err)
 	}

cmd/clair/main.go

@@ -20,11 +20,11 @@ import (
 	"runtime/pprof"
 	"strings"
 
+	"github.com/coreos/pkg/capnslog"
+
 	"github.com/coreos/clair"
 	"github.com/coreos/clair/config"
 
-	"github.com/coreos/pkg/capnslog"
-
 	// Register components
 	_ "github.com/coreos/clair/notifier/notifiers"
 
@@ -43,6 +43,8 @@ import (
 	_ "github.com/coreos/clair/worker/detectors/namespace/lsbrelease"
 	_ "github.com/coreos/clair/worker/detectors/namespace/osrelease"
 	_ "github.com/coreos/clair/worker/detectors/namespace/redhatrelease"
+
+	_ "github.com/coreos/clair/database/pgsql"
 )
 
 var log = capnslog.NewPackageLogger("github.com/coreos/clair/cmd/clair", "main")

config.example.yaml

@@ -15,13 +15,16 @@
 # The values specified here are the default values that Clair uses if no configuration file is specified or if the keys are not defined.
 clair:
   database:
-    # PostgreSQL Connection string
-    # http://www.postgresql.org/docs/9.4/static/libpq-connect.html
-    source:
+    # Database driver
+    type: pgsql
+    options:
+      # PostgreSQL Connection string
+      # http://www.postgresql.org/docs/9.4/static/libpq-connect.html
+      source:
 
-    # Number of elements kept in the cache
-    # Values unlikely to change (e.g. namespaces) are cached in order to save prevent needless roundtrips to the database.
-    cacheSize: 16384
+      # Number of elements kept in the cache
+      # Values unlikely to change (e.g. namespaces) are cached in order to save prevent needless roundtrips to the database.
+      cachesize: 16384
 
   api:
     # API server port

config/config.go

@@ -27,6 +27,14 @@ import (
 // ErrDatasourceNotLoaded is returned when the datasource variable in the configuration file is not loaded properly
 var ErrDatasourceNotLoaded = errors.New("could not load configuration: no database source specified")
 
+// RegistrableComponentConfig is a configuration block that can be used to
+// determine which registrable component should be initialized and pass
+// custom configuration to it.
+type RegistrableComponentConfig struct {
+	Type    string
+	Options map[string]interface{}
+}
+
 // File represents a YAML configuration file that namespaces all Clair
 // configuration under the top-level "clair" key.
 type File struct {
@@ -35,19 +43,12 @@ type File struct {
 
 // Config is the global configuration for an instance of Clair.
 type Config struct {
-	Database *DatabaseConfig
+	Database RegistrableComponentConfig
 	Updater  *UpdaterConfig
 	Notifier *NotifierConfig
 	API      *APIConfig
 }
 
-// DatabaseConfig is the configuration used to specify how Clair connects
-// to a database.
-type DatabaseConfig struct {
-	Source    string
-	CacheSize int
-}
-
 // UpdaterConfig is the configuration for the Updater service.
 type UpdaterConfig struct {
 	Interval time.Duration
@@ -72,8 +73,8 @@ type APIConfig struct {
 // DefaultConfig is a configuration that can be used as a fallback value.
 func DefaultConfig() Config {
 	return Config{
-		Database: &DatabaseConfig{
-			CacheSize: 16384,
+		Database: RegistrableComponentConfig{
+			Type: "pgsql",
 		},
 		Updater: &UpdaterConfig{
 			Interval: 1 * time.Hour,
@@ -116,12 +117,8 @@ func Load(path string) (config *Config, err error) {
 	}
 	config = &cfgFile.Clair
 
-	if config.Database.Source == "" {
-		err = ErrDatasourceNotLoaded
-		return
-	}
-
 	// Generate a pagination key if none is provided.
+	// TODO(Quentin-M): Move to the API code.
 	if config.API.PaginationKey == "" {
 		var key fernet.Key
 		if err = key.Generate(); err != nil {

database/database.go

@@ -17,7 +17,10 @@ package database
 
 import (
 	"errors"
+	"fmt"
 	"time"
+
+	"github.com/coreos/clair/config"
 )
 
 var (
@@ -28,11 +31,37 @@ var (
 	// ErrInconsistent is an error that occurs when a database consistency check
 	// fails (ie. when an entity which is supposed to be unique is detected twice)
 	ErrInconsistent = errors.New("database: inconsistent database")
-
-	// ErrCantOpen is an error that occurs when the database could not be opened
-	ErrCantOpen = errors.New("database: could not open database")
 )
 
+var drivers = make(map[string]Driver)
+
+// Driver is a function that opens a Datastore specified by its database driver type and specific
+// configuration.
+type Driver func(config.RegistrableComponentConfig) (Datastore, error)
+
+// Register makes a Constructor available by the provided name.
+//
+// If this function is called twice with the same name or if the Constructor is
+// nil, it panics.
+func Register(name string, driver Driver) {
+	if driver == nil {
+		panic("database: could not register nil Driver")
+	}
+	if _, dup := drivers[name]; dup {
+		panic("database: could not register duplicate Driver: " + name)
+	}
+	drivers[name] = driver
+}
+
+// Open opens a Datastore specified by a configuration.
+func Open(cfg config.RegistrableComponentConfig) (Datastore, error) {
+	driver, ok := drivers[cfg.Type]
+	if !ok {
+		return nil, fmt.Errorf("database: unknown Driver %q (forgotten configuration or import?)", cfg.Type)
+	}
+	return driver(cfg)
+}
+
 // Datastore is the interface that describes a database backend implementation.
 type Datastore interface {
 	// # Namespace

database/pgsql/complex_test.go

@@ -23,11 +23,12 @@ import (
 	"testing"
 	"time"
 
+	"github.com/pborman/uuid"
+	"github.com/stretchr/testify/assert"
+
 	"github.com/coreos/clair/database"
 	"github.com/coreos/clair/utils"
 	"github.com/coreos/clair/utils/types"
-	"github.com/pborman/uuid"
-	"github.com/stretchr/testify/assert"
 )
 
 const (
@@ -36,7 +37,7 @@ const (
 )
 
 func TestRaceAffects(t *testing.T) {
-	datastore, err := OpenForTest("RaceAffects", false)
+	datastore, err := openDatabaseForTest("RaceAffects", false)
 	if err != nil {
 		t.Error(err)
 		return

database/pgsql/feature_test.go

@@ -17,13 +17,14 @@ package pgsql
 import (
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+
 	"github.com/coreos/clair/database"
 	"github.com/coreos/clair/utils/types"
-	"github.com/stretchr/testify/assert"
 )
 
 func TestInsertFeature(t *testing.T) {
-	datastore, err := OpenForTest("InsertFeature", false)
+	datastore, err := openDatabaseForTest("InsertFeature", false)
 	if err != nil {
 		t.Error(err)
 		return

database/pgsql/keyvalue_test.go

@@ -21,7 +21,7 @@ import (
 )
 
 func TestKeyValue(t *testing.T) {
-	datastore, err := OpenForTest("KeyValue", false)
+	datastore, err := openDatabaseForTest("KeyValue", false)
 	if err != nil {
 		t.Error(err)
 		return

database/pgsql/layer.go

@@ -41,9 +41,7 @@ func (pgSQL *pgSQL) FindLayer(name string, withFeatures, withVulnerabilities boo
 	var namespaceName sql.NullString
 
 	t := time.Now()
-	err := pgSQL.QueryRow(searchLayer, name).
-		Scan(&layer.ID, &layer.Name, &layer.EngineVersion, &parentID, &parentName, &namespaceID,
-			&namespaceName)
+	err := pgSQL.QueryRow(searchLayer, name).Scan(&layer.ID, &layer.Name, &layer.EngineVersion, &parentID, &parentName, &namespaceID, &namespaceName)
 	observeQueryTime("FindLayer", "searchLayer", t)
 
 	if err != nil {

database/pgsql/layer_test.go

@@ -18,14 +18,15 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+
 	"github.com/coreos/clair/database"
 	cerrors "github.com/coreos/clair/utils/errors"
 	"github.com/coreos/clair/utils/types"
-	"github.com/stretchr/testify/assert"
 )
 
 func TestFindLayer(t *testing.T) {
-	datastore, err := OpenForTest("FindLayer", true)
+	datastore, err := openDatabaseForTest("FindLayer", true)
 	if err != nil {
 		t.Error(err)
 		return
@@ -102,7 +103,7 @@ func TestFindLayer(t *testing.T) {
 }
 
 func TestInsertLayer(t *testing.T) {
-	datastore, err := OpenForTest("InsertLayer", false)
+	datastore, err := openDatabaseForTest("InsertLayer", false)
 	if err != nil {
 		t.Error(err)
 		return

database/pgsql/lock_test.go

@@ -22,7 +22,7 @@ import (
 )
 
 func TestLock(t *testing.T) {
-	datastore, err := OpenForTest("InsertNamespace", false)
+	datastore, err := openDatabaseForTest("InsertNamespace", false)
 	if err != nil {
 		t.Error(err)
 		return

database/pgsql/namespace_test.go

@@ -18,12 +18,13 @@ import (
 	"fmt"
 	"testing"
 
-	"github.com/coreos/clair/database"
 	"github.com/stretchr/testify/assert"
+
+	"github.com/coreos/clair/database"
 )
 
 func TestInsertNamespace(t *testing.T) {
-	datastore, err := OpenForTest("InsertNamespace", false)
+	datastore, err := openDatabaseForTest("InsertNamespace", false)
 	if err != nil {
 		t.Error(err)
 		return
@@ -44,7 +45,7 @@ func TestInsertNamespace(t *testing.T) {
 }
 
 func TestListNamespace(t *testing.T) {
-	datastore, err := OpenForTest("ListNamespaces", true)
+	datastore, err := openDatabaseForTest("ListNamespaces", true)
 	if err != nil {
 		t.Error(err)
 		return

database/pgsql/notification_test.go

@@ -4,14 +4,15 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
+
 	"github.com/coreos/clair/database"
 	cerrors "github.com/coreos/clair/utils/errors"
 	"github.com/coreos/clair/utils/types"
-	"github.com/stretchr/testify/assert"
 )
 
 func TestNotification(t *testing.T) {
-	datastore, err := OpenForTest("Notification", false)
+	datastore, err := openDatabaseForTest("Notification", false)
 	if err != nil {
 		t.Error(err)
 		return