Go Plug-in/Module Support

This patch replaces PR thecodeteam#557 and introduces support for type-isolated Go
plug-ins. The 'api/types/v1' package represents an initial version of
the libStorage type system transformed into interfaces for use by
independent, separate module files.

api/mods/mods.go

@@ -0,0 +1,118 @@
+// +build go1.8,linux,mods
+
+package mods
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"plugin"
+	"strconv"
+	"sync"
+
+	"github.com/akutz/gotil"
+
+	"github.com/codedellemc/libstorage/api/registry"
+	"github.com/codedellemc/libstorage/api/types"
+)
+
+var (
+	loadedMods     = map[string]bool{}
+	loadedModsLock = sync.Mutex{}
+)
+
+// LoadModules loads the shared objects present on the file system
+// as libStorage plug-ins.
+func LoadModules(
+	ctx types.Context,
+	pathConfig *types.PathConfig) error {
+
+	disabled, _ := strconv.ParseBool(
+		os.Getenv("LIBSTORAGE_PLUGINS_DISABLED"))
+	if disabled {
+		ctx.Debug("plugin support disabled")
+		return nil
+	}
+
+	loadedModsLock.Lock()
+	defer loadedModsLock.Unlock()
+
+	if !gotil.FileExists(pathConfig.Mod) {
+		return fmt.Errorf("error: invalid mod dir: %v", pathConfig.Mod)
+	}
+
+	modFilePathMatches, err := filepath.Glob(path.Join(pathConfig.Mod, "/*.so"))
+	if err != nil {
+		// since the only possible error is ErrBadPattern then make sure
+		// it panics the program since it should never be an invalid pattern
+		panic(err)
+	}
+
+	for _, modFilePath := range modFilePathMatches {
+		ctx.WithField(
+			"path", modFilePath).Debug(
+			"loading module")
+
+		if loaded, ok := loadedMods[modFilePath]; ok && loaded {
+			ctx.WithField(
+				"path", modFilePath).Debug(
+				"already loaded")
+			continue
+		}
+
+		p, err := plugin.Open(modFilePath)
+		if err != nil {
+			ctx.WithError(err).WithField(
+				"path", modFilePath).Error(
+				"error opening module")
+			continue
+		}
+
+		if err := loadPluginTypes(ctx, p); err != nil {
+			continue
+		}
+
+		loadedMods[modFilePath] = true
+		ctx.WithField(
+			"path", modFilePath).Info(
+			"loaded module")
+	}
+
+	return nil
+}
+
+func loadPluginTypes(ctx types.Context, p *plugin.Plugin) error {
+	// lookup the plug-in's Types symbol; it's the type map used to
+	// register the plug-in's modules
+	tmapObj, err := p.Lookup("Types")
+	if err != nil {
+		ctx.WithError(err).Error("error looking up type map")
+		return err
+	}
+
+	// assert that the Types symbol is a *map[string]func() interface{}
+	tmapPtr, tmapOk := tmapObj.(*map[string]func() interface{})
+	if !tmapOk {
+		err := fmt.Errorf("invalid type map: %T", tmapObj)
+		ctx.Error(err)
+		return err
+	}
+
+	// assert that the type map pointer is not nil
+	if tmapPtr == nil {
+		err := fmt.Errorf("nil type map: type=%[1]T val=%[1]v", tmapPtr)
+		ctx.Error(err)
+		return err
+	}
+
+	// dereference the type map pointer
+	tmap := *tmapPtr
+
+	// register the plug-in's modules
+	for k, v := range tmap {
+		registry.RegisterModType(k, v)
+	}
+
+	return nil
+}

api/mods/nomods.go

@@ -0,0 +1,16 @@
+// +build !go1.8 !linux !mods
+
+package mods
+
+import (
+	"github.com/codedellemc/libstorage/api/types"
+)
+
+// LoadModules loads the shared objects present on the file system
+// as libStorage plug-ins.
+func LoadModules(
+	ctx types.Context,
+	pathConfig *types.PathConfig) {
+
+	// Do nothing
+}

api/registry/registry.go

@@ -3,16 +3,21 @@
 package registry
 
 import (
+	"fmt"
 	"strings"
 	"sync"
 
 	gofig "github.com/akutz/gofig/types"
 	"github.com/akutz/goof"
 
 	"github.com/codedellemc/libstorage/api/types"
+	apitypesV1 "github.com/codedellemc/libstorage/api/types/v1"
 )
 
 var (
+	modTypeCtors    = map[string]func() interface{}{}
+	modTypeCtorsRWL = &sync.RWMutex{}
+
 	storExecsCtors    = map[string]types.NewStorageExecutor{}
 	storExecsCtorsRWL = &sync.RWMutex{}
 
@@ -44,6 +49,13 @@ func RegisterConfigReg(name string, f types.NewConfigReg) {
 	cfgRegs = append(cfgRegs, &cregW{name, f})
 }
 
+// RegisterModType registers a type from a plug-in mod.
+func RegisterModType(name string, ctor func() interface{}) {
+	modTypeCtorsRWL.Lock()
+	defer modTypeCtorsRWL.Unlock()
+	modTypeCtors[strings.ToLower(name)] = ctor
+}
+
 // RegisterRouter registers a Router.
 func RegisterRouter(router types.Router) {
 	routersRWL.Lock()
@@ -80,6 +92,31 @@ func RegisterIntegrationDriver(name string, ctor types.NewIntegrationDriver) {
 	intDriverCtors[strings.ToLower(name)] = ctor
 }
 
+// NewModType returns a new instance of the specified module type.
+func NewModType(name string) (apitypesV1.Driver, error) {
+
+	var ok bool
+	var ctor func() interface{}
+
+	func() {
+		modTypeCtorsRWL.RLock()
+		defer modTypeCtorsRWL.RUnlock()
+		ctor, ok = modTypeCtors[name]
+	}()
+
+	if !ok {
+		return nil, goof.WithField("modType", name, "invalid type name")
+	}
+
+	d, ok := ctor().(apitypesV1.Driver)
+	if !ok {
+		return nil, goof.WithField(
+			"modType", fmt.Sprintf("%T", d), "invalid type")
+	}
+
+	return d, nil
+}
+
 // NewStorageExecutor returns a new instance of the executor specified by the
 // executor name.
 func NewStorageExecutor(name string) (types.StorageExecutor, error) {
@@ -177,6 +214,23 @@ func ConfigRegs(ctx types.Context) <-chan gofig.ConfigRegistration {
 	return c
 }
 
+// ModTypes returns a channel on which new instances of all registered
+// module types.
+func ModTypes() <-chan apitypesV1.Driver {
+	c := make(chan apitypesV1.Driver)
+	go func() {
+		modTypeCtorsRWL.RLock()
+		defer modTypeCtorsRWL.RUnlock()
+		for _, ctor := range modTypeCtors {
+			if d, ok := ctor().(apitypesV1.Driver); ok {
+				c <- d
+			}
+		}
+		close(c)
+	}()
+	return c
+}
+
 // StorageExecutors returns a channel on which new instances of all registered
 // storage executors can be received.
 func StorageExecutors() <-chan types.StorageExecutor {

api/types/types_paths.go

@@ -15,6 +15,9 @@ type PathConfig struct {
 	// Lib is the path to the lib directory.
 	Lib string
 
+	// Mod is the path to the mod directory.
+	Mod string
+
 	// Log is the path to the log directory.
 	Log string
 

api/types/v1/v1_auth.go

@@ -0,0 +1,42 @@
+package v1
+
+// AuthToken is a JSON Web Token.
+//
+// All fields related to times are stored as UTC epochs in seconds.
+type AuthToken interface {
+
+	// GetSubject is the intended principal of the token.
+	GetSubject() string
+
+	// GetExpires is the time at which the token expires.
+	GetExpires() int64
+
+	// GetNotBefore is the the time at which the token becomes valid.
+	GetNotBefore() int64
+
+	// GetIssuedAt is the time at which the token was issued.
+	GetIssuedAt() int64
+
+	// GetEncoded is the encoded JWT string.
+	GetEncoded() string
+}
+
+// AuthConfig is the auth configuration.
+type AuthConfig interface {
+
+	// GetDisabled is a flag indicating whether the auth configuration is
+	// disabled.
+	GetDisabled() bool
+
+	// GetAllow is a list of allowed tokens.
+	GetAllow() []string
+
+	// GetDeny is a list of denied tokens.
+	GetDeny() []string
+
+	// GetKey is the signing key.
+	GetKey() []byte
+
+	// GetAlg is the cryptographic algorithm used to sign and verify the token.
+	GetAlg() string
+}

api/types/v1/v1_config.go

@@ -0,0 +1,30 @@
+package v1
+
+// Config is the interface that enables retrieving configuration information.
+// The variations of the Get function, the Set, IsSet, and Scope functions
+// all take an interface{} as their first parameter. However, the param must be
+// either a string or a fmt.Stringer, otherwise the function will panic.
+type Config interface {
+
+	// GetString returns the value associated with the key as a string
+	GetString(k interface{}) string
+
+	// GetBool returns the value associated with the key as a bool
+	GetBool(k interface{}) bool
+
+	// GetStringSlice returns the value associated with the key as a string
+	// slice.
+	GetStringSlice(k interface{}) []string
+
+	// GetInt returns the value associated with the key as an int
+	GetInt(k interface{}) int
+
+	// Get returns the value associated with the key
+	Get(k interface{}) interface{}
+
+	// Set sets an override value
+	Set(k interface{}, v interface{})
+
+	// IsSet returns a flag indicating whether or not a key is set.
+	IsSet(k interface{}) bool
+}

api/types/v1/v1_context.go

@@ -0,0 +1,28 @@
+package v1
+
+import "context"
+
+// Context is an extension of the Go Context.
+type Context interface {
+	context.Context
+}
+
+// ContextLoggerFieldAware is used by types that will be logged by the
+// Context logger. The key/value pair returned by the type is then emitted
+// as part of  the Context's log entry.
+type ContextLoggerFieldAware interface {
+
+	// ContextLoggerField is the fields that is logged as part of a Context's
+	// log entry.
+	ContextLoggerField() (string, interface{})
+}
+
+// ContextLoggerFieldsAware is used by types that will be logged by the
+// Context logger. The fields returned by the type are then emitted as part of
+// the Context's log entry.
+type ContextLoggerFieldsAware interface {
+
+	// ContextLoggerFields are the fields that are logged as part of a
+	// Context's log entry.
+	ContextLoggerFields() map[string]interface{}
+}

api/types/v1/v1_driver.go

@@ -0,0 +1,28 @@
+package v1
+
+// Driver the interface for types that are drivers.
+type Driver interface {
+
+	// Do does the operation specified by the opID.
+	Do(
+		ctx interface{},
+		opID uint64,
+		args ...interface{}) (result interface{}, err error)
+
+	// Init initializes the driver instance.
+	Init(ctx, config interface{}) error
+
+	// Name returns the name of the driver.
+	Name() string
+
+	// Supports returns a mask of the operations supported by the driver.
+	Supports() uint64
+}
+
+const (
+	// DtStorage indicates the storage driver type.
+	DtStorage uint8 = 1 << iota
+
+	// DtIntegration indicates the integration driver type.
+	DtIntegration
+)

api/types/v1/v1_errors.go

@@ -0,0 +1,22 @@
+package v1
+
+import "errors"
+
+// ErrInvalidContext indicates an invalid object was provided as
+// the argument to a Context parameter.
+var ErrInvalidContext = errors.New("invalid context type")
+
+// ErrInvalidConfig indicates an invalid object was provided as
+// the argument to a Config parameter.
+var ErrInvalidConfig = errors.New("invalid config type")
+
+// ErrInvalidOp indicates an invalid operation ID.
+var ErrInvalidOp = errors.New("invalid op")
+
+// ErrInvalidArgsLen indicates the operation received an incorrect
+// number of arguments.
+var ErrInvalidArgsLen = errors.New("invalid args len")
+
+// ErrInvalidArgs indicates the operation received one or more
+// invalid arguments.
+var ErrInvalidArgs = errors.New("invalid args")