Go 1.8 Plug-in Support

This patch introduces support for loading Linux shared object (.so)
files as Go 1.8 plug-ins. This feature requires Linux.

Author: akutz

Makefile

@@ -305,7 +305,7 @@ GO_STDLIB := archive archive/tar archive/zip bufio builtin bytes compress \
 			 runtime/trace sort strconv strings sync sync/atomic syscall \
 			 testing testing/iotest testing/quick text text/scanner \
 			 text/tabwriter text/template text/template/parse time unicode \
-			 unicode/utf16 unicode/utf8 unsafe
+			 unicode/utf16 unicode/utf8 unsafe context plugin
 
 
 ################################################################################

api/mods/mods.go

@@ -0,0 +1,63 @@
+// +build go1.8,linux
+
+package mods
+
+import (
+	"io/ioutil"
+	"plugin"
+	"strings"
+	"sync"
+
+	"github.com/akutz/gotil"
+
+	"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) {
+
+	loadedModsLock.Lock()
+	defer loadedModsLock.Unlock()
+
+	if !gotil.FileExists(pathConfig.Mod) {
+		return
+	}
+	modFiles, err := ioutil.ReadDir(pathConfig.Mod)
+	if err != nil {
+		ctx.WithField("path", pathConfig.Mod).Warn(
+			"failed to list module files")
+		return
+	}
+	for _, f := range modFiles {
+		modFilePath := f.Name()
+		ctx.WithField(
+			"path", modFilePath).Debug(
+			"loading module")
+		lcModFilePath := strings.ToLower(modFilePath)
+		if loaded, ok := loadedMods[lcModFilePath]; ok && loaded {
+			ctx.WithField(
+				"path", modFilePath).Debug(
+				"already loaded")
+			continue
+		}
+		_, err := plugin.Open(modFilePath)
+		if err != nil {
+			ctx.WithError(err).WithField(
+				"path", modFilePath).Error(
+				"error opening module")
+			continue
+		}
+		loadedMods[lcModFilePath] = true
+		ctx.WithField(
+			"path", modFilePath).Info(
+			"loaded module")
+	}
+}

api/mods/nomods.go

@@ -0,0 +1,16 @@
+// +build !go1.8 !linux
+
+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) {
+
+	// NOOP
+}

api/types/types_paths.go

@@ -18,6 +18,9 @@ type PathConfig struct {
 	// Log is the path to the log directory.
 	Log string
 
+	// Mod is the path to the mod directory.
+	Mod string
+
 	// Run is the path to the run directory.
 	Run string
 

api/utils/utils_paths.go

@@ -36,6 +36,7 @@ func NewPathConfig(ctx types.Context, home, token string) *types.PathConfig {
 		envVarHomeEtc    = fmt.Sprintf("%s_HOME_ETC", ucTok)
 		envVarHomeEtcTLS = fmt.Sprintf("%s_HOME_ETC_TLS", ucTok)
 		envVarHomeLib    = fmt.Sprintf("%s_HOME_LIB", ucTok)
+		envVarHomeLibMod = fmt.Sprintf("%s_HOME_LIB_MOD", ucTok)
 		envVarHomeLog    = fmt.Sprintf("%s_HOME_LOG", ucTok)
 		envVarHomeRun    = fmt.Sprintf("%s_HOME_RUN", ucTok)
 		envVarHomeLSX    = fmt.Sprintf("%s_HOME_LSX", ucTok)
@@ -57,6 +58,7 @@ func NewPathConfig(ctx types.Context, home, token string) *types.PathConfig {
 	initPathConfigFieldWithEnvVar(ctx, envVarHomeEtc, &pathConfig.Etc)
 	initPathConfigFieldWithEnvVar(ctx, envVarHomeEtcTLS, &pathConfig.TLS)
 	initPathConfigFieldWithEnvVar(ctx, envVarHomeLib, &pathConfig.Lib)
+	initPathConfigFieldWithEnvVar(ctx, envVarHomeLibMod, &pathConfig.Mod)
 	initPathConfigFieldWithEnvVar(ctx, envVarHomeLog, &pathConfig.Log)
 	initPathConfigFieldWithEnvVar(ctx, envVarHomeRun, &pathConfig.Run)
 	initPathConfigFieldWithEnvVar(ctx, envVarHomeLSX, &pathConfig.LSX)
@@ -84,6 +86,8 @@ func NewPathConfig(ctx types.Context, home, token string) *types.PathConfig {
 		ctx, false, true, token, pathConfig.Etc, "tls", &pathConfig.TLS)
 	initPathConfigFieldWithPath(
 		ctx, root, true, token, pathConfig.Home, "var/lib", &pathConfig.Lib)
+	initPathConfigFieldWithPath(
+		ctx, false, true, token, pathConfig.Lib, "mod", &pathConfig.Mod)
 	initPathConfigFieldWithPath(
 		ctx, root, true, token, pathConfig.Home, "var/log", &pathConfig.Log)
 	initPathConfigFieldWithPath(

cli/lsx/lsx.go

@@ -14,6 +14,7 @@ import (
 	"github.com/akutz/goof"
 
 	"github.com/codedellemc/libstorage/api/context"
+	apimods "github.com/codedellemc/libstorage/api/mods"
 	"github.com/codedellemc/libstorage/api/registry"
 	apitypes "github.com/codedellemc/libstorage/api/types"
 	"github.com/codedellemc/libstorage/api/utils"
@@ -31,7 +32,12 @@ var cmdRx = regexp.MustCompile(
 func Run() {
 
 	ctx := context.Background()
-	ctx = ctx.WithValue(context.PathConfigKey, utils.NewPathConfig(ctx, "", ""))
+	pathConfig := utils.NewPathConfig(ctx, "", "")
+	ctx = ctx.WithValue(context.PathConfigKey, pathConfig)
+
+	// load shared objects
+	apimods.LoadModules(ctx, pathConfig)
+
 	registry.ProcessRegisteredConfigs(ctx)
 
 	args := os.Args