plugin: refactor plugin system to support initialization reporting

Signed-off-by: Stephen J Day <stephen.day@docker.com>

services/containers/service.go

@@ -23,7 +23,7 @@ func init() {
 		Requires: []plugin.Type{
 			plugin.MetadataPlugin,
 		},
-		Init: func(ic *plugin.InitContext) (interface{}, error) {
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
 			m, err := ic.Get(plugin.MetadataPlugin)
 			if err != nil {
 				return nil, err

services/content/service.go

@@ -41,19 +41,22 @@ func init() {
 		Requires: []plugin.Type{
 			plugin.MetadataPlugin,
 		},
-		Init: NewService,
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
+			m, err := ic.Get(plugin.MetadataPlugin)
+			if err != nil {
+				return nil, err
+			}
+
+			s, err := NewService(m.(*metadata.DB).ContentStore(), ic.Events)
+			return s, err
+		},
 	})
 }
 
-func NewService(ic *plugin.InitContext) (interface{}, error) {
-	m, err := ic.Get(plugin.MetadataPlugin)
-	if err != nil {
-		return nil, err
-	}
-
+func NewService(cs content.Store, publisher events.Publisher) (*Service, error) {
 	return &Service{
-		store:     m.(*metadata.DB).ContentStore(),
-		publisher: ic.Events,
+		store:     cs,
+		publisher: publisher,
 	}, nil
 }
 

services/diff/service.go

@@ -32,8 +32,8 @@ func init() {
 		Config: &config{
 			Order: []string{"walking"},
 		},
-		Init: func(ic *plugin.InitContext) (interface{}, error) {
-			differs, err := ic.GetAll(plugin.DiffPlugin)
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
+			differs, err := ic.GetByType(plugin.DiffPlugin)
 			if err != nil {
 				return nil, err
 			}
@@ -41,10 +41,15 @@ func init() {
 			orderedNames := ic.Config.(*config).Order
 			ordered := make([]plugin.Differ, len(orderedNames))
 			for i, n := range orderedNames {
-				differ, ok := differs[n]
+				differp, ok := differs[n]
 				if !ok {
 					return nil, errors.Errorf("needed differ not loaded: %s", n)
 				}
+				differ, err := differp.Instance()
+				if err != nil {
+					return nil, errors.Wrapf(err, "could not load required differ due plugin init error: %s", n)
+				}
+
 				ordered[i] = differ.(plugin.Differ)
 			}
 

services/events/service.go

@@ -15,7 +15,7 @@ func init() {
 	plugin.Register(&plugin.Registration{
 		Type: plugin.GRPCPlugin,
 		ID:   "events",
-		Init: func(ic *plugin.InitContext) (interface{}, error) {
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
 			return NewService(ic.Events), nil
 		},
 	})

services/healthcheck/service.go

@@ -16,11 +16,13 @@ func init() {
 	plugin.Register(&plugin.Registration{
 		Type: plugin.GRPCPlugin,
 		ID:   "healthcheck",
-		Init: NewService,
+		InitFn: func(*plugin.InitContext) (interface{}, error) {
+			return NewService()
+		},
 	})
 }
 
-func NewService(ic *plugin.InitContext) (interface{}, error) {
+func NewService() (*Service, error) {
 	return &Service{
 		health.NewServer(),
 	}, nil

services/images/service.go

@@ -23,7 +23,7 @@ func init() {
 		Requires: []plugin.Type{
 			plugin.MetadataPlugin,
 		},
-		Init: func(ic *plugin.InitContext) (interface{}, error) {
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
 			m, err := ic.Get(plugin.MetadataPlugin)
 			if err != nil {
 				return nil, err

services/namespaces/service.go

@@ -24,7 +24,7 @@ func init() {
 		Requires: []plugin.Type{
 			plugin.MetadataPlugin,
 		},
-		Init: func(ic *plugin.InitContext) (interface{}, error) {
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
 			m, err := ic.Get(plugin.MetadataPlugin)
 			if err != nil {
 				return nil, err

services/snapshot/service.go

@@ -25,7 +25,7 @@ func init() {
 		Requires: []plugin.Type{
 			plugin.MetadataPlugin,
 		},
-		Init: newService,
+		InitFn: newService,
 	})
 }
 

services/tasks/service.go

@@ -2,6 +2,7 @@ package tasks
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -46,15 +47,16 @@ func init() {
 			plugin.RuntimePlugin,
 			plugin.MetadataPlugin,
 		},
-		Init: New,
+		InitFn: New,
 	})
 }
 
 func New(ic *plugin.InitContext) (interface{}, error) {
-	rt, err := ic.GetAll(plugin.RuntimePlugin)
+	rt, err := ic.GetByType(plugin.RuntimePlugin)
 	if err != nil {
 		return nil, err
 	}
+
 	m, err := ic.Get(plugin.MetadataPlugin)
 	if err != nil {
 		return nil, err
@@ -62,9 +64,18 @@ func New(ic *plugin.InitContext) (interface{}, error) {
 	cs := m.(*metadata.DB).ContentStore()
 	runtimes := make(map[string]runtime.Runtime)
 	for _, rr := range rt {
-		r := rr.(runtime.Runtime)
+		ri, err := rr.Instance()
+		if err != nil {
+			log.G(ic.Context).WithError(err).Warn("could not load runtime instance due to initialization error")
+			continue
+		}
+		r := ri.(runtime.Runtime)
 		runtimes[r.ID()] = r
 	}
+
+	if len(runtimes) == 0 {
+		return nil, errors.New("no runtimes available to create task service")
+	}
 	return &Service{
 		runtimes:  runtimes,
 		db:        m.(*metadata.DB),

services/version/service.go

@@ -13,9 +13,9 @@ var _ api.VersionServer = &Service{}
 
 func init() {
 	plugin.Register(&plugin.Registration{
-		Type: plugin.GRPCPlugin,
-		ID:   "version",
-		Init: New,
+		Type:   plugin.GRPCPlugin,
+		ID:     "version",
+		InitFn: New,
 	})
 }