Add plugin's support for provider

Co-authored-by: Julien Salleyron <julien@traefik.io>

Makefile

@@ -123,7 +123,7 @@ shell: build-dev-image
 docs:
 	make -C ./docs docs
 
-## Serve the documentation site localy
+## Serve the documentation site locally
 docs-serve:
 	make -C ./docs docs-serve
 
@@ -135,6 +135,10 @@ docs-pull-images:
 generate-crd:
 	./script/update-generated-crd-code.sh
 
+## Generate code from dynamic configuration https://github.com/traefik/genconf
+generate-genconf:
+	go run ./cmd/internal/gen/
+
 ## Create packages for the release
 release-packages: generate-webui build-dev-image
 	rm -rf dist

cmd/internal/gen/centrifuge.go

@@ -0,0 +1,343 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"go/importer"
+	"go/token"
+	"go/types"
+	"io"
+	"log"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strings"
+
+	"golang.org/x/tools/imports"
+)
+
+// File a kind of AST element that represents a file.
+type File struct {
+	Package  string
+	Imports  []string
+	Elements []Element
+}
+
+// Element is a simplified version of a symbol.
+type Element struct {
+	Name  string
+	Value string
+}
+
+// Centrifuge a centrifuge.
+// Generate Go Structures from Go structures.
+type Centrifuge struct {
+	IncludedImports []string
+	ExcludedTypes   []string
+	ExcludedFiles   []string
+
+	TypeCleaner    func(types.Type, string) string
+	PackageCleaner func(string) string
+
+	rootPkg string
+	fileSet *token.FileSet
+	pkg     *types.Package
+}
+
+// NewCentrifuge creates a new Centrifuge.
+func NewCentrifuge(rootPkg string) (*Centrifuge, error) {
+	fileSet := token.NewFileSet()
+
+	pkg, err := importer.ForCompiler(fileSet, "source", nil).Import(rootPkg)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Centrifuge{
+		fileSet: fileSet,
+		pkg:     pkg,
+		rootPkg: rootPkg,
+
+		TypeCleaner: func(typ types.Type, _ string) string {
+			return typ.String()
+		},
+		PackageCleaner: func(s string) string {
+			return s
+		},
+	}, nil
+}
+
+// Run runs the code extraction and the code generation.
+func (c Centrifuge) Run(dest string, pkgName string) error {
+	files, err := c.run(c.pkg.Scope(), c.rootPkg, pkgName)
+	if err != nil {
+		return err
+	}
+
+	err = fileWriter{baseDir: dest}.Write(files)
+	if err != nil {
+		return err
+	}
+
+	for _, p := range c.pkg.Imports() {
+		if contains(c.IncludedImports, p.Path()) {
+			fls, err := c.run(p.Scope(), p.Path(), p.Name())
+			if err != nil {
+				return err
+			}
+
+			err = fileWriter{baseDir: filepath.Join(dest, p.Name())}.Write(fls)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return err
+}
+
+func (c Centrifuge) run(sc *types.Scope, rootPkg string, pkgName string) (map[string]*File, error) {
+	files := map[string]*File{}
+
+	for _, name := range sc.Names() {
+		if contains(c.ExcludedTypes, name) {
+			continue
+		}
+
+		o := sc.Lookup(name)
+		if !o.Exported() {
+			continue
+		}
+
+		filename := filepath.Base(c.fileSet.File(o.Pos()).Name())
+		if contains(c.ExcludedFiles, path.Join(rootPkg, filename)) {
+			continue
+		}
+
+		fl, ok := files[filename]
+		if !ok {
+			files[filename] = &File{Package: pkgName}
+			fl = files[filename]
+		}
+
+		elt := Element{
+			Name: name,
+		}
+
+		switch ob := o.(type) {
+		case *types.TypeName:
+
+			switch obj := ob.Type().(*types.Named).Underlying().(type) {
+			case *types.Struct:
+				elt.Value = c.writeStruct(name, obj, rootPkg, fl)
+
+			case *types.Map:
+				elt.Value = fmt.Sprintf("type %s map[%s]%s\n", name, obj.Key().String(), c.TypeCleaner(obj.Elem(), rootPkg))
+
+			case *types.Slice:
+				elt.Value = fmt.Sprintf("type %s []%v\n", name, c.TypeCleaner(obj.Elem(), rootPkg))
+
+			case *types.Basic:
+				elt.Value = fmt.Sprintf("type %s %v\n", name, obj.Name())
+
+			default:
+				log.Printf("OTHER TYPE::: %s %T\n", name, o.Type().(*types.Named).Underlying())
+				continue
+			}
+
+		default:
+			log.Printf("OTHER::: %s %T\n", name, o)
+			continue
+		}
+
+		if len(elt.Value) > 0 {
+			fl.Elements = append(fl.Elements, elt)
+		}
+	}
+
+	return files, nil
+}
+
+func (c Centrifuge) writeStruct(name string, obj *types.Struct, rootPkg string, elt *File) string {
+	b := strings.Builder{}
+	b.WriteString(fmt.Sprintf("type %s struct {\n", name))
+
+	for i := 0; i < obj.NumFields(); i++ {
+		field := obj.Field(i)
+
+		if !field.Exported() {
+			continue
+		}
+
+		fPkg := c.PackageCleaner(extractPackage(field.Type()))
+		if fPkg != "" && fPkg != rootPkg {
+			elt.Imports = append(elt.Imports, fPkg)
+		}
+
+		fType := c.TypeCleaner(field.Type(), rootPkg)
+
+		if field.Embedded() {
+			b.WriteString(fmt.Sprintf("\t%s\n", fType))
+			continue
+		}
+
+		b.WriteString(fmt.Sprintf("\t%s %s", field.Name(), fType))
+
+		tags := obj.Tag(i)
+		if tags != "" {
+			tg := extractJSONTag(tags)
+
+			if tg != `json:"-"` {
+				b.WriteString(fmt.Sprintf(" `%s`", tg))
+			}
+		}
+
+		b.WriteString("\n")
+	}
+
+	b.WriteString("}\n")
+
+	return b.String()
+}
+
+func extractJSONTag(value string) string {
+	fields := strings.Fields(value)
+
+	for _, field := range fields {
+		if strings.HasPrefix(field, `json:"`) {
+			return field
+		}
+	}
+
+	return ""
+}
+
+func extractPackage(t types.Type) string {
+	switch tu := t.(type) {
+	case *types.Named:
+		return tu.Obj().Pkg().Path()
+
+	case *types.Slice:
+		if v, ok := tu.Elem().(*types.Named); ok {
+			return v.Obj().Pkg().Path()
+		}
+		return ""
+
+	case *types.Map:
+		if v, ok := tu.Elem().(*types.Named); ok {
+			return v.Obj().Pkg().Path()
+		}
+		return ""
+
+	case *types.Pointer:
+		return extractPackage(tu.Elem())
+
+	default:
+		return ""
+	}
+}
+
+func contains(values []string, value string) bool {
+	for _, val := range values {
+		if val == value {
+			return true
+		}
+	}
+
+	return false
+}
+
+type fileWriter struct {
+	baseDir string
+}
+
+func (f fileWriter) Write(files map[string]*File) error {
+	err := os.MkdirAll(f.baseDir, 0755)
+	if err != nil {
+		return err
+	}
+
+	for name, file := range files {
+		err = f.writeFile(name, file)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (f fileWriter) writeFile(name string, desc *File) error {
+	if len(desc.Elements) == 0 {
+		return nil
+	}
+
+	filename := filepath.Join(f.baseDir, name)
+
+	file, err := os.Create(filename)
+	if err != nil {
+		return fmt.Errorf("failed to create file: %w", err)
+	}
+
+	defer func() { _ = file.Close() }()
+
+	b := bytes.NewBufferString("package ")
+	b.WriteString(desc.Package)
+	b.WriteString("\n")
+	b.WriteString("// Code generated by centrifuge. DO NOT EDIT.\n")
+
+	b.WriteString("\n")
+	f.writeImports(b, desc.Imports)
+	b.WriteString("\n")
+
+	for _, elt := range desc.Elements {
+		b.WriteString(elt.Value)
+		b.WriteString("\n")
+	}
+
+	// gofmt
+	source, err := format.Source(b.Bytes())
+	if err != nil {
+		log.Println(b.String())
+		return fmt.Errorf("failed to format sources: %w", err)
+	}
+
+	// goimports
+	process, err := imports.Process(filename, source, nil)
+	if err != nil {
+		log.Println(string(source))
+		return fmt.Errorf("failed to format imports: %w", err)
+	}
+
+	_, err = file.Write(process)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (f fileWriter) writeImports(b io.StringWriter, imports []string) {
+	if len(imports) == 0 {
+		return
+	}
+
+	uniq := map[string]struct{}{}
+
+	sort.Strings(imports)
+
+	_, _ = b.WriteString("import (\n")
+	for _, s := range imports {
+		if _, exist := uniq[s]; exist {
+			continue
+		}
+
+		uniq[s] = struct{}{}
+
+		_, _ = b.WriteString(fmt.Sprintf(`	"%s"`+"\n", s))
+	}
+
+	_, _ = b.WriteString(")\n")
+}

cmd/internal/gen/main.go

@@ -0,0 +1,124 @@
+package main
+
+import (
+	"fmt"
+	"go/build"
+	"go/types"
+	"io/ioutil"
+	"log"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+const rootPkg = "github.com/traefik/traefik/v2/pkg/config/dynamic"
+
+const (
+	destModuleName = "github.com/traefik/genconf"
+	destPkg        = "dynamic"
+)
+
+const marsh = `package %s
+
+import "encoding/json"
+
+type JSONPayload struct {
+	*Configuration
+}
+
+func (c JSONPayload) MarshalJSON() ([]byte, error) {
+	if c.Configuration == nil {
+		return nil, nil
+	}
+
+	return json.Marshal(c.Configuration)
+}
+`
+
+// main generate Go Structures from Go structures.
+// Allows to create an external module (destModuleName) used by the plugin's providers
+// that contains Go structs of the dynamic configuration and nothing else.
+// These Go structs do not have any non-exported fields and do not rely on any external dependencies.
+func main() {
+	dest := filepath.Join(path.Join(build.Default.GOPATH, "src"), destModuleName, destPkg)
+
+	log.Println("Output:", dest)
+
+	err := run(dest)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func run(dest string) error {
+	centrifuge, err := NewCentrifuge(rootPkg)
+	if err != nil {
+		return err
+	}
+
+	centrifuge.IncludedImports = []string{
+		"github.com/traefik/traefik/v2/pkg/tls",
+		"github.com/traefik/traefik/v2/pkg/types",
+	}
+
+	centrifuge.ExcludedTypes = []string{
+		// tls
+		"CertificateStore", "Manager",
+		// dynamic
+		"Message", "Configurations",
+		// types
+		"HTTPCodeRanges", "HostResolverConfig",
+	}
+
+	centrifuge.ExcludedFiles = []string{
+		"github.com/traefik/traefik/v2/pkg/types/logs.go",
+		"github.com/traefik/traefik/v2/pkg/types/metrics.go",
+	}
+
+	centrifuge.TypeCleaner = cleanType
+	centrifuge.PackageCleaner = cleanPackage
+
+	err = centrifuge.Run(dest, destPkg)
+	if err != nil {
+		return err
+	}
+
+	return ioutil.WriteFile(filepath.Join(dest, "marshaler.go"), []byte(fmt.Sprintf(marsh, destPkg)), 0666)
+}
+
+func cleanType(typ types.Type, base string) string {
+	if typ.String() == "github.com/traefik/traefik/v2/pkg/tls.FileOrContent" {
+		return "string"
+	}
+
+	if typ.String() == "[]github.com/traefik/traefik/v2/pkg/tls.FileOrContent" {
+		return "[]string"
+	}
+
+	if typ.String() == "github.com/traefik/paerser/types.Duration" {
+		return "string"
+	}
+
+	if strings.Contains(typ.String(), base) {
+		return strings.ReplaceAll(typ.String(), base+".", "")
+	}
+
+	if strings.Contains(typ.String(), "github.com/traefik/traefik/v2/pkg/") {
+		return strings.ReplaceAll(typ.String(), "github.com/traefik/traefik/v2/pkg/", "")
+	}
+
+	return typ.String()
+}
+
+func cleanPackage(src string) string {
+	switch src {
+	case "github.com/traefik/paerser/types":
+		return ""
+	case "github.com/traefik/traefik/v2/pkg/tls":
+		return path.Join(destModuleName, destPkg, "tls")
+	case "github.com/traefik/traefik/v2/pkg/types":
+		return path.Join(destModuleName, destPkg, "types")
+	default:
+		return src
+	}
+}

cmd/traefik/traefik.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/x509"
 	"encoding/json"
+	"fmt"
 	stdlog "log"
 	"net/http"
 	"os"
@@ -235,6 +236,20 @@ func setupServer(staticConfiguration *static.Configuration) (*server.Server, err
 		return nil, err
 	}
 
+	// Providers plugins
+
+	for s, i := range staticConfiguration.Providers.Plugin {
+		p, err := pluginBuilder.BuildProvider(s, i)
+		if err != nil {
+			return nil, fmt.Errorf("plugin: failed to build provider: %w", err)
+		}
+
+		err = providerAggregator.AddProvider(p)
+		if err != nil {
+			return nil, fmt.Errorf("plugin: failed to add provider: %w", err)
+		}
+	}
+
 	// Metrics
 
 	metricRegistries := registerMetricClients(staticConfiguration.Metrics)

go.mod

@@ -84,6 +84,7 @@ require (
 	golang.org/x/mod v0.3.0
 	golang.org/x/net v0.0.0-20210220033124-5f55cee0dc0d
 	golang.org/x/time v0.0.0-20201208040808-7e3f01d25324
+	golang.org/x/tools v0.0.0-20200904185747-39188db58858
 	google.golang.org/grpc v1.27.1
 	gopkg.in/DataDog/dd-trace-go.v1 v1.19.0
 	gopkg.in/fsnotify.v1 v1.4.7

pkg/api/handler_overview.go

@@ -212,6 +212,10 @@ func getProviders(conf static.Configuration) []string {
 			if !field.IsNil() {
 				providers = append(providers, v.Type().Field(i).Name)
 			}
+		} else if field.Kind() == reflect.Map && field.Type().Elem() == reflect.TypeOf(static.PluginConf{}) {
+			for _, value := range field.MapKeys() {
+				providers = append(providers, "plugin-"+value.String())
+			}
 		}
 	}
 

pkg/api/handler_overview_test.go

@@ -217,6 +217,9 @@ func TestHandler_Overview(t *testing.T) {
 					KubernetesCRD:     &crd.Provider{},
 					Rest:              &rest.Provider{},
 					Rancher:           &rancher.Provider{},
+					Plugin: map[string]static.PluginConf{
+						"test": map[string]interface{}{},
+					},
 				},
 			},
 			confDyn: runtime.Configuration{},

pkg/api/testdata/overview-providers.json

@@ -28,7 +28,8 @@
 		"KubernetesIngress",
 		"KubernetesCRD",
 		"Rest",
-		"Rancher"
+		"Rancher",
+		"plugin-test"
 	],
 	"tcp": {
 		"routers": {

pkg/config/static/plugins.go

@@ -0,0 +1,4 @@
+package static
+
+// PluginConf holds the plugin configuration.
+type PluginConf map[string]interface{}

pkg/config/static/static_config.go

@@ -190,6 +190,8 @@ type Providers struct {
 	ZooKeeper *zk.Provider     `description:"Enable ZooKeeper backend with default settings." json:"zooKeeper,omitempty" toml:"zooKeeper,omitempty" yaml:"zooKeeper,omitempty" label:"allowEmpty" file:"allowEmpty" export:"true"`
 	Redis     *redis.Provider  `description:"Enable Redis backend with default settings." json:"redis,omitempty" toml:"redis,omitempty" yaml:"redis,omitempty" label:"allowEmpty" file:"allowEmpty" export:"true"`
 	HTTP      *http.Provider   `description:"Enable HTTP backend with default settings." json:"http,omitempty" toml:"http,omitempty" yaml:"http,omitempty" label:"allowEmpty" file:"allowEmpty" export:"true"`
+
+	Plugin map[string]PluginConf `description:"" json:"plugin,omitempty" toml:"plugin,omitempty" yaml:"plugin,omitempty"`
 }
 
 // SetEffectiveConfiguration adds missing configuration parameters derived from existing ones.

pkg/plugins/builder.go

@@ -4,11 +4,7 @@ import (
 	"context"
 	"fmt"
 	"net/http"
-	"path"
-	"reflect"
-	"strings"
 
-	"github.com/mitchellh/mapstructure"
 	"github.com/traefik/yaegi/interp"
 	"github.com/traefik/yaegi/stdlib"
 )
@@ -34,13 +30,15 @@ type pluginContext struct {
 
 // Builder is a plugin builder.
 type Builder struct {
-	descriptors map[string]pluginContext
+	middlewareDescriptors map[string]pluginContext
+	providerDescriptors   map[string]pluginContext
 }
 
 // NewBuilder creates a new Builder.
 func NewBuilder(client *Client, plugins map[string]Descriptor, devPlugin *DevPlugin) (*Builder, error) {
 	pb := &Builder{
-		descriptors: map[string]pluginContext{},
+		middlewareDescriptors: map[string]pluginContext{},
+		providerDescriptors:   map[string]pluginContext{},
 	}
 
 	for pName, desc := range plugins {
@@ -52,17 +50,30 @@ func NewBuilder(client *Client, plugins map[string]Descriptor, devPlugin *DevPlu
 
 		i := interp.New(interp.Options{GoPath: client.GoPath()})
 		i.Use(stdlib.Symbols)
+		i.Use(ppSymbols())
 
 		_, err = i.Eval(fmt.Sprintf(`import "%s"`, manifest.Import))
 		if err != nil {
 			return nil, fmt.Errorf("%s: failed to import plugin code %q: %w", desc.ModuleName, manifest.Import, err)
 		}
 
-		pb.descriptors[pName] = pluginContext{
+		switch manifest.Type {
-			interpreter: i,
+		case "middleware":
-			GoPath:      client.GoPath(),
+			pb.middlewareDescriptors[pName] = pluginContext{
-			Import:      manifest.Import,
+				interpreter: i,
-			BasePkg:     manifest.BasePkg,
+				GoPath:      client.GoPath(),
+				Import:      manifest.Import,
+				BasePkg:     manifest.BasePkg,
+			}
+		case "provider":
+			pb.providerDescriptors[pName] = pluginContext{
+				interpreter: i,
+				GoPath:      client.GoPath(),
+				Import:      manifest.Import,
+				BasePkg:     manifest.BasePkg,
+			}
+		default:
+			return nil, fmt.Errorf("unknow plugin type: %s", manifest.Type)
 		}
 	}
 
@@ -74,101 +85,32 @@ func NewBuilder(client *Client, plugins map[string]Descriptor, devPlugin *DevPlu
 
 		i := interp.New(interp.Options{GoPath: devPlugin.GoPath})
 		i.Use(stdlib.Symbols)
+		i.Use(ppSymbols())
 
 		_, err = i.Eval(fmt.Sprintf(`import "%s"`, manifest.Import))
 		if err != nil {
 			return nil, fmt.Errorf("%s: failed to import plugin code %q: %w", devPlugin.ModuleName, manifest.Import, err)
 		}
 
-		pb.descriptors[devPluginName] = pluginContext{
+		switch manifest.Type {
-			interpreter: i,
+		case "middleware":
-			GoPath:      devPlugin.GoPath,
+			pb.middlewareDescriptors[devPluginName] = pluginContext{
-			Import:      manifest.Import,
+				interpreter: i,
-			BasePkg:     manifest.BasePkg,
+				GoPath:      devPlugin.GoPath,
+				Import:      manifest.Import,
+				BasePkg:     manifest.BasePkg,
+			}
+		case "provider":
+			pb.providerDescriptors[devPluginName] = pluginContext{
+				interpreter: i,
+				GoPath:      devPlugin.GoPath,
+				Import:      manifest.Import,
+				BasePkg:     manifest.BasePkg,
+			}
+		default:
+			return nil, fmt.Errorf("unknow plugin type: %s", manifest.Type)
 		}
 	}
 
 	return pb, nil
 }
-
-// Build builds a plugin.
-func (b Builder) Build(pName string, config map[string]interface{}, middlewareName string) (Constructor, error) {
-	if b.descriptors == nil {
-		return nil, fmt.Errorf("plugin: no plugin definition in the static configuration: %s", pName)
-	}
-
-	descriptor, ok := b.descriptors[pName]
-	if !ok {
-		return nil, fmt.Errorf("plugin: unknown plugin type: %s", pName)
-	}
-
-	m, err := newMiddleware(descriptor, config, middlewareName)
-	if err != nil {
-		return nil, err
-	}
-
-	return m.NewHandler, err
-}
-
-// Middleware is a HTTP handler plugin wrapper.
-type Middleware struct {
-	middlewareName string
-	fnNew          reflect.Value
-	config         reflect.Value
-}
-
-func newMiddleware(descriptor pluginContext, config map[string]interface{}, middlewareName string) (*Middleware, error) {
-	basePkg := descriptor.BasePkg
-	if basePkg == "" {
-		basePkg = strings.ReplaceAll(path.Base(descriptor.Import), "-", "_")
-	}
-
-	vConfig, err := descriptor.interpreter.Eval(basePkg + `.CreateConfig()`)
-	if err != nil {
-		return nil, fmt.Errorf("plugin: failed to eval CreateConfig: %w", err)
-	}
-
-	cfg := &mapstructure.DecoderConfig{
-		DecodeHook:       mapstructure.StringToSliceHookFunc(","),
-		WeaklyTypedInput: true,
-		Result:           vConfig.Interface(),
-	}
-
-	decoder, err := mapstructure.NewDecoder(cfg)
-	if err != nil {
-		return nil, fmt.Errorf("plugin: failed to create configuration decoder: %w", err)
-	}
-
-	err = decoder.Decode(config)
-	if err != nil {
-		return nil, fmt.Errorf("plugin: failed to decode configuration: %w", err)
-	}
-
-	fnNew, err := descriptor.interpreter.Eval(basePkg + `.New`)
-	if err != nil {
-		return nil, fmt.Errorf("plugin: failed to eval New: %w", err)
-	}
-
-	return &Middleware{
-		middlewareName: middlewareName,
-		fnNew:          fnNew,
-		config:         vConfig,
-	}, nil
-}
-
-// NewHandler creates a new HTTP handler.
-func (m *Middleware) NewHandler(ctx context.Context, next http.Handler) (http.Handler, error) {
-	args := []reflect.Value{reflect.ValueOf(ctx), reflect.ValueOf(next), m.config, reflect.ValueOf(m.middlewareName)}
-	results := m.fnNew.Call(args)
-
-	if len(results) > 1 && results[1].Interface() != nil {
-		return nil, results[1].Interface().(error)
-	}
-
-	handler, ok := results[0].Interface().(http.Handler)
-	if !ok {
-		return nil, fmt.Errorf("plugin: invalid handler type: %T", results[0].Interface())
-	}
-
-	return handler, nil
-}

pkg/plugins/middlewares.go

@@ -0,0 +1,94 @@
+package plugins
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"path"
+	"reflect"
+	"strings"
+
+	"github.com/mitchellh/mapstructure"
+)
+
+// Build builds a middleware plugin.
+func (b Builder) Build(pName string, config map[string]interface{}, middlewareName string) (Constructor, error) {
+	if b.middlewareDescriptors == nil {
+		return nil, fmt.Errorf("no plugin definition in the static configuration: %s", pName)
+	}
+
+	descriptor, ok := b.middlewareDescriptors[pName]
+	if !ok {
+		return nil, fmt.Errorf("unknown plugin type: %s", pName)
+	}
+
+	m, err := newMiddleware(descriptor, config, middlewareName)
+	if err != nil {
+		return nil, err
+	}
+
+	return m.NewHandler, err
+}
+
+// Middleware is a HTTP handler plugin wrapper.
+type Middleware struct {
+	middlewareName string
+	fnNew          reflect.Value
+	config         reflect.Value
+}
+
+func newMiddleware(descriptor pluginContext, config map[string]interface{}, middlewareName string) (*Middleware, error) {
+	basePkg := descriptor.BasePkg
+	if basePkg == "" {
+		basePkg = strings.ReplaceAll(path.Base(descriptor.Import), "-", "_")
+	}
+
+	vConfig, err := descriptor.interpreter.Eval(basePkg + `.CreateConfig()`)
+	if err != nil {
+		return nil, fmt.Errorf("failed to eval CreateConfig: %w", err)
+	}
+
+	cfg := &mapstructure.DecoderConfig{
+		DecodeHook:       mapstructure.StringToSliceHookFunc(","),
+		WeaklyTypedInput: true,
+		Result:           vConfig.Interface(),
+	}
+
+	decoder, err := mapstructure.NewDecoder(cfg)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create configuration decoder: %w", err)
+	}
+
+	err = decoder.Decode(config)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode configuration: %w", err)
+	}
+
+	fnNew, err := descriptor.interpreter.Eval(basePkg + `.New`)
+	if err != nil {
+		return nil, fmt.Errorf("failed to eval New: %w", err)
+	}
+
+	return &Middleware{
+		middlewareName: middlewareName,
+		fnNew:          fnNew,
+		config:         vConfig,
+	}, nil
+}
+
+// NewHandler creates a new HTTP handler.
+func (m *Middleware) NewHandler(ctx context.Context, next http.Handler) (http.Handler, error) {
+	args := []reflect.Value{reflect.ValueOf(ctx), reflect.ValueOf(next), m.config, reflect.ValueOf(m.middlewareName)}
+	results := m.fnNew.Call(args)
+
+	if len(results) > 1 && results[1].Interface() != nil {
+		return nil, results[1].Interface().(error)
+	}
+
+	handler, ok := results[0].Interface().(http.Handler)
+	if !ok {
+		return nil, fmt.Errorf("invalid handler type: %T", results[0].Interface())
+	}
+
+	return handler, nil
+}

pkg/plugins/plugins.go

@@ -81,7 +81,10 @@ func checkDevPluginConfiguration(plugin *DevPlugin) error {
 		return err
 	}
 
-	if m.Type != "middleware" {
+	switch m.Type {
+	case "middleware", "provider":
+		// noop
+	default:
 		return errors.New("unsupported type")
 	}
 

pkg/plugins/providers.go

@@ -0,0 +1,196 @@
+package plugins
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"path"
+	"reflect"
+	"strings"
+
+	"github.com/mitchellh/mapstructure"
+	"github.com/traefik/traefik/v2/pkg/config/dynamic"
+	"github.com/traefik/traefik/v2/pkg/log"
+	"github.com/traefik/traefik/v2/pkg/provider"
+	"github.com/traefik/traefik/v2/pkg/safe"
+)
+
+// PP the interface of a plugin's provider.
+type PP interface {
+	Init() error
+	Provide(cfgChan chan<- json.Marshaler) error
+	Stop() error
+}
+
+type _PP struct {
+	WInit    func() error
+	WProvide func(cfgChan chan<- json.Marshaler) error
+	WStop    func() error
+}
+
+func (p _PP) Init() error {
+	return p.WInit()
+}
+
+func (p _PP) Provide(cfgChan chan<- json.Marshaler) error {
+	return p.WProvide(cfgChan)
+}
+
+func (p _PP) Stop() error {
+	return p.WStop()
+}
+
+func ppSymbols() map[string]map[string]reflect.Value {
+	return map[string]map[string]reflect.Value{
+		"github.com/traefik/traefik/v2/pkg/plugins": {
+			"PP":  reflect.ValueOf((*PP)(nil)),
+			"_PP": reflect.ValueOf((*_PP)(nil)),
+		},
+	}
+}
+
+// BuildProvider builds a plugin's provider.
+func (b Builder) BuildProvider(pName string, config map[string]interface{}) (provider.Provider, error) {
+	if b.providerDescriptors == nil {
+		return nil, fmt.Errorf("no plugin definition in the static configuration: %s", pName)
+	}
+
+	descriptor, ok := b.providerDescriptors[pName]
+	if !ok {
+		return nil, fmt.Errorf("unknown plugin type: %s", pName)
+	}
+
+	return newProvider(descriptor, config, "plugin-"+pName)
+}
+
+// Provider is a plugin's provider wrapper.
+type Provider struct {
+	name string
+	pp   PP
+}
+
+func newProvider(descriptor pluginContext, config map[string]interface{}, providerName string) (*Provider, error) {
+	basePkg := descriptor.BasePkg
+	if basePkg == "" {
+		basePkg = strings.ReplaceAll(path.Base(descriptor.Import), "-", "_")
+	}
+
+	vConfig, err := descriptor.interpreter.Eval(basePkg + `.CreateConfig()`)
+	if err != nil {
+		return nil, fmt.Errorf("failed to eval CreateConfig: %w", err)
+	}
+
+	cfg := &mapstructure.DecoderConfig{
+		DecodeHook:       mapstructure.StringToSliceHookFunc(","),
+		WeaklyTypedInput: true,
+		Result:           vConfig.Interface(),
+	}
+
+	decoder, err := mapstructure.NewDecoder(cfg)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create configuration decoder: %w", err)
+	}
+
+	err = decoder.Decode(config)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode configuration: %w", err)
+	}
+
+	_, err = descriptor.interpreter.Eval(`package wrapper
+
+import (
+	"context"
+
+	` + basePkg + ` "` + descriptor.Import + `"
+	"github.com/traefik/traefik/v2/pkg/plugins"
+)
+
+func NewWrapper(ctx context.Context, config *` + basePkg + `.Config, name string) (plugins.PP, error) {
+	p, err := ` + basePkg + `.New(ctx, config, name)
+	var pv plugins.PP = p
+	return pv, err
+}
+`)
+	if err != nil {
+		return nil, fmt.Errorf("failed to eval wrapper: %w", err)
+	}
+
+	fnNew, err := descriptor.interpreter.Eval("wrapper.NewWrapper")
+	if err != nil {
+		return nil, fmt.Errorf("failed to eval New: %w", err)
+	}
+
+	ctx := context.Background()
+
+	args := []reflect.Value{reflect.ValueOf(ctx), vConfig, reflect.ValueOf(providerName)}
+	results := fnNew.Call(args)
+
+	if len(results) > 1 && results[1].Interface() != nil {
+		return nil, results[1].Interface().(error)
+	}
+
+	prov, ok := results[0].Interface().(PP)
+	if !ok {
+		return nil, fmt.Errorf("invalid provider type: %T", results[0].Interface())
+	}
+
+	return &Provider{name: providerName, pp: prov}, nil
+}
+
+// Init wraps the Init method of a plugin.
+func (p *Provider) Init() error {
+	return p.pp.Init()
+}
+
+// Provide wraps the Provide method of a plugin.
+func (p *Provider) Provide(configurationChan chan<- dynamic.Message, pool *safe.Pool) error {
+	defer func() {
+		if err := recover(); err != nil {
+			log.WithoutContext().WithField(log.ProviderName, p.name).Errorf("panic inside the plugin %v", err)
+		}
+	}()
+
+	cfgChan := make(chan json.Marshaler)
+
+	err := p.pp.Provide(cfgChan)
+	if err != nil {
+		return fmt.Errorf("error from %s: %w", p.name, err)
+	}
+
+	pool.GoCtx(func(ctx context.Context) {
+		logger := log.FromContext(log.With(ctx, log.Str(log.ProviderName, p.name)))
+
+		for {
+			select {
+			case <-ctx.Done():
+				err := p.pp.Stop()
+				if err != nil {
+					logger.Errorf("failed to stop the provider: %v", err)
+				}
+
+				return
+
+			case cfgPg := <-cfgChan:
+				marshalJSON, err := cfgPg.MarshalJSON()
+				if err != nil {
+					logger.Errorf("failed to marshal configuration: %v", err)
+					continue
+				}
+
+				cfg := &dynamic.Configuration{}
+				err = json.Unmarshal(marshalJSON, cfg)
+				if err != nil {
+					logger.Errorf("failed to unmarshal configuration: %v", err)
+					continue
+				}
+
+				configurationChan <- dynamic.Message{
+					ProviderName:  p.name,
+					Configuration: cfg,
+				}
+			}
+		}
+	})
+
+	return nil
+}

pkg/server/middleware/middlewares.go

@@ -347,12 +347,12 @@ func (b *Builder) buildConstructor(ctx context.Context, middlewareName string) (
 
 		pluginType, rawPluginConfig, err := findPluginConfig(config.Plugin)
 		if err != nil {
-			return nil, err
+			return nil, fmt.Errorf("plugin: %w", err)
 		}
 
 		plug, err := b.pluginBuilder.Build(pluginType, rawPluginConfig, middlewareName)
 		if err != nil {
-			return nil, err
+			return nil, fmt.Errorf("plugin: %w", err)
 		}
 
 		middleware = func(next http.Handler) (http.Handler, error) {

pkg/server/middleware/plugins.go

@@ -15,7 +15,7 @@ type PluginsBuilder interface {
 
 func findPluginConfig(rawConfig map[string]dynamic.PluginConf) (string, map[string]interface{}, error) {
 	if len(rawConfig) != 1 {
-		return "", nil, errors.New("plugin: invalid configuration: no configuration or too many plugin definition")
+		return "", nil, errors.New("invalid configuration: no configuration or too many plugin definition")
 	}
 
 	var pluginType string
@@ -27,11 +27,11 @@ func findPluginConfig(rawConfig map[string]dynamic.PluginConf) (string, map[stri
 	}
 
 	if pluginType == "" {
-		return "", nil, errors.New("plugin: missing plugin type")
+		return "", nil, errors.New("missing plugin type")
 	}
 
 	if len(rawPluginConfig) == 0 {
-		return "", nil, fmt.Errorf("plugin: missing plugin configuration: %s", pluginType)
+		return "", nil, fmt.Errorf("missing plugin configuration: %s", pluginType)
 	}
 
 	return pluginType, rawPluginConfig, nil

webui/src/components/_commons/PanelMiddlewares.vue

@@ -20,7 +20,7 @@
               <div class="text-subtitle2">PROVIDER</div>
               <div class="block-right-text">
                 <q-avatar class="provider-logo">
-                  <q-icon :name="`img:statics/providers/${middleware.provider}.svg`" />
+                  <q-icon :name="`img:${getProviderLogoPath(middleware.provider)}`" />
                 </q-avatar>
                 <div class="block-right-text-label">{{middleware.provider}}</div>
               </div>
@@ -1106,6 +1106,15 @@ export default {
         }
       }
       return exData
+    },
+    getProviderLogoPath (provider) {
+      const name = provider.name.toLowerCase()
+
+      if (name.includes('plugin-')) {
+        return 'statics/providers/plugin.svg'
+      }
+
+      return `statics/providers/${name}.svg`
     }
   },
   filters: {

webui/src/components/_commons/PanelMirroringServices.vue

@@ -31,7 +31,7 @@
             </div>
             <div class="col-3 text-right">
               <q-avatar class="provider-logo">
-                <q-icon :name="`img:statics/providers/${getProvider(service)}.svg`" />
+                <q-icon :name="`img:${getProviderLogoPath(service)}`" />
               </q-avatar>
             </div>
           </div>
@@ -61,6 +61,16 @@ export default {
       }
 
       return this.data.provider
+    },
+    getProviderLogoPath (service) {
+      const provider = this.getProvider(service)
+      const name = provider.toLowerCase()
+
+      if (name.includes('plugin-')) {
+        return 'statics/providers/plugin.svg'
+      }
+
+      return `statics/providers/${name}.svg`
     }
   }
 }

webui/src/components/_commons/PanelRouterDetails.vue

@@ -14,7 +14,7 @@
             <div class="text-subtitle2">PROVIDER</div>
             <div class="block-right-text">
               <q-avatar class="provider-logo">
-                <q-icon :name="`img:statics/providers/${data.provider}.svg`" />
+                <q-icon :name="`img:${getProviderLogoPath}`" />
               </q-avatar>
               <div class="block-right-text-label">{{data.provider}}</div>
             </div>
@@ -127,6 +127,17 @@ export default {
       }
       return value
     }
+  },
+  computed: {
+    getProviderLogoPath () {
+      const name = this.data.provider.toLowerCase()
+
+      if (name.includes('plugin-')) {
+        return 'statics/providers/plugin.svg'
+      }
+
+      return `statics/providers/${name}.svg`
+    }
   }
 }
 </script>

webui/src/components/_commons/PanelServiceDetails.vue

@@ -15,7 +15,7 @@
             <div class="text-subtitle2">PROVIDER</div>
             <div class="block-right-text">
               <q-avatar class="provider-logo">
-                <q-icon :name="`img:statics/providers/${data.provider}.svg`" />
+                <q-icon :name="`img:${getProviderLogoPath}`" />
               </q-avatar>
               <div class="block-right-text-label">{{data.provider}}</div>
             </div>
@@ -113,6 +113,15 @@ export default {
       }
 
       return null
+    },
+    getProviderLogoPath () {
+      const name = this.data.provider.toLowerCase()
+
+      if (name.includes('plugin-')) {
+        return 'statics/providers/plugin.svg'
+      }
+
+      return `statics/providers/${name}.svg`
     }
   },
   filters: {

webui/src/components/_commons/PanelWeightedServices.vue

@@ -31,7 +31,7 @@
             </div>
             <div class="col-4">
               <q-avatar>
-                <q-icon :name="`img:statics/providers/${getProvider(service)}.svg`" />
+                <q-icon :name="`img:${getProviderLogoPath(service)}`" />
               </q-avatar>
             </div>
           </div>
@@ -61,6 +61,16 @@ export default {
       }
 
       return this.data.provider
+    },
+    getProviderLogoPath (service) {
+      const provider = this.getProvider(service)
+      const name = provider.name.toLowerCase()
+
+      if (name.includes('plugin-')) {
+        return 'statics/providers/plugin.svg'
+      }
+
+      return `statics/providers/${name}.svg`
     }
   }
 }

webui/src/components/_commons/ProviderIcon.vue

@@ -1,12 +1,23 @@
 <template>
   <q-avatar class="provider-logo">
-    <q-icon :name="`img:statics/providers/${name}.svg`" />
+    <q-icon :name="`img:${getLogoPath}`" />
   </q-avatar>
 </template>
 
 <script>
 export default {
-  props: ['name']
+  props: ['name'],
+  computed: {
+    getLogoPath () {
+      const name = this.name.toLowerCase()
+
+      if (name.includes('plugin-')) {
+        return 'statics/providers/plugin.svg'
+      }
+
+      return `statics/providers/${name}.svg`
+    }
+  }
 }
 </script>
 

webui/src/components/dashboard/PanelProvider.vue

@@ -4,7 +4,7 @@
       <div class="row items-center no-wrap">
         <div class="col text-center">
           <q-avatar class="provider-logo">
-            <q-icon :name="`img:statics/providers/${getNameLogo}.svg`" />
+            <q-icon :name="`img:${getLogoPath}`" />
           </q-avatar>
         </div>
       </div>
@@ -25,8 +25,14 @@ export default {
     getName () {
       return this.name
     },
-    getNameLogo () {
+    getLogoPath () {
-      return this.getName.toLowerCase()
+      const name = this.getName.toLowerCase()
+
+      if (name.includes('plugin-')) {
+        return 'statics/providers/plugin.svg'
+      }
+
+      return `statics/providers/${name}.svg`
     }
   }
 }

webui/src/statics/providers/plugin.svg

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="32px" height="32px" viewBox="0 0 32 32" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+    <title>plugin</title>
+    <g id="Page-1" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
+        <g id="plugin" fill-rule="nonzero">
+            <circle id="Oval" fill="#6DC4A8" cx="16" cy="16" r="16"></circle>
+            <path d="M10.7517313,10.1738295 L22.2621133,19.1941905 L21.8304412,19.7449978 C20.0202381,22.0549461 17.2269562,23.0792113 14.836947,22.5465569 L14.5702202,22.8869226 C14.1903807,23.3716261 13.5380774,23.5005798 13.1206478,23.1734862 L12.1087414,22.3804984 L10.0368349,25.0243619 C9.65696684,25.5090655 9.00463498,25.6380191 8.58723393,25.3109255 L8.33426446,25.1126429 C7.9168634,24.7855208 7.88612346,24.1213154 8.26599153,23.6366119 L10.3379265,20.9927484 L9.32602009,20.199732 C8.90861904,19.8726385 8.87790764,19.2084045 9.25774716,18.723701 L9.43776279,18.4939934 C8.15541907,16.2757226 8.42328756,13.1450149 10.3200591,10.7246368 L10.7517313,10.1738295 Z M23.5543041,11.5531311 C24.1108484,11.9892558 24.1518349,12.8748916 23.6453537,13.5211725 L20.8654425,17.2106062 L18.8915999,15.6278127 L21.6215408,11.9351683 C22.1280221,11.2888874 22.9977598,11.1169778 23.5543041,11.5531311 Z M18.0521111,7.2411761 C18.6086553,7.67732938 18.6496134,8.56296514 18.1431321,9.20924605 L15.2398281,12.8891125 L13.3222617,11.3618714 L16.1193478,7.62324192 C16.6258005,6.97696101 17.4955668,6.80505137 18.0521111,7.2411761 Z" id="Shape" fill="#FFFFFF"></path>
+        </g>
+    </g>
+</svg>