traefik/pkg/plugins/builder.go

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2020-04-20 16:36:34 +00:00
package plugins
import (
"context"
"fmt"
"net/http"
"path"
"reflect"
"strings"
"github.com/containous/yaegi/interp"
"github.com/containous/yaegi/stdlib"
"github.com/mitchellh/mapstructure"
)
const devPluginName = "dev"
// pluginContext The static part of a plugin configuration.
type pluginContext struct {
// GoPath plugin's GOPATH
GoPath string `json:"goPath,omitempty" toml:"goPath,omitempty" yaml:"goPath,omitempty"`
// Import plugin's import/package
Import string `json:"import,omitempty" toml:"import,omitempty" yaml:"import,omitempty"`
// BasePkg plugin's base package name (optional)
BasePkg string `json:"basePkg,omitempty" toml:"basePkg,omitempty" yaml:"basePkg,omitempty"`
interpreter *interp.Interpreter
}
// Builder is a plugin builder.
type Builder struct {
descriptors 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{},
}
for pName, desc := range plugins {
manifest, err := client.ReadManifest(desc.ModuleName)
if err != nil {
_ = client.ResetAll()
return nil, fmt.Errorf("%s: failed to read manifest: %w", desc.ModuleName, err)
}
i := interp.New(interp.Options{GoPath: client.GoPath()})
i.Use(stdlib.Symbols)
_, 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{
interpreter: i,
GoPath: client.GoPath(),
Import: manifest.Import,
BasePkg: manifest.BasePkg,
}
}
if devPlugin != nil {
manifest, err := ReadManifest(devPlugin.GoPath, devPlugin.ModuleName)
if err != nil {
return nil, fmt.Errorf("%s: failed to read manifest: %w", devPlugin.ModuleName, err)
}
i := interp.New(interp.Options{GoPath: devPlugin.GoPath})
i.Use(stdlib.Symbols)
_, 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{
interpreter: i,
GoPath: devPlugin.GoPath,
Import: manifest.Import,
BasePkg: manifest.BasePkg,
}
}
return pb, nil
}
// Build builds a plugin.
func (b Builder) Build(pName string, config map[string]interface{}, middlewareName string) (*Middleware, 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)
}
return newMiddleware(descriptor, config, middlewareName)
}
// 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
}