refactor: plugin functions can be defined in any format

plugin/shared/interface.go

@@ -0,0 +1,103 @@
+package shared
+
+import (
+	"encoding/gob"
+	"net/rpc"
+
+	"github.com/hashicorp/go-plugin"
+	"github.com/rs/zerolog/log"
+)
+
+func init() {
+	gob.Register(new(funcData))
+}
+
+// funcData is used to transfer between plugin and host via RPC.
+type funcData struct {
+	Name string        // function name
+	Args []interface{} // function arguments
+}
+
+// FuncCaller is the interface that we're exposing as a plugin.
+type FuncCaller interface {
+	GetNames() ([]string, error)                                    // get all plugin function names list
+	Call(funcName string, args ...interface{}) (interface{}, error) // call plugin function
+}
+
+// functionRPC runs on the host side.
+type functionRPC struct {
+	client *rpc.Client
+}
+
+func (g *functionRPC) GetNames() ([]string, error) {
+	var resp []string
+	err := g.client.Call("Plugin.GetNames", new(interface{}), &resp)
+	if err != nil {
+		log.Error().Err(err).Msg("rpc call GetNames() failed")
+		return nil, err
+	}
+	return resp, nil
+}
+
+// host -> plugin
+func (g *functionRPC) Call(funcName string, funcArgs ...interface{}) (interface{}, error) {
+	log.Info().Str("funcName", funcName).Interface("funcArgs", funcArgs).Msg("call function via RPC")
+	f := funcData{
+		Name: funcName,
+		Args: funcArgs,
+	}
+
+	var args interface{} = f
+	var resp interface{}
+	err := g.client.Call("Plugin.Call", &args, &resp)
+	if err != nil {
+		log.Error().Err(err).
+			Str("funcName", funcName).Interface("funcArgs", funcArgs).
+			Msg("rpc call Call() failed")
+		return nil, err
+	}
+	return resp, nil
+}
+
+// functionRPCServer runs on the plugin side, executing the user custom function.
+type functionRPCServer struct {
+	Impl FuncCaller
+}
+
+// plugin execution
+func (s *functionRPCServer) GetNames(args interface{}, resp *[]string) error {
+	log.Info().Interface("args", args).Msg("GetNames called on plugin side")
+	var err error
+	*resp, err = s.Impl.GetNames()
+	if err != nil {
+		log.Error().Err(err).Msg("GetNames execution failed")
+		return err
+	}
+	return nil
+}
+
+// plugin execution
+func (s *functionRPCServer) Call(args interface{}, resp *interface{}) error {
+	log.Info().Interface("args", args).Msg("function called on plugin side")
+	f := args.(*funcData)
+	var err error
+	*resp, err = s.Impl.Call(f.Name, f.Args...)
+	if err != nil {
+		log.Error().Err(err).Interface("args", args).Msg("function execution failed")
+		return err
+	}
+	return nil
+}
+
+// HashicorpPlugin implements hashicorp's plugin.Plugin.
+type HashicorpPlugin struct {
+	Impl FuncCaller
+}
+
+func (p *HashicorpPlugin) Server(*plugin.MuxBroker) (interface{}, error) {
+	return &functionRPCServer{Impl: p.Impl}, nil
+}
+
+func (HashicorpPlugin) Client(b *plugin.MuxBroker, c *rpc.Client) (interface{}, error) {
+	return &functionRPC{client: c}, nil
+}