cmd/geth, rpc/api: extend metrics API, add a basic monitor command

rpc/xeth.go

@@ -0,0 +1,52 @@
+package rpc
+
+import (
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"sync/atomic"
+
+	"github.com/ethereum/go-ethereum/rpc/comms"
+	"github.com/ethereum/go-ethereum/rpc/shared"
+)
+
+// Xeth is a native API interface to a remote node.
+type Xeth struct {
+	client comms.EthereumClient
+	reqId  uint32
+}
+
+// NewXeth constructs a new native API interface to a remote node.
+func NewXeth(client comms.EthereumClient) *Xeth {
+	return &Xeth{
+		client: client,
+	}
+}
+
+// Call invokes a method with the given parameters are the remote node.
+func (self *Xeth) Call(method string, params []interface{}) (map[string]interface{}, error) {
+	// Assemble the json RPC request
+	data, err := json.Marshal(params)
+	if err != nil {
+		return nil, err
+	}
+	req := &shared.Request{
+		Id:      atomic.AddUint32(&self.reqId, 1),
+		Jsonrpc: "2.0",
+		Method:  method,
+		Params:  data,
+	}
+	// Send the request over and process the response
+	if err := self.client.Send(req); err != nil {
+		return nil, err
+	}
+	res, err := self.client.Recv()
+	if err != nil {
+		return nil, err
+	}
+	value, ok := res.(map[string]interface{})
+	if !ok {
+		return nil, fmt.Errorf("Invalid response type: have %v, want %v", reflect.TypeOf(res), reflect.TypeOf(make(map[string]interface{})))
+	}
+	return value, nil
+}