status-go/geth/rpc/client.go

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package rpc
import (
"context"
"encoding/json"
"errors"
"fmt"
"reflect"
"sync"
"github.com/ethereum/go-ethereum/log"
"github.com/status-im/status-go/geth/params"
gethrpc "github.com/ethereum/go-ethereum/rpc"
)
// Handler defines handler for RPC methods.
type Handler func(context.Context, ...interface{}) (interface{}, error)
// Client represents RPC client with custom routing
// scheme. It automatically decides where RPC call
// goes - Upstream or Local node.
type Client struct {
upstreamEnabled bool
upstreamURL string
local *gethrpc.Client
upstream *gethrpc.Client
router *router
handlersMx sync.RWMutex // mx guards handlers
handlers map[string]Handler // locally registered handlers
log log.Logger
}
// NewClient initializes Client and tries to connect to both,
// upstream and local node.
//
// Client is safe for concurrent use and will automatically
// reconnect to the server if connection is lost.
func NewClient(client *gethrpc.Client, upstream params.UpstreamRPCConfig) (*Client, error) {
c := Client{
local: client,
handlers: make(map[string]Handler),
log: log.New("package", "status-go/geth/rpc.Client"),
}
var err error
if upstream.Enabled {
c.upstreamEnabled = upstream.Enabled
c.upstreamURL = upstream.URL
c.upstream, err = gethrpc.Dial(c.upstreamURL)
if err != nil {
return nil, fmt.Errorf("dial upstream server: %s", err)
}
}
c.router = newRouter(c.upstreamEnabled)
return &c, nil
}
// Call performs a JSON-RPC call with the given arguments and unmarshals into
// result if no error occurred.
//
// The result must be a pointer so that package json can unmarshal into it. You
// can also pass nil, in which case the result is ignored.
//
// It uses custom routing scheme for calls.
func (c *Client) Call(result interface{}, method string, args ...interface{}) error {
ctx := context.Background()
return c.CallContext(ctx, result, method, args...)
}
// CallContext performs a JSON-RPC call with the given arguments. If the context is
// canceled before the call has successfully returned, CallContext returns immediately.
//
// The result must be a pointer so that package json can unmarshal into it. You
// can also pass nil, in which case the result is ignored.
//
// It uses custom routing scheme for calls.
func (c *Client) CallContext(ctx context.Context, result interface{}, method string, args ...interface{}) error {
// check locally registered handlers first
if handler, ok := c.handler(method); ok {
return c.callMethod(ctx, result, handler, args...)
}
if c.router.routeRemote(method) {
return c.upstream.CallContext(ctx, result, method, args...)
}
return c.local.CallContext(ctx, result, method, args...)
}
// RegisterHandler registers local handler for specific RPC method.
//
// If method is registered, it will be executed with given handler and
// never routed to the upstream or local servers.
func (c *Client) RegisterHandler(method string, handler Handler) {
c.handlersMx.Lock()
defer c.handlersMx.Unlock()
c.handlers[method] = handler
}
// callMethod calls registered RPC handler with given args and pointer to result.
// It handles proper params and result converting
//
// TODO(divan): use cancellation via context here?
func (c *Client) callMethod(ctx context.Context, result interface{}, handler Handler, args ...interface{}) error {
response, err := handler(ctx, args...)
if err != nil {
return err
}
// if result is nil, just ignore result -
// the same way as gethrpc.CallContext() caller would expect
if result == nil {
return nil
}
if err := setResultFromRPCResponse(result, response); err != nil {
return err
}
return nil
}
// handler is a concurrently safe method to get registered handler by name.
func (c *Client) handler(method string) (Handler, bool) {
c.handlersMx.RLock()
defer c.handlersMx.RUnlock()
handler, ok := c.handlers[method]
return handler, ok
}
// setResultFromRPCResponse tries to set result value from response using reflection
// as concrete types are unknown.
func setResultFromRPCResponse(result, response interface{}) (err error) {
defer func() {
if r := recover(); r != nil {
err = fmt.Errorf("invalid result type: %s", r)
}
}()
responseValue := reflect.ValueOf(response)
// If it is called via CallRaw, result has type json.RawMessage and
// we should marshal the response before setting it.
// Otherwise, it is called with CallContext and result is of concrete type,
// thus we should try to set it as it is.
// If response type and result type are incorrect, an error should be returned.
// TODO(divan): add additional checks for result underlying value, if needed:
// some example: https://golang.org/src/encoding/json/decode.go#L596
switch reflect.ValueOf(result).Elem().Type() {
case reflect.TypeOf(json.RawMessage{}), reflect.TypeOf([]byte{}):
data, err := json.Marshal(response)
if err != nil {
return err
}
responseValue = reflect.ValueOf(data)
}
value := reflect.ValueOf(result).Elem()
if !value.CanSet() {
return errors.New("can't assign value to result")
}
value.Set(responseValue)
return nil
}