package rpc import ( "context" "encoding/json" "errors" "fmt" "reflect" "sync" "time" "github.com/ethereum/go-ethereum/log" gethrpc "github.com/ethereum/go-ethereum/rpc" "github.com/status-im/status-go/params" ) const ( // DefaultCallTimeout is a default timeout for an RPC call DefaultCallTimeout = time.Minute ) // List of RPC client errors. var ( ErrMethodNotFound = fmt.Errorf("The method does not exist/is not available") ) // 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 { sync.RWMutex 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/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 } // UpdateUpstreamURL changes the upstream RPC client URL, if the upstream is enabled. func (c *Client) UpdateUpstreamURL(url string) error { if c.upstream == nil { return nil } rpcClient, err := gethrpc.Dial(url) if err != nil { return err } c.Lock() c.upstream = rpcClient c.upstreamURL = url c.Unlock() return 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. // If there are any local handlers registered for this call, they will handle it. func (c *Client) CallContext(ctx context.Context, result interface{}, method string, args ...interface{}) error { if c.router.routeBlocked(method) { return ErrMethodNotFound } // check locally registered handlers first if handler, ok := c.handler(method); ok { return c.callMethod(ctx, result, handler, args...) } return c.CallContextIgnoringLocalHandlers(ctx, result, method, args...) } // CallContextIgnoringLocalHandlers performs a JSON-RPC call with the given // arguments. // // If there are local handlers registered for this call, they would // be ignored. It is useful if the call is happening from within a local // handler itself. // Upstream calls routing will be used anyway. func (c *Client) CallContextIgnoringLocalHandlers(ctx context.Context, result interface{}, method string, args ...interface{}) error { if c.router.routeBlocked(method) { return ErrMethodNotFound } if c.router.routeRemote(method) { c.RLock() client := c.upstream c.RUnlock() return client.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 } return setResultFromRPCResponse(result, response) } // 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 }