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server.go
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server.go
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// Package jsonrpc implements a JSONRPC2.0 compliant server as described in https://www.jsonrpc.org/specification
package jsonrpc
import (
"bufio"
"bytes"
"context"
"encoding/json"
"errors"
"io"
"reflect"
"strings"
"sync"
"github.com/NethermindEth/juno/metrics"
"github.com/NethermindEth/juno/utils"
"github.com/prometheus/client_golang/prometheus"
"github.com/sourcegraph/conc/pool"
)
const (
InvalidJSON = -32700 // Invalid JSON was received by the server.
InvalidRequest = -32600 // The JSON sent is not a valid Request object.
MethodNotFound = -32601 // The method does not exist / is not available.
InvalidParams = -32602 // Invalid method parameter(s).
InternalError = -32603 // Internal JSON-RPC error.
)
var (
ErrInvalidID = errors.New("id should be a string or an integer")
contextInterface = reflect.TypeOf((*context.Context)(nil)).Elem()
)
type request struct {
Version string `json:"jsonrpc"`
Method string `json:"method"`
Params any `json:"params,omitempty"`
ID any `json:"id,omitempty"`
}
type response struct {
Version string `json:"jsonrpc"`
Result any `json:"result,omitempty"`
Error *Error `json:"error,omitempty"`
ID any `json:"id"`
}
type Error struct {
Code int `json:"code"`
Message string `json:"message"`
Data any `json:"data,omitempty"`
}
func Err(code int, data any) *Error {
switch code {
case InvalidJSON:
return &Error{Code: InvalidJSON, Message: "Parse error", Data: data}
case InvalidRequest:
return &Error{Code: InvalidRequest, Message: "Invalid Request", Data: data}
case MethodNotFound:
return &Error{Code: MethodNotFound, Message: "Method Not Found", Data: data}
case InvalidParams:
return &Error{Code: InvalidParams, Message: "Invalid Params", Data: data}
default:
return &Error{Code: InternalError, Message: "Internal Error", Data: data}
}
}
func (r *request) isSane() error {
if r.Version != "2.0" {
return errors.New("unsupported RPC request version")
}
if r.Method == "" {
return errors.New("no method specified")
}
if r.Params != nil {
paramType := reflect.TypeOf(r.Params)
if paramType.Kind() != reflect.Slice && paramType.Kind() != reflect.Map {
return errors.New("params should be an array or an object")
}
}
if r.ID != nil {
idType := reflect.TypeOf(r.ID)
floating := idType.Name() == "Number" && strings.Contains(r.ID.(json.Number).String(), ".")
if (idType.Kind() != reflect.String && idType.Name() != "Number") || floating {
return ErrInvalidID
}
}
return nil
}
type Parameter struct {
Name string
Optional bool
}
type Method struct {
Name string
Params []Parameter
Handler any
// The method takes a context as its first parameter.
// Set upon successful registration.
needsContext bool
}
type Server struct {
methods map[string]Method
validator Validator
pool *pool.Pool
log utils.SimpleLogger
// metrics
requests *prometheus.CounterVec
failedRequests *prometheus.CounterVec
requestLatencies *prometheus.HistogramVec
}
type Validator interface {
Struct(any) error
}
// NewServer instantiates a JSONRPC server
func NewServer(poolMaxGoroutines int, log utils.SimpleLogger) *Server {
s := &Server{
log: log,
methods: make(map[string]Method),
pool: pool.New().WithMaxGoroutines(poolMaxGoroutines),
requests: prometheus.NewCounterVec(prometheus.CounterOpts{
Namespace: "rpc",
Subsystem: "server",
Name: "requests",
}, []string{"method"}),
failedRequests: prometheus.NewCounterVec(prometheus.CounterOpts{
Namespace: "rpc",
Subsystem: "server",
Name: "failed_requests",
}, []string{"method"}),
requestLatencies: prometheus.NewHistogramVec(prometheus.HistogramOpts{
Namespace: "rpc",
Subsystem: "server",
Name: "requests_latency",
}, []string{"method"}),
}
metrics.MustRegister(s.requests, s.failedRequests, s.requestLatencies)
return s
}
// WithValidator registers a validator to validate handler struct arguments
func (s *Server) WithValidator(validator Validator) *Server {
s.validator = validator
return s
}
// RegisterMethod verifies and creates an endpoint that the server recognises.
//
// - name is the method name
// - handler is the function to be called when a request is received for the
// associated method. It should have (any, *jsonrpc.Error) as its return type
// - paramNames are the names of parameters in the order that they are expected
// by the handler
func (s *Server) RegisterMethod(method Method) error {
handlerT := reflect.TypeOf(method.Handler)
if handlerT.Kind() != reflect.Func {
return errors.New("handler must be a function")
}
numArgs := handlerT.NumIn()
if numArgs > 0 {
if handlerT.In(0).Implements(contextInterface) {
numArgs--
method.needsContext = true
}
}
if numArgs != len(method.Params) {
return errors.New("number of non-context function params and param names must match")
}
if handlerT.NumOut() != 2 {
return errors.New("handler must return 2 values")
}
if handlerT.Out(1) != reflect.TypeOf(&Error{}) {
return errors.New("second return value must be a *jsonrpc.Error")
}
// The method is valid. Mutate the appropriate fields and register on the server.
s.methods[method.Name] = method
return nil
}
// Handle processes a request to the server
// It returns the response in a byte array, only returns an
// error if it can not create the response byte array
func (s *Server) Handle(ctx context.Context, data []byte) ([]byte, error) {
return s.HandleReader(ctx, bytes.NewReader(data))
}
// HandleReader processes a request to the server
// It returns the response in a byte array, only returns an
// error if it can not create the response byte array
func (s *Server) HandleReader(ctx context.Context, reader io.Reader) ([]byte, error) {
bufferedReader := bufio.NewReader(reader)
requestIsBatch := isBatch(bufferedReader)
res := &response{
Version: "2.0",
}
dec := json.NewDecoder(bufferedReader)
dec.UseNumber()
if !requestIsBatch {
req := new(request)
if jsonErr := dec.Decode(req); jsonErr != nil {
res.Error = Err(InvalidJSON, jsonErr.Error())
} else if resObject, handleErr := s.handleRequest(ctx, req); handleErr != nil {
if !errors.Is(handleErr, ErrInvalidID) {
res.ID = req.ID
}
res.Error = Err(InvalidRequest, handleErr.Error())
} else {
res = resObject
}
} else {
var batchReq []json.RawMessage
if batchJSONErr := dec.Decode(&batchReq); batchJSONErr != nil {
res.Error = Err(InvalidJSON, batchJSONErr.Error())
} else if len(batchReq) == 0 {
res.Error = Err(InvalidRequest, "empty batch")
} else {
return s.handleBatchRequest(ctx, batchReq)
}
}
if res == nil {
return nil, nil
}
return json.Marshal(res)
}
func (s *Server) handleBatchRequest(ctx context.Context, batchReq []json.RawMessage) ([]byte, error) {
var (
responses []json.RawMessage
mutex sync.Mutex
)
addResponse := func(response any) {
if responseJSON, err := json.Marshal(response); err != nil {
s.log.Errorw("failed to marshal response", "err", err)
} else {
mutex.Lock()
responses = append(responses, responseJSON)
mutex.Unlock()
}
}
ctx, cancel := context.WithCancel(ctx)
defer cancel()
var wg sync.WaitGroup
for _, rawReq := range batchReq {
reqDec := json.NewDecoder(bytes.NewBuffer(rawReq))
reqDec.UseNumber()
req := new(request)
if err := reqDec.Decode(req); err != nil {
addResponse(&response{
Version: "2.0",
Error: Err(InvalidRequest, err.Error()),
})
continue
}
wg.Add(1)
s.pool.Go(func() {
defer wg.Done()
resp, err := s.handleRequest(ctx, req)
if err != nil {
resp = &response{
Version: "2.0",
Error: Err(InvalidRequest, err.Error()),
}
if !errors.Is(err, ErrInvalidID) {
resp.ID = req.ID
}
}
// for notification request response is nil
if resp != nil {
addResponse(resp)
}
})
}
wg.Wait()
// according to the spec if there are no response objects server must not return empty array
if len(responses) == 0 {
return nil, nil
}
return json.Marshal(responses)
}
func isBatch(reader *bufio.Reader) bool {
for {
char, err := reader.Peek(1)
if err != nil {
break
}
if char[0] == ' ' || char[0] == '\t' || char[0] == '\r' || char[0] == '\n' {
if discarded, err := reader.Discard(1); discarded != 1 || err != nil {
break
}
continue
}
return char[0] == '['
}
return false
}
func isNil(i any) bool {
return i == nil || reflect.ValueOf(i).IsNil()
}
func (s *Server) handleRequest(ctx context.Context, req *request) (*response, error) {
reqJSON, err := json.Marshal(req)
if err == nil {
s.log.Debugw("Serving RPC request", "request", string(reqJSON))
}
if err = req.isSane(); err != nil {
return nil, err
}
res := &response{
Version: "2.0",
ID: req.ID,
}
calledMethod, found := s.methods[req.Method]
if !found {
res.Error = Err(MethodNotFound, nil)
return res, nil
}
timer := prometheus.NewTimer(s.requestLatencies.WithLabelValues(req.Method))
args, err := s.buildArguments(ctx, req.Params, calledMethod)
if err != nil {
res.Error = Err(InvalidParams, err.Error())
return res, nil
}
defer func() {
took := timer.ObserveDuration()
s.log.Debugw("Responding to RPC request", "method", req.Method, "id", req.ID, "took", took)
}()
s.requests.WithLabelValues(req.Method).Inc()
tuple := reflect.ValueOf(calledMethod.Handler).Call(args)
if res.ID == nil { // notification
return nil, nil
}
if errAny := tuple[1].Interface(); !isNil(errAny) {
res.Error = errAny.(*Error)
s.failedRequests.WithLabelValues(req.Method).Inc()
return res, nil
}
res.Result = tuple[0].Interface()
return res, nil
}
func (s *Server) buildArguments(ctx context.Context, params any, method Method) ([]reflect.Value, error) {
if isNil(params) {
allParamsAreOptional := utils.All(method.Params, func(p Parameter) bool {
return p.Optional
})
if len(method.Params) > 0 && !allParamsAreOptional {
return nil, errors.New("missing non-optional param field")
}
return s.buildDefaultArguments(ctx, method)
}
handlerType := reflect.TypeOf(method.Handler)
numArgs := handlerType.NumIn()
args := make([]reflect.Value, 0, numArgs)
addContext := 0
if method.needsContext {
args = append(args, reflect.ValueOf(ctx))
addContext = 1
}
switch reflect.TypeOf(params).Kind() {
case reflect.Slice:
paramsList := params.([]any)
if len(paramsList) != numArgs-addContext {
return nil, errors.New("missing/unexpected params in list")
}
for i, param := range paramsList {
v, err := s.parseParam(param, handlerType.In(i+addContext))
if err != nil {
return nil, err
}
args = append(args, v)
}
case reflect.Map:
paramsMap := params.(map[string]any)
for i, configuredParam := range method.Params {
var v reflect.Value
if param, found := paramsMap[configuredParam.Name]; found {
var err error
v, err = s.parseParam(param, handlerType.In(i+addContext))
if err != nil {
return nil, err
}
} else if configuredParam.Optional {
// optional parameter
v = reflect.New(handlerType.In(i + addContext)).Elem()
} else {
return nil, errors.New("missing non-optional param")
}
args = append(args, v)
}
default:
// Todo: consider returning InternalError
return nil, errors.New("impossible param type: check request.isSane")
}
return args, nil
}
func (s *Server) buildDefaultArguments(_ context.Context, method Method) ([]reflect.Value, error) {
handlerType := reflect.TypeOf(method.Handler)
numArgs := handlerType.NumIn()
args := make([]reflect.Value, 0, numArgs)
for i := 0; i < numArgs; i++ {
arg := reflect.New(handlerType.In(i)).Elem()
args = append(args, arg)
}
return args, nil
}
func (s *Server) parseParam(param any, t reflect.Type) (reflect.Value, error) {
handlerParam := reflect.New(t)
valueMarshaled, err := json.Marshal(param) // we have to marshal the value into JSON again
if err != nil {
return reflect.ValueOf(nil), err
}
err = json.Unmarshal(valueMarshaled, handlerParam.Interface())
if err != nil {
return reflect.ValueOf(nil), err
}
elem := handlerParam.Elem()
if s.validator != nil {
if err = s.validateParam(elem); err != nil {
return reflect.ValueOf(nil), err
}
}
return elem, nil
}
func (s *Server) validateParam(param reflect.Value) error {
kind := param.Kind()
switch {
case kind == reflect.Struct ||
(kind == reflect.Pointer && param.Elem().Kind() == reflect.Struct):
/* struct or a struct pointer */
if err := s.validator.Struct(param.Interface()); err != nil {
return err
}
case kind == reflect.Slice || kind == reflect.Array:
for i := 0; i < param.Len(); i++ {
if err := s.validateParam(param.Index(i)); err != nil {
return err
}
}
case kind == reflect.Map:
for _, key := range param.MapKeys() {
if err := s.validateParam(param.MapIndex(key)); err != nil {
return err
}
}
}
return nil
}