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client.go
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client.go
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package jsonrpc
import (
"container/list"
"context"
"encoding/base64"
"encoding/json"
"fmt"
"net/http"
"reflect"
"sync/atomic"
"time"
"github.com/gorilla/websocket"
logging "github.com/ipfs/go-log/v2"
"go.opencensus.io/trace"
"go.opencensus.io/trace/propagation"
"golang.org/x/xerrors"
)
const (
methodRetryFrequency = time.Second * 3
)
var (
errorType = reflect.TypeOf(new(error)).Elem()
contextType = reflect.TypeOf(new(context.Context)).Elem()
log = logging.Logger("rpc")
)
// ErrClient is an error which occurred on the client side the library
type ErrClient struct {
err error
}
func (e *ErrClient) Error() string {
return fmt.Sprintf("RPC client error: %s", e.err)
}
// Unwrap unwraps the actual error
func (e *ErrClient) Unwrap(err error) error {
return e.err
}
type clientResponse struct {
Jsonrpc string `json:"jsonrpc"`
Result json.RawMessage `json:"result"`
ID int64 `json:"id"`
Error *respError `json:"error,omitempty"`
}
type makeChanSink func() (context.Context, func([]byte, bool))
type clientRequest struct {
req request
ready chan clientResponse
// retCh provides a context and sink for handling incoming channel messages
retCh makeChanSink
}
// ClientCloser is used to close Client from further use
type ClientCloser func()
// NewClient creates new jsonrpc 2.0 client
//
// handler must be pointer to a struct with function fields
// Returned value closes the client connection
// TODO: Example
func NewClient(addr string, namespace string, handler interface{}, requestHeader http.Header) (ClientCloser, error) {
return NewMergeClient(addr, namespace, []interface{}{handler}, requestHeader)
}
type client struct {
namespace string
requests chan clientRequest
exiting <-chan struct{}
idCtr int64
}
// NewMergeClient is like NewClient, but allows to specify multiple structs
// to be filled in the same namespace, using one connection
func NewMergeClient(addr string, namespace string, outs []interface{}, requestHeader http.Header, opts ...Option) (ClientCloser, error) {
var config Config
for _, o := range opts {
o(&config)
}
connFactory := func() (*websocket.Conn, error) {
conn, _, err := websocket.DefaultDialer.Dial(addr, requestHeader)
return conn, err
}
if config.proxyConnFactory != nil {
connFactory = config.proxyConnFactory(connFactory)
}
conn, err := connFactory()
if err != nil {
return nil, err
}
c := client{
namespace: namespace,
}
stop := make(chan struct{})
exiting := make(chan struct{})
c.requests = make(chan clientRequest)
c.exiting = exiting
handlers := map[string]rpcHandler{}
go (&wsConn{
conn: conn,
connFactory: connFactory,
reconnectInterval: config.ReconnectInterval,
handler: handlers,
requests: c.requests,
stop: stop,
exiting: exiting,
}).handleWsConn(context.TODO())
for _, handler := range outs {
htyp := reflect.TypeOf(handler)
if htyp.Kind() != reflect.Ptr {
return nil, xerrors.New("expected handler to be a pointer")
}
typ := htyp.Elem()
if typ.Kind() != reflect.Struct {
return nil, xerrors.New("handler should be a struct")
}
val := reflect.ValueOf(handler)
for i := 0; i < typ.NumField(); i++ {
fn, err := c.makeRpcFunc(typ.Field(i))
if err != nil {
return nil, err
}
val.Elem().Field(i).Set(fn)
}
}
return func() {
close(stop)
<-exiting
}, nil
}
func (c *client) makeOutChan(ctx context.Context, ftyp reflect.Type, valOut int) (func() reflect.Value, makeChanSink) {
retVal := reflect.Zero(ftyp.Out(valOut))
chCtor := func() (context.Context, func([]byte, bool)) {
// unpack chan type to make sure it's reflect.BothDir
ctyp := reflect.ChanOf(reflect.BothDir, ftyp.Out(valOut).Elem())
ch := reflect.MakeChan(ctyp, 0) // todo: buffer?
chCtx, chCancel := context.WithCancel(ctx)
retVal = ch.Convert(ftyp.Out(valOut))
incoming := make(chan reflect.Value, 32)
// gorotuine to handle buffering of items
go func() {
buf := (&list.List{}).Init()
for {
front := buf.Front()
cases := []reflect.SelectCase{
{
Dir: reflect.SelectRecv,
Chan: reflect.ValueOf(chCtx.Done()),
},
{
Dir: reflect.SelectRecv,
Chan: reflect.ValueOf(incoming),
},
}
if front != nil {
cases = append(cases, reflect.SelectCase{
Dir: reflect.SelectSend,
Chan: ch,
Send: front.Value.(reflect.Value).Elem(),
})
}
chosen, val, _ := reflect.Select(cases)
switch chosen {
case 0:
ch.Close()
return
case 1:
vvval := val.Interface().(reflect.Value)
buf.PushBack(vvval)
if buf.Len() > 1 {
if buf.Len() > 10 {
log.Warnw("rpc output message buffer", "n", buf.Len())
} else {
log.Infow("rpc output message buffer", "n", buf.Len())
}
}
case 2:
buf.Remove(front)
}
}
}()
return ctx, func(result []byte, ok bool) {
if !ok {
chCancel()
return
}
val := reflect.New(ftyp.Out(valOut).Elem())
if err := json.Unmarshal(result, val.Interface()); err != nil {
log.Errorf("error unmarshaling chan response: %s", err)
return
}
if ctx.Err() != nil {
log.Errorf("got rpc message with cancelled context: %s", ctx.Err())
return
}
select {
case incoming <- val:
case <-chCtx.Done():
}
}
}
return func() reflect.Value { return retVal }, chCtor
}
func (c *client) sendRequest(ctx context.Context, req request, chCtor makeChanSink) (clientResponse, error) {
rchan := make(chan clientResponse, 1)
creq := clientRequest{
req: req,
ready: rchan,
retCh: chCtor,
}
select {
case c.requests <- creq:
case <-c.exiting:
return clientResponse{}, fmt.Errorf("websocket routine exiting")
}
var ctxDone <-chan struct{}
var resp clientResponse
if ctx != nil {
ctxDone = ctx.Done()
}
// wait for response, handle context cancellation
loop:
for {
select {
case resp = <-rchan:
break loop
case <-ctxDone: // send cancel request
ctxDone = nil
cancelReq := clientRequest{
req: request{
Jsonrpc: "2.0",
Method: wsCancel,
Params: []param{{v: reflect.ValueOf(*req.ID)}},
},
}
select {
case c.requests <- cancelReq:
case <-c.exiting:
log.Warn("failed to send request cancellation, websocket routing exited")
}
}
}
return resp, nil
}
type rpcFunc struct {
client *client
ftyp reflect.Type
name string
nout int
valOut int
errOut int
hasCtx int
returnValueIsChannel bool
retry bool
}
func (fn *rpcFunc) processResponse(resp clientResponse, rval reflect.Value) []reflect.Value {
out := make([]reflect.Value, fn.nout)
if fn.valOut != -1 {
out[fn.valOut] = rval
}
if fn.errOut != -1 {
out[fn.errOut] = reflect.New(errorType).Elem()
if resp.Error != nil {
out[fn.errOut].Set(reflect.ValueOf(resp.Error))
}
}
return out
}
func (fn *rpcFunc) processError(err error) []reflect.Value {
out := make([]reflect.Value, fn.nout)
if fn.valOut != -1 {
out[fn.valOut] = reflect.New(fn.ftyp.Out(fn.valOut)).Elem()
}
if fn.errOut != -1 {
out[fn.errOut] = reflect.New(errorType).Elem()
out[fn.errOut].Set(reflect.ValueOf(&ErrClient{err}))
}
return out
}
func (fn *rpcFunc) handleRpcCall(args []reflect.Value) (results []reflect.Value) {
id := atomic.AddInt64(&fn.client.idCtr, 1)
params := make([]param, len(args)-fn.hasCtx)
for i, arg := range args[fn.hasCtx:] {
params[i] = param{
v: arg,
}
}
var ctx context.Context
var span *trace.Span
if fn.hasCtx == 1 {
ctx = args[0].Interface().(context.Context)
ctx, span = trace.StartSpan(ctx, "api.call")
defer span.End()
}
retVal := func() reflect.Value { return reflect.Value{} }
// if the function returns a channel, we need to provide a sink for the
// messages
var chCtor makeChanSink
if fn.returnValueIsChannel {
retVal, chCtor = fn.client.makeOutChan(ctx, fn.ftyp, fn.valOut)
}
req := request{
Jsonrpc: "2.0",
ID: &id,
Method: fn.client.namespace + "." + fn.name,
Params: params,
}
if span != nil {
span.AddAttributes(trace.StringAttribute("method", req.Method))
eSC := base64.StdEncoding.EncodeToString(
propagation.Binary(span.SpanContext()))
req.Meta = map[string]string{
"SpanContext": eSC,
}
}
var resp clientResponse
var err error
// keep retrying if got a forced closed websocket conn and calling method
// has retry annotation
for {
resp, err = fn.client.sendRequest(ctx, req, chCtor)
if err != nil {
return fn.processError(fmt.Errorf("sendRequest failed: %w", err))
}
if resp.ID != *req.ID {
return fn.processError(xerrors.New("request and response id didn't match"))
}
if fn.valOut != -1 && !fn.returnValueIsChannel {
val := reflect.New(fn.ftyp.Out(fn.valOut))
if resp.Result != nil {
log.Debugw("rpc result", "type", fn.ftyp.Out(fn.valOut))
if err := json.Unmarshal(resp.Result, val.Interface()); err != nil {
log.Warnw("unmarshaling failed", "message", string(resp.Result))
return fn.processError(xerrors.Errorf("unmarshaling result: %w", err))
}
}
retVal = func() reflect.Value { return val.Elem() }
}
retry := resp.Error != nil && resp.Error.Code == 2 && fn.retry
if !retry {
break
}
time.Sleep(methodRetryFrequency)
}
return fn.processResponse(resp, retVal())
}
func (c *client) makeRpcFunc(f reflect.StructField) (reflect.Value, error) {
ftyp := f.Type
if ftyp.Kind() != reflect.Func {
return reflect.Value{}, xerrors.New("handler field not a func")
}
fun := &rpcFunc{
client: c,
ftyp: ftyp,
name: f.Name,
retry: f.Tag.Get("retry") == "true",
}
fun.valOut, fun.errOut, fun.nout = processFuncOut(ftyp)
if ftyp.NumIn() > 0 && ftyp.In(0) == contextType {
fun.hasCtx = 1
}
fun.returnValueIsChannel = fun.valOut != -1 && ftyp.Out(fun.valOut).Kind() == reflect.Chan
return reflect.MakeFunc(ftyp, fun.handleRpcCall), nil
}