lotus/lib/jsonrpc/client.go
2019-07-24 02:40:19 +02:00

258 lines
6.1 KiB
Go

package jsonrpc
import (
"context"
"encoding/json"
"errors"
"fmt"
"net/http"
"reflect"
"sync/atomic"
"github.com/gorilla/websocket"
logging "github.com/ipfs/go-log"
"golang.org/x/xerrors"
)
var log = logging.Logger("rpc")
var (
errorType = reflect.TypeOf(new(error)).Elem()
contextType = reflect.TypeOf(new(context.Context)).Elem()
)
// 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 clientRequest struct {
req request
ready chan clientResponse
// retCh provides a context and sink for handling incoming channel messages
retCh func() (context.Context, func([]byte, bool))
}
// ClientCloser is used to close Client from further use
type ClientCloser func()
// NewClient creates new josnrpc 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)
}
// 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) (ClientCloser, error) {
var idCtr int64
conn, _, err := websocket.DefaultDialer.Dial(addr, requestHeader)
if err != nil {
return nil, err
}
stop := make(chan struct{})
requests := make(chan clientRequest)
handlers := map[string]rpcHandler{}
go (&wsConn{
conn: conn,
handler: handlers,
requests: requests,
stop: stop,
}).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++ {
f := typ.Field(i)
ftyp := f.Type
if ftyp.Kind() != reflect.Func {
return nil, xerrors.New("handler field not a func")
}
valOut, errOut, nout := processFuncOut(ftyp)
processResponse := func(resp clientResponse, rval reflect.Value) []reflect.Value {
out := make([]reflect.Value, nout)
if valOut != -1 {
out[valOut] = rval
}
if errOut != -1 {
out[errOut] = reflect.New(errorType).Elem()
if resp.Error != nil {
out[errOut].Set(reflect.ValueOf(resp.Error))
}
}
return out
}
processError := func(err error) []reflect.Value {
out := make([]reflect.Value, nout)
if valOut != -1 {
out[valOut] = reflect.New(ftyp.Out(valOut)).Elem()
}
if errOut != -1 {
out[errOut] = reflect.New(errorType).Elem()
out[errOut].Set(reflect.ValueOf(&ErrClient{err}))
}
return out
}
hasCtx := 0
if ftyp.NumIn() > 0 && ftyp.In(0) == contextType {
hasCtx = 1
}
retCh := valOut != -1 && ftyp.Out(valOut).Kind() == reflect.Chan
fn := reflect.MakeFunc(ftyp, func(args []reflect.Value) (results []reflect.Value) {
id := atomic.AddInt64(&idCtr, 1)
params := make([]param, len(args)-hasCtx)
for i, arg := range args[hasCtx:] {
params[i] = param{
v: arg,
}
}
var ctx context.Context
if hasCtx == 1 {
ctx = args[0].Interface().(context.Context)
}
var retVal reflect.Value
// if the function returns a channel, we need to provide a sink for the
// messages
var chCtor func() (context.Context, func([]byte, bool))
if retCh {
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?
retVal = ch.Convert(ftyp.Out(valOut))
return ctx, func(result []byte, ok bool) {
if !ok {
// remote channel closed, close ours too
ch.Close()
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
}
ch.Send(val.Elem()) // todo: select on ctx is probably a good idea
}
}
}
req := request{
Jsonrpc: "2.0",
ID: &id,
Method: namespace + "." + f.Name,
Params: params,
}
rchan := make(chan clientResponse, 1)
requests <- clientRequest{
req: req,
ready: rchan,
retCh: chCtor,
}
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
requests <- clientRequest{
req: request{
Jsonrpc: "2.0",
Method: wsCancel,
Params: []param{{v: reflect.ValueOf(id)}},
},
}
}
}
if valOut != -1 && !retCh {
retVal = reflect.New(ftyp.Out(valOut))
if resp.Result != nil {
log.Debugw("rpc result", "type", ftyp.Out(valOut))
if err := json.Unmarshal(resp.Result, retVal.Interface()); err != nil {
return processError(xerrors.Errorf("unmarshaling result: %w", err))
}
}
retVal = retVal.Elem()
}
if resp.ID != *req.ID {
return processError(errors.New("request and response id didn't match"))
}
return processResponse(resp, retVal)
})
val.Elem().Field(i).Set(fn)
}
}
return func() {
close(stop)
}, nil
}