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client.go
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client.go
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package srpc
import (
"context"
"io"
"github.com/pkg/errors"
)
// Client implements a SRPC client which can initiate RPC streams.
type Client interface {
// Invoke executes a unary RPC with the remote.
Invoke(ctx context.Context, service, method string, in, out Message) error
// NewStream starts a streaming RPC with the remote & returns the stream.
// firstMsg is optional.
NewStream(ctx context.Context, service, method string, firstMsg Message) (Stream, error)
}
// OpenStreamFunc opens a stream with a remote.
// msgHandler must not be called concurrently.
type OpenStreamFunc = func(ctx context.Context, msgHandler func(pkt *Packet) error) (Writer, error)
// client implements Client with a transport.
type client struct {
// openStream opens a new stream.
openStream OpenStreamFunc
}
// NewClient constructs a client with a OpenStreamFunc.
func NewClient(openStream OpenStreamFunc) Client {
return &client{
openStream: openStream,
}
}
// Invoke executes a unary RPC with the remote.
func (c *client) Invoke(rctx context.Context, service, method string, in, out Message) error {
ctx, ctxCancel := context.WithCancel(rctx)
defer ctxCancel()
firstMsg, err := in.MarshalVT()
if err != nil {
return err
}
clientRPC := NewClientRPC(ctx, service, method)
writer, err := c.openStream(ctx, clientRPC.HandlePacket)
if err != nil {
return err
}
if err := clientRPC.Start(writer, firstMsg); err != nil {
return err
}
msgs, err := clientRPC.ReadAll()
if err != nil {
// this includes any server returned error.
return err
}
if len(msgs) == 0 {
// no reply? return eof.
return io.EOF
}
// parse first message to out
if err := out.UnmarshalVT(msgs[0]); err != nil {
return errors.Wrap(ErrInvalidMessage, err.Error())
}
// done
return nil
}
// NewStream starts a streaming RPC with the remote & returns the stream.
// firstMsg is optional.
func (c *client) NewStream(ctx context.Context, service, method string, firstMsg Message) (Stream, error) {
var firstMsgData []byte
if firstMsg != nil {
var err error
firstMsgData, err = firstMsg.MarshalVT()
if err != nil {
return nil, err
}
}
clientRPC := NewClientRPC(ctx, service, method)
writer, err := c.openStream(ctx, clientRPC.HandlePacket)
if err != nil {
return nil, err
}
if err := clientRPC.Start(writer, firstMsgData); err != nil {
return nil, err
}
return NewRPCStream(ctx, clientRPC.writer, clientRPC.dataCh), nil
}
// _ is a type assertion
var _ Client = ((*client)(nil))