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transport.go
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transport.go
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package rpc
import (
"context"
"io"
"sync"
"time"
"go.uber.org/fx"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
rpcv1 "github.com/fluxninja/aperture/api/gen/proto/go/aperture/rpc/v1"
"github.com/fluxninja/aperture/pkg/log"
grpcclient "github.com/fluxninja/aperture/pkg/net/grpc"
)
const reconnectDelay = 10 * time.Second
// StreamClient is a client part of "stream" transport, which uses
// bidirectional grpc stream methods.
type StreamClient struct {
clientName string
handlers *HandlerRegistry
coordinatorClient rpcv1.CoordinatorClient
ctx context.Context
cancel context.CancelFunc
wg sync.WaitGroup
}
// RegisterStreamClient is an FX helper to connect new StreamClient to a given addr.
func RegisterStreamClient(
clientName string,
lc fx.Lifecycle,
handlers *HandlerRegistry,
connWrapper grpcclient.ClientConnectionWrapper,
addr string,
) {
var client *StreamClient
var conn *grpc.ClientConn
lc.Append(fx.Hook{
OnStart: func(ctx context.Context) error {
var err error
if conn, err = connWrapper.Dial(ctx, addr); err != nil {
return err
}
client = NewStreamClient(
clientName,
handlers,
rpcv1.NewCoordinatorClient(conn),
)
client.Start()
return nil
},
OnStop: func(ctx context.Context) error {
client.Stop()
conn.Close()
return nil
},
})
}
// NewStreamClient creates a new StreamClient.
func NewStreamClient(
name string,
handlers *HandlerRegistry,
client rpcv1.CoordinatorClient,
) *StreamClient {
return &StreamClient{
clientName: name,
handlers: handlers,
coordinatorClient: client,
}
}
// Start starts the StreamClient.
func (c *StreamClient) Start() {
c.ctx, c.cancel = context.WithCancel(context.Background())
c.wg.Add(1)
go c.runClient()
}
// Stop stops the StreamClient.
func (c *StreamClient) Stop() {
c.cancel()
c.wg.Wait()
}
func (c *StreamClient) runClient() {
defer c.wg.Done()
for {
c.runClientIteration()
select {
case <-c.ctx.Done():
return
default:
}
select {
case <-time.After(reconnectDelay):
log.Autosample().Info().Msg("stream client: reconnecting")
continue
case <-c.ctx.Done():
return
}
}
}
func (c *StreamClient) runClientIteration() {
ctx, cancel := context.WithCancel(c.ctx)
defer cancel()
conn, err := c.coordinatorClient.Connect(ctx)
if err != nil {
log.Autosample().Warn().Err(err).Msg("stream client: failed to connect")
return
}
err = conn.Send(&rpcv1.ClientToServer{
Msg: &rpcv1.ClientToServer_Hello_{
Hello: &rpcv1.ClientToServer_Hello{
Name: c.clientName,
// We're creating a fresh dispatcher for every connection,
// thus we can start from 0 each time.
NextId: 0,
},
},
})
if err != nil {
log.Warn().Err(err).Msg("stream client: failed to hello")
return
}
dispatcher := c.handlers.StartDispatcher()
defer dispatcher.Stop()
var wg sync.WaitGroup
wg.Add(1)
defer wg.Wait()
go func() {
defer wg.Done()
for {
// if ctx expires or conn disconnects, this should return error
// and the loop should end, no need to explicitly wait on
// ctx.done().
serverToClient, err := conn.Recv()
if err != nil {
log.Warn().Err(err).Msg("stream client: disconnected")
cancel()
return
}
dispatcher.ProcessCommand(serverToClient)
}
}()
for {
select {
case <-ctx.Done():
return
case response := <-dispatcher.Chan():
err := conn.Send(&rpcv1.ClientToServer{
Msg: &rpcv1.ClientToServer_Response{
Response: response,
},
})
if err != nil {
log.Warn().Err(err).Msg("stream client: failed to send")
// Note: This cancel is deferred already, but we want to cancel
// to force-stop serverToClient goroutine before joining it.
cancel()
return
}
}
}
}
// StreamServer is a server part of "stream" transport, which uses
// bidirectional grpc stream methods.
//
// Implements rpc.v1.Coordinator.
type StreamServer struct {
clients *Clients
}
// NewStreamServer creates new StreamServer plugging into given Clients as a transport.
func NewStreamServer(clients *Clients) *StreamServer {
return &StreamServer{
clients: clients,
}
}
// Connect implements rpcv1.CoordinatorServer.
func (s *StreamServer) Connect(conn rpcv1.Coordinator_ConnectServer) error {
firstMsg, err := conn.Recv()
if err != nil {
return err
}
hello, ok := firstMsg.Msg.(*rpcv1.ClientToServer_Hello_)
if !ok {
return status.Error(codes.InvalidArgument, "expected hello msg")
}
requests, responses := s.clients.Join(hello.Hello.Name, hello.Hello.NextId)
defer close(responses)
// Note: Capacity set to one, so goroutine would never block on sending to this channel.
clientDisconnected := make(chan error, 1)
go func() {
for {
msg, err := conn.Recv()
if err != nil {
if err == io.EOF {
clientDisconnected <- nil
} else {
clientDisconnected <- err
}
return
}
switch msg := msg.Msg.(type) {
case *rpcv1.ClientToServer_Response:
responses <- msg.Response
case *rpcv1.ClientToServer_Hello_:
clientDisconnected <- status.Error(codes.InvalidArgument, "unexpected hello")
return
default:
log.Bug().Msg("unknown client to server message")
}
}
}()
// Note: not waiting for this goroutine in defer, see below.
for {
select {
case serverToClient, ok := <-requests:
if !ok {
// Close the stream.
// Note: The goroutine should receive err from Recv and finish immediately.
return nil
}
if err := conn.Send(serverToClient); err != nil {
return err
}
case err := <-clientDisconnected:
return err
}
}
}