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grpcproxy.go
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grpcproxy.go
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// Copyright 2022 Namespace Labs Inc; All rights reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
package cluster
import (
"context"
"fmt"
"io"
"net"
"sync"
"time"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/credentials/insecure"
"google.golang.org/grpc/keepalive"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/status"
"google.golang.org/protobuf/types/known/emptypb"
"namespacelabs.dev/foundation/internal/console"
"namespacelabs.dev/go-ids"
controlapi "github.com/moby/buildkit/api/services/control"
)
func serveGRPCProxy(workerInfo *controlapi.ListWorkersResponse, listener net.Listener, connect func(context.Context) (net.Conn, error)) error {
p, err := newGrpcProxy(workerInfo, connect)
if err != nil {
return err
}
return p.Serve(listener)
}
type grpcProxy struct {
connect func(context.Context) (net.Conn, error)
*grpc.Server
workerInfo *controlapi.ListWorkersResponse
mu sync.Mutex
// Fields protected by mutex go below
backendClient *grpc.ClientConn
}
func newGrpcProxy(workerInfo *controlapi.ListWorkersResponse, connect func(context.Context) (net.Conn, error)) (*grpcProxy, error) {
g := &grpcProxy{
connect: connect,
workerInfo: workerInfo,
}
g.Server = grpc.NewServer(grpc.UnknownServiceHandler(g.handler))
return g, nil
}
func (g *grpcProxy) newBackendClient(ctx context.Context) (*grpc.ClientConn, error) {
g.mu.Lock()
defer g.mu.Unlock()
if g.backendClient != nil {
connState := g.backendClient.GetState()
if connState == connectivity.Ready || connState == connectivity.Connecting {
fmt.Fprintf(console.Debug(ctx), "reused grpc connection: %v\n", connState)
return g.backendClient, nil
}
closingErr := g.backendClient.Close()
fmt.Fprintf(console.Debug(ctx), "cached grpc connection invalidated: %v, closing err: %v\n", connState, closingErr)
g.backendClient = nil
}
client, err := grpc.DialContext(ctx, "",
grpc.WithKeepaliveParams(keepalive.ClientParameters{
//gRPC server default minimum is 5m, more frequent keepalives can cause "too_many_pings" error
Time: time.Minute * 5,
Timeout: time.Second * 30,
}),
grpc.WithTransportCredentials(insecure.NewCredentials()),
grpc.WithContextDialer(func(context.Context, string) (net.Conn, error) {
return g.connect(ctx)
}))
if err != nil {
return nil, err
}
fmt.Fprintf(console.Debug(ctx), "created new grpc connection\n")
g.backendClient = client
return client, nil
}
func (g *grpcProxy) handler(srv interface{}, serverStream grpc.ServerStream) error {
ctx := serverStream.Context()
fullMethodName, ok := grpc.MethodFromServerStream(serverStream)
if !ok {
err := status.Errorf(codes.Internal, "reading method failed")
fmt.Fprintf(console.Debug(ctx), "reading method failed: %v\n", err)
return err
}
id := ids.NewRandomBase32ID(4)
fmt.Fprintf(console.Debug(ctx), "[%s] handler %s\n", id, fullMethodName)
if fullMethodName == "/moby.buildkit.v1.Control/ListWorkers" && g.workerInfo != nil {
return shortcutListWorkers(ctx, id, g.workerInfo, serverStream)
}
md, _ := metadata.FromIncomingContext(serverStream.Context())
outgoingCtx := metadata.NewOutgoingContext(serverStream.Context(), md.Copy())
backendConn, err := g.newBackendClient(outgoingCtx)
if err != nil {
fmt.Fprintf(console.Debug(ctx), "creating backend connection failed: %v\n", err)
return status.Errorf(codes.Internal, "failed to connect to backend: %v", err)
}
clientStreamDescForProxying := &grpc.StreamDesc{
ServerStreams: true,
ClientStreams: true,
}
clientCtx, clientCancel := context.WithCancel(outgoingCtx)
defer clientCancel()
clientStream, err := grpc.NewClientStream(clientCtx, clientStreamDescForProxying, backendConn, fullMethodName)
if err != nil {
fmt.Fprintf(console.Debug(ctx), "failed to create client stream: %v\n", err)
return status.Errorf(codes.Internal, "failed create client: %v", err)
}
s2cErrChan := proxyServerToClient(serverStream, clientStream)
c2sErrChan := proxyClientToServer(clientStream, serverStream)
// Make sure to close both client and server connections
for i := 0; i < 2; i++ {
select {
case s2cErr := <-s2cErrChan:
s2cErrChan = nil // Receive on closed channel does not block, set to nil
if s2cErr == io.EOF {
clientStream.CloseSend()
} else {
clientCancel()
fmt.Fprintf(console.Debug(ctx), "failed proxying s2c: %v\n", s2cErr)
return status.Errorf(codes.Internal, "failed proxying s2c: %v", s2cErr)
}
case c2sErr := <-c2sErrChan:
c2sErrChan = nil // Receive on closed channel does not block, set to nil
serverStream.SetTrailer(clientStream.Trailer())
// c2sErr will contain RPC error from client code. If not io.EOF return the RPC error as server stream error.
if c2sErr != io.EOF {
fmt.Fprintf(console.Debug(ctx), "failed proxying c2s: %v\n", c2sErr)
return c2sErr
}
// Happy case
return nil
case <-ctx.Done():
err := ctx.Err()
fmt.Fprintf(console.Debug(ctx), "server stream context is done: %v\n", err)
return err
}
}
return status.Errorf(codes.Internal, "gRPC proxy should never reach this stage.")
}
func proxyClientToServer(src grpc.ClientStream, dst grpc.ServerStream) chan error {
ret := make(chan error, 1)
go func() {
defer close(ret)
// Server headers are only readable after first client msg is
// received but must be written to server stream before the first msg is sent
if err := propagateHeaders(src, dst); err != nil {
ret <- err
return
}
if err := doProxy(src, dst); err != nil {
ret <- err
return
}
}()
return ret
}
func proxyServerToClient(src grpc.ServerStream, dst grpc.ClientStream) chan error {
ret := make(chan error, 1)
go func() {
defer close(ret)
if err := doProxy(src, dst); err != nil {
ret <- err
}
}()
return ret
}
func shortcutListWorkers(ctx context.Context, id string, workerInfo *controlapi.ListWorkersResponse, dst grpc.ServerStream) error {
md := map[string][]string{
"content-type": {"application/grpc"},
}
if err := dst.SendHeader(md); err != nil {
return err
}
if err := dst.SendMsg(workerInfo); err != nil {
return err
}
fmt.Fprintf(console.Debug(ctx), "[%s] ListWorkers injected worker info\n", id)
return nil
}
func propagateHeaders(src grpc.ClientStream, dst grpc.ServerStream) error {
f := &emptypb.Empty{}
if err := src.RecvMsg(f); err != nil {
return err // this can be io.EOF which is happy case
}
// Server headers are only readable after first client msg is
// received but must be written to server stream before the first msg is sent
md, err := src.Header()
if err != nil {
return err
}
if err := dst.SendHeader(md); err != nil {
return err
}
if err := dst.SendMsg(f); err != nil {
return err
}
return nil
}
type Stream interface {
SendMsg(m interface{}) error
RecvMsg(m interface{}) error
}
func doProxy(src Stream, dst Stream) error {
// Not really empty message. All fields are unmarshalled in Empty.unknownFields.
f := &emptypb.Empty{}
for {
if err := src.RecvMsg(f); err != nil {
return err
}
if err := dst.SendMsg(f); err != nil {
return err
}
}
}