swarm: integrate OpenTracing; propagate ctx to internal APIs (#17169)

* swarm: propagate ctx, enable opentracing

* swarm/tracing: log error when tracing is misconfigured

p2p/protocols/protocol.go

@@ -29,6 +29,8 @@ devp2p subprotocols by abstracting away code standardly shared by protocols.
 package protocols
 
 import (
+	"bufio"
+	"bytes"
 	"context"
 	"fmt"
 	"io"
@@ -39,6 +41,10 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/metrics"
 	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/swarm/spancontext"
+	"github.com/ethereum/go-ethereum/swarm/tracing"
+	opentracing "github.com/opentracing/opentracing-go"
 )
 
 // error codes used by this  protocol scheme
@@ -109,6 +115,13 @@ func errorf(code int, format string, params ...interface{}) *Error {
 	}
 }
 
+// WrappedMsg is used to propagate marshalled context alongside message payloads
+type WrappedMsg struct {
+	Context []byte
+	Size    uint32
+	Payload []byte
+}
+
 // Spec is a protocol specification including its name and version as well as
 // the types of messages which are exchanged
 type Spec struct {
@@ -201,7 +214,7 @@ func NewPeer(p *p2p.Peer, rw p2p.MsgReadWriter, spec *Spec) *Peer {
 // the handler argument is a function which is called for each message received
 // from the remote peer, a returned error causes the loop to exit
 // resulting in disconnection
-func (p *Peer) Run(handler func(msg interface{}) error) error {
+func (p *Peer) Run(handler func(ctx context.Context, msg interface{}) error) error {
 	for {
 		if err := p.handleIncoming(handler); err != nil {
 			if err != io.EOF {
@@ -225,14 +238,47 @@ func (p *Peer) Drop(err error) {
 // message off to the peer
 // this low level call will be wrapped by libraries providing routed or broadcast sends
 // but often just used to forward and push messages to directly connected peers
-func (p *Peer) Send(msg interface{}) error {
+func (p *Peer) Send(ctx context.Context, msg interface{}) error {
 	defer metrics.GetOrRegisterResettingTimer("peer.send_t", nil).UpdateSince(time.Now())
 	metrics.GetOrRegisterCounter("peer.send", nil).Inc(1)
+
+	var b bytes.Buffer
+	if tracing.Enabled {
+		writer := bufio.NewWriter(&b)
+
+		tracer := opentracing.GlobalTracer()
+
+		sctx := spancontext.FromContext(ctx)
+
+		if sctx != nil {
+			err := tracer.Inject(
+				sctx,
+				opentracing.Binary,
+				writer)
+			if err != nil {
+				return err
+			}
+		}
+
+		writer.Flush()
+	}
+
+	r, err := rlp.EncodeToBytes(msg)
+	if err != nil {
+		return err
+	}
+
+	wmsg := WrappedMsg{
+		Context: b.Bytes(),
+		Size:    uint32(len(r)),
+		Payload: r,
+	}
+
 	code, found := p.spec.GetCode(msg)
 	if !found {
 		return errorf(ErrInvalidMsgType, "%v", code)
 	}
-	return p2p.Send(p.rw, code, msg)
+	return p2p.Send(p.rw, code, wmsg)
 }
 
 // handleIncoming(code)
@@ -243,7 +289,7 @@ func (p *Peer) Send(msg interface{}) error {
 // * checks for out-of-range message codes,
 // * handles decoding with reflection,
 // * call handlers as callbacks
-func (p *Peer) handleIncoming(handle func(msg interface{}) error) error {
+func (p *Peer) handleIncoming(handle func(ctx context.Context, msg interface{}) error) error {
 	msg, err := p.rw.ReadMsg()
 	if err != nil {
 		return err
@@ -255,11 +301,38 @@ func (p *Peer) handleIncoming(handle func(msg interface{}) error) error {
 		return errorf(ErrMsgTooLong, "%v > %v", msg.Size, p.spec.MaxMsgSize)
 	}
 
+	// unmarshal wrapped msg, which might contain context
+	var wmsg WrappedMsg
+	err = msg.Decode(&wmsg)
+	if err != nil {
+		log.Error(err.Error())
+		return err
+	}
+
+	ctx := context.Background()
+
+	// if tracing is enabled and the context coming within the request is
+	// not empty, try to unmarshal it
+	if tracing.Enabled && len(wmsg.Context) > 0 {
+		var sctx opentracing.SpanContext
+
+		tracer := opentracing.GlobalTracer()
+		sctx, err = tracer.Extract(
+			opentracing.Binary,
+			bytes.NewReader(wmsg.Context))
+		if err != nil {
+			log.Error(err.Error())
+			return err
+		}
+
+		ctx = spancontext.WithContext(ctx, sctx)
+	}
+
 	val, ok := p.spec.NewMsg(msg.Code)
 	if !ok {
 		return errorf(ErrInvalidMsgCode, "%v", msg.Code)
 	}
-	if err := msg.Decode(val); err != nil {
+	if err := rlp.DecodeBytes(wmsg.Payload, val); err != nil {
 		return errorf(ErrDecode, "<= %v: %v", msg, err)
 	}
 
@@ -268,7 +341,7 @@ func (p *Peer) handleIncoming(handle func(msg interface{}) error) error {
 	// which the handler is supposed to cast to the appropriate type
 	// it is entirely safe not to check the cast in the handler since the handler is
 	// chosen based on the proper type in the first place
-	if err := handle(val); err != nil {
+	if err := handle(ctx, val); err != nil {
 		return errorf(ErrHandler, "(msg code %v): %v", msg.Code, err)
 	}
 	return nil
@@ -288,14 +361,14 @@ func (p *Peer) Handshake(ctx context.Context, hs interface{}, verify func(interf
 		return nil, errorf(ErrHandshake, "unknown handshake message type: %T", hs)
 	}
 	errc := make(chan error, 2)
-	handle := func(msg interface{}) error {
+	handle := func(ctx context.Context, msg interface{}) error {
 		rhs = msg
 		if verify != nil {
 			return verify(rhs)
 		}
 		return nil
 	}
-	send := func() { errc <- p.Send(hs) }
+	send := func() { errc <- p.Send(ctx, hs) }
 	receive := func() { errc <- p.handleIncoming(handle) }
 
 	go func() {