kvserver/rangefeed: move perRangeEventSink to rangefeed pacakge

Previously, perRangeEventSink was defined in pkg/server/node.go. This patch
relocates it to the rangefeed package to facilitate future commits testing
within the rangefeed package itself.

Part of: cockroachdb#126560
Release note: none

pkg/kv/kvserver/rangefeed/BUILD.bazel

@@ -14,6 +14,7 @@ go_library(
         "resolved_timestamp.go",
         "scheduled_processor.go",
         "scheduler.go",
+        "stream.go",
         "stream_muxer.go",
         "stream_muxer_test_helper.go",
         "task.go",

pkg/kv/kvserver/rangefeed/registry.go

@@ -22,16 +22,6 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 )
 
-// Stream is a object capable of transmitting RangeFeedEvents.
-type Stream interface {
-	kvpb.RangeFeedEventSink
-	// Disconnect disconnects the stream with the provided error. Note that this
-	// function can be called by the processor worker while holding raftMu, so it
-	// is important that this function doesn't block IO or try acquiring locks
-	// that could lead to deadlocks.
-	Disconnect(err *kvpb.Error)
-}
-
 // registration defines an interface for registration that can be added to a
 // processor registry. Implemented by bufferedRegistration.
 type registration interface {

pkg/kv/kvserver/rangefeed/stream.go

@@ -0,0 +1,78 @@
+// Copyright 2024 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package rangefeed
+
+import (
+	"context"
+
+	"github.com/cockroachdb/cockroach/pkg/kv/kvpb"
+	"github.com/cockroachdb/cockroach/pkg/roachpb"
+)
+
+// Stream is an object capable of transmitting RangeFeedEvents from a server
+// rangefeed to a client.
+type Stream interface {
+	kvpb.RangeFeedEventSink
+	// Disconnect disconnects the stream with the provided error. Note that this
+	// function can be called by the processor worker while holding raftMu, so it
+	// is important that this function doesn't block IO or try acquiring locks
+	// that could lead to deadlocks.
+	Disconnect(err *kvpb.Error)
+}
+
+// PerRangeEventSink is an implementation of Stream which annotates each
+// response with rangeID and streamID. It is used by MuxRangeFeed.
+type PerRangeEventSink struct {
+	ctx      context.Context
+	rangeID  roachpb.RangeID
+	streamID int64
+	wrapped  *StreamMuxer
+}
+
+func NewPerRangeEventSink(
+	ctx context.Context, rangeID roachpb.RangeID, streamID int64, wrapped *StreamMuxer,
+) *PerRangeEventSink {
+	return &PerRangeEventSink{
+		ctx:      ctx,
+		rangeID:  rangeID,
+		streamID: streamID,
+		wrapped:  wrapped,
+	}
+}
+
+var _ kvpb.RangeFeedEventSink = (*PerRangeEventSink)(nil)
+var _ Stream = (*PerRangeEventSink)(nil)
+
+func (s *PerRangeEventSink) Context() context.Context {
+	return s.ctx
+}
+
+// SendIsThreadSafe is a no-op declaration method. It is a contract that the
+// Send method is thread-safe. Note that Send wraps StreamMuxer which declares
+// its Send method to be thread-safe.
+func (s *PerRangeEventSink) SendIsThreadSafe() {}
+
+func (s *PerRangeEventSink) Send(event *kvpb.RangeFeedEvent) error {
+	response := &kvpb.MuxRangeFeedEvent{
+		RangeFeedEvent: *event,
+		RangeID:        s.rangeID,
+		StreamID:       s.streamID,
+	}
+	return s.wrapped.Send(response)
+}
+
+// Disconnect implements the Stream interface. It requests the StreamMuxer to
+// detach the stream. The StreamMuxer is then responsible for handling the
+// actual disconnection and additional cleanup. Note that Caller should not rely
+// on immediate disconnection as cleanup takes place async.
+func (s *PerRangeEventSink) Disconnect(err *kvpb.Error) {
+	s.wrapped.DisconnectStreamWithError(s.streamID, s.rangeID, err)
+}

pkg/server/node.go

@@ -1925,44 +1925,6 @@ func (n *Node) RangeLookup(
 	return resp, nil
 }
 
-// perRangeEventSink is an implementation of rangefeed.Stream which annotates
-// each response with rangeID and streamID. It is used by MuxRangeFeed.
-type perRangeEventSink struct {
-	ctx      context.Context
-	rangeID  roachpb.RangeID
-	streamID int64
-	wrapped  *rangefeed.StreamMuxer
-}
-
-var _ kvpb.RangeFeedEventSink = (*perRangeEventSink)(nil)
-var _ rangefeed.Stream = (*perRangeEventSink)(nil)
-
-func (s *perRangeEventSink) Context() context.Context {
-	return s.ctx
-}
-
-// SendIsThreadSafe is a no-op declaration method. It is a contract that the
-// Send method is thread-safe. Note that Send wraps rangefeed.StreamMuxer which
-// declares its Send method to be thread-safe.
-func (s *perRangeEventSink) SendIsThreadSafe() {}
-
-func (s *perRangeEventSink) Send(event *kvpb.RangeFeedEvent) error {
-	response := &kvpb.MuxRangeFeedEvent{
-		RangeFeedEvent: *event,
-		RangeID:        s.rangeID,
-		StreamID:       s.streamID,
-	}
-	return s.wrapped.Send(response)
-}
-
-// Disconnect implements the rangefeed.Stream interface. It requests the
-// StreamMuxer to detach the stream. The StreamMuxer is then responsible for
-// handling the actual disconnection and additional cleanup. Note that Caller
-// should not rely on immediate disconnection as cleanup takes place async.
-func (s *perRangeEventSink) Disconnect(err *kvpb.Error) {
-	s.wrapped.DisconnectStreamWithError(s.streamID, s.rangeID, err)
-}
-
 // lockedMuxStream provides support for concurrent calls to Send. The underlying
 // MuxRangeFeedServer (default grpc.Stream) is not safe for concurrent calls to
 // Send.
@@ -2021,12 +1983,7 @@ func (n *Node) MuxRangeFeed(stream kvpb.Internal_MuxRangeFeedServer) error {
 			streamCtx = logtags.AddTag(streamCtx, "s", req.Replica.StoreID)
 			streamCtx = logtags.AddTag(streamCtx, "sid", req.StreamID)
 
-			streamSink := &perRangeEventSink{
-				ctx:      streamCtx,
-				rangeID:  req.RangeID,
-				streamID: req.StreamID,
-				wrapped:  streamMuxer,
-			}
+			streamSink := rangefeed.NewPerRangeEventSink(streamCtx, req.RangeID, req.StreamID, streamMuxer)
 			streamMuxer.AddStream(req.StreamID, req.RangeID, cancel)
 
 			// Rangefeed attempts to register rangefeed a request over the specified