Introduce TSDB service (#31520)

* Introduce TSDB service

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

Co-authored-by: Erik Sundell <erik.sundell87@gmail.com>
Co-authored-by: Will Browne <will.browne@grafana.com>
Co-authored-by: Torkel Ödegaard <torkel@grafana.org>
Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>
Co-authored-by: Zoltán Bedi <zoltan.bedi@gmail.com>

pkg/plugins/backendplugin/manager/resource_response_stream.go

@@ -0,0 +1,57 @@
+package manager
+
+import (
+	"context"
+	"errors"
+	"io"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+)
+
+func newCallResourceResponseStream(ctx context.Context) *callResourceResponseStream {
+	return &callResourceResponseStream{
+		ctx:    ctx,
+		stream: make(chan *backend.CallResourceResponse),
+	}
+}
+
+type callResourceResponseStream struct {
+	ctx    context.Context
+	stream chan *backend.CallResourceResponse
+	closed bool
+}
+
+func (s *callResourceResponseStream) Send(res *backend.CallResourceResponse) error {
+	if s.closed {
+		return errors.New("cannot send to a closed stream")
+	}
+
+	select {
+	case <-s.ctx.Done():
+		return errors.New("cancelled")
+	case s.stream <- res:
+		return nil
+	}
+}
+
+func (s *callResourceResponseStream) Recv() (*backend.CallResourceResponse, error) {
+	select {
+	case <-s.ctx.Done():
+		return nil, s.ctx.Err()
+	case res, ok := <-s.stream:
+		if !ok {
+			return nil, io.EOF
+		}
+		return res, nil
+	}
+}
+
+func (s *callResourceResponseStream) Close() error {
+	if s.closed {
+		return errors.New("cannot close a closed stream")
+	}
+
+	close(s.stream)
+	s.closed = true
+	return nil
+}