Merge pull request #29456 from cpuguy83/fix_client_events_race

Fixes a race condition in client events monitoring
Upstream-commit: 8a8416ccbdaf08598f4ac38255e4267859682bb9
Component: engine

components/engine/client/events.go

@@ -22,17 +22,20 @@ func (cli *Client) Events(ctx context.Context, options types.EventsOptions) (<-c
 	messages := make(chan events.Message)
 	errs := make(chan error, 1)
 
+	started := make(chan struct{})
 	go func() {
 		defer close(errs)
 
 		query, err := buildEventsQueryParams(cli.version, options)
 		if err != nil {
+			close(started)
 			errs <- err
 			return
 		}
 
 		resp, err := cli.get(ctx, "/events", query, nil)
 		if err != nil {
+			close(started)
 			errs <- err
 			return
 		}
@@ -40,6 +43,7 @@ func (cli *Client) Events(ctx context.Context, options types.EventsOptions) (<-c
 
 		decoder := json.NewDecoder(resp.body)
 
+		close(started)
 		for {
 			select {
 			case <-ctx.Done():
@@ -61,6 +65,7 @@ func (cli *Client) Events(ctx context.Context, options types.EventsOptions) (<-c
 			}
 		}
 	}()
+	<-started
 
 	return messages, errs
 }