fix(sink): rule hang when buffer full (#2244)

Signed-off-by: Jiyong Huang <huangjy@emqx.io>

internal/topo/node/sink_node.go

@@ -224,7 +224,8 @@ func (m *SinkNode) Open(ctx api.StreamContext, result chan<- error) {
 							} else {
 								select {
 								case dataCh <- outs:
-								case <-ctx.Done():
+								default:
+									ctx.GetLogger().Warnf("sink node %s instance %d buffer is full, drop data %v", m.name, instance, outs)
 								}
 							}
 							if resendCh != nil {