code: func (c *InternalClient) SendMessage(ctx context.Context, uri *pilosa.URI, msg []byte) error {
  	span, ctx := tracing.StartSpanFromContext(ctx, "InternalClient.SendMessage")
  	defer span.Finish()
  
  	u := uriPathToURL(uri, "/internal/cluster/message")
  	req, err := http.NewRequest("POST", u.String(), bytes.NewReader(msg))
  	if err != nil {
  		return errors.Wrap(err, "making new request")
  	}
  	req.Header.Set("Content-Type", "application/x-protobuf")
  	req.Header.Set("User-Agent", "pilosa/"+pilosa.Version)
  	req.Header.Set("Accept", "application/json")
  
  	// Execute request.
  	resp, err := c.executeRequest(req.WithContext(ctx))
  	if err != nil {
  		return errors.Wrap(err, "executing request")
  	}
  	return errors.Wrap(resp.Body.Close(), "closing response body")
  }
docs: // SendMessage posts a message synchronously.