How to generate static pages with edge side includes.

I would like to utilize the Rendering/Caching system to create static pages that have ESI (Edge Side Include) markup instead of the placeholders used in the caching system. This is similar to the Drupal 7 Static module (Drupal.org/project/static), which outputs static pages with ESI markup. I am working a Drupal 8 version of the Static module, which has been moved to Drupal.org/project/static_generator, in order to avoid use of the reserved word "static".

It seems the Dynamic Page Cache is creating close to what is needed, except the placeholder markup needs to be changed, similar to how Big Pipe's placeholder strategy works. Would anyone have an idea as to the best approach? I would need to create pages similar to the partial pages currently created by the Dynamic Cache module, except that the placeholders are replaced with ESI markup. I will also need to create the html fragments that are referenced by the ESI markup.

For example, to create a static file for a node, wouldn't I need to get the markup from the Dynamic Page cache (using $cache_entry = \Drupal::cache('dynamic_page_cache')->get($cid);) and then have a placeholder strategy that modifies the placeholders to be ESI's? Or perhaps I need to get the render array for the node and use a renderer service, e.g.

    $entity_type = 'node';
    $view_mode = 'full';
    $node = \Drupal::entityTypeManager()->getStorage($entity_type)->load(1);
    $node_render_array = \Drupal::entityTypeManager()
      ->getViewBuilder($entity_type)
      ->view($node, $view_mode);
    $renderer = $this->classResolver->getInstanceFromDefinition($this->mainContentRenderers['html']);
    $request = new Request();
    $response = $renderer->renderResponse($node_render_array, $request, $this->routeMatch);
    $content = $response->getContent();

Note that the content that needs ESI placeholders is different than what needs caching placeholders. ESI's are needed for any block that is displayed on more than one page, while caching placeholders are for content that changes, and therefor can not be cached.

A point of confusion is that the rendering/caching code is all request/response based. But the process needed to output the static files with ESI placeholders will not have a request for each static file generated, as they are generated on the server, so there is no request/response needed. How can the core rendering system render a page without a request? In the above code example, a dummy blank response is used, but that causes an error.

Thank for your help,

captaindav