404/403 responses for non-existing nodes are cached in Page Cache/reverse proxy, are not invalidated when the node is created

Note that #2472281: 404/403 responses for non-existing nodes are cached in Page Cache/reverse proxy, are not invalidated when the node is created already gets the basic infrastructure in to fix this.

#3: yes, obviously, I was just using a concrete example :)

If we collectively agree that a shorter TTL for non-2xx responses is a good idea, can somebody file an issue for that? :) Thanks!

Looks good already!

Only nits.

1. +++ b/core/modules/system/src/Tests/Bootstrap/PageCacheTest.php
   @@ -308,6 +309,57 @@ function testPageCacheAnonymousRolePermissions() {
   +    $config = $this->config('system.performance');
   +    $config->set('cache.page.use_internal', 1);
   +    $config->set('cache.page.max_age', 300);
   +    $config->save();
   

   Unnecessary: page caching is enabled by default.

2. +++ b/core/modules/system/src/Tests/Bootstrap/PageCacheTest.php
   @@ -308,6 +309,57 @@ function testPageCacheAnonymousRolePermissions() {
   +      $this->assertEqual($this->drupalGetHeader('X-Drupal-Cache'), 'MISS');
   +      $cache_tags = explode(' ', $this->drupalGetHeader('X-Drupal-Cache-Tags'));
   +      $this->assertTrue(in_array('4xx-response', $cache_tags));
   

   $this->assertCacheTag('4xx-response');

3. +++ b/core/modules/system/src/Tests/Bootstrap/PageCacheTest.php
   @@ -308,6 +309,57 @@ function testPageCacheAnonymousRolePermissions() {
   +      // Saving an entity clears 4xx cache tag.
   

   s/clears/invalidates the/

4. +++ b/core/modules/system/src/Tests/Bootstrap/PageCacheTest.php
   @@ -308,6 +309,57 @@ function testPageCacheAnonymousRolePermissions() {
   +      // Rebuilding the router should clear the 4xx cache tag.
   

   s/clear/invalidate/

Perfect.

Green :)