StackedKernelPass

Provides a compiler pass for stacked HTTP kernels.

Builds the HTTP kernel by collecting all services tagged 'http_middleware' and assembling them into a StackedKernel. The middleware with the lowest priority ends up as the outermost while the highest priority middleware wraps the actual HTTP kernel defined by the http_kernel.basic service.

The 'http_middleware' service tag additionally accepts a 'responder' parameter. It should be set to TRUE if many or most requests will be handled directly by the middleware. Any underlying middleware and the HTTP kernel are then flagged as 'lazy'. As a result those low priority services and their dependencies are only initialized if the 'responder' middleware fails to generate a response and the request is delegated to the underlying kernel.

In general middlewares should not have heavy dependencies. This is especially important for high-priority services which need to run before the internal page cache.

An example of a high priority middleware.

http_middleware.reverse_proxy:
  class: Drupal\Core\StackMiddleware\ReverseProxyMiddleware
  arguments: ['@settings']
  tags:
    - { name: http_middleware, priority: 300 }

An example of a responder middleware:

http_middleware.page_cache:
  class: Drupal\page_cache\StackMiddleware\PageCache
  arguments: ['@cache.render', '@page_cache_request_policy', '@page_cache_response_policy']
  tags:
    - { name: http_middleware, priority: 200, responder: true }

Hierarchy

• class \Drupal\Core\DependencyInjection\Compiler\StackedKernelPass implements CompilerPassInterface

See also

\Stack\Builder

File

core/lib/Drupal/Core/DependencyInjection/Compiler/StackedKernelPass.php, line 48

Namespace

Drupal\Core\DependencyInjection\Compiler

Members