I wanted to get an overview of the HTTP.sys request method for working in IIS 7.0 and higher. To do this, I read the post at http://www.iis.net/learn/get-started/introduction-to-iis/introduction-to-iis-architecture . However, in this post there are two points that seem contradictory and confuse me.
Point 1: The second marker point mentioned in the Hypertext Transfer Protocol Stack (HTTP.sys) section is as follows.
The kernel mode request queue. Requests cause less overhead when switching contexts because the kernel forwards requests directly to the correct workflow. If no worker process is available to accept the request, the kernel mode request queue holds the request until the worker process picks it up.
My conclusion on this issue is as follows: HTTP.sys redirects the request "directly" to the workflow bypassing the WWW service. If the workflow is unavailable, HTTP.sys queues the request in the kernel mode request queue, and the WAS service starts a new workflow. This workflow then selects the requests from the kernel mode queue itself.
Point 2: The process control subsection in the Windows Activation Service (WAS) section is as follows.
WAS manages application pools and workflows for HTTP and non-HTTP requests. When the protocol listener receives a client request, the WAS determines whether the workflow is running or not. If the application pool already has a workflow serving the requests, the listener adapter passes the request to the workflow for processing. If there is no workflow in the application pool, WAS will start the workflow so that the listener adapter can pass the request for processing.
My conclusion on this issue is as follows: HTTP.sys redirects the request to the workflow "through the WWW service", since it is a listener adapter. If the workflow is unavailable, HTTP.sys queues the request in the kernel mode request queue, and the WAS service starts a new workflow. The request from the kernel mode queue is then picked up by the WWW service and redirected to the workflow.
Can someone please tell me which of my two conclusions is correct? If both are wrong, tell me the correct thread.
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