Hi,
we are having a bit of a problem with content delivery from the server (IIS7 on Windows Server 2008) that's running a couple PHP web sites. Quite often, small batches of requests end up taking a long time to complete for no apparent reason. This mostly happens with static content, but some php page requests are also affected similarly. They show up in the request queue as being stuck in "SendResponse" stage:
REQUEST "f70000438000116a" (url:GET /gfx/public/upload/45849.JPG, time:11934 msec, client:87.59.109.41, stage:SendResponse, module:IIS Web Core)
REQUEST "fb00000180002198" (url:GET /gfx/public/upload/45844.JPG, time:11825 msec, client:87.59.109.41, stage:SendResponse, module:IIS Web Core)
REQUEST "5b0000428000080a" (url:GET /gfx/public/upload/45845.JPG, time:11809 msec, client:87.59.109.41, stage:SendResponse, module:IIS Web Core)
REQUEST "d100004280000e40" (url:GET /gfx/public/upload/47222.JPG, time:56722 msec, client:110.36.20.149, stage:SendResponse, module:IIS Web Core)
Some of such stuck requests end up in the logs with "sc-win32-status" codes of 64/121/1236, which would seem to suggest the requests hitting some sort of time limit before being finally killed.
I also tried gathering some failed request logs, but all request steps there are shown as taking 0ms, with the last one being "GENERAL_RESPONSE_ENTITY_FILE" or "GENERAL_RESPONSE_ENTITY_BUFFER". Is this normal, or should all requests end up with the "GENERAL_REQUEST_END" step instead?
Anyway, this is all rather puzzling to me and I can't spot any clues that would let me move forward. Is there perhaps a way to look deeper into what's happening in the "SendResponse" stage? I.e.: whether data is being sent at all, if the connection is stuck waiting for packets from server/client side or something else entirely?