Thanks Maxim, that's what I needed to know. How common would you say it is to use accept filters / deferred accept on nginx in production?
Also to be perfectly certain: connections.idle <http://nginx.org/en/docs/http/ngx_http_status_module.html#data> in Plus is the same as Waiting <http://nginx.org/en/docs/http/ngx_http_stub_status_module.html#data> in Open, right? Is "Active" on the status demo <http://demo.nginx.com/status.html> = read+write? On Thu, Feb 19, 2015 at 8:02 AM, Maxim Dounin <mdou...@mdounin.ru> wrote: > Hello! > > On Wed, Feb 18, 2015 at 09:25:01PM -0500, K Young wrote: > > > Hello, I've been reading through nginx source to understand the metrics > > <http://nginx.org/en/docs/http/ngx_http_stub_status_module.html> that > are > > reported. I've got an idea of what is happening, but since the flow is > > asynchronous, I'm not 100% confident, and would love your feedback. > > > > Is the following correct? > > > > - 'accepts' is incremented when a worker gets a new request for a > > connection from the OS > > - 'handled' is incremented when a worker gets a new connection for a > > request > > > > > > And then once a connection is opened: > > > > - 'active' is incremented (actually, it is incremented right before > > 'handled', but will be decremented if the worker doesn't handle the > > connection request). > > - then the connection briefly goes into a waiting state while the > > request is waiting to be processed > > - then the connection goes into a short reading state while request > > headers are read. Simultaneously, 'request' is incremented every time > a new > > request header begins to be read. > > - then the connection goes into a writing state while all work is done > > by nginx and by upstream components > > - then if the connection will be kept alive, it goes back into waiting > > state, which is synonymous with 'idle' > > - finally when the connection is closed, active is decremented > > > > The things I'm least certain of about the 'waiting' state: > > > > - Does active always sum up to waiting+reading+writing? > > Generally yes. There are nuances with SPDY where additional > connections are emulated for SPDY streams being handled, and > waiting+reading+writing may be bigger than active. > > > - Does each new connection enter a waiting state just before it goes > > into the reading state? > > No. If there are data available right after connect (this usually > happens with accept filters / deferred accept), nginx will not > mark a newly accepted connection as waiting, and will start > reading a request directly. > > > - While waiting for upstream responses, is the connection in writing > > state or waiting state? > > Writing. > > > - While waiting for new client requests on an open connection, is the > > connection in a waiting state? > > Yes. > > > Is the attached sketch of the above connection states correct? > (underneath > > "READ" it says "request++" to indicate that this is where the request > > counter gets incremented). > > [image: Inline image 1] > > Mostly, see above. > > -- > Maxim Dounin > http://nginx.org/ > > _______________________________________________ > nginx mailing list > nginx@nginx.org > http://mailman.nginx.org/mailman/listinfo/nginx >
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