Re: making sense of the timer(s) sequence
On Die 19.08.2008 17:36, Jeffrey 'jf' Lim wrote:
>hi guys, i'm hoping to get a better sense of the timers and values in
>the logs, and am looking to clarify my own understanding in terms of
>both the sequence, and the meaning of the various timers. The following
>is what i've arrived at. Is the following understanding correct?
>In terms of a timeline, this is what happens: (assuming option
>httpclose, to make things simpler)
>half of Tw - a connection comes in, and may spend some time waiting in
>the listener's queue (*INCLUDING connection establishment)
>Tq - client sends request over
>the other half of Tw - time in the server queue
>Tc - syn, syn-ack delay to server
>Tr - server header response time
>Td (which is not logged directly)
>Am i correct?
=> 4.2.3) Timing events
Please check it by your own ;-)
Timers provide a great help in trouble shooting network problems. All
are reported in milliseconds (ms). In HTTP mode, four control points are
reported under the form 'Tq/Tw/Tc/Tr/Tt' :
- Tq: total time to get the client request.
It's the time elapsed between the moment the client connection was
and the moment the proxy received the last HTTP header. The value
indicates that the end of headers (empty line) has never been seen.
- Tw: total time spent in the queues waiting for a connection slot. It
accounts for listener's queue as well as the server's queue, and
on the queue size, and the time needed for the server to complete
sessions. The value '-1' means that the request was killed before
- Tc: total time to establish the TCP connection to the server.
It's the time elapsed between the moment the proxy sent the
request, and the moment it was acknowledged, or between the TCP SYN
and the matching SYN/ACK in return. The value '-1' means that the
connection never established.
- Tr: server response time. It's the time elapsed between the moment
TCP connection was established to the server and the moment it send
complete response header. It purely shows its request processing
without the network overhead due to the data transmission. The value
means that the last the response header (empty line) was never seen.
- Tt: total session duration time, between the moment the proxy
and the moment both ends were closed. The exception is when the
option is specified. In this case, it only equals (Tq+Tw+Tc+Tr), and
prefixed with a '+' sign. From this field, we can deduce Td, the
transmission time, by substracting other timers when valid :
Td = Tt - (Tq + Tw + Tc + Tr)
Timers with '-1' values have to be excluded from this equation.
Received on 2008/08/20 16:04
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: 2008/08/20 16:16 CEST