Reg: exact field for response time
hetardik.p at gmail.com
Thu Apr 4 05:54:30 UTC 2019
Thanks a lot Geoff.
I was ill and off work for few days so did not reply.
I am reading second field now. In future to give only response time from
varnish, will try to sum other time stamps as you said.
On Wed, 20 Mar 2019 at 17:15, Geoff Simmons <geoff at uplex.de> wrote:
> On 3/20/19 07:14, Hardik wrote:
> > what time should give to customer as a response time? Is it 2nd
> > round trip time) or 3rd field(only response time after processed fetched
> > content) ?
> > Timestamp Resp: 1501601912.806787* 0.048125* *0.000037*
> > Reason of asking this question is, Only first time request will go to
> > origin. After that next all the request will be served from cache. Also
> > generally we do not have control over other network (customer's network)
> > when request goes to origin. As per this understanding, I should give 3rd
> > field to customer as per response time. Please correct me if I am wrong.
> The third field of Resp is not a useful measurement. It's the time taken
> for Varnish userland code to complete network send operations -- when
> the syscalls say they're done, there's essentially nothing left for
> Varnish to do with the response, so Varnish writes the final timestamp.
> But return from the syscalls for network send may mean nothing more
> than: the data has been placed on queues in the TCP stack. It doesn't
> tell you anything about the network send, or even if the data has been
> sent on the network yet at all.
> As a practical matter, if you tell your customer that "response time"
> was 37 microseconds, they probably won't believe you. (I wouldn't.)
> From what you've said, it sounds like you're looking for something like:
> the time taken to process the request, but not including the time for a
> fetch from the origin server. Is that about right?
> For that, you'd need to do more than read one field from one Timestamp
> entry -- you'll need to read at least two, maybe more, and then do some
> The best measure for the total time of request processing is the 2nd
> field in Timestamp:Resp, 48ms in your example above.
> The best measure for the fetch time is in the backend log, the 3rd field
> of Timestamp:Beresp, maybe added to the 3rd field of
> Timestamp:BerespBody. So you'd have to find the backend log
> corresponding to client log. -g request can help you with that.
> Then (if this is what you're after), subtract the fetch time from the
> total request processing time.
> There are some other ways to go about it, but it depends on what exactly
> you want to measure as "response time". And since I may have
> misunderstood what you're trying to measure, I'll stop there.
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