Reg: exact field for response time

[Geoff Simmons]

On 3/19/19 11:00, Hardik wrote:
> 
> Please help with understanding.

Well I tried with my previous answer, but you didn't seem to be
satisfied with that. I'm not sure what else I can say.

>> This line is creating confusion for me..
>>
>> https://github.com/jib/libvmod-timers/blob/master/src/vmod_timers.c
>> The sixth and last number (0.000025988) is the time from we start
>> delivering the object until the request completes.

That appears to be exactly the same as what we had in the old wiki,
which as I recall was the only documentation we ever had for ReqEnd in
Varnish 3:

https://varnish-cache.org/trac/wiki/Varnishlog

The statement about the sixth and last number has a bit of a grammatical
error, but what it's saying is that it's the duration of delivery -- the
time needed to send the client response.

>>> I am not getting difference between varnish 3 and varnish 6.

That's where you're losing me, and I suspect the problem is that you're
looking for something Varnish 6 that corresponds exactly to what you
were reading in Varnish 3.

Generally speaking, they don't correspond. At the risk of repeating the
answer that you didn't like, timestamps in Varnish 6 give you three values:

* an absolute time (Unix epoch)
* time elapsed since the beginning of request processing
* time elapsed since the last timestamp

However displeasing it may be, that's the way it is.

In *practical* terms, you probably *are* getting a corresponding value
in the third field of Timestamp:Resp, because of the fact that it
follows Timestamp:Process.

Again repeating the reference to
https://varnish-cache.org/docs/trunk/reference/vsl.html#timestamps:

Process
    Processing finished, ready to deliver the client response.
Resp
    Delivery of response to the client finished.

Since Timestamp:Resp follows Timestamp:Process, and the third field is
the difference since the last timestamp, then the third field of
Timestamp:Resp is the difference between "ready to deliver the client
response" and "Delivery of response to the client finished". In other
words, the duration of delivery.

So if you're insisting on asking "is that field in Varnish 6 the same as
the field in Varnish 3", then fine, they're essentially the same thing.

The reason I'm reluctant to just say yes is that it's possible (although
very uncommon) for some *other* timestamp to appear before
Timestamp:Resp in the log. If that does happen (a rare case, if at all),
then they're not the same.

Hardik, I believe you'll be much better off if you come to terms with
the fact that the timestamps in Varnish 3 and Varnish 6 just aren't the
same. You're using Varnish 6 now, so go with the way it works.


Trying my best,
Geoff
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