Re: communicating server timing data to the client.. Server Timing?

One thing that could potentially be useful is allowing start & end times
(relative to the time the header was sent on the server). That can be used
to give a timeline of server events in devtools (it takes a bit of work to
correlate server timestamps to client ones, but is doable)

I'd also like to see the spec explicitly talk about how to send server
metrics for pages that do chunked encoding / early flush. I'd like to make
sure that's something that implementers are testing.



On Wed, Nov 19, 2014 at 7:08 AM, Ilya Grigorik <igrigorik@google.com> wrote:

> A (really) rough draft:
> https://cdn.rawgit.com/igrigorik/f940a4705a83f6ec2225/raw/0533e5809606abe2ee9c514a95ca6e7da02975be/server-timing.html
>
> Does the general shape and functionality feel about right? I've tried to
> capture the use cases we've discussed on this thread and map those to
> existing HTTP syntax for parameters and modifiers.
>
> - I've omitted timestamps, because we can't reasonably map those into the
> client's timeline.
> - Metrics can have an optional value, description, or both... i.e. you can
> report a [name], [name, duration], [name, duration, description], [name,
> description]. I think that covers all the necessary cases?
>
> For now, I've also intentionally omitted the plumbing to expose the
> metrics... I think we have two options:
> 1) Extend NavTiming / ResourceTiming entries to contain a "serverMetrics"
> (or some such), which would be an array of above server metrics.
> 2) Expose server metrics as own type alongside other existing metrics.
>
> Thoughts, feedback?
>
> ig
>
> On Wed, Nov 12, 2014 at 8:18 PM, Ilya Grigorik <igrigorik@google.com>
> wrote:
>
>>
>> On Wed, Nov 12, 2014 at 9:40 AM, Eli Perelman <eperelman@mozilla.com>
>> wrote:
>>
>>> I agree with this, and so I believe that any timestamps sent through
>>> this proposal should probably not be displayed in a timeline. If you want
>>> to do calculations between any of the existing timings and the "server"
>>> timings, it should be manual.
>>>
>>
>> This breaks one of the primary use cases for this proposal - i.e. to
>> surface additional request timing data in developer tools. That's a -1 for
>> me.
>>
>>
>>> So it appears that Server Timing may be a bit of a misnomer to get at
>>> what I'm trying to achieve here, which is to get meaningful timestamps
>>> generated externally from the client to the client. If we were only
>>> handling the use case of a server communicating information about itself to
>>> the client then I could understand, but I believe this API could be more
>>> powerful and extensible if we don't limit it with the server-to-browser
>>> standard model. I guess what I am getting at is let's make this less about
>>> the server, and more about external timing which would include the server.
>>> External Timing, Supplemental Timing, I digress...
>>>
>>
>> Just because it's not a remote server doesn't make this any easier. For
>> example, request gets routed to ServiceWorker, which then goes on to do
>> some arbitrary amount of work (check cache, update cache, <whatever>), and
>> then returns a response... Any timestamp that it generates is not directly
>> relatable to the timeline of the document that initiated the request -- the
>> only thing we can communicate safely is the duration of one or more events.
>>
>> I'm still of the mind that we should stay away from timestamps... That
>> said, if you *really* wanted them, and if we add some form of annotations,
>> you could communicate your timestamps as annotation and implement your app
>> logic to process them accordingly.
>>
>> ig
>>
>>
>