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Re: [Server Timing] Proposal how a user-agent can request that a server adds the server-timing header response field

From: Patrick Meenan <pmeenan@webpagetest.org>
Date: Thu, 16 Jun 2016 10:00:09 -0400
Message-ID: <CAKHu2GmgtCgLtTCsCQ2PgGfqrHbxpj+eDE683MYE30UCrEKkuQ@mail.gmail.com>
To: "Zurmuehl, Martin" <martin.zurmuehl@sap.com>
Cc: "public-web-perf@w3.org" <public-web-perf@w3.org>
Have you looked over the server timing draft
<https://www.w3.org/TR/server-timing/> to see how closely it matches your

On Thu, Jun 16, 2016 at 9:48 AM, Zurmuehl, Martin <martin.zurmuehl@sap.com>

> On the one hand side Server-Timing information would  very beneficial for
> some user agents, but on the other hand side many user-agents are not
> interested in server-timing data.
> Have you thought about providing the server timing data via the header
> field only when they are requested by the client/user-agent?
> One mechanism to request server timing data would be to use a prefer
> header as specified in rfc 7240 (https://tools.ietf.org/html/rfc7240);
> Preference: Server-Timing
> Description: Indicates that the client/user-agent prefers that the server
> adds the header field Server-Timing to the response.
> Example:
> > GET /resource HTTP/1.1
> > Host: example.com
> > Prefer: Server-Timing
> < HTTP/1.1 200 OK
> < Server-Timing: miss, db=53, app=47.2;
> < Server-Timing: customView, dc;atl
> The prefer header could be automatically set, if an "observer" exists on
> the client side - e.g. an observer defined in the Java-Script layer or a
> developer tool in the browser displaying timing data.
> Since this is only  a *preference* of the client, the server still have
> all the freedom - e.g. the server may only provide metrics to authenticated
> users or provide metrics to all users independent from the preference
> header, because the server is in a "performance testing" mode.
> -- Martin
Received on Thursday, 16 June 2016 14:00:38 UTC

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