Web Performance Working Group Teleconference

Frame timing

yoav: I believe Intersection observer will help answer my RUM use cases
... still need to talk to David Baron about :visited

Ilya: looking at implementation feedback

Todd: new proposal needs to be circulated within MS
... current proposal seems acceptable

Ilya: google and firefox did implementations of the first proposal

<plh> ACTION: plh to clean up frame timing [recorded in http://www.w3.org/2015/10/26-webperf-minutes.html#action01]

<trackbot> Created ACTION-166 - Clean up frame timing [on Philippe Le Hégaret - due 2015-11-03].

Page Visibility

<plh> https://github.com/w3c/page-visibility/pull/16

Todd: you could merge the PR for the time being while still figuring if we got the right task source
... do we have tests for PV?
... our interop is weak when you include life cycles

Ilya: firefox fires a transition from visible to hidden when the page is being unloaded

plh: we need a test for prerender

<plh> ACTION: plh to look into testing prerender in Page Visibility [recorded in http://www.w3.org/2015/10/26-webperf-minutes.html#action02]

<trackbot> Created ACTION-167 - Look into testing prerender in page visibility [on Philippe Le Hégaret - due 2015-11-03].

Ilya: in FF, they fire hidden hidden in all cases

Ilya: I don't think we need to transition when it's unloaded
... we could tell devs that they should always listen to visibility events, ie background transition or close tabs
... but that's handle by pagehide
... ie we could use a combination of visitibilityState and pagehide

<plh> https://github.com/w3c/page-visibility/issues/18

Ilya: no explicit definition of when the page is unloaded
... with the new update

speculation that an example in the spec might have lead to hidden being true while a tab is being unloaded in some implementations

<plh> [discussion regarding differences between pagehide and unload]

Resolved: publish page visbility as a Working Draft

<plh> ACTION: plh to publish PV2 [recorded in http://www.w3.org/2015/10/26-webperf-minutes.html#action03]

<trackbot> Created ACTION-168 - Publish pv2 [on Philippe Le Hégaret - due 2015-11-03].

preload

Ilya: implemented in blink. needs to get it shipped and align in the spec.
... need to talk to the webkit folks
... push and preload don't connect but there are some use cases for preload that can be resolved with push
... http://www.w3.org/TR/preload/#issue-1
... we need to define the caching more formaly
... there is magic there
... we retain the page for the navigation session if no cache is requested
... if preload is activated
... fetch needs tobe aware since the subsequent fetch will need to take it into account

yoav: in terms of interop, do prefetch live for the duration of the next navigation?

Todd: we don't do preload and preconnect yet

Ilya: for preload, it's a declarative fetch, so I don't think we're exposing anything special here in terms of security and privacy

yoav: depending on the cross origin attribute and the as, we would send credentials

Ilya: if I do a preload with as image, no credentials. if I add crossorigin, we'll add them

plh: maybe we should say that preload is equivalent to adding an image

nick: can we list what it means to be equivalent?

plh: we would be duplicating other specs by doing so.
... not the right approach imho

yoav: the only difference here is that these fetch don't block and can start early
... header based csp are taking into account

Ilya: we don't say that we process the csp headers are processed atomically

<plh> http://www.w3.org/TR/resource-hints/#security-and-privacy

yoav: csp can prevent from the preload to happen
... csp is about protecting the html, not the link headers

Ilya: if you start touse link headers, you should move the csp into link headers as well

Ilya: fetch was updated to add a check at the exit
... the ordering of link/meta between preload and csp isn't relevant. the implementation may do preemptive fetch on preload and have to discard it because of csp
... the question here because the impact on caching

Beacon

Ilya: step 10 of processing model
... the mode is "CORS"
... it means the origin you send the request must respond with two headers
... ... we don't care about the response
... we should change it not to use "CORS"
... we need to check that we're not breaking anything
... otherwise we're forcing the origin to respond with dynamic headers

Todd: indeed, it's unecessary
... for the spec, you would preflight and not send the POST

Ilya: there could be a beacon-age
... that nobody implements
... but it would force a preflight
... it also depends on the content type
... a blob would trigger a preflight

nick: form submission implies no new headers
... so due to beacon-age and content type, we're increasing the potential attack area
... servers have to accomodate POST request from crossorigin that look like post submission
... but if you get things that aren't like post submission, that's different

yoav: I've never seen crf protection as a strick headers check

nick: the conditions we have in cors. we're changing the assumption on form submissions.

yoav: can we include the beacon age in the data?

plh: no because we allow abitrary post

Todd: if we remove beacon-age and restrict to form-data, we are the same as forms

nick: it wouldn't create new attack surfaces indeed

plh: are we llike xhr then?

yoav: no, because of cors

nick: you could force cors, ie preflight request

Todd: can we make it beacon age a simple header?

nick: user agents dont preflight in case of new headers
... (according to Jonas)

Ilya: we should clarify beacon-age with respect with user agents added headers
... are user agent addefd headers treated simple headers

<plh> (that's issue 1)

Todd: should we only send form-data , even if it's a blob?

nick: that seems confusing

Ilya: I don't think we have telemetry on media type usage for beacon
... half the time, people just send a uri
... the whole payload thing isn't used

Todd: folks with more advanced payload are probably sending json

Ilya: the fetch spec doesn't do anything smart with json object

Todd: ie you're responsible for the serilization and then fetch send a string

Ilya: correct

nick: if you send a different content type, you culd incurred the preflight

Todd: cost is non-trivial

Ilya: current implementation aren't doing preflight
... if type comes from a blob

plh: so we're breaking CORS and fetch specs then

yoav: I understand when you don't arbitrary headers, but the mime types...
... I think the restriction on mime types is uncessary

plh: we should stop by the webapp secs
... and talk about this over with them

<plh> [Todd is updating https://github.com/w3c/beacon/issues/10 ]

nick: https://github.com/w3c/beacon/issues/9

nick: "This specification defines an interoperable means for site developers to asynchronously transfer small HTTP data from the User Agent to a web server."
... doesn't say what the spec does

editorial comments in this email: https://lists.w3.org/Archives/Public/public-web-perf/2014Jul/0109.html

not small and "asynchronous" doesn't quite capture what the spec is about

nick: separate privacy considerations from security considerations
... privacy concern is the browser making a request on you behalf after you closed the page
... are the users going to be aware of that?

<plh> .... similar geafencing
... you might have a different IP adress
... we had a discussion about this in web platform yesterday but no conclusion
... at the very least, we should mention it in the privacy section

Ilya: we don't want to block on unload
.... ie avoid sync XHR
... you can use beacon to send things every 2 hours

Todd: with beacon-age, you have the ability to send it much later
... but no one implements it

nick: we need some guidances to implementrs on what to tell the users when sending a quest after the close

yoav: how is that different from background syncs in service workers?

nick: same issue :)

Todd: it may be simplier to spec it down for the short term

Ilya: agents could pile up beacons to wait for the next network request

Ilya: perharps we should more clearly define beacon-age?
... what are the use cases for beacon age?

nick: the processing model speaks about multiple attempts

Todd: but with service workers, it seems handled now

plh: at the minimum, we should say it's sent after the close

nick: even if we say it's equivalent to an existing practice, it would affect users

nick: do UAs have the option to desactivate beacon?

plh: no, like we don't have the option to desactivate XHR. Beacon is generic, not restricted to telemetry data

Ilya: we limit body size in chrome

nick: if it's only used for telemetry, what do you do in private mode?
... you might want to add a note in privacy sectio that you considered the case of giving the user the ability to desactivate beacons and decided against it.
... I'm not sure you want to say that the user can't have the ability to deactivate it, just because it's obviously true that user agents can turn off beacon functionality or do whatever the user wants
... but you could explain why you're not putting conditions on when Beacon is used, because you think there is an advantage to users on the whole

Ilya: btw, our size limit is 64Kb

Network Error Logging

looking at the open issues

ilya: how are the NEL requests treated? client requests?
... NEL. you as an origin have registered to receive error reports
... some site embeds your widget, and you want to know when your social media widget has failed to load
... but if the embedding site has a service worker that intercepts requests
... the service worker might pass through the request, which might fail
... the report shouldn't be sent to the embedding site owner, but to the widget owner
... any other report should be treated as client requests which bypass service workers

todd: should we go over network error logging in more detail?

ilya: lots of things could go wrong: DNS failures, route issues, etc. you as a site owner have no way to observe that this failure happened
... large vendors have nodes around the world that will ping their site to try to identify these failures and work around them
... NEL is supposed to notify you that we have failed to reach your site
... specify a report-uri on a first successful reach, the report-uri should be a different domain, on a different subnet, etc.

Bartek: would be good to have more than one endpoint

ilya: yes, we do support that, with fallback through the list
... modified after HSTS, can note that it applies to all subdomains as well
... a well-structured report of failure, including the resolving IP address

Bartek: have a list of items in notes that I would like in addition

todd: would be great to have those as Github issues

ilya: are the errors that we define here reasonable?
... this is restricted to HTTPS origins, and the report location must also be HTTPS

[note, "trustworthy origins" is out of date terminology]

ilya: noticed that we have multiple places in the Web platform that are delivering reports
... would like to extract that into one common thing, a group of report uris
... then other specs can reference this to say, "queue a report to group Security"

todd: privacy questions regarding these general out of band reporting mechanisms?

npdoty: sure, it was debated regarding csp, for example

plh: we could say for this spec, the user agent should provide a way to disable NEL
... worth it to mention in the NEL spec that user agents should provide a way to disable NEL reports
... question about whether SHOULD or MAY

ilya: the out of band reporting just has general restrictions, like clearing the cache
... but for particular specs that have reporting, they should specify when to send requests, when they might not want to
... the general out of band reporting is just under mkwest's repo for now

Bartek: what if we have reporting list not as a fallback, but simultaneous to more endpoints for auditing purposes?

ilya: could you do that yourself?

Bartek: you could, and it would be more efficient, but auditors might want independent reports
... for example, if ads are served from within our origin

ilya: the fact that the user agent delivers it doesn't make it provably, just a convenience
... wouldn't want to open it up to a very large list

Bartek: potentially lack of trust between parties

todd: if there are particular regulatory requirements, that might make it easier
... what if we had a concrete number: 2 or 3

npdoty: can we provide the assumption that error reporting uri's should be common across users? if so, it would make it easier to detect abuse for supercookies

ilya: there are use cases where you would want the value to differ, between regions, for example

bartek__: could also have the report-uri in the DNS record (as a TXT record, say)
... as a fallback if you never successfully reached the server

ilya: interesting, please raise

todd: could ship with a pre-loaded list in browsers, like with HSTS pre-load list

bartek__: dns should be considered as a fallback, just in case you can't load the policy on first load

[humorous tangent about how much policy can be pushed into DNS records]

ilya: don't typically load all DNS TXT records

npdoty: but would only need to when you had a network failure
... DNS doesn't give you the security of HTTPS

ilya: yeah, so DNSSEC?
... some information is reported that others wouldn't have received

Primer

<xiaoqian> primer -> http://siusin.github.io/perf-timing-primer/

<igrigorik> Andy's waterfall repo: https://github.com/andydavies/waterfall

<igrigorik> https://github.com/addyosmani/timing.js/

plh: should we use perf observers in examples?

Ilya: let's rule that we need at least one shipping implementation before we use those in the primer

Xiaoqian: should I list/describe every attribute for entries?

plh: nope. goal is intro here. folks should look at specs for list/description

TODO: update graphics, add links to caniuse, add link to timing.js, add one sentence or two on frame timing and server timing, then ship

CustomPerformanceEntry

Ilya: how about we allow apps to add their own performance entry objects in the timeline so that one can observe those?

Todd: that would allow the use case of adding your own payload to an entry
... sounds cool
... and it cleans up the story around clear*

plh: we should open an issue/feature request

Ilya: I'll open one

<igrigorik> https://github.com/w3c/user-timing/issues/3

Ilya: but it means we would allow huge payload into the observers and those are doing deep clones...

Todd: that's actually a diff between Edge and Chrome/FF in getEntries*. Edge does a deep clone before returning the entries, others don't.

redirects

Ilya: besides security/privacy, what's the hold?

Todd: not a high priority

Ilya: we already reveal the fact that there was at least on redirect (since we return 0)
... but we don't say how many

plh: is this what you meant? -> //TAO only Redirect Timing{ URL }

Ilya: Not exactly.

yoav: just the entries

plh: Resource Timing{
... redirectCount;
... redirect URL
... }
... if I have two with the same name

yoav: you can link everything back together
... If you go to HTTP server, we can expose it
... expose Redirect there will be a concern

todd: you couldn't make guess

plh: change 2 attrs only, redirectend and redirect start

Ilya: yeah, drop them

todd: you are also missing info about the chain

yoav: if redirect, you can change your cookie

plh: if I have a redirect in the middle

Ilya: it will take longer

plh: I won’t get url in the end, so I won’t expose that

yoav: you can measure the time you took
... if you want to avoid this expose privacy problem, you will have to remove from a lot html

todd: that’s why we hide a lot of redirects
... image people are choosing to expose, can we add the feature?
... if a website choose redirect as feature...
... can you get the data? with xhr?

Yoav: if you site tell you to expose, redirects maybe the same pattern
... TAO is already used today

Todd: Google phone has already turn TAO on

Yoav: If FB has no interest to expose TAO

Ilya: their widget do

Yoav: if we review all the redirect there, will it be private proper?
... let bring it to the Security folks

todd: strange to turn it on... go to log in server, use cookie, user redirect just not enough

Ilya: this question is a block of a lot of others
... privacy issue will be a major change to the API

todd: I'd not recommend change the API in this way, what about NT-2?

plh: unless we are told NT do not get into the buffer

todd: more entries?

Ilya: back cases are ad force users to change
... when you click those links, you are force to change

plh: any option is not to change RT and NT, and provide another entry
... listen to resource, will have to do sth to get redirect

todd: have buffer on server time

Ilya: leave it as it is
... for those new to the API, just look at Observer

Todd: yeah, historical reasons

plh: entry type for redirect will be what?

Ilya: resource
... call it a new thing?

Todd: that will cause sudden changes for redirects in timeline
... RT with TAO, if no TAO, no redirects

plh: keep redirectCount in RT

Ilya: we need a new name

plh: get a R-entry for A

Ilya: B, C will never be seem today, name for B's entry will have some info about A

plh: if a is a fetch start C

Ilya: it should be the fetch start of A

yoav: people will assume that /TR is not the latest draft

plh: that's not true with the auto-publication system

Priorities and next charter

plh: our goal is try to apply the auto-pub system and have as less worry as possible

todd: which are the spec we want to move?

plh: hr-2, pr-2

todd: pr-2 is a clean up for the failures in pr-1?
... how about RT?

plh: never shipped a level 1

todd: but 3 vendors implement it

plh: but it relies on PR-2, may need a clean-up version, but not touch the ED

Todd: User Timing? 3 implementations

plh: That's already a REC
... UT-2, same as RT, need a subset

Todd: already UT REC, not sure that's necessary to subset UT
... for the specs blocked by performance Observer, how long do we need to wait?

Ilya: We don't know the intention of Moz yet

plh: HR-2, need a test for worker. PR-2, need to clean up the test suite

Todd: We have written quite a few test in the past 6 month, we'd like to share them with W3C
... but there are a lot of spec corner cases in those cases

plh: Do we want to write test case for corner cases?
... Beacon, will need to write another python parser under w-p-t
... I will need to fire an issue, and James will add support for that

yoav: there are some blink test for Beacon. How do you get resource response in w-p-t?

plh: I wrote a test that can explain the process

Ilya: RIC, no update on implementation

Todd: It's on my list
... Beacon in apps, what if it's closed? f.ex. WebView

Ilya: Independent to vendors

Todd: Resource Hints...

plh: How can we prove implementation?
... how about a pre-fetch from the server?

todd: browsers can be triggered...

yoav: pre-connect should be a separate host

todd: need a new case for each attribute

plh: We'll need commends from WebDriver folks

Todd: pre-fetch and pre-render are implemented by Firefox

plh: Is it possible for you to write a query for the usage?

Todd: not sure
... pre-connect smells the highest one

Ilya: It isn't ready yet
... the issue refers to Fetch

todd: same as SW

Ilya: Telconf ... any complain?

Yoav: I can do later

todd: it's difficult to schedule a time from Asia and the chairs

resolve: 1 hour early

todd: we should switch goal for the next charter

Ilya: we got feedback from Moz

plh: we can do some minor update, add the primer

todd: and Memory API

Ilya: we should start from use cases

yoav: let's create a report and collect use cases

Ilya: a general use case report

plh: we have a repo for WebPerf, which is a good place for that report