Infrequently Noted

Alex Russell on browsers, standards, and the process of progress.

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I don't mind vulgarity, wrongness, or even the mild ad-homenim...as long as it contributes to the discussion. Should you post a comment here that does not contribute, expect it to be binned or treated as spam -- without warning. Be witty, be carefree, be data-driven, be on point, but most of all, write something that will try to convince someone else you're right. The elation of asserting something you feel is self-evident is a joy that falls into despair far too quickly and is too easily dashed by argument and evidence.

Use-Case Zero

Some weeks back I lobbed an overly terse "noooooooooo!!!!!" at the W3C Web Application Security Working Group over revisions to the CSP 1.1 API; specifically a proposed reduction of the surface area to include only bits for which they could think of direct use-cases in a face-to-face meeting. At the time I didn't have the bandwidth to fully justify my objections. Better late than never.

For those who aren't following the minutiae of the CSP spec, it began life as a Mozilla-driven effort to enable page authors to control the runtime behavior of their documents via an HTTP header. It was brought to the W3C, polished, and shipped last year as CSP 1.0; a much better declarative spec than it started but without much in the way of API. This is a very good way for any spec to get off the ground. Having a high-level declarative form gives implementers something they can ship and prove interop with very quickly. The obvious next step is to add an API.

Late last year I started digging into CSP, both for a personal project to implement a "user CSP" extension for Chrome, and to work with the spec authors to see what state the proposed API was in and how it could be improved. The short form of my analysis of the original CSP proposal was that it was pretty good, but missed a few notes. The new proposal, however, is a reflection of the declarative machinery, not an explanation of that machine.

Not coincidentally, this is also the essential difference between thinking in terms of a welded-shut C++ implementation and a user-serviceable JavaScript design.

For example, the previously proposed API provided methods on a SecurityPolicy class like allowsConnectionTo(url) which outline an API that the browser might plausibly need to enforce a policy at runtime. The new API includes no such methods. As someone working with CSP, you suspect the browser indeed has such a method on just such an object, but the ability to use it yourself to compose new and useful behaviors is now entirely curtailed. This is the extreme version of the previous issues: an API that explains would make an attempt to show how the parser is invoked -- presumably as a string argument to a constructor for SecurityPolicy. Similarly, showing how multiple policies combine to form a single effective policy would have lead away from document.securityPolicy as something that appears to be a single de-serialized SecurityPolicy and instead be written in terms of a list of SecurityPolicy instances which might have static methods that are one-liners for the .forEach(...) iteration that yeilds the aggregate answer.

So why should any WG bother with what I just described?

First, because they'll have to eventually, and by showing only enough skin to claim to have an API in this round, the question will be raised: how does one implement new rules without waiting for the spec to evolve? The Extend The Web Forward idea that flows naturally from p(r)ollyfills has shown real power which this new design puts further from reach...but it won't keep people from doing it. What about implementing something at runtime using other primitives like a Navigation Controller? Indeed, the spec might get easier to reason about if it considered itself a declarative layer on top of something like the Navigation Controller design for all of the aspects that interact with the network.

There are dozens of things that no over-worked spec author in a face-to-face will think to do with each of the platform primitives we create that are made either easier or harder for the amount of re-invention that's needed to augment each layer. Consider CSS vs. HTML's respective parsing and object models: both accept things they don't understand, but CSS throws that data away. HTML, by contrast, keeps that data around and reflects it in attributes, meaning that it has been possible for more than a decade to write behavioral extensions to HTML that don't require re-parsing documents, only looking at the results of parsing. CSS has resisted all such attempts at gradual runtime augmentation in part because of the practical difficulties in getting that parser-removed data back and it's a poorer system for it. CSP can either enable these sorts of rich extensions (with obvious caveats!) or it can assume its committee knows best. This ends predictably: with people on the committee re-implementing large bits of the algorithms over and over and over again for lack of extension points, only to try to play with new variations. This robs CSP and its hoped-for user-base of momentum.

Next, the desire to reflect and not explain has helped the spec avoid reckoning with poor use of JavaScript types. The document.securityPolicy object doesn't conceptually de-sugar to anything reasonable except a list of policy objects...but that more primitive SecurityPolicy object type doesn't appear anywhere in the description. This means that if anyone wants to later extend or change the policy in a page, a new mechanism will need to be invented for showing how that happens: meta tags parsed via DOM, not objects created in script and added to a collection. All of which is objectionable on the basis that all that will happen is that some objects will be created and added to the collection that everyone suspects is back there anyway. This is like only having innerHTML and not being able to construct DOM objects any other way, and the right way to be presented with the need to go build idiomatic types for what will eventually be exposed one way or another is to try to design the API as though it was being used to implement the declarative form. JavaScript first gets you both good API and a solid explanation of the lifecycle of the system.

There is, of course, another option: CSP 1.1 could punt on an API entirely. That's a coherent position that eliminates these frictions, and I'm not sure it's a bad option given how badly the API has been mangled recently. But it's not the best solution.

I've got huge hope for CSP; I think it's one of the best things to happen to webappsec ever. What happens about the API will always be overshadowed by the value that it is already delivering. But as a design microcosm, its API is a petri-dish sized version of scenario-solving vs. layering, and a great example of how layering can deliver value over time; particularly to people who aren't in the room when the design is being considered. An API that explains by showing how declarative layers on top of imperative is one that satisfies use case zero: show your work.

I Swear This Blog Isn't About Elections...

...but if it were, there would be time to cover the W3C Advisory Board election. This is truly inside-baseball stuff, as most of the AB's work happens in member-only areas of the W3C website and most of what they effect is W3C process.

So why care? Because spec licensing matters, sadly.

Let me first outline my view: in an ideal world, specification language for web standards would be in the public domain or dedicated to it. The body of intellectual property that is non-copyright is fought over via an independent process, and to the extent that it accumulates in a standards organization, it should also be possible for the group of members that have contributed to take their ball and start again somewhere else.

Why does this matter? Competition.

Standards bodies should not be insulated from the pressure to try to deliver better results. There are, of course, pathologies around this; some of which are common enough to have names: "pay for play", "venue shopping", etc. But in general, to the extent that many bodies can produce substitue goods, it gives them a reason to differentiate. The concrete example here is WHATWG vs. W3C. I don't think it's controversial to assert that without the WHATWG, the current W3C would be f'd. Competition makes everyone better, even for products that are "free" for consumers and are the product of community effort.

This, then, is why it's such a terrible idea for the W3C's Advisory Committee (the people who have some power) to elect representatives to the Advisory Board (who have even more power) that are willing to take the self-interested side of the W3C against liberal licensing of specs over the competition-enabling position that liberal licensing makes everyone better off (to a first approximation).

If you are an AC rep, the time is now to quiz candidates on this point. If you truly think that the W3C is a unique community, it's important to realize that what makes it that special is a set of shared values, not a death-grip on legacy intellectual property rights. Fixating on that ownership is the fast-path to making everyone worse off; by the time it truly becomes important, it's so likely that the organization that cares about it needs competition to right the ship or get out of the way.

The Case Against Synchronous Worker APIs

Several times in the past few months I've been presented with this question: is it good or useful to provide synchronous APIs to web workers?

Having considered the question at some length, it seems to me the answer must now be "no".

Consider IndexedDB. It's not implemented in any browser yet, but some hard-working soul did the arduous work to specify a second synchronous version of its API which is meant to be available only in Workers where it can't lock up the UI thread. That spec work was probably done because it was thought that a synchronous API would be nicer to use than the async version. As a result, the API is now double the size, but only in some contexts. I came across this while attempting to rework the IDB API to use Futures in order to improve usability in a backwards-compatible way.

So why not the sync version? At least 2 reasons:

It's this second concern that I think it truly fatal to the cause of sync worker APIs: assuming they work and are popular, they will create a world in which it's necessary to put limits on their overall running time...limits that will be circumvented by breaking up the work into smaller chunks and dealing with it asynchronously inside the worker. Likewise, anyone building a serious app that's trying to do the right thing by the user will factor their worker's tasks into small enough chunks that they can both service "stop" messages and distribute progress notifications to the UI. There might be scenarios where such messages aren't necessary and where users aren't coveting CPUs and batteries...where sending SIGHUP doesn't matter. But the intersection of those scenarios and the client-side web seems mostly to be a happy accident: your code might not have encountered enough data to create the problems. Yet.

This is particularly clear in the IDB cases: upgrading, iterating over, and updating hundreds of thousands of items of data is the sort of thing that will take a while, and is likely in response to some application semantic the user cares about: synchronizing mail, migrating to a faster schema layout in the process of some upgrade, etc. A blind for loop is asking for trouble. All of this might work fine in a dev environment with a (small) staging set of data...but it's recipe for disaster when power-users with tons of data encounter it. What then? If the APIs an app depends on are all synchronous, it's a huge boulder to roll up a hill to provide notifications, chunk up work, and refactor around async-ish patterns that chunk work up. If the work was async in the first place, the burden is much lower. So even apps that aren't Doing It Right (TM) are likely to reap some benefit down the line from thinking in terms of async first.

There are other arguments that you can field against these sorts of APIs, particularly ones that double-up API surface area, but it doesn't seem to me that they're necessary. The person attempting to justify synchronous worker APIs who provides a good argument for ergonomics and learnability still has all their work ahead of them: they must show that these APIs are not harmful to the user experience. After all, Workers were added to the platform as a way of improving UX (by moving work off the main thread). And I fear they cannot do so without violating core JS semantics.

So let's pour one out for our sync API dreams: we're gonna miss you, control flow integration. But not for too long. Generators, iterators, and yield will see you avenged.

Why What You're Reading About Blink Is Probably Wrong

By now you've seen the news about Blink on HN or Techmeme or wherever. At this moment, every pundit and sage is attempting to write their angle into the annoucement and tell you "what it means". The worst of these will try to link-bait some "hot" business or tech phrase into the title. True hacks will weave a Google X and Glass reference into it, or pawn off some "GOOGLE WEB OF DART AND NACL AND EVIL" paranoia as prescience (sans evidence, of course). The more clueful of the ink-stained clan will constrain themselves to objective reality and instead pen screeds for/against diversity despite it being a well-studied topic to which they're not adding much.

May the deities we've invented forgive us for the tripe we're about to sell each other as "news".

What's bound to be missing in most of this coverage is what's plainly said, if not in so many words, in the official blog post: going faster matters.

Not (just) code execution, but cycle times: how long does it take you to build a thing you can try out, poke at, improve, or demolish? We mere humans do better when we have directness of action. This is what Bret Victor points us towards -- the inevitable constraints of our ape-derived brains. Directness of action matters, and when you're swimming through build files for dozens of platforms you don't work on, that's a step away from directness. When you're working to fix or prevent regressions you can't test against, that's a step away. When compiles and checkouts take too long, that's a step away. When landing a patch in both WebKit and Chromium stretches into a multi-day dance of flags, stub implementations, and dep-rolls, that's many steps away. And each step hurts by a more-than-constant factor.

This hit home for me when I got my first workstation refresh. I'd been working on Chrome on Windows for nearly a year in preparation for the Chrome Frame release, and all the while I'd been hesitant to ask for one of the shiny new boxes that the systems people were peddling like good-for-you-crack -- who the hell was I to ask for new hardware? They just gave me this shiny many-core thing a year ago, after all. And I had a linux box besides. And a 30" monitor. What sort of unthankful bastard asks for more? Besides, as the junior member of the team, surely somebody else should get the allocation first.

Months later they gave me one anyway. Not ungrateful, I viewed the new system with trepidation: it'd take a while to set up and I was in the middle of a marathon weekend debugging session over a crazy-tastic re-entracy bug in a GCF interaction with urlmon.dll that was blocking the GCF launch. If there was a wrong time to change horses, surely this was it. At some point it dawned that 5-10 minute link times provided enough time to start staging/configuring at the shiny i7 box.

A couple of hours later the old box was still force-heating the eerily dark, silent, 80-degree floor of the SF office -- it wasn't until a couple of weeks later that I mastered the after-hours A/C -- when my new, even hotter workstation had an OS, a checkout, compiler, and WinDBG + cargo-culted symserver config. One build on the new box and I was hooked.

5-10 minute links went to 1-2...and less in many cases because I could now enable incremental linking! And HT really worked on the i7's, cutting build times further. Hot damn! In what felt like no-time at all, my drudgery turned to sleuthing/debugging bliss (if there is such a thing). I could make code changes, compile them, and be working with the results in less time than it took to make coffee. Being able to make changes and then feel them near-instantly turned the tide, keeping me in the loop longer, letting me explore faster, and making me less afraid to change things for fear of the time it would take to roll back to a previous state. It wasn't the webdev nirvana of ctrl-r, but it was so liberating that it nearly felt that way. What had been a week-long investigation was wrapped up in a day. The launch was un-blocked (at least by that bug) and the world seemed new.

The difference was directness.

The same story repeats itself over and over again throughout the history of Chrome: shared-library builds, ever-faster workstations, trybots and then faster trybots, gyp (instead of Scons), many different forms of distributed builds, make builds for gyp (courtesy of Evan Martin), clang, and of course ninja (also Evan...dude's a frickin hero). Did I mention faster workstations? They've made all the same sort of liberating difference. Truly and honestly, in ways I cannot describe to someone who has not felt the difference between ctrl-r development and the traditional Visual Studio build of a massive project, these are the things that change your life for the better when you're lashed to the mast of a massive C++ behemoth.

If there is wisdom in the Chrome team, it is that these projects are not only recognized as important, but the very best engineers volunteer to take them on. They seem thankless, but Chrome is an environment that rewards this sort of group-adaptive behavior: the highest good you can do as an engineer is to make your fellow engineers more productive.

And that's what you're missing from everything else you're reading about this announcement today. To make a better platform faster, you must be able to iterate faster. Steps away from that are steps away from a better platform. Today's WebKit defeats that imperative in ways large and small. It's not anybody's fault, but it does need to change. And changing it will allow us to iterate faster, working through the annealing process that takes a good idea from drawing board to API to refined feature. We've always enjoyed this freedom in the Chromey bits of Chrome, and unleashing Chrome's Web Platform team will deliver the same sorts of benefits to the web platform that faster iteration and cycle times have enabled at the application level in Chrome.

Why couldn't those cycle-time-improving changes happen inside WebKit? After all, much work has happened in the past 4 years (often by Googlers) to improve the directness of WebKit work: EWS bots, better code review flow, improved scripts and tools for managing checkins, the commit queue itself. The results have been impressive and have enabled huge growth and adoption by porters. WebKit now supports multiple multi-process architecture designs, something like a half-dozen network stack plug-ins, and similar diversity at every point where the engine calls back to outside systems for low-level implementation (GPU, network, storage, databases, fonts...you name it). The community is now committed to enabling porters, and due to WebKit's low-ish level of abstraction each new port raises the tax paid by every other port. As James Robinson has observed, this diversity creates an ongoing drag when the dependencies are intertwined with core APIs in such a way that they can bite you every time you go to make a change. The Content API boundary is Blink's higher-level "embedding" layer and encapsulates all of those concerns, enabling much cleaner lines of sight through the codebase and the removal of abstractions that seek only to triangulate between opaque constraints of other ports. Blink gives developers much more assurance that when they change something, it's only affecting the things they think it's affecting. Moving without fear is the secret of all good programming. Putting your team in a position to move with more surety and less fear is hugely enabling.

Yes, there are losses. Separating ourselves from a community of hugely talented people who have worked with us for years to build a web engine is not easy. The decision was wrenching. We'll miss their insight, intelligence, and experience. In all honesty, we may have paid too high a price for too long because of this desire to stay close to WebKit. But whatever the "right" timing may have been, the good that will come from this outweighs the ill in my mind.

Others will cover better than I can how this won't affect your day-to-day experience of WebKit-derived browser testing, or how it won't change the feature-set of Chrome over-night, or how the new feature governance process is more open and transparent. But the most important thing is that we'll all be going faster, either directly via Blink-embedding browsers or via benchmarks and standards conformance shaming. You won't feel it overnight, but it's the sort of change in model that enables concrete changes in architecture and performance and that is something to cheer about -- change is the predicate for positive change, after all.

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