Nov 12, 2012
Software libraries suck

Here's why, in a sentence: they promise to be abstractions, but they end up becoming services. An abstraction frees you from thinking about its internals every time you use it. A service allows you to never learn its internals. A service is not an abstraction. It isn't 'abstracting' away the details. Somebody else is thinking about the details so you can remain ignorant.

Programmers manage abstraction boundaries, that's our stock in trade. Managing them requires bouncing around on both sides of them. If you restrict yourself to one side of an abstraction, you're limiting your growth as a programmer.1 You're chopping off your strength and potential, one lock of hair at a time, and sacrificing it on the altar of convenience.

A library you're ignorant of is a risk you're exposed to, a now-quiet frontier that may suddenly face assault from some bug when you're on a deadline and can least afford the distraction. Better to take a day or week now, when things are quiet, to save that hour of life-shortening stress when it really matters.

You don't have to give up the libraries you currently rely on. You just have to take the effort to enumerate them, locate them on your system, install the sources if necessary, and take ownership the next time your program dies within them, or uncovers a bug in them. Are these activities more time-consuming than not doing them? Of course. Consider them a long-term investment.

Just enumerating all the libraries you rely on others to provide can be eye-opening. Tot up all the open bugs in their trackers and you have a sense of your exposure to risks outside your control. In fact, forget the whole system. Just start with your Gemfile or npm_modules. They're probably lowest-maturity and therefore highest risk.

Once you assess the amount of effort that should be going into each library you use, you may well wonder if all those libraries are worth the effort. And that's a useful insight as well. “Achievement unlocked: I've stopped adding dependencies willy-nilly.”

Update: Check out the sequel. Particularly if this post left you scratching your head about what I could possibly be going on about.

(This birth was midwifed by conversations with Ross Angle, Dan Grover, and Manuel Simoni.)


1. If you don't identify as a programmer, if that isn't your core strength, if you just program now and then because it's expedient, then treating libraries as services may make more sense. If a major issue pops up you'll need to find more expert help, but you knew that already.


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Aug 1, 2012
Marx's engines of plenty

From "Red Plenty" by Francis Spufford:

The problem was that Marx had predicted the wrong revolution. He had said that socialism would come, not in backward agricultural Russia, but in the most developed and advanced industrial countries. Capitalism (he'd argued) created misery, but it also created progress, and the revolution that was going to liberate mankind from misery would only happen once capitalism had contributed all the progress that it could, and all the misery too. At that point the infrastructure for producing things would have attained a state of near-perfection. At the same time, the search for higher profits would have driven the wages of the working class down to near-destitution. It would be a world of wonderful machines and ragged humans. When the contradiction became unbearable, the workers would act. And paradise would quickly lie within their grasp, because Marx expected that the victorious socialists of the future would be able to pick up the whole completed apparatus of capitalism and carry it forward into the new society, still humming, still prodigally producing. There might be a need for a brief period of decisive government during the transition to the new world of plenty, but the 'dictatorship of the proletariat' Marx imagined was modelled on the 'dictatorships' of ancient Rome, when the republic would now and again draft some respected citizen to give orders in an emergency. The dictatorship of Cincinnatus lasted one day; then, having extracted the Roman army from the mess it was in, he went back to his plough. The dictatorship of the proletariat would presumably last a little longer, perhaps a few years. And of course there would also be an opportunity to improve on the sleek technology inherited from capitalism, now that society as a whole was pulling the levers of the engines of plenty. But it wouldn't take long. There'd be no need to build up productive capacity for the new world. Capitalism had already done that. Very soon it would no longer be necessary even to share out the rewards of work in proportion to how much work people did. All the 'springs of co-operative wealth' would flow abundantly, and anyone could have anything, or be anything. No wonder that Marx's pictures of the society to come were so vague: it was going to be an idyll, a rather soft-focus gentlemanly idyll, in which the inherited production lines whirring away in the background allowed the humans in the foreground to play, 'to hunt in the morning, fish in the afternoon, rear cattle in the evening, criticise after dinner, just as I have a mind…'

None of this was of the slightest use to the Marxists trying to run the economy of Russia after 1917. Not only had capitalist development not reached its climax of perfection and desperation in Russia; it had barely even begun. Russia had fewer railroads, fewer roads and less electricity than any other European power. Within living memory, the large majority of the population had been slaves. It became inescapably clear that, in Russia, socialism was going to have to do what Marx had never expected, and to carry out the task of development he'd seen as belonging strictly to capitalism. Socialism would have to mimic capitalism's ability to run an industrial revolution, to marshal investment, to build modern life.

But how?

There was in fact an international debate in the 1920s, partly prompted by the Bolsheviks' strange situation, over whether a state-run economy could really find substitutes for all of capitalism's working parts. No, said the Austrian economist Ludwig von Mises, it could not: in particular, it couldn't replace markets, and the market prices that made it possible to tell whether it was advantageous to produce any particular thing. Yes, it could, replied a gradually expanding group of socialist economists. A market was only a mathematical device for allocating goods to the highest bidder, and so a socialist state could easily equip itself with a replica marketplace, reduced entirely to maths. For a long time, the 'market socialists' were judged to have won the argument. The Bolsheviks, however, paid very little attention. Marx had not thought markets were very important — as far as he was concerned market prices just reflected the labour that had gone into products, plus some meaningless statistical fuzz. And the Bolsheviks were mining Marx's analysis of capitalism for hints to follow. They were not assembling an elegant mathematical version of capitalism. They were building a brutish, pragmatic simulacrum of what Marx and Engels had seen in the boom towns of the mid-nineteenth century, in Manchester when its sky was dark at noon with coal smoke. And they didn't easily do debate, either. In their hands, Marx's temporary Roman-style dictatorship had become permanent rule by the Party itself, never to be challenged, never to be questioned. There had been supposed to be a space preserved inside the Party for experiment and policy-making, but the police methods used on the rest of Russian society crept inexorably inward. The space for safe talk shrank till, with Stalin's victory over the last of his rivals, it closed altogether, and the apparatus of votes, committee reports and 'discussion journals' became purely ceremonious, a kind of fetish of departed civilisation.

Until 1928, the Soviet Union was a mixed economy. Industry was in the hands of the state but tailors' shops and private cafes were still open, and farms still belonged to the peasant families who'd received them when the Bolsheviks broke up the great estates. Investment for industry, therefore, had to come the slow way, by taxing the farmers; meanwhile the farmers' incomes made them dangerously independent, and food prices bounced disconcertingly up and down. Collectivisation saw to all these problems at once. It killed several million more people in the short term, and permanently dislocated the Soviet food supply; but forcing the whole country population into collective farms let the central government set the purchase price paid for crops, and so let it take as large a surplus for investment as it liked. In effect, all but a fraction of the proceeds of farming became suddenly available for industry.

Between them, these policies created a society that was utterly hierarchical. Metaphysically speaking, Russian workers owned the entire economy, with the Party acting as their proxy. But in practice, from 8.30 a.m. on Monday morning until 6 p.m. on Saturday night, they were expected simply to obey. At the very bottom of the heap came the prisoner-labourers of the Gulag. Stalin appears to have believed that, since according to Marx all value was created by labour, slave labour was a tremendous bargain. You got all that value, all that Arctic nickel mined and timber cut and rail track laid, for no wages, just a little millet soup. Then came the collective farmers, in theory free, effectively returned to the serfdom of their grandfathers. A decisive step above them, in turn, came the swelling army of factory workers, almost all recent escapees or refugees from the land. It was not an easy existence. Discipline at work was enforced through the criminal code. Arrive late three times in a row, and you were a 'saboteur'. Sentence: ten years. But from the factory workers on up, this was also a society in a state of very high mobility, with fairytale-rapid rises. You could start a semi-literate rural apparatchik, be the mayor of a city at twenty-five, a minister of the state at thirty; and then, if you were unlucky or maladroit, a corpse at thirty-two, or maybe a prisoner in the nickel mines, having slid from the top of the Soviet ladder right back down its longest snake. But mishaps apart, life was pretty good at the top, with a dacha in the country, from whose verandah the favoured citizen could survey the new world growing down below.

And it did grow. Market economies, so far as they were 'designed' at all, were designed to match buyers and sellers. They grew, but only because the sellers might decide, from the eagerness of the buyers, to make a little more of what they were selling. Growth wasn't intrinsic. The planned economy, on the other hand, was explicitly and deliberately a ratchet, designed to effect a one-way passage from scarcity to plenty by stepping up output each year, every year, year after year. Nothing else mattered: not profit, not accidents, not the effect of the factories on the land or the air. The planned economy measured its success in terms of the amount of physical things it produced. Money was treated as secondary, merely a tool for accounting. Indeed, there was a philosophical issue involved here, a point on which it was important for Soviet planners to feel that they were keeping faith with Marx, even if in almost every other respect their post-revolutionary world parted company with his. Theirs was a system that generated use-values rather than exchange-values, tangible human benefits rather than the marketplace delusion of value turned independent and imperious. For a society to produce less than it could, because people could not 'afford' the extra production, was ridiculous. Instead of calculating Gross Domestic Product, the sum of all incomes earned, the USSR calculated Net Material Product, the country's total output of stuff — expressed, for convenience, in roubles.

This made it difficult to compare Soviet growth with growth elsewhere. After the Second World War, when the numbers coming out of the Soviet Union started to become more and more worryingly radiant, it became a major preoccupation of the newly-formed CIA to try to translate the official Soviet figures from NMP to GDP, discounting for propaganda, guessing at suitable weighting for the value of products in the Soviet environment, subtracting items 'double-counted' in the NMP, like the steel that appeared there once in its naked new-forged self, twice when panel-beaten into an automobile. The CIA figures were always lower than the glowing stats from Moscow. Yet they were still worrying enough to cause heart-searching among Western governments, and anxious editorialising in Western newspapers. For a while, in the late 1950s and the early 1960s, people in the West felt the same mesmerising disquiet over Soviet growth they were going to feel for Japanese growth in the 1970s and 1980s, and for Chinese and Indian growth from the 1990s on. Nor were they being deceived. Beneath several layers of varnish, the phenomenon was real. Since the fall of the Soviet Union, historians from both Russia and the West have recalculated the Soviet growth record one more time: and even using the most pessimistic of these newest estimates, all lower again than the Kremlin's numbers and the CIA's, the Soviet Union still shows up as growing faster than any country in the world except Japan. Officially it grew 10.1% a year; according to the CIA it grew 7% a year; now the estimates range upward from 5% a year. Still enough to squeak past West Germany, and to cruise past the US average of around 3.3%.

On the strength of this performance, Stalin's successors set about civilising their savage growth machine. Most of the prisoners were released from the labour camps. Collective farmers were allowed to earn incomes visible without a microscope, and eventually given old-age pensions. Workers' wages were raised, and the salaries of the elite were capped, creating a much more egalitarian spread of income. The stick of terror driving managers was discarded too; reporting a bad year's growth now meant only a lousy bonus. The work day shrank to eight hours, the work week to five days. The millions of families squeezed into juddering tsarist tenements were finally housed in brand-new suburbs. It was clear that another wave of investment was going to be needed, bigger if anything than the one before, to build the next generation of industries: plastics, artificial fibers, the just-emerging technologies of information. But it all seemed to be affordable now. The Soviet Union could give its populace some jam today, and reinvest for tomorrow, and pay the weapons bill of a super power, all at once. The Party could even afford to experiment with a little gingerly discussion; a little closely-monitored blowing of the dust off the abandoned mechanisms for talking about aims and objectives, priorities and possibilities.

And this was fortunate, because as it happened the board of USSR Inc. was in need of some expert advice. The growth figures were marvellous, amazing, outstanding — but there was something faintly disturbing about them, even in their rosiest versions. For each extra unit of output it gained, the Soviet Union was far more dependent than other countries on throwing in extra inputs: extra labour, extra raw materials, extra investment. This kind of 'extensive' growth (as opposed to the 'intensive' growth of rising productivity) came with built-in limits, and the Soviet economy was already nearing them. Whisper it quietly, but the capital productivity of the USSR was a disgrace. With a government that could choose what money meant, the Soviet Union already got less return for its investments than any of its capitalist rivals. Between 1950 and 1960, for instance, it had sunk 9.4% of extra capital a year into the economy, to earn only 5.8% a year more actual production. In effect, they were spraying Soviet industry with they money they had so painfully extracted from the populace, wasting more than a third of it in the process.


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Jul 4, 2012

In the enthusiasm of our rapid mechanical conquests we have overlooked some things. We have perhaps driven men into the service of the machine, instead of building machinery for the service of man. But could anything be more natural? So long as we were engaged in conquest, our spirit was the spirit of conquerors. The time has now come when we must be colonists, must make this house habitable which is still without character.


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Jun 18, 2012
How to use a profiler

All of us programmers have at some point tried to speed up a large program. We remember "measure before optimizing" and profile it, and end up (a few hours later) with something intimidating like this and.. what next? If you're like me, you scratch your head at the prospect of optimizing StringAppend, and the call-graph seems to tell you what you already know: Your program spends most of its time in the main loop, divided between the main subtasks.

I used to imagine the optimization process like this:

1. Run a profiler
2. Select a hot spot
3. ...
4. Speedup!

But the details were hazy. Especially in step 3. Michael Abrash was clearly doing a lot more than this. What was it?

Worse, I kept forgetting to use the profiler. I'd have a split-second idea and blunder around for hours before remembering the wisdom of "measure before optimizing." I was forgetting to measure because I was getting so little out of it, because I'd never learned to do it right.

After a lot of trial and error in the last few months, I think I have a better sense of the process. Optimization is like science. You can't start with experiments. You have to start with a hypothesis. "My program is spending too much time in _." Fill in the blanks, then translate the sentence for a profile. "I expect to see more time spent in function A than B." Then run the profile and check your results. Skip the low-level stuff, look for just A and B in the cumulative charts. Which takes more time? Is one much more of a bottleneck? Keep an eye out for a peer function that you hadn't considered, something that's a sibling of A and B in the call-graph, about the same level of granularity.

Do this enough times and you gain an intuition of what your program is doing, and where it's spending its time.

When you do find a function at a certain level of granularity that seems to be taking too long, it's time to focus on what it does and how it works. This is what people mean when they say, "look for a better algorithm." Can the data structures be better organized from the perspective of this function? Is it being called needlessly? Can we prevent it being called too often? Can we specialize a simpler variant for 90% of the calls?

If none of that generates any ideas, then it's time to bite the bullet and drop down to a lower level.

But remember: optimization is about understanding your program. Begin there, and profiling and other tools will come to hand more naturally.


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Mar 14, 2012
The opposite of exponential backoff

Every few days I'm on IM with some coworker from a different building. The conversation goes something like this:

Them: Lunch?
(6 minutes)
Me: Sounds good! Meet downstairs?
(1 minute)
Me: Now?
(2 minutes)
Them: Yes!
(1 minute)
Them: You there?
(3 minutes)
Me: Oops, sorry. Heading down now.

Now I never know whether to wait for a response, or to run down because I'm already late. But today I finally figured out the answer:

Me: New rule. Head down when both of us say 'ready' within 1 minute of each

That's it. No more ambiguity. It's kind of a silly example, but the general idea feels deep, complementary somehow to exponential backoff. Exponential backoff is the ideal game-theoretic strategy for competitive situations where two people need to contend for a common resource, like trying to call someone back after a dropped call and getting a busy signal. Both try to diverge away from a network-defined window of conflict by waiting longer and longer. Here both parties are trying to converge into an agreed window of agreement. Defining the size of the window by diktat should be handy anytime two parties (people, computers, ..) need to cooperate synchronously atop an asynchronous channel.

I'm sure there's a paper on this idea, perhaps something like that one by Lamport pdf on Buridan's ass. If you have a pointer I'd love to hear about it.


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Jul 14, 2011
Evolution of a rails programmer

Idiomatic rails action for registering a user if he doesn't exist:

After a year of programming in lisp, I find it most natural to write:

Is this overly concise/obfuscated? I like it because it concisely expresses the error case as an early exit; most of the space is devoted to the successful save, which is straight-line code without distracting branches. It's clearer that we either pick an existing user or create a new one. Form follows function.


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May 12, 2011
My latest project

Two of us have been building hackerstream, a real-time UI for Hacker News that a dozen addicts have been using since March. This won't matter to you if you don't frequent HN, or even if you swing by just once a day. But try it out if you go to HN every couple of hours like I do. You'll see comments on all the stories on the entire HN frontpage as they stream in. You can slice and dice the stream by story or by author. You can even set it up to highlight, say, all comments by security guy Thomas Ptacek and all comments about today's silicon valley brouhaha. If you use Twitter the UI will seem familiar.

Is such a firehose useful? Is it too much of a good thing? I find I see more of HN for the same time investment, and I waste less time scanning stories I've already read. What's more, when I started using it I found my comments getting more votes and more responses. It turns out the biggest factor affecting responses is not how good my comment is but just how early it shows up on a story. By biasing my reading to be more timely I was giving my few comments improved odds of a response.

It's not for everyone, but hackerstream is geared to help you have higher-quality conversation on Hacker News. Try it out and tell me what you think.


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Mar 4, 2011
Backup theory for startups

You run a startup. Your company has been given data by users, data that it would be embarrassing to lose. You make backups. You're aware of the best-practices:

  • Make backups.
  • Make backups automatic. Or they won't happen.
  • Make backups yourself. Outsourcing them is for suckers.
  • Regularly restore from your backups. A backup doesn't exist if it's never read.


    This paranoia is useful, but it's intended for personal data. For business data it's incomplete. Businesses have automation. Lots of automation. Dumb automation that can do stupid things, like corrupting data. Businesses also develop nooks and crannies where important data may go unread for periods of time. The combination of automation and dusty corners can cause insidious data loss: some obscure-yet-critical corner of your data gets deleted or corrupted, and you don't notice until the corruption has infected the backup copy.

    Stale is good

    You can guard against catastrophic data loss with just a regular backup at a remote location. Insidious loss is harder to guard against. Insidious data loss is the reason companies have more than one backup, the reason journalled file systems have multiple .snapshot directories, the reason slicehost and linode provide a daily and a weekly backup. Daily/weekly is perhaps the simplest backup cascade. It gives you a week to detect corrupted data in your server. As operations get complex you'll want longer cascades with more levels. The lower levels backup frequently to capture recent changes, and higher levels backup less frequently as a cushion to detect data corruption.

    More best-practices

  • Make cascading backups.
  • Make sure you can detect corruption to anything important before it reaches the highest level of your cascade. The 'height' of your cascade defines how far back in time you can undo damage.

    Failure modes

    Whatever your backup strategy, ask yourself what it can't handle. I can think of two scenarios cascades can't handle: extremely insidious corruption that doesn't get detected in time, and short-lived data. If many records in your database get deleted everyday, most of them may never make it into a weekly backup.

    What else?


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  • Dec 19, 2010
    What do Moody's and the patent office have in common? [0]

    They're in the business of fielding complex applications from just about anybody. They can't just pick the best ones—they must accept or deny every last application.

    This is a really bad situation to be in. To understand why, put yourself in the shoes of an employee at the patent office[1] who must judge these applications.


    Each application you see has its own deep complexities and needs time and expertise to understand, perhaps even expertise you don't have and experts you must track down. But when you're done understanding one application you haven't learned anything that helps you process the next one faster. Your supervisor is shielded from these complexities and inevitably judges you on the basis of one metric: number of applications processed.

    Inevitably, employees in this situation employ a heuristic: they try to race through the simple applications, and half-ass the complex ones. There's now an incentive for poor applicants to craft complex applications; if your idea stinks a simple application is certain to be denied, while a complex, weighty-looking application has some chance of randomly being granted. Meanwhile, genuinely complex applications now face more randomness and may be undeservedly denied.


    Over time applicants complain, usually the deserving but complex ones. Everytime you the employee catch heat for such a complaint you loosen your constraints. Complex applications get handled more and more perfunctorily.[2] Instead you spend more and more time with the simple applications, probing them intensely for weaknesses, ‘bike-shedding’ them in more and more adversarial fashion, looking for the vaguest of undeniable reasons to deny applications. After all, the acceptance rate is going up in that complex pile. The denials have to come from somewhere, lest you stand out in somebody's metrics.

    Predator vs Prey

    Over time applicants start to notice that even genuine applications have more chance of being granted if they are large and complex and seem weighty. As more and more applications grow complex, standards change. What was complex 10 years ago is now considered simple, and more likely to be denied. Nothing's being read in any sort of detail anymore. Every applicant wants to end up in the complex half of the pile. They aren't antagonistic to the application process anymore, but to each other. You the employee are now in a position of power, like a lion in the savannah, culling the herds of their weakest, least weighty-seeming applications. Your prey isn't trying to convince you of anything anymore, just to outgun some other application.

    Red Queen

    It starts being taken for granted that ‘you have to spend a month on the application,’ no matter how clear and deserving it is at the outset. “Standards” go up. You have to pay a lawyer to craft it. The number of lawyers, the expense of the lawyers, the armies of paralegals, everything's spiralling up, until not everybody can afford a patent anymore. Like the Red Queen, everybody is running as hard and as fast as they can just to stay in the same place.

    Well, not everybody has managed to stay on the treadmill. The one thing that's been lost is the line in the sand showing a good patent application.

    Zoom out

    This dynamic has played out throughout history. It is how bureaucracies are created. To some extent it is inevitable; humans don't yet know a better way to deal with complexity. If you're planning an application process, be aware of these pitfalls. Consider ranking rather than judging, so that you don't have to grow your employees with the number of incoming applications. Consider some sort of limit on application length and complexity so that you don't have to grow your employees faster than the number of incoming applications. Think hard about how your employees will judge applications. Consider bounties for finding misjudged applications. Any of these ‘outs’ will help you avoid the worst-case scenario: high costs, which grow faster than incoming applications.


    0. Thanks to Walter Chang for the conversation that got me to write this.

    1. Two other examples: financial regulators and the US EB1 green card process.

    2. Sure, processes will grow up around them, but less and less of the process will be devoted to actually reading them.


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    Dec 17, 2010
    Don't apologize

    As a teenager it drove me crazy that my father would never apologize to me. Ever. Even when something was obviously his fault. I swore to myself that I would be more intellectually honesti, that I would admit when I was wrong. That emphasis on intellectual honesty gave me a scientific bent and took me to engineering college, and to grad school. For 12 years I unquestioningly assumed the virtue — and importance — of intellectual honesty. Coincidentally, I also spent most of those years working alone.

    Now that I've worked in teams for a while I'm starting to change my mind. In many social situations being apologetic sucks. It makes others around you feel awkward. If you're leading a team it makes you seem weak. If you're the rookie you sound like you're making excuses. If others aren't intimately familiar with the details it can magnify your screwups and make things seem worse than they are. And always it's a distraction, diluting your focus and that of your team. I'm learning to not apologize until it's clearly expected. Better to err on that side.

    All this may seem crazy obvious to you. Apologizing isn't really part of western culture. I can remember others telling me dozens of times, "don't apologize." Somehow it never sunk in. Perhaps it's not even an eastern thing, just a personal fetish.

    Looking back, I have a different perspective on my father. I realize he was an army officer who spent much of his day telling subordinates what to do. You can't be apologizing in that situation. You just don't think about whose fault it was, because the entire focus is on adjusting to a constantly-changing situation, and on what needs to be done next. I want that mindset.


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