diff options
Diffstat (limited to 'src/content/blog/2020/10')
| -rw-r--r-- | src/content/blog/2020/10/05/cargo2nix-demo.tar.gz | bin | 0 -> 174080 bytes | |||
| -rw-r--r-- | src/content/blog/2020/10/05/cargo2nix.adoc | 80 | ||||
| -rw-r--r-- | src/content/blog/2020/10/05/cargo2nix.tar.gz | bin | 0 -> 143360 bytes | |||
| -rw-r--r-- | src/content/blog/2020/10/05/swift2nix-demo.tar.gz | bin | 0 -> 174080 bytes | |||
| -rw-r--r-- | src/content/blog/2020/10/05/swift2nix.adoc | 199 | ||||
| -rw-r--r-- | src/content/blog/2020/10/05/swift2nix.tar.gz | bin | 0 -> 143360 bytes | |||
| -rw-r--r-- | src/content/blog/2020/10/19/feature-flags.adoc | 305 | ||||
| -rw-r--r-- | src/content/blog/2020/10/20/wrong-interviewing.adoc | 331 |
8 files changed, 915 insertions, 0 deletions
diff --git a/src/content/blog/2020/10/05/cargo2nix-demo.tar.gz b/src/content/blog/2020/10/05/cargo2nix-demo.tar.gz Binary files differnew file mode 100644 index 0000000..281a91c --- /dev/null +++ b/src/content/blog/2020/10/05/cargo2nix-demo.tar.gz diff --git a/src/content/blog/2020/10/05/cargo2nix.adoc b/src/content/blog/2020/10/05/cargo2nix.adoc new file mode 100644 index 0000000..1db3d0c --- /dev/null +++ b/src/content/blog/2020/10/05/cargo2nix.adoc @@ -0,0 +1,80 @@ += cargo2nix: Dramatically simpler Rust in Nix + +date: 2020-10-05 2 + +layout: post + +lang: en + +ref: cargo2nix-dramatically-simpler-rust-in-nix + +--- + +In the same vein of my earlier post on +[swift2nix]({% link _articles/2020-10-05-swift2nix-run-swift-inside-nix-builds.md %}), I +was able to quickly prototype a Rust and Cargo variation of it: +[cargo2nix]. + + +The initial prototype is even smaller than swift2nix: it has only +37 lines of code. + +[cargo2nix]: https://euandre.org/static/attachments/cargo2nix.tar.gz + +Here's how to use it (snippet taken from the repo's README): + +```nix +let + niv-sources = import ./nix/sources.nix; + mozilla-overlay = import niv-sources.nixpkgs-mozilla; + pkgs = import niv-sources.nixpkgs { overlays = [ mozilla-overlay ]; }; + src = pkgs.nix-gitignore.gitignoreSource [ ] ./.; + cargo2nix = pkgs.callPackage niv-sources.cargo2nix { + lockfile = ./Cargo.lock; + }; +in pkgs.stdenv.mkDerivation { + inherit src; + name = "cargo-test"; + buildInputs = [ pkgs.latest.rustChannels.nightly.rust ]; + phases = [ "unpackPhase" "buildPhase" ]; + buildPhase = '' + # Setup dependencies path to satisfy Cargo + mkdir .cargo/ + ln -s ${cargo2nix.env.cargo-config} .cargo/config + ln -s ${cargo2nix.env.vendor} vendor + + # Run the tests + cargo test + touch $out + ''; +} +``` + +That `cargo test` part on line 20 is what I have been fighting with every +"\*2nix" available for Rust out there. I don't want to bash any of them. All I +want is to have full control of what Cargo commands to run, and the "*2nix" tool +should only setup the environment for me. Let me drive Cargo myself, no need to +parameterize how the tool runs it for me, or even replicate its internal +behaviour by calling the Rust compiler directly. + +Sure it doesn't support private registries or Git dependencies, but how much +bigger does it has to be to support them? Also, it doesn't support those **yet**, +there's no reason it can't be extended. I just haven't needed it yet, so I +haven't added. Patches welcome. + +The layout of the `vendor/` directory is more explicit and public then what +swift2nix does: it is whatever the command `cargo vendor` returns. However I +haven't checked if the shape of the `.cargo-checksum.json` is specified, or +internal to Cargo. + +Try out the demo (also taken from the repo's README): + +```shell +pushd "$(mktemp -d)" +wget -O- https://euandre.org/static/attachments/cargo2nix-demo.tar.gz | + tar -xv +cd cargo2nix-demo/ +nix-build +``` + +Report back if you wish. diff --git a/src/content/blog/2020/10/05/cargo2nix.tar.gz b/src/content/blog/2020/10/05/cargo2nix.tar.gz Binary files differnew file mode 100644 index 0000000..8a9985a --- /dev/null +++ b/src/content/blog/2020/10/05/cargo2nix.tar.gz diff --git a/src/content/blog/2020/10/05/swift2nix-demo.tar.gz b/src/content/blog/2020/10/05/swift2nix-demo.tar.gz Binary files differnew file mode 100644 index 0000000..f688572 --- /dev/null +++ b/src/content/blog/2020/10/05/swift2nix-demo.tar.gz diff --git a/src/content/blog/2020/10/05/swift2nix.adoc b/src/content/blog/2020/10/05/swift2nix.adoc new file mode 100644 index 0000000..84f4d34 --- /dev/null +++ b/src/content/blog/2020/10/05/swift2nix.adoc @@ -0,0 +1,199 @@ += swift2nix: Run Swift inside Nix builds + +date: 2020-10-05 1 + +layout: post + +lang: en + +ref: swift2nix-run-swift-inside-nix-builds + +--- + +While working on a Swift project, I didn't find any tool that would allow Swift +to run inside [Nix][nix] builds. Even thought you *can* run Swift, the real +problem arises when using the package manager. It has many of the same problems +that other package managers have when trying to integrate with Nix, more on this +below. + +I wrote a simple little tool called [swift2nix] that allows you trick +Swift's package manager into assuming everything is set up. Here's the example +from swift2nix's README file: + +``` +let + niv-sources = import ./nix/sources.nix; + pkgs = import niv-sources.nixpkgs { }; + src = pkgs.nix-gitignore.gitignoreSource [ ] ./.; + swift2nix = pkgs.callPackage niv-sources.swift2nix { + package-resolved = ./Package.resolved; + }; +in pkgs.stdenv.mkDerivation { + inherit src; + name = "swift-test"; + buildInputs = with pkgs; [ swift ]; + phases = [ "unpackPhase" "buildPhase" ]; + buildPhase = '' + # Setup dependencies path to satisfy SwiftPM + mkdir .build + ln -s ${swift2nix.env.dependencies-state-json} .build/dependencies-state.json + ln -s ${swift2nix.env.checkouts} .build/checkouts + + # Run the tests + swift test + touch $out + ''; +} +``` + +The key parts are lines 15~17: we just fake enough files inside `.build/` that +Swift believes it has already downloaded and checked-out all dependencies, and +just moves on to building them. + +I've worked on it just enough to make it usable for myself, so beware of +unimplemented cases. + +[nix]: https://nixos.org/ +[swift2nix]: https://euandre.org/static/attachments/swift2nix.tar.gz + +## Design + +What swift2nix does is just provide you with the bare minimum that Swift +requires, and readily get out of the way: + +1. I explicitly did not want to generated a `Package.nix` file, since + `Package.resolved` already exists and contains the required information; +2. I didn't want to have an "easy" interface right out of the gate, after + fighting with "*2nix" tools that focus too much on that. + +The final actual code was so small (46 lines) that it made me +think about package managers, "*2nix" tools and some problems with many of them. + +## Problems with package managers + +I'm going to talk about solely language package managers. Think npm and cargo, +not apt-get. + +Package managers want to do too much, or assume too much, or just want to take +control of the entire build of the dependencies. + +This is a recurrent problem in package managers, but I don't see it as an +intrinsic one. There's nothing about a "package manager" that prevents it from +*declaring* what it expects to encounter and in which format. The *declaring* +part is important: it should be data, not code, otherwise you're back in the +same problem, just like lockfiles are just data. Those work in any language, and +tools can cooperate happily. + +There's no need for this declarative expectation to be standardized, or be made +compatible across languages. That would lead to a poor format that no package +manager really likes. Instead, If every package manager could say out loud what +it wants to see exactly, than more tools like swift2nix could exist, and they +would be more reliable. + +This could even work fully offline, and be simply a mapping from the lockfile +(the `Package.resolved` in Swift's case) to the filesystem representation. For +Swift, the `.build/dependencies-state.json` comes very close, but it is internal +to the package manager. + +Even though this pain only exists when trying to use Swift inside Nix, it sheds +light into this common implicit coupling that package managers have. They +usually have fuzzy boundaries and tight coupling between: + +1. resolving the dependency tree and using some heuristic to pick a package + version; +2. generating a lockfile with the exact pinned versions; +3. downloading the dependencies present on the lockfile into some local cache; +4. arranging the dependencies from the cache in a meaningful way for itself inside + the project; +5. work using the dependencies while *assuming* that step 4 was done. + +When you run `npm install` in a repository with no lockfile, it does 1~4. If you +do the same with `cargo build`, it does 1~5. That's too much: many of those +assumptions are implicit and internal to the package manager, and if you ever +need to rearrange them, you're on your own. Even though you can perform some of +those steps, you can't compose or rearrange them. + +Instead a much saner approach could be: + +1. this stays the same; +2. this also stays the same; +3. be able to generate some JSON/TOML/edn which represents the local expected + filesystem layout with dependencies (i.e. exposing what the package manager + expects to find), let's call it `local-registry.json`; +4. if a `local-registry.json` was provided, do a build using that. Otherwise + generate its own, by downloading the dependencies, arranging them, *etc.* + +The point is just making what the package manager requires visible to the +outside world via some declarative data. If this data wasn't provided, it can +move on to doing its own automatic things. + +By making the expectation explicit and public, one can plug tools *à la carte* +if desired, but doesn't prevent the default code path of doing things the exact +same way they are now. + +## Problems with "*2nix" tools + +I have to admit: I'm unhappy with most of they. + +They conflate "using Nix" with "replicating every command of the package manager +inside Nix". + +The avoidance of an "easy" interface that I mentioned above comes from me +fighting with some of the "\*2nix" tools much like I have to fight with package +managers: I don't want to offload all build responsibilities to the "*2nix" +tool, I just want to let it download some of the dependencies and get out of the +way. I want to stick with `npm test` or `cargo build`, and Nix should only +provide the environment. + +This is something that [node2nix] does right. It allows you to build +the Node.js environment to satisfy NPM, and you can keep using NPM for +everything else: + +```shell +ln -s ${node2nix-package.shell.nodeDependencies}/lib/node_modules ./node_modules +npm test +``` + +Its natural to want to put as much things into Nix as possible to benefit from +Nix's advantages. Isn't that how NixOS itself was born? + +But a "*2nix" tool should leverage Nix, not be coupled with it. The above +example lets you run any arbitrary NPM command while profiting from isolation +and reproducibility that Nix provides. It is even less brittle: any changes to +how NPM runs some things will be future-compatible, since node2nix isn't trying +to replicate what NPM does, or fiddling with NPM's internal. + +**A "*2nix" tool should build the environment, preferably from the lockfile +directly and offload everything else to the package manager**. The rest is just +nice-to-have. + +swift2nix itself could provide an "easy" interface, something that allows you to +write: + +```shell +nix-build -A swift2nix.release +nix-build -A swift2nix.test +``` + +The implementation of those would be obvious: create a new +`pkgs.stdenv.mkDerivation` and call `swift build -c release` and `swift test` +while using `swift2nix.env` under the hood. + +[node2nix]: https://github.com/svanderburg/node2nix + +## Conclusion + +Package managers should provide exact dependencies via a data representation, +i.e. lockfiles, and expose via another data representation how they expect those +dependencies to appear on the filesystem, i.e. `local-registry.json`. This +allows package managers to provide an API so that external tools can create +mirrors, offline builds, other registries, isolated builds, *etc.* + +"\*2nix" tools should build simple functions that leverage that +`local-registry.json`[^local-registry] data and offload all the rest back to the +package manager itself. This allows the "*2nix" to not keep chasing the package +manager evolution, always trying to duplicate its behaviour. + +[^local-registry]: This `local-registry.json` file doesn't have to be checked-in + the repository at all. It could be always generated on the fly, much like + how Swift's `dependencies-state.json` is. diff --git a/src/content/blog/2020/10/05/swift2nix.tar.gz b/src/content/blog/2020/10/05/swift2nix.tar.gz Binary files differnew file mode 100644 index 0000000..bfab3f1 --- /dev/null +++ b/src/content/blog/2020/10/05/swift2nix.tar.gz diff --git a/src/content/blog/2020/10/19/feature-flags.adoc b/src/content/blog/2020/10/19/feature-flags.adoc new file mode 100644 index 0000000..c62c2d1 --- /dev/null +++ b/src/content/blog/2020/10/19/feature-flags.adoc @@ -0,0 +1,305 @@ +--- +title: "Feature flags: differences between backend, frontend and mobile" +date: 2020-10-19 +updated_at: 2020-11-03 +layout: post +lang: en +ref: feature-flags-differences-between-backend-frontend-and-mobile +eu_categories: presentation +--- + +*This article is derived from a [presentation][presentation] on the same +subject.* + +When discussing about feature flags, I find that their +costs and benefits are often well exposed and addressed. Online articles like +"[Feature Toggle (aka Feature Flags)][feature-flags-article]" do a great job of +explaining them in detail, giving great general guidance of how to apply +techniques to adopt it. + +However the weight of those costs and benefits apply differently on backend, +frontend or mobile, and those differences aren't covered. In fact, many of them +stop making sense, or the decision of adopting a feature flag or not may change +depending on the environment. + +In this article I try to make the distinction between environments and how + feature flags apply to them, with some final best practices I've acquired when + using them in production. + +[presentation]: {% link _slides/2020-10-19-rollout-feature-flag-experiment-operational-toggle.slides %} +[feature-flags-article]: https://martinfowler.com/articles/feature-toggles.html + +## Why feature flags + +Feature flags in general tend to be cited on the context of +[continuous deployment][cd]: + +> A: With continuous deployment, you deploy to production automatically + +> B: But how do I handle deployment failures, partial features, *etc.*? + +> A: With techniques like canary, monitoring and alarms, feature flags, *etc.* + +Though adopting continuous deployment doesn't force you to use feature +flags, it creates a demand for it. The inverse is also true: using feature flags +on the code points you more obviously to continuous deployment. Take the +following code sample for example, that we will reference later on the article: + +```javascript +function processTransaction() { + validate(); + persist(); + // TODO: add call to notifyListeners() +} +``` + +While being developed, being tested for suitability or something similar, +`notifyListeners()` may not be included in the code at once. So instead of +keeping it on a separate, long-lived branch, a feature flag can decide when the +new, partially implemented function will be called: + +```javascript +function processTransaction() { + validate(); + persist(); + if (featureIsEnabled("activate-notify-listeners")) { + notifyListeners(); + } +} +``` + +This allows your code to include `notifyListeners()`, and decide when to call it +at runtime. For the price of extra things around the code, you get more +dynamicity. + +So the fundamental question to ask yourself when considering adding a feature +flag should be: + +> Am I willing to pay with code complexity to get dynamicity? + +It is true that you can make the management of feature flags as +straightforward as possible, but having no feature flags is simpler than having +any. What you get in return is the ability to parameterize the behaviour of the +application at runtime, without doing any code changes. + +Sometimes this added complexity may tilt the balance towards not using a feature +flag, and sometimes the flexibility of changing behaviour at runtime is +absolutely worth the added complexity. This can vary a lot by code base, feature, but +fundamentally by environment: its much cheaper to deploy a new version of a +service than to release a new version of an app. + +So the question of which environment is being targeted is key when reasoning +about costs and benefits of feature flags. + +[cd]: https://www.atlassian.com/continuous-delivery/principles/continuous-integration-vs-delivery-vs-deployment + +## Control over the environment + +The key differentiator that makes the trade-offs apply differently is how much +control you have over the environment. + +When running a **backend** service, you usually are paying for the servers +themselves, and can tweak them as you wish. This means you have full control do +to code changes as you wish. Not only that, you decide when to do it, and for +how long the transition will last. + +On the **frontend** you have less control: even though you can choose to make a +new version available any time you wish, you can't force[^force] clients to +immediately switch to the new version. That means that a) clients could skip +upgrades at any time and b) you always have to keep backward and forward +compatibility in mind. + +Even though I'm mentioning frontend directly, it applies to other environment +with similar characteristics: desktop applications, command-line programs, +*etc*. + +On **mobile** you have even less control: app stores need to allow your app to +be updated, which could bite you when least desired. Theoretically you could +make you APK available on third party stores like [F-Droid][f-droid], or even +make the APK itself available for direct download, which would give you the same +characteristics of a frontend application, but that happens less often. + +On iOS you can't even do that. You have to get Apple's blessing on every single +update. Even though we already know that is a [bad idea][apple] for over a +decade now, there isn't a way around it. This is where you have the least +control. + +In practice, the amount of control you have will change how much you value +dynamicity: the less control you have, the more valuable it is. In other words, +having a dynamic flag on the backend may or may not be worth it since you could +always update the code immediately after, but on iOS it is basically always +worth it. + +[f-droid]: https://f-droid.org/ +[^force]: Technically you could force a reload with JavaScript using + `window.location.reload()`, but that not only is invasive and impolite, but + also gives you the illusion that you have control over the client when you + actually don't: clients with disabled JavaScript would be immune to such + tactics. + +[apple]: http://www.paulgraham.com/apple.html + +## Rollout + +A rollout is used to *roll out* a new version of software. + +They are usually short-lived, being relevant as long as the new code is being +deployed. The most common rule is percentages. + +On the **backend**, it is common to find it on the deployment infrastructure +itself, like canary servers, blue/green deployments, +[a kubernetes deployment rollout][k8s], *etc*. You could do those manually, by +having a dynamic control on the code itself, but rollbacks are cheap enough that +people usually do a normal deployment and just give some extra attention to the +metrics dashboard. + +Any time you see a blue/green deployment, there is a rollout happening: most +likely a load balancer is starting to direct traffic to the new server, until +reaching 100% of the traffic. Effectively, that is a rollout. + +On the **frontend**, you can selectively pick which user's will be able to +download the new version of a page. You could use geographical region, IP, +cookie or something similar to make this decision. + +CDN propagation delays and people not refreshing their web +pages are also rollouts by themselves, since old and new versions of the +software will coexist. + +On **mobile**, the Play Store allows you to perform +fine-grained [staged rollouts][staged-rollouts], and the App Store allows you to +perform limited [phased releases][phased-releases]. + +Both for Android and iOS, the user plays the role of making the download. + +In summary: since you control the servers on the backend, you can do rollouts at +will, and those are often found automated away in base infrastructure. On the +frontend and on mobile, there are ways to make new versions available, but users +may not download them immediately, and many different versions of the software +end up coexisting. + +[k8s]: https://kubernetes.io/docs/concepts/workloads/controllers/deployment/#creating-a-deployment +[staged-rollouts]: https://support.google.com/googleplay/android-developer/answer/6346149?hl=en +[phased-releases]: https://help.apple.com/app-store-connect/#/dev3d65fcee1 + +## Feature flag + +A feature flag is a *flag* that tells the application on runtime to turn on or +off a given *feature*. That means that the actual production code will have more +than one possible code paths to go through, and that a new version of a feature +coexists with the old version. The feature flag tells which part of the code to +go through. + +They are usually medium-lived, being relevant as long as the new code is being +developed. The most common rules are percentages, allow/deny lists, A/B groups +and client version. + +On the **backend**, those are useful for things that have a long development +cycle, or that needs to done by steps. Consider loading the feature flag rules +in memory when the application starts, so that you avoid querying a database +or an external service for applying a feature flag rule and avoid flakiness on +the result due to intermittent network failures. + +Since on the **frontend** you don't control when to update the client software, +you're left with applying the feature flag rule on the server, and exposing the +value through an API for maximum dynamicity. This could be in the frontend code +itself, and fallback to a "just refresh the page"/"just update to the latest +version" strategy for less dynamic scenarios. + +On **mobile** you can't even rely on a "just update to the latest version" +strategy, since the code for the app could be updated to a new feature and be +blocked on the store. Those cases aren't recurrent, but you should always assume +the store will deny updates on critical moments so you don't find yourself with +no cards to play. That means the only control you actually have is via +the backend, by parameterizing the runtime of the application using the API. In +practice, you should always have a feature flag to control any relevant piece of +code. There is no such thing as "too small code change for a feature flag". What +you should ask yourself is: + +> If the code I'm writing breaks and stays broken for around a month, do I care? + +If you're doing an experimental screen, or something that will have a very small +impact you might answer "no" to the above question. For everything else, the +answer will be "yes": bug fixes, layout changes, refactoring, new screen, +filesystem/database changes, *etc*. + +## Experiment + +An experiment is a feature flag where you care about analytical value of the +flag, and how it might impact user's behaviour. A feature flag with analytics. + +They are also usually medium-lived, being relevant as long as the new code is +being developed. The most common rule is A/B test. + +On the **backend**, an experiment rely on an analytical environment that will +pick the A/B test groups and distributions, which means those can't be held in +memory easily. That also means that you'll need a fallback value in case +fetching the group for a given customer fails. + +On the **frontend** and on **mobile** they are no different from feature flags. + +## Operational toggle + +An operational toggle is like a system-level manual circuit breaker, where you +turn on/off a feature, fail over the load to a different server, *etc*. They are +useful switches to have during an incident. + +They are usually long-lived, being relevant as long as the code is in +production. The most common rule is percentages. + +They can be feature flags that are promoted to operational toggles on the +**backend**, or may be purposefully put in place preventively or after a +postmortem analysis. + +On the **frontend** and on **mobile** they are similar to feature flags, where +the "feature" is being turned on and off, and the client interprets this value +to show if the "feature" is available or unavailable. + +## Best practices + +### Prefer dynamic content + +Even though feature flags give you more dynamicity, they're still somewhat +manual: you have to create one for a specific feature and change it by hand. + +If you find yourself manually updating a feature flags every other day, or +tweaking the percentages frequently, consider making it fully dynamic. Try +using a dataset that is generated automatically, or computing the content on the +fly. + +Say you have a configuration screen with a list of options and sub-options, and +you're trying to find how to better structure this list. Instead of using a +feature flag for switching between 3 and 5 options, make it fully dynamic. This +way you'll be able to perform other tests that you didn't plan, and get more +flexibility out of it. + +### Use the client version to negotiate feature flags + +After effectively finishing a feature, the old code that coexisted with the new +one will be deleted, and all traces of the transition will vanish from the code +base. However if you just remove the feature flags from the API, all of the old +versions of clients that relied on that value to show the new feature will go +downgrade to the old feature. + +This means that you should avoid deleting client-facing feature flags, and +retire them instead: use the client version to decide when the feature is +stable, and return `true` for every client with a version greater or equal to +that. This way you can stop thinking about the feature flag, and you don't break +or downgrade clients that didn't upgrade past the transition. + +### Beware of many nested feature flags + +Nested flags combine exponentially. + +Pick strategic entry points or transitions eligible for feature flags, and +beware of their nesting. + +### Include feature flags in the development workflow + +Add feature flags to the list of things to think about during whiteboarding, and +deleting/retiring a feature flags at the end of the development. + +### Always rely on a feature flag on the app + +Again, there is no such thing "too small for a feature flag". Too many feature +flags is a good problem to have, not the opposite. Automate the process of +creating a feature flag to lower its cost. diff --git a/src/content/blog/2020/10/20/wrong-interviewing.adoc b/src/content/blog/2020/10/20/wrong-interviewing.adoc new file mode 100644 index 0000000..9cdfefb --- /dev/null +++ b/src/content/blog/2020/10/20/wrong-interviewing.adoc @@ -0,0 +1,331 @@ +--- +title: How not to interview engineers +date: 2020-10-20 +updated_at: 2020-10-24 +layout: post +lang: en +ref: how-not-to-interview-engineers +--- +This is a response to Slava's +"[How to interview engineers][how-to-interview-engineers]" article. I initially +thought it was a satire, [as have others][poes-law-comment], but he has +[doubled down on it][slava-on-satire]: + +> (...) Some parts are slightly exaggerated for sure, but the essay isn't meant +> as a joke. + +That being true, he completely misses the point on how to improve hiring, and +proposes a worse alternative on many aspects. It doesn't qualify as provocative, +it is just wrong. + +I was comfortable taking it as a satire, and I would just ignore the whole thing +if it wasn't (except for the technical memo part), but friends of mine +considered it to be somewhat reasonable. This is a adapted version of parts of +the discussions we had, risking becoming a gigantic showcase of +[Poe's law][poes-law-wiki]. + +In this piece, I will argument against his view, and propose an alternative +approach to improve hiring. + +It is common to find people saying how broken technical hiring is, as well put +in words by a phrase on [this comment][hn-satire]: + +> Everyone loves to read and write about how developer interviewing is flawed, +> but no one wants to go out on a limb and make suggestions about how to improve +> it. + +I guess Slava was trying to not fall on this trap, and make a suggestion on how +to improve instead, which all went terribly wrong. + +[how-to-interview-engineers]: https://defmacro.substack.com/p/how-to-interview-engineers +[poes-law-comment]: https://defmacro.substack.com/p/how-to-interview-engineers/comments#comment-599996 +[slava-on-satire]: https://twitter.com/spakhm/status/1315754730740617216 +[poes-law-wiki]: https://en.wikipedia.org/wiki/Poe%27s_law +[hn-satire]: https://news.ycombinator.com/item?id=24757511 + +## What not to do + +### Time candidates + +Timing the candidate shows up on the "talent" and "judgment" sections, and they +are both bad ideas for the same reason: programming is not a performance. + +What do e-sports, musicians, actors and athletes have in common: performance +psychologists. + +For a pianist, their state of mind during concerts is crucial: they not only +must be able to deal with stage anxiety, but to become really successful they +will have to learn how to exploit it. The time window of the concert is what +people practice thousands of hours for, and it is what defines one's career, +since how well all the practice went is irrelevant to the nature of the +profession. Being able to leverage stage anxiety is an actual goal of them. + +That is also applicable to athletes, where the execution during a competition +makes them sink or swim, regardless of how all the training was. + +The same cannot be said about composers, though. They are more like book +writers, where the value is not on very few moments with high adrenaline, but on +the aggregate over hours, days, weeks, months and years. A composer may have a +deadline to finish a song in five weeks, but it doesn't really matter if it is +done on a single night, every morning between 6 and 9, at the very last week, or +any other way. No rigid time structure applies, only whatever fits best to the +composer. + +Programming is more like composing than doing a concert, which is another way of +saying that programming is not a performance. People don't practice algorithms +for months to keep them at their fingertips, so that finally in a single +afternoon they can sit down and write everything at once in a rigid 4 hours +window, and launch it immediately after. + +Instead software is built iteratively, by making small additions, than +refactoring the implementation, fixing bugs, writing a lot at once, *etc*. +all while they get a firmer grasp of the problem, stop to think about it, come +up with new ideas, *etc*. + +Some specifically plan for including spaced pauses, and call it +"[Hammock Driven Development][hammock-driven-development]", which is just +artist's "creative idleness" for hackers. + +Unless you're hiring for a live coding group, a competitive programming team, or +a professional live demoer, timing the candidate that way is more harmful than +useful. This type of timing doesn't find good programmers, it finds performant +programmers, which isn't the same thing, and you'll end up with people who can +do great work on small problems but who might be unable to deal with big +problems, and loose those who can very well handle huge problems, slowly. If you +are lucky you'll get performant people who can also handle big problems on the +long term, but maybe not. + +An incident is the closest to a "performance" that it gets, and yet it is still +dramatically different. Surely it is a high stress scenario, but while people +are trying to find a root cause and solve the problem, only the downtime itself +is visible to the exterior. It is like being part of the support staff backstage +during a play: even though execution matters, you're still not on the spot. +During an incident you're doing debugging in anger rather than live coding. + +Although giving a candidate the task to write a "technical memo" has +potential to get a measure of the written communication skills of someone, doing +so in a hard time window also misses the point for the same reasons. + +[hammock-driven-development]: https://www.youtube.com/watch?v=f84n5oFoZBc + +### Pay attention to typing speed + +Typing is speed in never the bottleneck of a programmer, no matter how great +they are. + +As [Dijkstra said][dijkstra-typing]: + +> But programming, when stripped of all its circumstantial irrelevancies, boils +> down to no more and no less than very effective thinking so as to avoid +> unmastered complexity, to very vigorous separation of your many different +> concerns. + +In other words, programming is not about typing, it is about thinking. + +Otherwise, the way to get those star programmers that can't type fast enough a +huge productivity boost is to give them a touch typing course. If they are so +productive with typing speed being a limitation, imagine what they could +accomplish if they had razor sharp touch typing skills? + +Also, why stop there? A good touch typist can do 90 WPM (words per minute), and +a great one can do 120 WPM, but with a stenography keyboard they get to 200 +WPM+. That is double the productivity! Why not try +[speech-to-text][perl-out-loud]? Make them all use [J][j-lang] so they all need +to type less! How come nobody thought of that? + +And if someone couldn't solve the programming puzzle in the given time window, +but could come back in the following day with an implementation that is not only +faster, but uses less memory, was simpler to understand and easier to read than +anybody else? You'd be losing that person too. + +[dijkstra-typing]: https://www.cs.utexas.edu/users/EWD/transcriptions/EWD05xx/EWD512.html +[j-lang]: https://www.jsoftware.com/#/ +[perl-out-loud]: https://www.youtube.com/watch?v=Mz3JeYfBTcY + +### IQ + +For "building an extraordinary team at a hard technology startup", intelligence +is not the most important, [determination is][pg-determination]. + +And talent isn't "IQ specialized for engineers". IQ itself isn't a measure of how +intelligent someone is. Ever since Alfred Binet with Théodore Simon started to +formalize what would become IQ tests years later, they already acknowledged +limitations of the technique for measuring intelligence, which is +[still true today][scihub-paper]. + +So having a high IQ tells only how smart people are for a particular aspect of +intelligence, which is not representative of programming. There are numerous +aspects of programming that are covered by IQ measurement: how to name variables +and functions, how to create models which are compatible with schema evolution, +how to make the system dynamic for runtime parameterization without making it +fragile, how to measure and observe performance and availability, how to pick +between acquiring and paying technical debt, *etc*. + +Not to say about everything else that a programmer does that is not purely +programming. Saying high IQ correlates with great programming is a stretch, at +best. + +[pg-determination]: http://www.paulgraham.com/determination.html +[scihub-paper]: https://sci-hub.do/https://psycnet.apa.org/doiLanding?doi=10.1037%2F1076-8971.6.1.33 + +### Ditch HR + +Slava tangentially picks on HR, and I will digress on that a bit: + +> A good rule of thumb is that if a question could be asked by an intern in HR, +> it's a non-differential signaling question. + +Stretching it, this is a rather snobbish view of HR. Why is it that an intern in +HR can't make signaling questions? Could the same be said of an intern in +engineering? + +In other words: is the question not signaling because the one +asking is from HR, or because the one asking is an intern? If the latter, than +he's just arguing that interns have no place in interviewing, but if the former +than he was picking on HR. + +Extrapolating that, it is common to find people who don't value HR's work, and +only see them as inferiors doing unpleasant work, and who aren't capable enough +(or *smart* enough) to learn programming. + +This is equivalent to people who work primarily on backend, and see others working on +frontend struggling and say: "isn't it just building views and showing them on +the browser? How could it possibly be that hard? I bet I could do it better, +with 20% of code". As you already know, the answer to it is "well, why don't you +go do it, then?". + +This sense of superiority ignores the fact that HR have actual professionals +doing actual hard work, not unlike programmers. If HR is inferior and so easy, +why not automate everything away and get rid of a whole department? + +I don't attribute this world view to Slava, this is only an extrapolation of a +snippet of the article. + +### Draconian mistreating of candidates + +If I found out that people employed theatrics in my interview so that I could +feel I've "earned the privilege to work at your company", I would quit. + +If your moral compass is so broken that you are comfortable mistreating me while +I'm a candidate, I immediately assume you will also mistreat me as an employee, +and that the company is not a good place to work, as +[evil begets stupidity][evil-begets-stupidity]: + +> But the other reason programmers are fussy, I think, is that evil begets +> stupidity. An organization that wins by exercising power starts to lose the +> ability to win by doing better work. And it's not fun for a smart person to +> work in a place where the best ideas aren't the ones that win. I think the +> reason Google embraced "Don't be evil" so eagerly was not so much to impress +> the outside world as to inoculate themselves against arrogance. + +Paul Graham goes beyond "don't be evil" with a better motto: +"[be good][pg-be-good]". + +Abusing the asymmetric nature of an interview to increase the chance that the +candidate will accept the offer is, well, abusive. I doubt a solid team can +actually be built on such poor foundations, surrounded by such evil measures. + +And if you really want to give engineers "the measure of whoever they're going +to be working with", there are plenty of reasonable ways of doing it that don't +include performing fake interviews. + +[pg-be-good]: http://www.paulgraham.com/good.html +[evil-begets-stupidity]: http://www.paulgraham.com/apple.html + +### Personality tests + +Personality tests around the world need to be a) translated, b) adapted and c) +validated. Even though a given test may be applicable and useful in a country, +this doesn't imply it will work for other countries. + +Not only tests usually come with translation guidelines, but also its +applicability needs to be validated again after the translation and adaptation +is done to see if the test still measures what it is supposed to. + +That is also true within the same language. If a test is shown to work in +England, it may not work in New Zealand, in spite of both speaking english. The +cultural context difference is influent to the point of invalidating a test and +making it be no longer valid. + +Irregardless of the validity of the proposed "big five" personality test, +saying "just use attributes x, y and z this test and you'll be fine" is a rough +simplification, much like saying "just use Raft for distributed systems, after +all it has been proven to work" shows he throws all of that background away. + +So much as applying personality tests themselves is not a trivial task, and +psychologists do need special training to become able to effectively apply one. + +### More cargo culting + +He calls the ill-defined "industry standard" to be cargo-culting, but his +proposal isn't sound enough to not become one. + +Even if the ideas were good, they aren't solid enough, or based on solid +enough things to make them stand out by themselves. Why is it that talent, +judgment and personality are required to determine the fitness of a good +candidate? Why not 2, 5, or 20 things? Why those specific 3? Why is talent +defined like that? Is it just because he found talent to be like that? + +Isn't that definitionally also +[cargo-culting][cargo-culting][^cargo-culting-archive]? Isn't he just repeating +whatever he found to work form him, without understanding why? + +What Feynman proposes is actually the opposite: + +> In summary, the idea is to try to give **all** of the information to help others +> to judge the value of your contribution; not just the information that leads +> to judgment in one particular direction or another. + +What Slava did was just another form of cargo culting, but this was one that he +believed to work. + +[cargo-culting]: http://calteches.library.caltech.edu/51/2/CargoCult.htm +[^cargo-culting-archive]: [Archived version](https://web.archive.org/web/20201003090303/http://calteches.library.caltech.edu/51/2/CargoCult.htm). + +## What to do + +I will not give you a list of things that "worked for me, thus they are +correct". I won't either critique the current "industry standard", nor what I've +learned from interviewing engineers. + +Instead, I'd like to invite you to learn from history, and from what other +professionals have to teach us. + +Programming isn't an odd profession, where everything about it is different from +anything else. It is just another episode in the "technology" series, which has +seasons since before recorded history. It may be an episode where things move a +bit faster, but it is fundamentally the same. + +So here is the key idea: what people did *before* software engineering? + +What hiring is like for engineers in other areas? Don't civil, electrical and +other types of engineering exist for much, much longer than software engineering +does? What have those centuries of accumulated experience thought the world +about technical hiring? + +What studies were performed on the different success rate of interviewing +strategies? What have they done right and what have they done wrong? + +What is the purpose of HR? Why do they even exist? Do we need them, and if so, +what for? What is the value they bring, since everybody insist on building an HR +department in their companies? Is the existence of HR another form of cargo +culting? + +What is industrial and organizational psychology? What is that field of study? +What do they specialize in? What have they learned since the discipline +appeared? What have they done right and wrong over history? Is is the current +academic consensus on that area? What is a hot debate topic in academia on that +area? What is the current bleeding edge of research? What can they teach us +about hiring? What can they teach us about technical hiring? + +## Conclusion + +If all I've said makes me a "no hire" in the proposed framework, I'm really +glad. + +This says less about my programming skills, and more about the employer's world +view, and I hope not to be fooled into applying for a company that adopts this +one. + +Claiming to be selecting "extraordinary engineers" isn't an excuse to reinvent +the wheel, poorly. |