Posts Tagged ‘clojure’
Posted by Jakub Holý on March 31, 2014
- Timo Mihaljov’s Pimp My REPL (3/2014)- really great tips – user.clj, :dev profile, user-wide config in .lein/profiles.clj, tools.namespace, making funs available everywhere & more via Vinyasa, form println with Spyscope, debug-repl, difform, clj-ns-browser
- clj-ds – Clojure immutable datastructures extracted from Clojure and made easier for use directly in Java
Posted in General, Top links of month | Tagged: clojure | Leave a Comment »
Posted by Jakub Holý on February 28, 2014
- Nathan Marz: Principles of Software Engineering, Part 1 - Nathan has worked with Big Data at Twitter and other places and really knows the perils or large, distributed, real-time systems and this post contains plenty of valuable advice for making robust, reliable SW. Main message: “there’s a lot of uncertainty in software engineering“; every SW operates correctly only for a certain range of inputs (including volume, HW it runs on, …) and you never control all of them so there always is an opportunity for failure; you can’t predict what inputs you will encounter in the wild. “[..] while software is deterministic, you can’t treat it as deterministic in any sort of practical sense if you want to build robust software.” “Making software robust is an iterative process: you build and test it as best you can, but inevitably in production you’ll discover new areas of the input space that lead to failure. Like rockets, it’s crucial to have excellent monitoring in place so that these issues can be diagnosed.“. From the content: Sources of uncertainty (bugs, humans, requirements, inputs, ..), Engineering for uncertainty (minimize dependencies, lessen % of cascading failure [JH: -> Hystrix], measure and monitor)
- Suffering-oriented programming is certainly also worth reading (summary: do not start with great designs; only start generalizing and creating libs when you have suffered enough from doing things more manually and thus learned the domain; make it possible > make it beautiful > make it fast, repeat)
- ThoughtWorks open-sources Go, continuous delivery platform - good bye, Jenkins! – better support for pipelines etc., see features and elementary concepts
- Cloud Design Patterns: Prescriptive Architecture Guidance for Cloud Applications (recommended by @markusbk so it must be good); Patterns: Cache-aside, Circuit Breaker, Compensating Transaction, Competing Consumers, Compute Resource Consolidation, Command and Query Responsibility Segregation (CQRS), Event Sourcing, External Configuration Store, Federated Identity, Gatekeeper, Health Endpoint Monitoring, Index Table, Leader Election, Materialized View, Pipes and Filters, Priority Queue, Queue-based Load Leveling, Retry, Runtime Reconfiguration, Scheduler Agent Supervisor, (data) Sharding, Static Content Hosting (-> CDN), Throttling, Valet Key.
Guidance topics: Asynchronous Messaging Primer, Autoscaling, Caching, Compute Partitioning, Data Consistency Primer, Data Partitioning, Data Replication and Synchronization, Instrumentation and Telemetry, Multiple Datacenter Deployment, Service Metering
- MOOC course Functional programming with Clojure at Uni of Helsinki – to get started you need, I suppose, follow the “Material and course content” – essentially read the text for each chapter, clone its repo, submit pull requests to get your work graded
- Jez Humble: The Case for Continuous Delivery - read to persuade manager about CD: “Still, many managers and executives remain unconvinced as to the benefits [of CD], and would like to know more about the economic drivers behind CD.” CD reduces waste: “[..]online controlled experiments (A/B tests) at Amazon. This approach created hundreds of millions of dollars of value[..],” reduces risks: “[..] Etsy, has a great presentation which describes how deploying more frequently improves the stability of web services.” CD makes development cheaper by reducing the cost of non-value-adding activities such as integration and testing. F.ex. HP got dev. costs down by 40%, dev cost/program by 78%
- Request Quest (via @jraregris) – entertaining and educational intractive quiz regarding what does (not) trigger a request in browsers and differences between them (and deviances from the standard) – img, script, css, etc.
- The REST Statelessness Constraint - a nice post about statelessness in REST if you, like me, don’t know REST so much in depth; highlights: Statelesness (and thus the requirement for clients to send their state with every request) is a trade-off crucial for web-scale and partially balanced by caching – while typical enterprise apps have different needs (more state, less scale) so REST isn’t a perfect match. Distinguish application (client-side) and server (resources) state. Using a DB to hold the state still violates the requirement. Use links to transfer some state (e.g. contain a link to fetch the next page of records in the response).
- CodeMesh 2013 presentations - good stuff! F.ex. Refactoring Functional Programs: Past and Future, Distribution, Scale and Flexibility with ZeroMQ, Deepak Giridharagopal on Puppet, Immutable Deployments, Analyzing Systems with PuppetDB, Francesco Cesarini and Viktor Klang on the Reactive Manifesto and more
- Cognitive Biases in Times of Uncertainty - people under pressure/stress start to focus on risks over gains and (very) short-term rather than long-term and thus also adopt 0-some mindset (i.e. if sb. else wins, I loose) => polarization into we x them and focus on getting as big piece of the cake possible at any price, now, dismissal of collaboration. With accelerating rate of change in the society due to technology, this is exactly what is happening. How to counter it? Create more positive narratives than the threat-based ones (views of the world), support them via short-term gains. Bottom line: each of us must work on spreading a more positive attitude to save us from bleak future.
- Book – Nathan Marz: Big Data - I dislike the big data hype (and, with passion, Hadoop) but would love to read this book; it presents a fresh look at big data processing, heavily inspired by functional programming. Nathan has plenty of experiences from Twitter and creating Storm and Cascalog (both in Clojure, btw.). Read ch 1: A new paradigm for big data.
- Facebook Engineering: The Mature Optimization Handbook (or go directly to the pdf, ePub, Mobi). If you get bored, jump directly to ch 5. Instrumentation.
Posted by Jakub Holý on December 31, 2013
- HBR: Want to Build Resilience? Kill the Complexity – a highly interesting, thought provoking article relevant both to technology in particular and the society in general; f.ex.: more security features are bad for they make us behave less safely (risk compensation) and are more fragile w.r.t. unexpected events. “Complexity is a clear and present danger to both firms and the global financial system: it makes both much harder to manage, govern, audit, regulate and support effectively in times of crisis. [..] Combine complex, Robust-Yet-Fragile systems, risk-compensating human psyches, and risk-homeostatic organizational cultures, and you inevitably get catastrophes of all kinds: meltdowns, economic crises, and the like.” The solution to future financial crisis is primarily not more regulation but simplification of the system – to make it easier to police, tougher to game. We also need to decrease interconnectednes (of banks etc.), one of the primary sources of complexity. Also a great example of US Army combatting complex, high-risk situations by employing “devil’s advocates / professional skeptics” trained to help “avoid the perils of overconfidence, strategic brittleness, and groupthink. The goal is to respectfully help leaders in complex situations unearth untested assumptions, consider alternative interpretations and “think like the other”“.
- The Dark Side of Technology – technologies provide great opportunities – but also risks we should be aware of – they create a world of mounting performance pressure for all of us (individuals, companies, states), accelerate the rate of change, increasing uncertanity (=> risk of Taleb’s black swans). “All of this mounting pressure has an understandable but very dangerous consequence. It draws out and intensifies certain cognitive biases [..]” – magnify our perception of risk, shrink our time horizons, foster a more and more reactive approach to the world, the “if you win, I will lose” view, erode our ability to trust anyone – and “combined effect of these cognitive biases increases the temptation to use these new digital infrastructures in a dysfunctional way: surveillance and control in all aspects of our economic, social and political life.” => “significantly increase[d] the likelihood of an economic, social and political backlash, driven by an unholy alliance between those who have power today and those who have achieved some modest degree of income and success.“
Complexity theory: the more connected a system is, the more vulnerable it becomes to cascades of disruptive information/action.
- What Do Government Agencies Have Against 23andMe, Uber, and Airbnb? – innovative startups do not fit into established rules and thus bureaucrats do not know how to handle them and resort to their favourite weapon: saying no, i.e. enforcing rules that harm them (f.ex. France recently passed a law that requires Uber etc. drivers to wait 15 min before picking up a customer so that established taxi services have it easier; wot?!)
- Nonviolent communication in action – wonderful stories about NVC being applied in difficult situations with a great success
- Quora: Michael Wolfe’s answer to Engineering Management: Why are software development task estimations regularly off by a factor of 2-3? – a wonderful story explaining to a layman why estimation is hard, on the example of a hike from SF to LA
- Johannes Brodwall: Why I stopped using Spring [IoC] – worth to read criticism of Spring by a respected and experienced architect and developer; summary – dependency injection is good bug “magical” frameworks decrease understandability and encourage unnecessarily complex code => smaller code, , easier to navigate and understand and easier to test
- Misunderstanding technical debt – a brief discussion of the various forms of tech. debt (crappy code x misaligned design and problem domain x competence debt)
- Tension and Flaws Before Health Website Crash – surprising lack of understanding and tensions between the government and contractors on HealthCare.gov – “a huge gap between the administration’s grand hopes and the practicalities of building a website that could function on opening day” – also terribly decision making, shifting requirements (what news!), management’s lack of decision power, CGI’s blame-shifting. A nice horror story. The former head knew that they should “greatly simplify the site’s functions” – but the current head wasn’t able to “talk them out of it”.
- The Log: What every software engineer should know about real-time data’s unifying abstraction – logs are everywhere and especially important in distributed apps – DB logs, append-only logs, transaction logs – “You can’t fully understand databases, NoSQL stores, key value stores, replication, paxos, hadoop, version control, or almost any software system without understanding logs” – I have only read a small part but it looks useful
- What I Wish I Knew When Learning Haskell tl;dr
- Better Than Unit Tests – a good overview of testing approaches beyond unit tests – including “Automated Contract Testing” (ability to define a contract for a web service, use it to test it and to simulate it; see Internet of Strings for more info), Property-based Testing (test generic properties using random data/calls as with Quickcheck), Fault Injection (run on multiple VMs, simulate network failures), Simulation Testing as with Simulant.
- Use #NoEstimates to create options and deliver value reliably – a brief post with an example of an estimation-based vs. no-estimates project (i.e. more focus on delivering early, discovery)
- How Google Sold Its Engineers on Management – managers may be useful after all :-); a report about Google’s research into management and subsequent (sometimes radical) improvements in management style/skills and people satisfaction; I love that Google hasn’t HR but “people ops”
- Roy Osherove: Technical Disobedience – take nothing for granted, don’t let the system/process stop you, be creative about finding ways to improve your team’s productivity; there always is a way. Nice examples.
- Uncle Bob: Extreme Programming, a Reflection – a reflection on changes in the past ~ 14 years since XP that have seen many of the “extreme” practices becoming mainstream
- The Anti-Meeting Manifesto – essentially a checklist and tips for limitting meetings to minimum
- Ethics Daily – a freuently published collection of ethics-related links, articles, talks etc.
- British Library uploads one million public domain images to the net for remix and reuse – from 17th-19th century books, available at Flicker; it asks for help categorizing and documenting them, metadata of the images at GitHub (with links to Flicker); great project, interesting pics
- The Software Engineers’ Oath – lets bring ethics back to our daily (work) lives – respect the knowledge of others, use technology for good (!!!), keep learning, writing code for people, not ashamed to admit lack of knowledge, respect for privacy, obligation to make lifes of humans better, …
- David Pollak: Some musings on Scala and Clojure by a long time Scala dude (46 min) – a subjective but balanced comparison of Scala and Clojure and their strengths/weaknesses by the author of the Scala Lift framework (doing Scala since 2006, Clojure since 2013)
- Apache Sirona – a new monitoring tool in the Apache incubator – “a simple but extensible monitoring solution for Java applications” with support for HTTP, JDBC, JAX-RS, CDI, ehcache, with data published e.g. to Graphite or Square Cube. It is still very new.
- GenieJS – Ctrl-Space to popup a command-prompt for your web page, inspired by Alfred (type ‘ to see all possible commands)
A good #agile team considers their backlog inaccurate. It is merely a list of assumptions that must be tested & refined by shipping product
- @mick maguire 12/10
Ada Lovelace (1st program), Grace Hopper (1st compiler), Adele Goldberg (1st OO language), why would anyone think women aren’t in computing?
- @Dan North 12/11
There will always be a shortage of talented, self-motivated creative professionals who will unquestioningly follow orders.
- @Thomas K Nilsson 12/7
Estimation paradox = If something unpredictable happens, predict how long it will take to fix it
- me 12/7
IT systems can be inspired by AK-47 a.k.a. Kalashnikov. The rifle was purposefully designed to be simple and to be tolerant to imperfections in most parts; as a result, it required essentially no maintenance and was extremely reliable.
- summarized from Roman Pichlík’s Odkaz Michaila Kalašnikova softwarovému vývoji
Posted by Jakub Holý on November 30, 2013
Some interesting topics this time despite me spending lot of time on the Principles of Reactive Programming course: Java x Node.js, REST x other future-proof architectures, scary legacy code. Of course, also plenty of Clojure.
People, organizations, teams, development:
- Chris Argyris (1923-2013): An Appreciation – Thinkers 50 – recently departed Ch. Argyris is a person whose work you should know, if a bit interested in learning and organizations and how they (dis)function; and since we all work in organizations and want our work to be pleasant, this means all of us. We all want to work in orgs that do double-loop learning, i.e. they actually evovle as they learn. “Argyris argued that organizations depend fundamentally on people and that personal development is and can be related to work.” Now stop and go read it!
- Bob Marshall: The Antimatter Principle – “the only principle we need for becoming wildly effective at collaborative knowledge work” – can be summarized as “attend to folks’ needs” (importantly, including your own) => find out what people actually need, interpret their behavior (including anger, seemingly irrational or stupid requests etc.) in terms of needs; mastering this will make you excell in communication and effective work. Read the post to find out more.
- It’s a state of mind: some practical indicators on doing agile vs. being agile – are you agile or are just “doing agile”? Read on ti find out, if you dare! F.ex. “Non Agile teams have a process that slows the review of the changes.” Cocnlusion: “An Agile mindset is just that – a state of mind, a set of values. Its a constant questioning, and an opening up to possibilities. Its a predisposition to produce great things.“
- Johannes Brodwall: Humble architects – how to avoid being an architect that does more harm than good, as so many out there? Some tips: Don’t assume stupidity, Be aware that you might be wrong, Be careful with technology (i.e. simplicity beats everything; applies so much to us developers too!), Consistency isn’t as important as you think (or beware context), Tactical reuse in across systems is suboptimization (i.e. reuse has a cost), separate between (coding) rules and dogma (i.e. is that way unsafe, incomprehensible, or just a heresy w.r.t. a dogma?) Very valuable insights into creating good technical solutions and teams that work.
- Liz Keogh’s The Dream Team Nightmare: a Review – a very good review of this adventure-style book about coaching “agile” teams through (around?) common pitfalls, provides a good base for deciding whether you shall read the book (Liz essentially says yes)
- Fibonacci Kittens: One Idea One Commit – a short story of coming from biannual releases to frequent release of individual features; I link to this primarily to spread optimism, if this company managed it then, perhaps, we other can too?
- The Eternal Struggle Between Business and Programmers – “Business: More features! Now! Programmers: More refactoring! Now!” How can we resolve this eternal conflict of needs? This post reveals how the two parties can find a common ground and mutual understanding (beware, everybody must give up on something) and thus work together rather than against each other.
Coding, architecture, legacy
- Why the future is NOT RESTful – always refreshing to read something against the mainstream; “REST is not fit for the next generation of smart client applications because it has not been designed for smart clients.” According to the author, a smart client app stack needs: “1. persistence (storage and query), 2. documents/orm (conversion to tree-like datastructures), 3. data authorization (once authenticated), 4. pub/sub (websocket communications), 5. client db (client-side caching and querying), 6. templating (presentation level)” Meteor.js has nearly all but #3 thanks to mongodb (1+2), dpp (4), mongo on the client (5), spark (6). The author considers a similar but Clojure-based stack (with Datomic, Angular etc.) and looks at authorization possibilities. “Secured, personalised, CRUD operations are the future to a more simplified web.” We may agree or not but it certainly is worth reading.
- Michael Feathers (of Working Effectively With Legacy fame): Unconditional Programming – “Over and over again, I find that better code has fewer if-statements, fewer switches, and fewer loops. Often this happens because developers are using languages with better abstractions. [..] The problem with control structures is that they often make it easy to modify code in bad ways.” Includes a nice example of replacing if-else with much more readable and safer code.
- The Quality of Embedded Software, or the Mess Has Happened – an interesting and scary read about terrible spaghetti code (and hardware) that makes some Toyotas to accelerate when the driver tries to break; 11,000 global variables, the key function showing so high cyclomatix complexity that “makes it impossible not only to test but even maintain this program in any way.” Then 80k violations of the car industry coding standard cannot surprise. And a safety control that does not work. Interesting that a great manufacturer may have so terrible IT (and Toyota isn’t the only one).
- The string type is broken – the String type is M. Feathers’ favourite example of a leaky abstraction – most languages fail to process/split/count less common Unicode characters properly, the fact that String is implemented as a series of bytes leaks through (UTF-16 langs like Java); worth reading to be aware of the limitations
- Why I’m Productive In Clojure – some interesting points about simplicity, consciousness, interactive development, power without overwhelming fatures, etc. “With it [Clojure] I can always easily derive a solution to a particular problem from a small set of general patterns. [..] However, the number of ways that these concepts can be combined to solve all manner of problems appears to be inexhaustible.“
- Node.js at PayPal – PayPal is switching from Java to Node.js (among others to promote language consistency) and, as a part of that, has implemented the same app in Node and Java; results: Node was done earlier, had less code, performed better (though, as Daniel Kvasnička pointed out, “Comparing Node.js and servlet-based archs is not fair… compare Node with @vertx_project and you’ll get a whole different story ;)”; also, as Charles Nutter said, “The
@PayPal numbers for their Java to Node move are absurd. A JVM app doing 1.8 pages/s isn’t slow…it’s broken.“)
- IBM: Developing mobile apps with Node.js and MongoDB, Part 1: A team’s methods and results – also IBM has implemented the same (REST) app once with Java and DB2, once with Node and Mongo where Node+Mongo required less work and performed better; one of the great wins was having JSON as a native structure everywhere instead of transforming from/to it so Mongo is, in my opinion, an important factor in this particular case
- Dynamics of Programming: Benefits of Scala in CS1 – reasons for and experiences with using Scala in an introductory computer science course, worth reading; some of the advantages over Java are consistency (.asInt on String and Double vs. casting/parsing, no “primitive” types), REPL with time inference good for learning, functional style enables focus on what rather than how; quite persuasive arguments
- Stuart Sierra’s Component – a library for making it easier to implement Stuart’s reloadable workflow; a component is something that can be started, stopped, and depend on other components so that it is easier to do interactive REPL development
- Logan Linn: Clojure/conj 2013 – a pretty good overview of the conference
- Caribou – “the kernel of usefulness that has emerged from years of this basic practice“- a new Clojure web framework – seems to be interesting
- Results of the 2013 State of Clojure & ClojureScript survey and drill-down into what features people want – the most interesting fact is how many more participants use Clojure in production than last year and perhaps also the relatively wide adoption of Datomic among the respondents. Light Table has become the 3rd most popular dev. env., after Emacs and Vim. Some of the most mentioned language features requested were types (=> core.typed, Prismatic’s Schema), better error reporting (=> slingshot, dire, clj-stacktrace, io.aviso:pretty, etc.), debuger (though progress is being made)
- Book: Clojure High Performance Programming
- Improving Clojure Feedback : Stack Traces – making Clojure stacktraces more usable by filtering out noise and linking to relevant content – io.aviso:pretty, io.aviso:twixt
- Clojure Dev discussion: Hashing strategies – Executive summary – “In Clojure, however, it is far more common than in Java to use longs, vectors, sets, maps and compound objects comprised of those components (e.g., a map from vectors of longs to sets) as keys in other hash maps. It appears that Java’s hash strategy is not well-tuned for this kind of usage. Clojure’s hashing for longs, vectors, sets, and maps each suffer from some weaknesses that can multiply together to create a crippling number of collisions.” Ex.: An implementation of N-Queens took forever, spending most time on hash collisions. But be calm, smart Clojurians are working on a solution.
- Datomic Pro Starter Edition – Datomic with all storages, Datomic Console, a year of updates, full Datomic programming model; limitations: no HA transactor, no integrated memcached, max 2 peers and 1 transactor
- AirPair.com – a new site that enables developers to get help from other devs via remote pairing, code review, code mentoring etc. – a good opportunity to get help / help others (and earn something); I haven’t tried it but it sounds pretty interesting
MongoDB web stacks
- Meteor: JS frontend + MongoDB backend with changes in the DB pushed live to the clients, i.e. MongoDB is used both as the “application server” and storage. It seems great for apps where users need to collaborate in real-time with each other, certainly great for quick proof of concepts etc.; worth checking out; it also comes with free (at least for start?) hosting so really good for prototyping – “an open-source platform for building top-quality web apps in a fraction of the time.” The intro screencast will give you a good overview (10 min).
- Mean.io – MEAN (Mongo, Express, Angular, Node) stack Boilerplate – frontend, backend and storage using the same language and some of the most popular technologies (not that popular = best fit for you :)); it seems to be very new but since it just glues together 4 popular and documented technologies, that should not be an obstacle. There is an intro on the MongoDB blog.
[..] no organization should exist unless it is “of service” to its employees, its customers, its community.
- @Tom_Peters 28/11
I hope you’ll agree that there is a certain amount of irony involved in having to write repetitive code
- Dmitri Sotnikov in Why I’m Productive In Clojure
Happy teams are productive teams but:
Morale is 95% a function of the prevailing system (the way the work works). Which in turn is a function of the prevailing collective mindset
- @flowchainsensei Nov 10th
Posted in General, Languages, Top links of month | Tagged: agile, book, clojure, continuous_deployment, diy, legacy, mongodb, nodejs, SbE, scala, security | Comments Off
Posted by Jakub Holý on October 31, 2013
- Google engineers insist 20% time is not dead—it’s just turned into 120% time – it is interesting to see how has this evolved; “I have done many engineering/coding 20% projects and other non-engineering projects, with probably 20-40% producing “real” results (which over 7 years I think has been more than worth it for the company). But these projects are generally not rewarded.” [highlight mine]
- The Worst Daily Scrum Ever – a story whose bad part is a too common reality; if energy is low, nobody asks for / offers help, and people only report status / plans then you are doing the daily scrum wrong and should stop now (but it also documents a nice example of a good, effective scrum)
- Why Responsive Design is a Waste of Time – a refreshingly critical take on responsive design; the author now aknowledges that it is sometimes worth the pain but the points are still valid – responsive design requires (lot of) extra work, the attempt to create a one-size-fits-all site of course adds considerable complexity (having two separate simple frontends might be better than one that is too complex), also many sites are good enough as they are (especially taking into account the capabilities of mobile browsers)
- How to lose $172,222 a second for 45 minutes – i.e. your bugs are likely not so serious after all :-) A financial company screwed big and ended up bankrupt. The cause? Chaotic DevOps, not removing old unused code, reusing a feature flag instead of creating a new one, lack of monitoring. The story in short: They deployed new trading code but failed to notice that it has not been deployed to one of the 8 servers; due to the flag reuse, the old, 10 years unused code has been activated instead. Due to the lack of monitoring they did not notice the cause, tried to roll back while leaving the flag enabled thus effectively activating the bad code on all the servers. => have proper automated and self-checking deployments, delete old code, do not repurpose old switches.
- 40 Inappropriate Actions to Take Against an Unlocked (Windows) PC – good tips for promoting security and having fun at the same time; I shall keep this at hand :-)
- How to go about ‘proving’ why dynamically typed languages are better – a cultivated and interesting discussion; as argueed, thinking in this direction is itself wrong and in different contexts, different languages will be more appropriate. I also like Phil Lord’s “Programming is a highly fashion-centric occupation for any number of reasons.” and “For me, the main advantage is that you are not forced to build complex hierarchies just to support the type system ([..]), and that having only a few abstractions makes it worthwhile adding lots of functions operating over them.” and L. Petit’s “IMHO, the question is irrelevant. It implicitly assumes that statically typed vs dynamically typed is a black / white choice, and that either ‘static wins over dynamic’ or ‘dynamic wins over static’ will be a true statement whatever the context.” Also a good observation that types are only a subset of function contract enforcement and one of possible implementations.
- The Failure of Governmental IT (Learnings From HealthCare.gov) – links to a few really good articles about the problems with governmental IT in general and my summary of them
- Inside the Arctic Circle, Where Your Facebook Data Lives – the designs of data centers used to be proprietary secrets until Fb developed its own and open-sourced them, enabling many Asian manufactures to start creating cheaper datacenters and thus started a revolution in this domain. Facebook’s data centers are not general purpose but suitable ot the kind of work they need, but it is still widely applicable. Cool to see how they use natural conditions to get energy needs down and make HW that fits best their needs – that is what I call innovation!
- Academia.edu (via @RiczWest) – a rich source of free research papers – just register as an independant researcher; also lean/agile/systems thinking and other interesting topics
+ Username +
- Johannes Brodwall: A canonical web test – a simple web app end-to-end smoke test – using an embedded Jetty, a test DB (preferably in-memory), WebDriver to test it (simple: browser.get(“/people”), assertThat(browser.findElement(<person id>.contains(<person’s name>)); simple, nice, useful
- LearnGitBranching – an online game to learn branching & rebase in git; use the menu in the lower-right corner to navigate between the levels etc. You can also execute commands “show goal”, “hint”, “level” to navigate around; pretty cool and great for learning the command line commands
Society & people
Not a typical topic I share here but really worth it this time.
- The ocean is broken – a saddening story worth reading to learn what does your tuna sandwitch cost and where does all the plastic we use end up. From a sailing trip from Melbourne to US where there were plenty of fish (and birds) 10 years ago – and 2 this year, killed to a noticable degree by huge fishing ships that catch tuna – and kill and throw away all the other “junk” fish. Nowadays fish are replaced by plastic and other waste that actually prevents usage of the engine unless somebody can watch for dangerous nets and ropes leftovers. Earth, where are you falling to?
- The Guardian: Why have young people in Japan stopped having sex? – sad and interesting to observe what happens when the system is set up so that people “can’t be bothered” to have inter-sexual relationships, partnership, and children. Japan needs a good deal of systems thinking to fix its broken society where women do not want children because it would cost them their career and neither men nor women are willing to subjects themselves to the social pressure and demands associated with relationships.
- The Guardian: 29 million people enslaved, says first global index on slavery – welcome to the 21st century! The leading slave countries are India (14M), China (3M), Pakistan (2M). Also, slaves are building the world cup stadion in Qatar.
- They’re Taking Over! – how we managed to destroy sea ecosystems and helped the now unstoppable return of jellyfish – Jellyfish are evidently very veried and extemely resilient and have been hold at bay only by rather complex ecosystems that we managed to destabilize so much that Jellyfish are on their way back to ruling all the sees again (destroying the rests of the ecosystems – i.e. fish – on the way); a sad future for the sea, Earht, and us
- LightTable 0.5.9 got elementary paredit commands
- Amazonica: A comprehensive Clojure client for the entire Amazon AWS api – best with a REPL!
- Clojure Understood: the Rush Hour Platform – application of the design best practices promoted in the Clojure community (separation of concerns, simplicity, …) on a project – “highly accurate vehicle traffic simulations”; I have only started reading it but it looks highly interesting
- Clojure content at InfoQ – articles, news, interviews, presentations etc.
- A bitter taste [of EuroClojure] – we as a community must embrace diversity and stop fostering our egos by mocking other than our holy editor (and, I would add, by mocking other languages and in general mocking whatever); respect and open minds, please!
- Garden – Clojure alternative to scss/less – still needs time to mature and gain tooling support but it is cool that it exists
- C. Emerick’s Austin, the ClojureScript REPL over nREPL – 1) Start nREPL (via lein repl, from your editor…), 2.a) Execute austin’s exec to start a ClojureScript REPL in it, backed by headless PhantomJS or a real browser – or, alternatively, 2.b) create a C.S. REPL connected to your webapp, as described in the browser-connected-repl-sample. You should watch this 8 min demo.
- WhiteHat Aviator – A Safer Web Browser – WhiteHat, a well-known security company, has released a browser that aims at improving privacy by preventing user tracking (f.ex. but not sending referral URL) and blocking ads even at the cost of occassional slight discomfort, i.e. something that the mainstream browsers are not interested in. So far for OS X only.
- EnvPane – a preference pane for environment variables for Mac OS X 10.8 (Mountain Lion) – set env. vars for GUI/terminal apps, no need to log out upon change
Weinberg: Bureaucracy is what we do when we no longer remember why we are doing it
- via Ben Simo, no source specified so it may be fake but anyway it is valid
Posted in General, Languages, Testing, Top links of month | Tagged: aws, clojure, ClojureScript, design, earth, ecology, Git, innovation, privacy, science, scrum, security | 4 Comments »
Posted by Jakub Holý on October 28, 2013
EuroClojure 2013 was a nice, small conference. The talks were mostly interesting and often useful and it was wonderful to meet in reality people I only knew from the virtual life or from stories. You can get an impression what it was like from the #euroclojure tweets.
Below are some noteworthy things from the talks and chats.
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Posted in Languages | Tagged: clojure, conference | Comments Off
Posted by Jakub Holý on September 30, 2013
- Stuff The Internet Says On Scalability For September 13, 2013 – a collection of interesting performance related articles with summaries (via @_dagi)
- Can you copy a culture? The NUMMI story (audio/transcript) – how the GM factory with the worst workforce has been turned around via a good application of Toyota Production System – “a truly inspiring story of human potential and how systems can be designed to bring the best or worst of of people.” And how GM failed to learn from it and to copy Toyota’s culture.
- The Reactive Manifesto – why to write reactive SW – “Reactive applications represent a balanced approach to addressing a wide range of contemporary challenges in software development. Building on an event-driven, message-based foundation, they provide the tools needed to ensure scalability and resilience. On top of this they support rich, responsive user interactions. We expect that a rapidly increasing number of systems will follow this blueprint in the years ahead.“
- NYT: Eiji Toyoda, Promoter of the Toyota Way and Engineer of Its Growth, Dies at 100 – learn about the life of one of the founders of lean thinking
- Gojko Adzic: How we solved our #1 product management problem – valuable experience of false assumptions, learning from users, and a much helpful UI remake: even if you build a product to scratch your itch, you have to test it with real users
- Don’t use Hadoop – your data isn’t that big – a great post about the downside of Hadoop and that there are much better options (large disks, large RAM, Pandas/R/Postgres) for data up to few TBs. “In addition to being more difficult to code for, Hadoop will also nearly always be slower than the simpler alternatives.”
- Gartner On Big Data: Everyone’s Doing It, No One Knows Why – golf talk / hype -driven initiatives FTW! “According to a recent Gartner report, 64% of enterprises surveyed indicate that they’re deploying or planning Big Data projects. Yet even more acknowledge that they still don’t know what to do with Big Data.”
- What makes Spark exciting – why it might be a good replacement for Hive/Hadoop, based on experiences with H/H: “Hive has served us well for quite a while now. [...] That said, it has gotten to the point where Hive is more frequently invoked in negative contexts (“damn it, Hive”) than positive. (Primarily due to being hard to test, hard to extend.)” “We had heard about Spark, but did not start trying it until being so impressed by the Spark presentation at AWS re:Invent [..] that we wanted to learn more. [..] Spark, either intentionally or serendipitously, addresses both of Hive’s primary shortcomings, and turns them into huge strengths. (Easy to test, extend.) [..] I find the codebase small and very easy to read, [..] –which is a nice consolation compared to the daunting codebases of Hadoop and Hive.” Cons.: Spark is only pre-1.0, the author hasn’t yet tested it heavily.
- 10 Ways to Make Your Office Fun To Work In – because we spend there plenty of our time so why not have a pleasant/cosy, inspiring environment? Some tips: plants, not-your-boring-enteprprise-look-and-feel, open it to the nature (I want this!), design it as home, not office, provide play space (I am too into work to want to play but having a resting place for a nap is st. I’d love).
- Book: The Architecture of Open Source Applications (via @rmz) – learn by studying architectures of existing systems – “In these two books, the authors of four dozen open source applications explain how their software is structured, and why. What are each program’s major components? How do they interact? And what did their builders learn during their development?“
- Book: Seven Concurrency Models in Seven Weeks: When Threads Unravel – “how to exploit different parallel architectures to improve your code’s performance, scalability, and resilience” – threads & locks, actors, FP + immutability/futures/promisses, Software Transactional Memory etc., GPU, MapReduce on clusters, … (intro) Personally, I would prefer from theory to practice approach and mention of CSP (-> Go’s channels, core.async) and more.
- Books Amazon CEO requires his top execs to read (The Effective Executive by Peter Drucker, The Innovator’s Solution by Clayton Christensen, The Goal by Eliyahu Goldratt)
- Stanford engineers build computer using carbon nanotube technology (via
- NYT: The Banality of Systemic Evil – a good article about human tendency to “obey the system” thus potentially causing evil – and thus the need to resist the system, as heroic individuals such as Snowden, Hammond, Schwartz, Manning. See the famous Eichmann in Jerusalem for how “doing your job” can create evil – “[..] what happens when people play their “proper” roles within a system, following prescribed conduct with respect to that system, while remaining blind to the moral consequences of what the system was doing — or at least compartmentalizing and ignoring those consequences.” (Tip: The book Moral Mazes explores the ethics of decision making within several corporate bureaucracies => mid-managers rules of life: (1) never go around your boss, (2) tell the boss what she wants to hear, (3) drop what she wants dropped, (4) anticipate what the boss wants so that she doesn’t need to act as a boss to get it, (5) do not report something the boss does not want reported, cover it up; the the job & keep your mouth shut.) “The bureaucracy was telling him [Snowden] to shut up and move on (in accord with the five rules in “Moral Mazes”), but Snowden felt that doing so was morally wrong.” “[..] there can be no expectation that the system will act morally of its own accord. Systems are optimized for their own survival and preventing the system from doing evil may well require breaking with organizational niceties, protocols or laws.“
- Fairphone – “A seriously cool smartphone that puts social values first” (likely the only one not built by poorly paid workers and creating too much ecological burden), for just €325. You can see detailed cost breakdown, list of suppliers, specs, and essentially everything. This is, in my opinion, super cool! Go and read the story!
- Amazonica – “A comprehensive Clojure client for the entire Amazon AWS api.”
- Talk Ritz, The Missing Clojure Tooling (40min, 9/2013) – thanks to this I finally understood how to use Ritz but it still seems not to work well, f.ex. setting a breakpoint always reported “Set 0 breakpoints” (lein ritz/middleware 0.7.0, nrepl-ritz.el 0.7.1); according to callen, debug-repl is simpler and nicer if you only care about local vars and evaluation. To try ritz: use M-x nrepl-ritz-jack-in, then M-x nrepl-ritz-break-on-exception, exec. f.ex. “(/ 1 0)”. In the poped-up buffer, t or enter to show frame locals, e to eval a code in the context of the frame etc. If you managed to trigger the debug buffer through a breakpoint, the actions lists would contain STEP etc. (See fun. nrepl-ritz-line-breakpoint)
- C. Grand’s spreadmap – “library to turn Excel spreadsheets in persistent reactive associative structures” => access content via map functions; changing a value updates formula cells using it
- Alembic Reloads your Leiningen project.clj Dependencies – add a dependency to your project.clj w/o needing to restart your REPL (just call (alembic.still/load-project), provided you have it in your lein dependencies). Limitations: cannot remove deps or change versions.
- Defeating stack overflows – techniques for transforming mutually recursive calls etc. into something that won’t blow the stack – “Priming the pump” (memoize subresults first), core.async
- Google Groups: Clean Architecture for Functional Programming – How do the Clean Architecture and the Clean Code best practices apply to FP (Clojure/Haskell)? Some points: OOP isn’t worse than FP, only people do class-oriented programming instead; OO better e.g. for UIs, combining them (func. core, imperative shell) can be sometimes best. Some clean arch. patterns are actually more like functions – “Interactors and Presenters, for example, do not maintain any state of their own. Even those objects that do imply some kind of state, such as entities and gateways, keep that state hidden behind boundaries and present a functional interface instead.“
- night-vision: Handy, super light weight debugging utility – add it to your lein profile and then call
(night-vision.goggles/introspect-ns! '<name of ns>) and it will print each entry/exit of a function within the scope of the namespace with the argument/return values
- Nil Punning (Or Null Pointers Considered Not So Bad) – a great post about why nil in Clojure is not bad contrary to Java’s null (because it is actually an object, you can call functions on it, treat it as false/empty list/map/set, most core functions work on it)
Posted by Jakub Holý on August 24, 2013
All Clojure REPL variants (nREPL, REPLy, ..) share some common characteristics, inherited from clojure.main and clojure.repl. One of them, that isn’t easy to find out (unless you read e.g. Clojure Programming) is the fact that the last three results of evaluating your code are stored in the vars
*3. The last exception that has occured is stored in
;; Inside lein repl, with the user=> prefix removed and output prefixed with ;; =>
;; => 1
;; => 2
;; => 3
;; => 4
(println "results - latest:" *1 "prev:" *2 "oldest:" *3)
;; => results - latest: 4 prev: 3 oldest: 2
;; => nil
(/ 42 0)
;; => ArithmeticException Divide by zero clojure.lang.Numbers.divide (Numbers.java:156)
(println "res" *1 "exception" *e)
;; => res nil exception #<ArithmeticException java.lang.ArithmeticException: Divide by zero>
;; => nil
clojure.repl defines in its namespace some very useful functions and macros such as
dir (prints a sorted list of public vars in a ns; ex.:
(root-cause throwable) – check out their docs at ClojureDocs/clojure.repl.
Posted in Languages | Tagged: clojure, repl | 2 Comments »
Posted by Jakub Holý on July 31, 2013
This month focuses on languages and approaches (reactive programming, F#, Erlang, FP talks etc.), agile (need for speed, recommended books), Clojure/Linux/cloud tools and libs.
- The Need For Speed – the top 10 reasons for fast development flow (with time to market being one of the less important) – more learning, focus on the MVP, focus on the puprose/goal, happier customers/leadership, better quality (sic!), higher morale (I concur!), push for cotninuous improvement, “one of the only sustainable differentiators”; => “sense of urgency and motivation”; “[..] I continue to meet people and teams that not only move very slow, they don’t understand the relationship between speed and innovation, or speed and quality.”
- agile42 Summer Reading List 2013 – books recommanded by experienced people/agile experts – lot of interesting stuff! Topics: Communication and Coaching (f.ex. Practicing Nonviolent Communication), Business (How Great Companies Get Their Mojo from Maslow ,..), Learning From the Military, Agile and Technology (e.g. The Art of Action: How Leaders Close the Gaps between Plans, Actions and Results), Agile and Technology (f.ex. The people’s Scrum)
- Dan North: Are we nearly there yet? – optimize for time to business impact; SW dev as mountaineering (impossible to estimate correctly, many unknown details, dead ends, …); go fast – but sustainable; the tyranny of backglog (there are multiple paths to the top yet backlog defines only one; have you ever considerably changed it?) “Instead we could embrace the fact that today we always know more than we did yesterday, and that tomorrow we will know even more. We can take a fresh look up the mountain every time we pause to regroup, to plan.” => we ask 1) what gives us the shortest lead time to business impact? 2) what can help us to learn/invalidate more? 3) how to assure our stakeholders we are approaching the goal?
- Joel on Software: Software Inventory (7/2012) – a classical article about the evilness of software inventory (backlogs, issue trackers, undeployed features, …) ‘When I hear about product teams that regularly have “backlog grooming” sessions, in which they carefully waste a tiny amount of time and mental energy every day or every week thinking about every single feature which will never be implemented, I want to poke my eyes out.‘
- Job satisfaction self-test: Twelve questions that define a great place to work – check yourself how satisfied you are with your job (example questions: How well do I know what is expected of me? How often in the past seven days have I received recognition or feedback on my work? How much does the mission/purpose of the company make me feel like my work is important?)
- Coaching Anti-Patterns: Prescriptive Agile – a prescriptive coach “knows” what is “right” and forces it onto the client, without listening to her; instead, we should “Meet them where they are and leave them in a better place” => “[..] my first responsibility is to understand how and why they came to this practice. How did they come to this decision? What challenges does this approach address? What benefits are they optimizing for?” Worth remembering AND practicing :)
Languages, paradigms, approaches
- The Trouble with Erlang (or Erlang is a ghetto) - an objective criticism of Erlang by somebody who seems to be quite experienced with it; as I know very little about Erlang, it was interesting to learn about its weaknesses (no map/dict data structure, slow memory management, poor “JIT,” not usable for shared-state concurrency (contrary to e.g. Clojure), immutable state is not necessary and makes some things bad, inconsistent and ugly standard lib, …)
- Adventures in Multi Paradigm Programming – different programming paradigms/approaches re-implemented in Emacs Lisp – interesting 1) to see and compare these different approaches and 2) the flexibility of Lisp. Including iteration – Ruby’s map, Python’s list comprehension ([an_expression for x in list]), Scala’s default argument (_); search – Java’s for; arguments: direct, variadic (i.e. any number of args), named args; destructuring and pattern matching in CoffeScript/OCaml style; Haskell-like monads; objects with mixins; namespaces.
- Why bugs don’t like F# – no nulls, immutable data, strong type system, composition of small functions, asynchronous programming abstractions, higher-order functions over collections (no off-by-one), units of measure
- IBM high-fives Netflix open-source tools – it is interesting to see the spreading of Netflix’s open source tools for better cloud infrastructures; f.ex. “Karyon, is what Netflix calls the base container for applications and services built using the NetflixOSS ecosystem; Eureka is mid-tier load balancing; Hystrix controls interactions between myriad distributed services to nip cascading failures in the bud; and Ribbon is a Remote Procedure Call library.”
- ZeroMQ instead of HTTP, for internal services (with implementation in Clojure) – an interesting idea of using ZeroMQ – the sockets on steroids library – instead of HTTP in a way compatible with existing HTTP routing libs; advantages of ZeroMQ: automatic retrial (=> can restart the target service withou noticing), speed, reuse of a connection. The trick is to send a http-like structure (i.e. with method, uri, body) and pass that to Compojure or similar (update: there are now Clojure/core.async bindings for ZeroMQ)
- Joel on Software: Victory Lap for Ask Patents – killing a bad Microsoft patent request in 15 minutes – Ask Patents is a new StackExchange site that enables experts to look at SW patent requests and point to previous existing works that invalidate them; as Joel describes in his successful patent kill story, it is not difficult at all. Hopefully this will manage to really help the patent office and hit woul-be patent trolls hard! #victory
- The Dangers Of “Gamification” In Education by Kathy Sierra (a former game designer, a trainer of trainers at Sun, author of the Head First book series) – gamification is often regarded as something very desirable that will improve our lives; however, as Kathy discusses, it has also dark sides and, applied unappropriately, can actually decrease our intrinsic motivation (therefore it should be nearly never used in e.g. education)
- Choosing an OSS license doesn’t need to be scary (by GitHub) – a human-readable overview of OSS licenses; you should always assign a license to your GitHub account (Add A License can help with that; otherwise it is considered to be “all rights reserved” and you are not giving back to the community (I use the same as Clojure, Eclipse Public License)
- FunctionalTalks.org – “Brilliant people giving brilliant talks on functional programming” – f.ex. Wilkes Joiner: Functional Reactive Programming, Alexander Gounares: All your cores are belong to us, Katie Miller: Superhero monads, Bryan O’Sullivan: Running A Startup On Haskell, Rich Hickey: Introduction To Clojure, John A. De Goes: Building a Data Science Platform in Scala and many more.
- Types vs. Tests: An Epic Battle? – “Amanda Laucher and Paul Snively debate solving problems through types and tests using different approaches.” – can type system replace tests or vice versa? Interesting intro into the discussion for me. Using F#, Scala & more. Same claims: types don’t pay out so much for “small” codebases but scale better than tests. Types – Tests is a spectrum, not two single extremes. When a property should hold “for all,” a type would be a good match. Inductive types (Scala, Haskell?) can become quite complex, dependant types (as in Coq) would be much nicer [if I got that right].
- Paul Irish on Web Application Development Workflow (via M. Noddeland) – if you need to do some web development but are not up to date on the state of art, this might be useful – an overview of tools, utilities, services by a Googler and the person behind Modernizr, HTML5 Boilerplate, Yeoman etc. Including effective shell & dotfiles.GH, better ssh via .ssh/config and authorized_hosts, the all-in-one dev/build tool Yeoman with live reload, BrowserStack for testing, LocalTunnel to easily share anything running locally, Chrome Dev Tools support for SASS and testing devices (emulate touch events, screen sizes), JetBrains’ WebStorm, sharing tools via setapp.me. A genous idea to use GoogleAnalytics to track usage of features in a CLI app!
Other Interesting Stuff
Azul Systems’ high-performance JVM on the Vega architecture (from The Trouble with Erlang (or Erlang is a ghetto)) looks very interesting:
The other night I tweeted “If you’re looking for a language that gets multicore concurrency right, look at how Azul implemented Java on their Vega architecture” and I definitely stand by that. Azul is a company that got a lot of smart hardware and software people together and had them work on designing a custom system which would scale to hundreds of CPU cores (up to 768 of them), heaps that topped 500 GB (up to 768GB), and had the GC pause only 10-20ms at a time. The realtime performance characteristics Azul managed to eek out of their system lead them to often describe their GC as “pauseless”.
- Discussion: How core.async compares to agents, future and promise? – future/promise: 1 producer, 1 value, multiple consumers; agent: an unbounded queue of functions mutating a single value, with multiple producers and consumers (reading the latest value produced); channel: multiple 1:1 producers/consumers, i.e. a value can only be taken once from the channel, using a bounded queue (=> slow consumers can block fast producers). As mentioned elsewhere, channels is a relatively low-level abstraction and other things can be built on the top of it.
- Clojure Tradeoffs (design implications and why you should care) – perhaps not very unbiased but interesting anyway :) (shared-memory over other computing paradigms, i.e. message-passing, dynamic over static, speed over convenience, composition over IoC, …)
- Rich Hickey’s post introducing core.async with its Go-like channels as a better alternative to a collback hell (I know everybody has already read it but it is still an important link :))
- Tools etc.
- Faster Clojure Startup with Class Data Sharing – use JVM’s capability to include any classes in its boot image and include clojure in it
- lein-ancient – checks for outdated dependencies and plugins => run “lein ancient :all”
- lein-try – a Leiningen plugin that enables you to try a library in a REPL in the context of your project without having to add it to project.clj; simply run “lein try clj-time 0.5.1″ and then in the REPL “(require ‘[clj-time.core :refer :all])” and e.g. “(date-time 1986 10 14)”
- Lemur: tool to launch a Hadoop job locally/on EMR from a job definition file + actions before/after
- Emacs: sexp fold/expand is very useful for exploring source code (hide all but the first lines of all top-level forms with hs-hide-all) – the built-in hs-minor-mode can hide/show all, or hide/show/toggle one but the keys for it are cumbersome; hideshow-org makes it possible to toggle hide/show with TAB, while preserving the original TAB behavior (it does the normal TAB first only only if nothing changes does it expand/fold); very useful!
- devdocs.io (via @palruud): “an all-in-one API documentation reader for [web] developers,” navigable via keyboard – JS, HTML, CSS, DOM, DOM events, jQuery, Underscore.js
- Kilim – a message-passing framework for Java that provides ultra-lightweight threads and facilities for fast, safe, zero-copy messaging between these threads.
- AssertJ – a library of assertions similar to fest-assert but providing a richer set of assertions (nicer API then fest-assert, according to a friend)
- NetflixOSS – Netflix, the online streaming gigant, has open-sourced many fascinating components of its cloud infrastructure such as Karyon, a blueprint for web-ready components with many features (monitoring,…), Genie/Hadoop as a Service, Servo for monitoring, Archaius for configuration management – too many to list. Check out Chris Fregly’s fluxcapacitor, a demo distributed application that uses many of the components
- Tools to keep a daemon running:
Posted by Jakub Holý on July 27, 2013
Running a Java/Clojure app as a daemon on Linux used to be hard but is pretty simple with Ubuntu Upstart (docs). The short story:
- Create an all-in one uberjar via “lein with-profile production ring uberjar” (using the lein-ring plugin; a simple lein uberjar would suffice for an app with a
- Create an upstart <service name>.conf file in /etc/init/
- Run sudo start/stop/status <service name>
And of course it works with Puppet too.
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Posted in General | Tagged: clojure, DevOps, linux | Comments Off