Sunday, April 17, 2016

Things to read when you're reading

That is, when you're not following the Warriors, or taking a walk on a beautiful spring day...

  • Google Compute Engine Incident #16007
    on this occasion our network configuration management software detected an inconsistency in the newly supplied configuration. The inconsistency was triggered by a timing quirk in the IP block removal - the IP block had been removed from one configuration file, but this change had not yet propagated to a second configuration file also used in network configuration management. In attempting to resolve this inconsistency the network management software is designed to ‘fail safe’ and revert to its current configuration rather than proceeding with the new configuration. However, in this instance a previously-unseen software bug was triggered, and instead of retaining the previous known good configuration, the management software instead removed all GCE IP blocks from the new configuration and began to push this new, incomplete configuration to the network.

    One of our core principles at Google is ‘defense in depth’, and Google’s networking systems have a number of safeguards to prevent them from propagating incorrect or invalid configurations in the event of an upstream failure or bug. These safeguards include a canary step where the configuration is deployed at a single site and that site is verified to still be working correctly, and a progressive rollout which makes changes to only a fraction of sites at a time, so that a novel failure can be caught at an early stage before it becomes widespread. In this event, the canary step correctly identified that the new configuration was unsafe. Crucially however, a second software bug in the management software did not propagate the canary step’s conclusion back to the push process, and thus the push system concluded that the new configuration was valid and began its progressive rollout.

  • Evaluating Database Compression Methods: Update
    This blog post is an update to our last post discussing database compression methods, and how they stack up against each other.

    When Vadim and I wrote about Evaluating Database Compression Methods last month, we claimed that evaluating database compression algorithms was easy these days because there are ready-to-use benchmark suites such as lzbench.

    As easy as it was to do an evaluation with this tool, it turned out it was also easy to make a mistake. Due to a bug in the benchmark we got incorrect results for the LZ4 compression algorithm, and as such made some incorrect claims and observations in the original article.

  • DIY Jepsen Testing CockroachDB
    When you work on Jepsen, you usually only look at problems (like claims to serializability and linearizability) that involve a combination of A, C, and I in a distributed environment because you can assume the database engine already worked very hard on A, C, I, and D individually. After all, these engines have been around for a while and have plenty of users already who would have complained earlier if their transactions were not atomic or durable, or if they could see gross consistency anomalies.

    In contrast, CockroachDB is still rather young, so a few more ACID checks were warranted. We figured we could learn how to use Jepsen by implementing a few simple tests first.

  • How to write a Bloom filter in C++
    Bloom filters are data structures which can efficiently determine whether an element is possibly a member of a set or definitely not a member of a set. This article will cover a simple implementation of a C++ bloom filter. It’s not going to cover what bloom filters are or much of the math behind them, as there are other great resources covering those topics.
  • Frog and Toad are Cofounders
    The characters you loved as a child, all grown up and working in San Francisco
  • Visual Studio Code 1.0!
    We wanted to build a native development tool that developers could install and use anywhere, for any source code. And, from our experience, we believed that it was important to not just have an editor, but one that could help developers accomplish their most common tasks: navigating code, debugging, and working with Git. And, so, Visual Studio Code was born.

    Being built on web technologies made it easy to host the tool in a native cross-platform shell. We decided early on to use, and contribute to, a number of open source technologies – including GitHub’s great Electron shell, which combines web and native UI with a Node.js API.

  • When Bitcoin Grows Up
    In time, even the US joined the system of state-backed money dispensed through a central bank. This is the system we still have everywhere in the developed world today. The reason a lot of people are excited about bitcoin and its associated technologies is that for the first time there is a genuine possibility of real change in this area. Money has evolved in jumps, from the invention of writing to the invention of the balance sheet and the bank to the creation of the central bank, with all of these changes being variations on the theme of money as a register of credits and debits. And we’re now at a point when another jump is possible.
  • Statistics for Software
    Questions about software performance cannot be answered, or even appropriately articulated, without statistics.

    Yet most developers can’t tell you much about statistics. Much like math, statistics simply don’t come up for typical projects. Between coding the new and maintaining the old, who has the time?

  • Remote Procedure Call
    This is one post in a series about programming models and languages for distributed computing that I’m writing as part of my history of distributed programming techniques.

    Remote Procedure Call (RPC) is a general term for executing a subroutine in a different address space without writing the actual code used to perform the remote execution. To provide an example, we can imagine a user wishing to invoke the random number generator function on another machine, but, the only difference between the local and remote invocation is supplying an additional node identifier where it should occur.

  • Questions to Ask a Potential Tech Employer
    This is a list of things to ask a potential employer when you're interviewing for a technology job. It's compiled from books, the web, contributors, and personal experience. Asking good questions will not only give you a better idea of what a company is like, but they will respect you for digging (if they don't -- run!).
  • Ominous new cracks found on Bay Bridge rods
    Tiny cracks found on some of the rods on the new Bay Bridge tower potentially endanger the rest of the more than 400 remaining fasteners that secure the tower to the foundation in an earthquake, Caltrans officials said Tuesday.

    They also acknowledged that one of four high-strength tower anchor rods they have examined apparently snapped after it was exposed to water and became brittle. That was the same headache that cost the agency $45 million to fix in 2013 when 32 rods on seismic stabilizers failed after sitting in water.

    Brian Maroney, Caltrans’ chief engineer on the bridge project, said the microscopic cracks found on at least two rods lead him to believe that the problem could be widespread and that the rods could be repaired or even replaced if necessary. Nearly all the rods have been exposed to water, and about a quarter of them have sleeves that routinely flood with bay water within days of being drained.

  • The secret rules of the internet: The murky history of moderation, and how it’s shaping the future of free speech.
    Mora-Blanco is one of more than a dozen current and former employees and contractors of major internet platforms from YouTube to Facebook who spoke to us candidly about the dawn of content moderation. Many of these individuals are going public with their experiences for the first time. Their stories reveal how the boundaries of free speech were drawn during a period of explosive growth for a high-stakes public domain, one that did not exist for most of human history. As law professor Jeffrey Rosen first said many years ago of Facebook, these platforms have "more power in determining who can speak and who can be heard around the globe than any Supreme Court justice, any king or any president."

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