Search Results: "ana"

5 July 2017

Yakking: Open your minds, and your data (formats)

Whether I am writing my own program, or chosing between existing solutions, one aspect of the decision making process which always weighs heavily on my mind is that of the input and output data formats. I have been spending a lot of my work days recently working on converting data from a proprietary tool's export format into another tool's input format. This has involved a lot of XML diving, a lot more swearing, and a non-trivial amount of pain. This drove home to me once more that the format of input and output of data is such a critical part of software tooling that it must weigh as heavily as, or perhaps even more heavily than, the software's functionality. As Tannenbaum tells us, the great thing about standards is that there's so many of them to choose from. XKCD tells us, how that comes about. Data formats are many and varied, and suffer from specifications as vague as "plain text" to things as complex as the structure of data stored in custom database formats. If you find yourself writing software which requires a brand new data format then, while I might caution you to examine carefully if it really does need a new format, you should ensure that you document the format carefully and precisely. Ideally give your format specification to a third party and get them to implement a reader and writer for your format, so that they can check that you've not missed anything. Tests and normative implementations can help prop up such an endeavour admirably. Be sceptical of data formats which have "implementation specific" areas, or "vendor specific extension" space because this is where everyone will put the most important and useful data. Do not put such beasts into your format design. If you worry that you've made your design too limiting, deal with that after you have implemented your use-cases for the data format. Don't be afraid to version the format and extend later; but always ensure that a given version of the data format is well understood; and document what it means to be presented with data in a format version you do not normally process. Phew.
Given all that, I exhort you to consider carefully how your projects manage their input and output data, and for these things to be uppermost when you are choosing between different solutions to a problem at hand. Your homework is, as you may have grown to anticipate at this time, to look at your existing projects and check that their input and output data formats are well documented if appropriate.

4 July 2017

Raphaël Hertzog: My Free Software Activities in June 2017

My monthly report covers a large part of what I have been doing in the free software world. I write it for my donors (thanks to them!) but also for the wider Debian community because it can give ideas to newcomers and it s one of the best ways to find volunteers to work with me on projects that matter to me. Debian LTS I was allocated 12 hours to work on security updates for Debian 7 Wheezy. During this time I did the following: Debian packaging Django. A last-minute update to Django in stretch before the release, I uploaded python-django 1:1.10.7-2 fixing two bugs (among which one was release critical) and filed the corresponding unblock request. schroot. I tried to prepare another last-minute update, this time for schroot. The goal was to fix the bash completion (#855283) and a problem encountered by the Debian sysadmins (#835104). Those issues are fixed in unstable/testing but my unblock request got turned into a post-release stretch update because the release managers wanted to give the package some more testing time in unstable. Even now, they are wondering whether they should accept the new systemd service file. live-build, live-config and live-boot. On live-build, I merged a patch to add a keyboard shortcut for the advanced option menu entry (#864386). For live-config, I uploaded version 5.20170623 to fix a broken boot sequence when you have multiple partitions (#827665). For live-boot, I uploaded version 1:20170623 to fix the path to udevadm (#852570) and avoiding a file duplication in the initrd (864385). zim. I packaged a release candidate (0.67~rc2) in Debian Experimental and started to use it. I quickly discovered two annoying regressions that I reported upstream (here and here). logidee-tools. This is a package I authored a long time ago and that I m no longer actively using. It does still work but I sometimes wonder if it still has real users. Anyway I wanted to quickly replace the broken dependency on pgf but I ended up converting the Subversion repository to Git and I also added autopkgtests. At least those tests will inform me when the package no longer works otherwise I would not notice since I m no longer using it. Bugs filed. I filed #865531 on lintian because the new check testsuite-autopkgtest-missing is giving some bad advice and probably does its check in a bad way. I also filed #865541 on sbuild because sbuild --apt-distupgrade can under some circumstances remove build-essential and break the build chroot. I filed an upstream ticket on publican to forward the request I received in #864648. Sponsorship. I sponsored a jessie update for php-tcpdf (#814030) and dolibarr 5.0.4+dfsg3-1 for unstable. I sponsored many other packages, but all in the context of the pkg-security team. pkg-security work Now that the Stretch freeze is over, the team became more active again and I have been overwhelmed with the number of packages to review and sponsor: I also updated hashcat to a new upstream release (3.6.0) and had to discuss with upstream about its weird versioning change. Looks like we will have to introduce an epoch to be able to get back in sync with upstream. To be able to get in sync with Kali, I introduced an hashcat-meta source package (in contrib) providing hashcat-nvidia to make it easy to install hashcat for owners of NVidia hardware. Misc stuff Distro Tracker. I merged a small CSS fix from Aur lien Couderc (#858101) and added a missing constraint on the data model (found through an unexpected traceback that I received by email). I also updated the list of repositories shortly after the stretch release (#865070). Salt formulas. As part of my Kali work, I did setup a build daemon on Debian stretch host and I encountered a couple of issues with my Salt rules. I reported one against salt-formula (here) and I pushed updates for debootstrap-formula, apache-formula and schroot-formula. Thanks See you next month for a new summary of my activities.

No comment Liked this article? Click here. My blog is Flattr-enabled.

Foteini Tsiami: Internationalization, part two

Now that sch-scripts has been renamed to ltsp-manager and translated to English, it was time to set up a proper project site for it in launchpad: http://www.launchpad.net/ltsp-manager The following subpages were created for LTSP Manager there: We currently have an initial version of LTSP Manager running in Debian Stretch; although more testing and more bug reports will be needed before we start the localization phase. Attaching a first screenshot!

3 July 2017

Antoine Beaupr : My free software activities, June 2017

Debian Long Term Support (LTS) This is my monthly Debian LTS report. This time I worked on Mercurial, sudo and Puppet.

Mercurial remote code execution I issued DLA-1005-1 to resolve problems with the hg server --stdio command that could be abused by "remote authenticated users to launch the Python debugger, and consequently execute arbitrary code, by using --debugger as a repository name" (CVE-2017-9462). Backporting the patch was already a little tricky because, as is often the case in our line of work, the code had changed significantly in newer version. In particular, the commandline dispatcher had been refactored which made the patch non-trivial to port. On the other hand, mercurial has an extensive test suite which allowed me to make those patches in all confidence. I also backported a part of the test suite to detect certain failures better and to fix the output so that it matches the backported code. The test suite is slow, however, which meant slow progress when working on this package. I also noticed a strange issue with the test suite: all hardlink operations would fail. Somehow it seems that my new sbuild setup doesn't support doing hardlinks. I ended up building a tarball schroot to build those types of packages, as it seems the issue is related to the use of overlayfs in sbuild. The odd part is my tests of overlayfs, following those instructions, show that it does support hardlinks, so there maybe something fishy here that I misunderstand. This, however, allowed me to get a little more familiar with sbuild and the schroots. I also took this opportunity to optimize the builds by installing an apt-cacher-ng proxy to speed up builds, which will also be useful for regular system updates.

Puppet remote code execution I have issued DLA-1012-1 to resolve a remote code execution attack against puppetmaster servers, from authenticated clients. To quote the advisory: "Versions of Puppet prior to 4.10.1 will deserialize data off the wire (from the agent to the server, in this case) with a attacker-specified format. This could be used to force YAML deserialization in an unsafe manner, which would lead to remote code execution." The fix was non-trivial. Normally, this would have involved fixing the YAML parsing, but this was considered problematic because the ruby libraries themselves were vulnerable and it wasn't clear we could fix the problem completely by fixing YAML parsing. The update I proposed took the bold step of switching all clients to PSON and simply deny YAML parsing from the server. This means all clients need to be updated before the server can be updated, but thankfully, updated clients will run against an older server as well. Thanks to LeLutin at Koumbit for helping in testing patches to solve this issue.

Sudo privilege escalation I have issued DLA-1011-1 to resolve an incomplete fix for a privilege escalation issue (CVE-2017-1000368 from CVE-2017-1000367). The backport was not quite trivial as the code had changed quite a lot since wheezy as well. Whereas mercurial's code was more complex, it's nice to see that sudo's code was actually simpler and more straightforward in newer versions, which is reassuring. I uploaded the packages for testing and uploaded them a year later. I also took extra time to share the patch in the Debian bugtracker, so that people working on the issue in stable may benefit from the backported patch, if needed. One issue that came up during that work is that sudo doesn't have a test suite at all, so it is quite difficult to test changes and make sure they do not break anything.

Should we upload on fridays? I brought up a discussion on the mailing list regarding uploads on fridays. With the sudo and puppet uploads pending, it felt really ... daring to upload both packages, on a friday. Years of sysadmin work hardwired me to be careful on fridays; as the saying goes: "don't deploy on a friday if you don't want to work on the weekend!" Feedback was great, but I was surprised to find that most people are not worried worried about those issues. I have tried to counter some of the arguments that were brought up: I wonder if there could be a disconnection here between the package maintainer / programmer work and the sysadmin work that is at the receiving end of that work. Having myself to deal with broken updates in the past, I'm surprised this has never come up in the discussions yet, or that the response is so underwhelming. So far, I'll try to balance the need for prompt security updates and the need for stable infrastructure. One does not, after all, go without the other...

Triage I also did small fry triage: Hopefully some of those will come to fruitition shortly.

Other work My other work this month was a little all over the place.

Stressant Uploaded a new release (0.4.1) of stressant to split up the documentation from the main package, as the main package was taking up too much space according to grml developers. The release also introduces limited anonymity option, by blocking serial numbers display in the smartctl output.

Debiman Also did some small followup on the debiman project to fix the FAQ links.

Local server maintenance I upgraded my main server to Debian stretch. This generally went well, althought the upgrade itself took way more time than I would have liked (4 hours!). This is partly because I have a lot of cruft installed on the server, but also because of what I consider to be issues in the automation of major Debian upgrades. For example, I was prompted for changes in configuration files at seemingly random moments during the upgrade, and got different debconf prompts to answer. This should really be batched together, and unfortunately I had forgotten to use the home-made script I established when i was working at Koumbit which shortens the upgrade a bit. I wish we would improve on our major upgrade mechanism. I documented possible solutions for this in the AutomatedUpgrade wiki page, but I'm not sure I see exactly where to go from here. I had a few regressions after the upgrade:
  • the infrared remote control stopped working: still need to investigate
  • my home-grown full-disk encryption remote unlocking script broke, but upstream has a nice workaround, see Debian bug #866786
  • gdm3 breaks bluetooth support (Debian bug #805414 - to be fair, this is not a regression in stretch, it's just that I switched my workstation from lightdm to gdm3 after learning that the latter can do rootless X11!)

Docker and Subsonic I did my first (and late?) foray into Docker and containers. My rationale was that I wanted to try out Subsonic, an impressive audio server which some friends have shown me. Since Subsonic is proprietary, I didn't want it to contaminate the rest of my server and it seemed like a great occasion to try out containers to keep things tidy. Containers may also allow me to transparently switch to the FLOSS fork LibreSonic once the trial period is over. I have learned a lot and may write more about the details of that experience soon, for now you can look at the contributions I made to the unofficial Subsonic docker image, but also the LibreSonic one. Since Subsonic also promotes album covers as first-class citizens, I used beets to download a lot of album covers, which was really nice. I look forward to using beets more, but first I'll need to implement two plugins.

Wallabako I did a small release of wallabako to fix the build with the latest changes in the underlying wallabago library, which led me to ask upstream to make versionned releases. I also looked into creating a separate documentation site but it looks like mkdocs doesn't like me very much: the table of contents is really ugly...

Small fry That's about it! And that was supposed to be a slow month...

2 July 2017

Bits from Debian: New Debian Developers and Maintainers (May and June 2017)

The following contributors got their Debian Developer accounts in the last two months: The following contributors were added as Debian Maintainers in the last two months: Congratulations!

Ritesh Raj Sarraf: apt-offline 1.8.1 released

apt-offline 1.8.1 released. This is a bug fix release fixing some python3 glitches related to module imports. Recommended for all users. apt-offline (1.8.1) unstable; urgency=medium * Switch setuptools to invoke py3
* No more argparse needed on py3
* Fix genui.sh based on comments from pyqt mailing list
* Bump version number to 1.8.1 -- Ritesh Raj Sarraf <rrs@debian.org> Sat, 01 Jul 2017 21:39:24 +0545
What is apt-offline 
Description: offline APT package manager
 apt-offline is an Offline APT Package Manager.
 .
 apt-offline can fully update and upgrade an APT based distribution without
 connecting to the network, all of it transparent to APT.
 .
 apt-offline can be used to generate a signature on a machine (with no network).
 This signature contains all download information required for the APT database
 system. This signature file can be used on another machine connected to the
 internet (which need not be a Debian box and can even be running windows) to
 download the updates.
 The downloaded data will contain all updates in a format understood by APT and
 this data can be used by apt-offline to update the non-networked machine.
 .
 apt-offline can also fetch bug reports and make them available offline.

Categories:

Keywords:

Like:

1 July 2017

Keith Packard: DRM-lease-4

DRM leasing part three (vblank) The last couple of weeks have been consumed by getting frame sequence numbers and events handled within the leasing environment (and Vulkan) correctly. Vulkan EXT_display_control extension This little extension provides the bits necessary for applications to track the display of frames to the user. 
VkResult
vkGetSwapchainCounterEXT(VkDevice           device,
             VkSwapchainKHR         swapchain,
             VkSurfaceCounterFlagBitsEXT    counter,
             uint64_t           *pCounterValue);
This function just retrieves the current frame count from the display associated with swapchain. 
VkResult
vkRegisterDisplayEventEXT(VkDevice          device,
              VkDisplayKHR          display,
              const VkDisplayEventInfoEXT   *pDisplayEventInfo,
              const VkAllocationCallbacks   *pAllocator,
              VkFence           *pFence);
This function creates a fence that will be signaled when the specified event happens. Right now, the only event supported is when the first pixel of the next display refresh cycle leaves the display engine for the display. If you want something fancier (like two frames from now), you get to do that on your own using this basic function. drmWaitVBlank drmWaitVBlank is the existing interface for all things sequence related and has three modes (always nice to have one function do three things, I think). It can:
  1. Query the current vblank number
  2. Block until a specified vblank number
  3. Queue an event to be delivered at a specific vblank number
This interface has a few issues: For leases, figuring out the index into the kernel list of crtcs is pretty tricky -- our lease has a subset of those crtcs, so we can't actually compute the global crtc index. drmCrtcGetSequence 
int drmCrtcGetSequence(int fd, uint32_t crtcId,
               uint64_t *sequence, uint64_t *ns);
Here's a simple new function hand it a crtc ID and it provides the current frame sequence number and the time when that frame started (in nanoseconds). drmCrtcQueueSequence 
int drmCrtcQueueSequence(int fd, uint32_t crtcId,
                 uint32_t flags, uint64_t sequence,
             uint64_t user_data);
struct drm_event_crtc_sequence  
    struct drm_event    base;
    __u64           user_data;
    __u64           time_ns;
    __u64           sequence;
 ;
This will cause a CRTC_SEQUENCE event to be delivered at the start of the specified frame sequence. That event will include the frame when the event was actually generated (in case it's late), along with the time (in nanoseconds) when that frame was started. The event also includes a 64-bit user_data value, which can be used to hold a pointer to whatever data the application wants to see in the event handler. The 'flags' argument contains a combination of: 
#define DRM_CRTC_SEQUENCE_RELATIVE      0x00000001  /* sequence is relative to current */
#define DRM_CRTC_SEQUENCE_NEXT_ON_MISS      0x00000002  /* Use next sequence if we've missed */
#define DRM_CRTC_SEQUENCE_FIRST_PIXEL_OUT   0x00000004  /* Signal when first pixel is displayed */
These are similar to the values provided for the drmWaitVBlank function, except I've added a selector for when the event should be delivered to align with potential future additions to Vulkan. Right now, the only time you can ask for is first-pixel-out, which says that the event should correspond to the display of the first pixel on the screen. DRM events Vulkan fences With the kernel able to deliver a suitable event at the next frame, all the Vulkan code needed was a to create a fence and hook it up to such an event. The existing fence code only deals with rendering fences, so I added window system interface (WSI) fencing infrastructure and extended the radv driver to be able to handle both kinds of fences within that code. Multiple waiting threads I've now got three places which can be waiting for a DRM event to appear:
  1. Frame sequence fences.
  2. Wait for an idle image. Necessary when you want an image to draw the next frame to.
  3. Wait for the previous flip to complete. The kernel can only queue one flip at a time, so we have to make sure the previous flip is complete before queuing another one.
Vulkan allows these to be run from separate threads, so I needed to deal with multiple threads waiting for a specific DRM event at the same time. XCB has the same problem and goes to great lengths to manage this with a set of locking and signaling primitives so that only one thread is ever doing poll or read from the socket at time. If another thread wants to read at the same time, it will block on a condition variable which is then signaled by the original reader thread at the appropriate time. It's all very complicated, and it didn't work reliably for a number of years. I decided to punt and just create a separate thread for processing all DRM events. It blocks using poll(2) until some events are readable, processes those and then broadcasts to a condition variable to notify any waiting threads that 'something' has happened. Each waiting thread simply checks for the desired condition and if not satisfied, blocks on that condition variable. It's all very simple looking, and seems to work just fine. Code Complete, Validation Remains At this point, all of the necessary pieces are in place for the VR application to take advantage of an HMD using only existing Vulkan extensions. Those will be automatically mapped into DRM leases and DRM events as appropriate. The VR compositor application is working pretty well; tests with Dota 2 show occasional jerky behavior in complex scenes, so there's clearly more work to be done somewhere. I need to go write a pile of tests to independently verify that my code is working. I wonder if I'll need to wire up some kind of light sensor so I can actually tell when frames get displayed as it's pretty easy to get consistent-but-wrong answers in this environment. Source Code

Russ Allbery: End of month haul

For some reason, June is always incredibly busy for me. It's historically the most likely month in which I don't post anything here at all except reviews (and sometimes not even that). But I'm going to tell you about what books I bought (or were given to me) on the very last day of the month to break the pattern of no journal postings in June. Ted Chiang Arrival (Stories of Your Life) (sff collection)
Eoin Colfer Artemis Fowl (sff)
Philip K. Dick The Man Who Japed (sff)
Yoon Ha Lee Raven Strategem (sff)
Paul K. Longmore Why I Burned My Book (nonfiction)
Melina Marchetta The Piper's Son (mainstream)
Jules Verne For the Flag (sff, sort of) This is a more than usually eclectic mix. The Chiang is his Stories of Your Life collection reissued under the title of Arrival to cash in on the huge success of the movie based on one of his short stories. I'm not much of a short fiction reader, but I've heard so many good things about Chiang that I'm going to give it a try. The Longmore is a set of essays about disability rights that has been on my radar for a while. I finally got pushed into buying it (plus the first Artemis Fowl book and the Marchetta) because I've been reading back through every review Light has written. (I wish I were even close to that amusingly snarky in reviews, and she manages to say in a few paragraphs what usually takes me a whole essay.) Finally, the Dick and the Verne were gifts from a co-worker from a used book store in Ireland. Minor works by both authors, but nice, old copies of the books.

Russ Allbery: Review: Make It Stick

Review: Make It Stick, by Peter C. Brown, et al.
Author: Peter C. Brown
Author: Henry L. Roediger III
Author: Mark A. McDaniel
Publisher: Belknap Press
Copyright: 2014
ISBN: 0-674-72901-3
Format: Kindle
Pages: 255
Another read for the work book club. "People generally are going about learning in the wrong ways." This is the first sentence of the preface of this book by two scientists (Roediger and McDaniel are both psychology researchers specializing in memory) and a novelist and former management consultant (Brown). The goal of Make It Stick is to apply empirical scientific research to the problem of learning, specifically retention of information for long-term use. The authors aim to convince the reader that subjective impressions of the effectiveness of study habits are highly deceptive, and that scientific evidence points strongly towards mildly counter-intuitive learning methods that don't feel like they're producing as good of results. I have such profound mixed feelings about this book. Let's start with the good. Make It Stick is a book containing actual science. The authors quote the studies, results, and scientific argument at length. There are copious footnotes and an index, as well as recommended reading. And the science is concrete and believable, as is the overlaid interpretation based on cognitive and memory research. The book's primary argument is that short-term and long-term memory are very different things, that what we're trying to achieve when we say "learning" is based heavily on long-term memory and recall of facts for an extended time after study, and that building this type of recall requires not letting our short-term memory do all the work. We tend towards study patterns that show obvious short-term improvement and that produce an increased feeling of effortless recall of the material, but those study patterns are training short-term memory and mean the knowledge slips away quickly. Choosing learning methods that instead make us struggle a little with what we're learning are significantly better. It's that struggle that leads to committing the material to long-term memory and building good recall pathways for it. On top of this convincingly-presented foundation, the authors walk through learning methods that feel worse in the moment but have better long-term effects: mixing practice of different related things (different types of solids when doing geometry problems, different pitches in batting practice) and switching types before you've mastered the one you're working on, forcing yourself to interpret and analyze material (such as writing a few paragraphs of summary in your own words) instead of re-reading it, and practicing material at spaced intervals far enough apart that you've forgotten some of the material and have to struggle to recall it. Possibly the most useful insight here (at least for me) was the role of testing in learning, not as just a way of measuring progress, but as a learning tool. Frequent, spaced, cumulative testing forces exactly the type of recall that builds long-term memory. The tests themselves help improve our retention of what we're learning. It's bad news for people like me who were delighted to leave school and not have to take a test again, but viewing tests as a more effective learning tool than re-reading and review (which they are) does cast them in a far more positive light. This is all solid stuff, and I'm very glad the research underlying this book exists and that I now know about it. But there are some significant problems with its presentation. The first is that there just isn't much here. The two long paragraphs above summarize nearly all of the useful content of this book. The authors certainly provide more elaboration, and I haven't talked about all of the study methods they mention or some of the useful examples of their application. But 80% of it is there, and the book is intentionally repetitive (because it tries to follow the authors' advice on learning theory). Make It Stick therefore becomes tedious and boring, particularly in the first four chapters. I was saying a lot of "yes, yes, you said that already" and falling asleep while trying to read it. The summaries at the end of the book are a bit better, but you will probably not need most of this book to get the core ideas. And then there's chapter five, which ends in a train wreck. Chapter five is on cognitive biases, and I see why the authors wanted to include it. The Dunning-Kruger effect is directly relevant to their topic. It undermines our ability to learn, and is yet another thing that testing helps avoid. Their discussion of Daniel Kahneman's two system theory (your fast, automatic, subconscious reactions and your slow, thoughtful, conscious processing) is somewhat less directly relevant, but it's interesting stuff, and it's at least somewhat related to the short-term and long-term memory dichotomy. But some of the stories they choose to use to illustrate this are... deeply unfortunate. Specifically, the authors decided to use US police work in multiple places as their example of choice for two-system thinking, and treat it completely uncritically. Some of you are probably already wincing because you can see where this is going. They interview a cop who, during scenario training for traffic stops, was surprised by the car trunk popping open and a man armed with a shotgun popping out of it. To this day, he still presses down on the trunk of the car as he walks up; it's become part of his checklist for every traffic stop. This would be a good example if the authors realized how badly his training has failed and deconstructed it, but they're apparently oblivious. I wanted to reach into the book and shake them. People have a limited number of things they can track and follow as part of a procedure, and some bad trainer has completely wasted part of this cop's attention in every traffic stop and thereby made him less safe! Just calculate the chances that someone would be curled up in an unlocked trunk with a shotgun and a cop would just happen to stop that car for some random reason, compared to any other threat the cop could use that same attention to watch for. This is exactly the type of scenario that's highly memorable but extremely improbable and therefore badly breaks human risk analysis. It's what Bruce Schneier calls a movie plot threat. The correct reaction to movie plot threats is to ignore them; wasting effort on mitigating them means not having that effort to spend on mitigating some other less memorable but more likely threat. This isn't the worst, though. The worst is the very next paragraph, also from police training, of showing up at a domestic call, seeing an armed person on the porch who stands up and walks away when ordered to drop their weapon, and not being sure how to react, resulting in that person (in the simulated exercise) killing the cop before they did anything. The authors actually use this as an example of how the cop was using system two and needed to train to use system one in that situation to react faster, and that this is part of the point of the training. Those of us who have been paying attention to the real world know what using system one here means: the person on the porch gets shot if they're black and doesn't get shot if they're white. The authors studiously refuse to even hint at this problem. I would have been perfectly happy if this book avoided the unconscious bias aspect of system one thinking. It's a bit far afield of the point of the book, and the authors are doubtless trying to stay apolitical. But that's why you pick some other example. You cannot just drop this kind of thing on the page and then refuse to even comment on it! It's like writing a chapter about the effect of mass transit on economic development, choosing Atlanta as one of your case studies, and then never mentioning race. Also, some editor seriously should have taken an ax to the sentence where the authors (for no justified reason) elaborate a story to describe a cop maiming a person, solely to make a cliched joke about how masculinity is defined by testicles and how people who lose body parts are less human. Thanks, book. This was bad enough that it dominated my memory of this chapter, but, reviewing the book for this review, I see it was just a few badly chosen examples at the end of the chapter and one pointless story at the start. The rest of the chapter is okay, although it largely summarizes things covered better in other books. The most useful part that's relevant to the topic of the book is probably the discussion of peer instruction. Just skip over all the police bits; you won't be missing anything. Thankfully, the rest of the book mostly avoids failing quite this hard. Chapter six does open with the authors obliviously falling for a string of textbook examples of survivorship bias (immediately after the chapter on cognitive biases!), but they shortly thereafter settle down to the accurate and satisfying work of critiquing theories of learning methods and types of intelligence. And by critiquing, I mean pointing out that they're mostly unscientific bullshit, which is fighting the good fight as far as I'm concerned. So, mixed feelings. The science seems solid, and is practical and directly applicable to my life. Make It Stick does an okay job at presenting it, but gets tedious and boring in places, particularly near the beginning. And there are a few train-wreck examples that had me yelling at the book and scribbling notes, which wasn't really the cure for boredom I was looking for. I recommend being aware of this research, and I'm glad the authors wrote this book, but I can't really recommend the book itself as a reading experience. Rating: 6 out of 10

Paul Wise: FLOSS Activities June 2017

Changes

Issues

Review

Administration
  • Debian: redirect 2 users to support channels, redirect 1 person to the mirrors team, investigate SMTP TLS question, fix ACL issue, restart dead exim4 service
  • Debian mentors: service restarts, security updates & reboot
  • Debian QA: deploy my changes
  • Debian website: release related rebuilds, rebuild installation-guide
  • Debian wiki: whitelist several email addresses, whitelist 1 domain
  • Debian package tracker: deploy my changes
  • Debian derivatives census: deploy my changes
  • Openmoko: security updates & reboots.

Communication

Sponsors All work was done on a volunteer basis.

30 June 2017

Chris Lamb: Free software activities in June 2017

Here is my monthly update covering what I have been doing in the free software world (previous month):
Reproducible builds

Whilst anyone can inspect the source code of free software for malicious flaws, most software is distributed pre-compiled to end users. The motivation behind the Reproducible Builds effort is to allow verification that no flaws have been introduced either maliciously or accidentally during this compilation process by promising identical results are always generated from a given source. Multiple third-parties then can come to a consensus on whether a build was compromised or not. I have generously been awarded a grant from the Core Infrastructure Initiative to fund my work in this area. This month I:
  • Chaired our monthly IRC meeting. (Summary, logs, etc.)
  • Presented at Hong Kong Open Source Conference 2017.
  • Presented at LinuxCon China.
  • Submitted the following patches to fix reproducibility-related toolchain issues within Debian:
    • cracklib2: Ensuring /var/cache/cracklib/src-dicts are reproducible. (#865623)
    • fontconfig: Ensuring the cache files are reproducible. (#864082)
    • nfstrace: Make the PDF footers reproducible. (#865751)
  • Submitted 6 patches to fix specific reproducibility issues in cd-hit, janus, qmidinet, singularity-container, tigervnc & xabacus.
  • Submitted a wishlist request to the TeX mailing list to ensure that PDF files are reproducible even if generated from a difficult path after identifying underlying cause. (Thread)
  • Categorised a large number of packages and issues in the Reproducible Builds notes.git repository.
  • Worked on publishing our weekly reports. (#110, #111, #112 & #113)
  • Updated our website with 13 missing talks (e291180), updated the metadata for some existing talks (650a201) and added OpenEmbedded to the projects page (12dfcf0).
I also made the following changes to our tooling:
diffoscope

diffoscope is our in-depth and content-aware diff utility that can locate and diagnose reproducibility issues.


strip-nondeterminism

strip-nondeterminism is our tool to remove specific non-deterministic results from a completed build.

  • Add libarchive-cpio-perl with the !nocheck build profile. (01e408e)
  • Add dpkg-dev dependency build profile. (f998bbe)


Debian My activities as the current Debian Project Leader are covered in my "Bits from the DPL" email to the debian-devel-announce mailing list. However, I:
Debian LTS

This month I have been paid to work 16 hours hours on Debian Long Term Support (LTS). In that time I did the following:
  • "Frontdesk" duties, triaging CVEs, etc.
  • Issued DLA 974-1 fixing a command injection vulnerability in picocom, a dumb-terminal emulation program.
  • Issued DLA 972-1 which patches a double-free vulnerability in the openldap LDAP server.
  • Issued DLA 976-1 which corrects a buffer over-read vulnerability in the yodl ("Your Own Document Language") document processor.
  • Issued DLA 985-1 to address a vulnerability in libsndfile (a library for reading/writing audio files) where a specially-crafted AIFF file could result in an out-of-bounds memory read.
  • Issued DLA 990-1 to fix an infinite loop vulnerability in the expat, an XML parsing library.
  • Issued DLA 999-1 for the openvpn VPN server if clients used a HTTP proxy with NTLM authentication, a man-in-the-middle attacker could cause the client to crash or disclose stack memory that was likely to contain the proxy password.
Uploads
  • bfs (1.0.2-1) New upstream release, add basic/smoke autopkgtests.
  • installation-birthday (5) Add some basic autopkgtest smoke tests and correct the Vcs- Git,Browser headers.
  • python-django:
    • 1:1.11.2-1 New upstream minor release & backport an upstream patch to prevent a test failure if the source is not writable. (#816435)
    • 1:1.11.2-2 Upload to unstable, use !nocheck profile for build dependencies that are only required for tests and various packaging updates.

I also made the following non-maintainer uploads (NMUs):
  • kluppe (0.6.20-1.1) Fix segmentation fault caused by passing a truncated pointer instead of a GtkType. (#863421)
  • porg (2:0.10-1.1) Fix broken LD_PRELOAD path for libporg-log.so. (#863495)
  • ganeti-instance-debootstrap (0.16-2.1) Fix "illegal option for fgrep" error by using "--" to escape the search needle. (#864025)
  • pavuk (0.9.35-6.1) Fix segmentation fault when opening the "Limitations" window due to pointer truncation in src/gtkmulticol.[ch]. (#863492)
  • timemachine (0.3.3-2.1) Fix two segmentation faults in src/gtkmeter.c and gtkmeterscale.c caused by passing a truncated pointers using guint instead of a GtkType. (#863420)
  • jackeq (0.5.9-2.1) Fix another segmentation fault caused by passing a truncated pointer instead of a GtkType. (#863416)
Debian bugs filed
  • debhelper: Don't run dh_installdocs if nodoc is specified in DEB_BUILD_PROFILES? (#865869)
  • python-blessed: Non-determistically FTBFS due to unreliable timing in tests. (#864337)
  • apt: Please print a better error message if zero certificates are loaded from the system CA store. (#866377)

Daniel Pocock: A FOSScamp by the beach

I recently wrote about the great experience many of us had visiting OSCAL in Tirana. Open Labs is doing a great job promoting free, open source software there. They are now involved in organizing another event at the end of the summer, FOSScamp in Syros, Greece. Looking beyond the promise of sun and beach, FOSScamp is also just a few weeks ahead of the Outreachy selection deadline so anybody who wants to meet potential candidates in person may find this event helpful. If anybody wants to discuss the possibilities for involvement in the event then the best place to do that may be on the Open Labs forum topic. What will tomorrow's leaders look like? While watching a talk by Joni Baboci, head of Tirana's planning department, I was pleasantly surprised to see this photo of Open Labs board members attending the town hall for the signing of an open data agreement: It's great to see people finding ways to share the principles of technological freedoms far and wide and it will be interesting to see how this relationship with their town hall grows in the future.

27 June 2017

Daniel Pocock: How did the world ever work without Facebook?

Almost every day, somebody tells me there is no way they can survive without some social media like Facebook or Twitter. Otherwise mature adults fearful that without these dubious services, they would have no human contact ever again, they would die of hunger and the sky would come crashing down too. It is particularly disturbing for me to hear this attitude from community activists and campaigners. These are people who aspire to change the world, but can you really change the system using the tools the system gives you? Revolutionaries like Gandhi and the Bolsheviks don't have a lot in common: but both of them changed the world and both of them did so by going against the system. Gandhi, of course, relied on non-violence while the Bolsheviks continued to rely on violence long after taking power. Neither of them needed social media but both are likely to be remembered far longer than any viral video clip you have seen recently. With US border guards asking visitors for their Facebook profiles and Mark Zuckerberg being a regular participant at secretive Bilderberg meetings, it should be clear that Facebook and conventional social media is not on your side, it's on theirs. Kettling has never been easier When street protests erupt in major cities such as London, the police build fences around the protesters, cutting them off from the rest of the world. They become an island in the middle of the city, like a construction site or broken down bus that everybody else goes around. The police then set about arresting one person at a time, taking their name and photograph and then slowly letting them leave in different directions. This strategy is called kettling. Facebook helps kettle activists in their arm chair. The police state can gather far more data about them, while their impact is even more muted than if they ventured out of their home. You are more likely to win the lottery than make a viral campaign Every week there is news about some social media campaign that has gone viral. Every day, marketing professionals, professional campaigners and motivated activists sit at their computer spending hours trying to replicate this phenomenon. Do the math: how many of these campaigns can really be viral success stories? Society can only absorb a small number of these campaigns at any one time. For most of the people trying to ignite such campaigns, their time and energy is wasted, much like money spent buying lottery tickets and with odds that are just as bad. It is far better to focus on the quality of your work in other ways than to waste any time on social media. If you do something that is truly extraordinary, then other people will pick it up and share it for you and that is how a viral campaign really begins. The time and effort you put into trying to force something to become viral is wasting the energy and concentration you need to make something that is worthy of really being viral. An earthquake and an escaped lion never needed to announce themselves on social media to become an instant hit. If your news isn't extraordinary enough for random people to spontaneously post, share and tweet it in the first place, how can it ever go far? The news media deliberately over-rates social media News media outlets, including TV, radio and print, gain a significant benefit crowd-sourcing live information, free of charge, from the public on social media. It is only logical that they will cheer on social media sites and give them regular attention. Have you noticed that whenever Facebook's publicity department makes an announcement, the media are quick to publish it ahead of more significant stories about social or economic issues that impact our lives? Why do you think the media puts Facebook up on a podium like this, ahead of all other industries, if the media aren't getting something out of it too? The tail doesn't wag the dog One particular example is the news media's fascination with Donald Trump's Twitter account. Some people have gone as far as suggesting that this billionaire could have simply parked his jet and spent the whole of 2016 at one of his golf courses sending tweets and he would have won the presidency anyway. Suggesting that Trump's campaign revolved entirely around Twitter is like suggesting the tail wags the dog. The reality is different: Trump has been a prominent public figure for decades, both in the business and entertainment world. During his presidential campaign, he had at least 220 major campaign rallies attended by over 1.2 million people in the real world. Without this real-world organization and history, the Twitter account would have been largely ignored like the majority of Twitter accounts. On the left of politics, the media have been just as quick to suggest that Bernie Sanders and Jeremy Corbyn have been supported by the "Facebook generation". This label is superficial and deceiving. The reality, again, is a grass roots movement that has attracted young people to attend local campaign meetings in pubs up and down the country. Getting people to get out and be active is key. Social media is incidental to their campaign, not indispensible. Real-world meetings, big or small, are immensely more powerful than a social media presence. Consider the Trump example again: if 100,000 people receive one of his tweets, how many even notice it in the non-stop stream of information we are bombarded with today? On the other hand, if 100,000 bellow out a racist slogan at one of his rallies, is there any doubt whether each and every one of those people is engaged with the campaign at that moment? If you could choose between 100 extra Twitter followers or 10 extra activists attending a meeting every month, which would you prefer? Do we need this new definition of a Friend? Facebook is redefining what it means to be a friend. Is somebody who takes pictures of you and insists on sharing them with hundreds of people, tagging your face for the benefit of biometric profiling systems, really a friend? If you want to find out what a real friend is and who your real friends really are, there is no better way to do so then blowing away your Facebook and Twitter account and waiting to see who contacts you personally about meeting up in the real world. If you look at a profile on Facebook or Twitter, one of the most prominent features is the number of friends or followers they have. Research suggests that humans can realistically cope with no more than about 150 stable relationships. Facebook, however, has turned Friending people into something like a computer game. This research is also given far more attention then it deserves though: the number of really meaningful friendships that one person can maintain is far smaller. Think about how many birthdays and spouse's names you can remember and those may be the number of real friendships you can manage well. In his book Busy, Tony Crabbe suggests between 10-20 friendships are in this category and you should spend all your time with these people rather than letting your time be spread thinly across superficial Facebook "friends". This same logic can be extrapolated to activism and marketing in its many forms: is it better for a campaigner or publicist to have fifty journalists following him on Twitter (where tweets are often lost in the blink of an eye) or three journalists who he meets for drinks from time to time? Facebook alternatives: the ultimate trap? Numerous free, open source projects have tried to offer an equivalent to Facebook and Twitter. GNU social, Diaspora and identi.ca are some of the more well known examples. Trying to persuade people to move from Facebook to one of these platforms rarely works. In most cases, Metcalfe's law suggests the size of Facebook will suck them back in like the gravity of a black hole. To help people really beat these monstrosities, the most effective strategy is to help them live without social media, whether it is proprietary or not. The best way to convince them may be to give it up yourself and let them see how much you enjoy life without it. Share your thoughts The FSFE community has recently been debating the use of propriety software and services. Please feel free to join the list and click here to reply on the thread.

Reproducible builds folks: Reproducible Builds: week 113 in Stretch cycle

Here's what happened in the Reproducible Builds effort between Sunday June 18 and Saturday June 24 2017: Upcoming and Past events Our next IRC meeting is scheduled for the 6th of July at 17:00 UTC with this agenda currently:
  1. Introductions
  2. Reproducible Builds Summit update
  3. NMU campaign for buster
  4. Press release: Debian is doing Reproducible Builds for Buster
  5. Reproducible Builds Branding & Logo
  6. should we become an SPI member
  7. Next meeting
  8. Any other business
On June 19th, Chris Lamb presented at LinuxCon China 2017 on Reproducible Builds. On June 23rd, Vagrant Cascadian held a Reproducible Builds question and answer session at Open Source Bridge. Reproducible work in other projects LEDE: firmware-utils and mtd-utils/mkfs.jffs2 now honor SOURCE_DATE_EPOCH. Toolchain development and fixes There was discussion on #782654 about packaging bazel for Debian. Dan Kegel wrote a patch to use ar determinitiscally for Homebrew, a package manager for MacOS. Dan Kegel worked on using SOURCE_DATE_EPOCH and other reproduciblity fixes in fpm, a multi plattform package builder. The Fedora Haskell team disabled parallel builds to achieve reproducible builds. Bernhard M. Wiedemann submitted many patches upstream: Packages fixed and bugs filed Patches submitted upstream: Other patches filed in Debian: Reviews of unreproducible packages 573 package reviews have been added, 154 have been updated and 9 have been removed in this week, adding to our knowledge about identified issues. 1 issue type has been updated: Weekly QA work During our reproducibility testing, FTBFS bugs have been detected and reported by: diffoscope development Version 83 was uploaded to unstable by Chris Lamb. It also moved the previous changes from experimental (to where they were uploaded) to unstable. It included contributions from previous weeks. You can read about these changes in our previous weeks' posts, or view the changelog directly (raw form). We plan to maintain a backport of this and future versions in stretch-backports. Ximin Luo also worked on better html-dir output for very very large diffs such as those for GCC. So far, this includes unreleased work on a PartialString data structure which will form a core part of a new and more intelligent recursive display algorithm. strip-nondeterminism development Versions 0.035-1 was uploaded to unstable from experimental by Chris Lamb. It included contributions from: Later in the week Mattia Rizzolo uploaded 0.035-2 with some improvements to the autopkgtest and to the general packaging. We currently don't plan to maintain a backport in stretch-backports like we did for jessie-backports. Please speak up if you think otherwise. reproducible-website development tests.reproducible-builds.org Misc. This week's edition was written by Ximin Luo, Holger Levsen, Bernhard M. Wiedemann, Mattia Rizzolo, Chris Lamb & reviewed by a bunch of Reproducible Builds folks on IRC & the mailing lists.

Colin Watson: New address book

I ve had a kludgy mess of electronic address books for most of two decades, and have got rather fed up with it. My stack consisted of: The biggest practical problem with this was that I had the address book that was most convenient for me to add things to (Google Contacts) and the one I used when sending email, and no sensible way to merge them or move things between them. I also wasn t especially comfortable with having all my contact information in a proprietary web service. My goals for a replacement address book system were: I think I have all this now! New stack The obvious basic technology to use is CardDAV: it s fairly complex, admittedly, but lots of software supports it and one of my goals was not having to write my own thing. This meant I needed a CardDAV server, some way to sync the database to and from both Android and the system where I run mutt, and whatever query glue was necessary to get mutt to understand vCards. There are lots of different alternatives here, and if anything the problem was an embarrassment of choice. In the end I just decided to go for things that looked roughly the right shape for me and tried not to spend too much time in analysis paralysis. CardDAV server I went with Xandikos for the server, largely because I know Jelmer and have generally had pretty good experiences with their software, but also because using Git for history of the backend storage seems like something my future self will thank me for. It isn t packaged in stretch, but it s in Debian unstable, so I installed it from there. Rather than the standalone mode suggested on the web page, I decided to set it up in what felt like a more robust way using WSGI. I installed uwsgi, uwsgi-plugin-python3, and libapache2-mod-proxy-uwsgi, and created the following file in /etc/uwsgi/apps-available/xandikos.ini which I then symlinked into /etc/uwsgi/apps-enabled/xandikos.ini: 
[uwsgi]
socket = 127.0.0.1:8801
uid = xandikos
gid = xandikos
umask = 022
master = true
cheaper = 2
processes = 4
plugin = python3
module = xandikos.wsgi:app
env = XANDIKOSPATH=/srv/xandikos/collections
The port number was arbitrary, as was the path. You need to create the xandikos user and group first (adduser --system --group --no-create-home --disabled-login xandikos). I created /srv/xandikos owned by xandikos:xandikos and mode 0700, and I recommend setting a umask as shown above since uwsgi s default umask is 000 (!). You should also run sudo -u xandikos xandikos -d /srv/xandikos/collections --autocreate and then Ctrl-c it after a short time (I think it would be nicer if there were a way to ask the WSGI wrapper to do this). For Apache setup, I kept it reasonably simple: I ran a2enmod proxy_uwsgi, used htpasswd to create /etc/apache2/xandikos.passwd with a username and password for myself, added a virtual host in /etc/apache2/sites-available/xandikos.conf, and enabled it with a2ensite xandikos: 
<VirtualHost *:443>
        ServerName xandikos.example.org
        ServerAdmin me@example.org
        ErrorLog /var/log/apache2/xandikos-error.log
        TransferLog /var/log/apache2/xandikos-access.log
        <Location />
                ProxyPass "uwsgi://127.0.0.1:8801/"
                AuthType Basic
                AuthName "Xandikos"
                AuthBasicProvider file
                AuthUserFile "/etc/apache2/xandikos.passwd"
                Require valid-user
        </Location>
</VirtualHost>
Then service apache2 reload, set the new virtual host up with Let s Encrypt, reloaded again, and off we go. Android integration I installed DAVdroid from the Play Store: it cost a few pounds, but I was OK with that since it s GPLv3 and I m happy to help fund free software. I created two accounts, one for my existing Google Contacts database (and in fact calendaring as well, although I don t intend to switch over to self-hosting that just yet), and one for the new Xandikos instance. The Google setup was a bit fiddly because I have two-step verification turned on so I had to create an app-specific password. The Xandikos setup was straightforward: base URL, username, password, and done. Since I didn t completely trust the new setup yet, I followed what seemed like the most robust option from the DAVdroid contacts syncing documentation, and used the stock contacts app to export my Google Contacts account to a .vcf file and then import that into the appropriate DAVdroid account (which showed up automatically). This seemed straightforward and everything got pushed to Xandikos. There are some weird delays in syncing contacts that I don t entirely understand, but it all seems to get there in the end. mutt integration First off I needed to sync the contacts. (In fact I happen to run mutt on the same system where I run Xandikos at the moment, but I don t want to rely on that, and going through the CardDAV server means that I don t have to poke holes for myself using filesystem permissions.) I used vdirsyncer for this. In ~/.vdirsyncer/config: 
[general]
status_path = "~/.vdirsyncer/status/"
[pair contacts]
a = "contacts_local"
b = "contacts_remote"
collections = ["from a", "from b"]
[storage contacts_local]
type = "filesystem"
path = "~/.contacts/"
fileext = ".vcf"
[storage contacts_remote]
type = "carddav"
url = "<Xandikos base URL>"
username = "<my username>"
password = "<my password>"
Running vdirsyncer discover and vdirsyncer sync then synced everything into ~/.contacts/. I added an hourly crontab entry to run vdirsyncer -v WARNING sync. Next, I needed a command-line address book tool based on this. khard looked about right and is in stretch, so I installed that. In ~/.config/khard/khard.conf (this is mostly just the example configuration, but I preferred to sort by first name since not all my contacts have neat first/last names): 
[addressbooks]
[[contacts]]
path = ~/.contacts/<UUID of my contacts collection>/
[general]
debug = no
default_action = list
editor = vim
merge_editor = vimdiff
[contact table]
# display names by first or last name: first_name / last_name
display = first_name
# group by address book: yes / no
group_by_addressbook = no
# reverse table ordering: yes / no
reverse = no
# append nicknames to name column: yes / no
show_nicknames = no
# show uid table column: yes / no
show_uids = yes
# sort by first or last name: first_name / last_name
sort = first_name
[vcard]
# extend contacts with your own private objects
# these objects are stored with a leading "X-" before the object name in the vcard files
# every object label may only contain letters, digits and the - character
# example:
#   private_objects = Jabber, Skype, Twitter
private_objects = Jabber, Skype, Twitter
# preferred vcard version: 3.0 / 4.0
preferred_version = 3.0
# Look into source vcf files to speed up search queries: yes / no
search_in_source_files = no
# skip unparsable vcard files: yes / no
skip_unparsable = no
Now khard list shows all my contacts. So far so good. Apparently there are some awkward vCard compatibility issues with creating or modifying contacts from the khard end. I ve tried adding one address from ~/.mutt/aliases using khard and it seems to at least minimally work for me, but I haven t explored this very much yet. I had to install python3-vobject 0.9.4.1-1 from experimental to fix eventable/vobject#39 saving certain vCard files. Finally, mutt integration. I already had set query_command="lbdbq '%s'" in ~/.muttrc, and I wanted to keep that in place since I still wanted to use LDAP querying as well. I had to write a very small amount of code for this (perhaps I should contribute this to lbdb upstream?), in ~/.lbdb/modules/m_khard: 
#! /bin/sh
m_khard_query ()  
    khard email --parsable --remove-first-line --search-in-source-files "$1"
My full ~/.lbdb/rc now reads as follows (you probably won t want the LDAP stuff, but I ve included it here for completeness): 
MODULES_PATH="$MODULES_PATH $HOME/.lbdb/modules"
METHODS='m_muttalias m_khard m_ldap'
LDAP_NICKS='debian canonical'
Next steps I ve deleted one account from Google Contacts just to make sure that everything still works (e.g. I can still search for it when composing a new message), but I haven t yet deleted everything. I won t be adding anything new there though. I need to push everything from ~/.mutt/aliases into the new system. This is only about 30 contacts so shouldn t take too long. Overall this feels like a big improvement! It wasn t a trivial amount of setup for just me, but it means I have both better usability for myself and more independence from proprietary services, and I think I can add extra users with much less effort if I need to. Postscript A day later and I ve consolidated all my accounts from Google Contacts and ~/.mutt/aliases into the new system, with the exception of one group that I had defined as a mutt alias and need to work out what to do with. This all went smoothly. I ve filed the new lbdb module as #866178, and the python3-vobject bug as #866181.

Benjamin Mako Hill: Learning to Code in One s Own Language

I recently published a paper with Sayamindu Dasgupta that provides evidence in support of the idea that kids can learn to code more quickly when they are programming in their own language. Millions of young people from around the world are learning to code. Often, during their learning experiences, these youth are using visual block-based programming languages like Scratch, App Inventor, and Code.org Studio. In block-based programming languages, coders manipulate visual, snap-together blocks that represent code constructs instead of textual symbols and commands that are found in more traditional programming languages. The textual symbols used in nearly all non-block-based programming languages are drawn from English consider if statements and for loops for common examples. Keywords in block-based languages, on the other hand, are often translated into different human languages. For example, depending on the language preference of the user, an identical set of computing instructions in Scratch can be represented in many different human languages:
Examples of a short piece of Scratch code shown in four different human languages: English, Italian, Norwegian Bokm l, and German.
Although my research with Sayamindu Dasgupta focuses on learning, both Sayamindu and I worked on local language technologies before coming back to academia. As a result, we were both interested in how the increasing translation of programming languages might be making it easier for non-English speaking kids to learn to code. After all, a large body of education research has shown that early-stage education is more effective when instruction is in the language that the learner speaks at home. Based on this research, we hypothesized that children learning to code with block-based programming languages translated to their mother-tongues will have better learning outcomes than children using the blocks in English. We sought to test this hypothesis in Scratch, an informal learning community built around a block-based programming language. We were helped by the fact that Scratch is translated into many languages and has a large number of learners from around the world. To measure learning, we built on some of our our own previous work and looked at learners cumulative block repertoires similar to a code vocabulary. By observing a learner s cumulative block repertoire over time, we can measure how quickly their code vocabulary is growing. Using this data, we compared the rate of growth of cumulative block repertoire between learners from non-English speaking countries using Scratch in English to learners from the same countries using Scratch in their local language. To identify non-English speakers, we considered Scratch users who reported themselves as coming from five primarily non-English speaking countries: Portugal, Italy, Brazil, Germany, and Norway. We chose these five countries because they each have one very widely spoken language that is not English and because Scratch is almost fully translated into that language. Even after controlling for a number of factors like social engagement on the Scratch website, user productivity, and time spent on projects, we found that learners from these countries who use Scratch in their local language have a higher rate of cumulative block repertoire growth than their counterparts using Scratch in English. This faster growth was despite having a lower initial block repertoire. The graph below visualizes our results for two prototypical learners who start with the same initial block repertoire: one learner who uses the English interface, and a second learner who uses their native language.
Summary of the results of our model for two prototypical individuals.
Our results are in line with what theories of education have to say about learning in one s own language. Our findings also represent good news for designers of block-based programming languages who have spent considerable amounts of effort in making their programming languages translatable. It s also good news for the volunteers who have spent many hours translating blocks and user interfaces. Although we find support for our hypothesis, we should stress that our findings are both limited and incomplete. For example, because we focus on estimating the differences between Scratch learners, our comparisons are between kids who all managed to successfully use Scratch. Before Scratch was translated, kids with little working knowledge of English or the Latin script might not have been able to use Scratch at all. Because of translation, many of these children are now able to learn to code.
This blog post and the work that it describes is a collaborative project with Sayamindu Dasgupta. Sayamindu also published a very similar version of the blog post in several places. Our paper is open access and you can read it here. The paper was published in the proceedings of the ACM Learning @ Scale Conference. We also recently gave a talk about this work at the International Communication Association s annual conference. We received support and feedback from members of the Scratch team at MIT (especially Mitch Resnick and Natalie Rusk), as well as from Nathan TeBlunthuis at the University of Washington. Financial support came from the US National Science Foundation.

26 June 2017

Jonathan Dowland: Coming in from the cold

I've been using a Mac day-to-day since around 2014, initially as a refreshing break from the disappointment I felt with GNOME3, but since then a few coincidences have kept me on the platform. Something happened earlier in the year that made me start to think about a move back to Linux on the desktop. My next work hardware refresh is due in March next year, which gives me about nine months to "un-plumb" myself from the Mac ecosystem. From the top of my head, here's the things I'm going to have to address: I think that's probably it: not a big list! Notably, I'm not locked into iTunes, which I avoid where possible; Apple's Photo app (formerly iPhoto) which is a bit of a disaster; nor Time Machine, which is excellent, but I have a backup system for other things in place that I can use.

25 June 2017

Steinar H. Gunderson: Frame queue management in Nageru 1.6.1

Nageru 1.6.1 is on its way, and what was intended to only be a release centered around monitoring improvements (more specifically a full set of native Prometheus] metrics) actually ended up getting a fairly substantial change to how Nageru manages its frame queues. To understand what's changing and why, it's useful to first understand the history of Nageru's queue management. Nageru 1.0.0 started out with a fairly simple scheme, but with some basics that are still relevant today: One of the input cards was deemed the master card, and whenever it delivers a frame, the master clock ticks and an output frame is produced. (There are some subtleties about dropped frames and/or the master card changing frame rates, but I'm going to ignore them, since they're not important to the discussion.) To this end, every card keeps a preallocated frame queue; when a card delivers a frame, it's put into the queue, and when the master clock ticks, it tries picking out one frame from each of the other card's queues to mix together. Note that mix here could be as simple as picking one input and throwing all the other ones away; the queueing algorithm doesn't care, it just feeds all of them to the theme and lets that run whatever GPU code it needs to match the user's preferences. The only thing that really keeps the queues bounded is that the frames in them are preallocated (in GPU memory), so if one queue gets longer than 16 frames, Nageru starts dropping it. But is 16 the right number? There are two conflicting demands here, ignoring memory usage: The 1.0.0 scheme does about as well as one could possibly hope in never dropping frames, but unfortunately, it can be pretty poor at latency. For instance, if your master card runs at 50 Hz and you have a 60 Hz card, the latter will eventually build up a delay of 16 * 16.7 ms = 266.7 ms clearly unacceptable, and rather unneeded. You could ask the user to specify a queue length, but the user probably doesn't know, and also shouldn't really have to care more knobs to twiddle are a bad thing, and even more so knobs the user is expected to twiddle. Thus, Nageru 1.2.0 introduced queue autotuning; it keeps a running estimate on how big the queue needs to be to avoid underruns, simply based on experience. If we've been dropping frames on a queue and then there's an underrun, the safe queue length is increased by one, and if the queue has been having excess frames for more than a thousand successive master clock ticks, we reduce it by one again. Whenever the queue has more than this safe number, we drop frames. This was simple, effective and largely fixed the problem. However, when adding metrics, I noticed a peculiar effect: Not all of my devices have equally good clocks. In particular, when setting up for 1080p50, my output card's internal clock (which assumes the role of the master clock when using HDMI/SDI output) seems to tick at about 49.9998 Hz, and my simple home camcorder delivers frames at about 49.9995 Hz. Over the course of an hour, this means it produces one more frame than you should have which should of course be dropped. Having an SDI setup with synchronized clocks (blackburst/tri-level) would of course fix this problem, but most people are not so lucky with their cameras, not to mention the price of PC graphics cards with SDI outputs! However, this happens very slowly, which means that for a significant amount of time, the two clocks will very nearly be in sync, and thus racing. Who ticks first is determined largely by luck in the jitter (normal is maybe 1ms, but occasionally, you'll see delayed delivery of as much as 10 ms), and this means that the 1000 frames estimate is likely to be thrown off, and the result is hundreds of dropped frames and underruns in that period. Once the clocks have diverged enough again, you're off the hook, but again, this isn't a good place to be. Thus, Nageru 1.6.1 change the algorithm around yet again, by incorporating more data to build an explicit jitter model. 1.5.0 was already timestamping each frame to be able to measure end-to-end latency precisely (now also exposed in Prometheus metrics), but from 1.6.1, they are actually used in the queueing algorithm. I ran several eight- to twelve-hour tests and simply stored all the event arrivals to a file, and then simulated a few different algorithms (including the old algorithm) to see how they fared in measures such as latency and number of drops/underruns. I won't go into the full details of the new queueing algorithm (see the commit if you're interested), but the gist is: Based on the last 5000 frames, it tries to estimate the maximum possible jitter for each input (ie., how late the frame could possibly be). Based on this as well as clock offsets, it determines whether it's really sure that there will be an input frame available on the next master tick even if it drops the queue, and then trims the queue to fit. The result is pretty satisfying; here's the end-to-end latency of my camera being sent through to the SDI output: As you can see, the latency goes up, up, up until Nageru figures it's now safe to drop a frame, and then does it in one clean drop event; no more hundreds on drops involved. There are very late frame arrivals involved in this run two extra frame drops, to be precise but the algorithm simply determines immediately that they are outliers, and drops them without letting them linger in the queue. (Immediate dropping is usually preferred to sticking around for a bit and then dropping it later, as it means you only get one disturbance event in your stream as opposed to two. Of course, you can only do it if you're reasonably sure it won't lead to more underruns later.) Nageru 1.6.1 will ship before Solskogen, as I intend to run it there :-) And there will probably be lovely premade Grafana dashboards from the Prometheus data. Although it would have been a lot nicer if Grafana were more packaging-friendly, so I could pick it up from stock Debian and run it on armhf. Hrmf. :-)

Shirish Agarwal: Dreams don t cost a penny, mumma s boy :)

This one I promise will be short After the last two updates, I thought it was time for something positive to share. While I m doing the hard work (of physiotherapy which is gruelling), the only luxury I have nowadays is of falling on to dreams which are also rare. The dream I m going to share is totally unrealistic as my mum hates travel but I m sure many sons and daughters would identify with it. Almost all travel outside of relatives is because I dragged her onto it. In the dream, I am going to a Debconf, get bursary and the conference is being held somewhere in Europe, maybe Paris (2019 probably) . I reach and attend the conference, present and generally have a great time sharing and learning from my peers. As we all do in these uncertain times, I too phone home every couple of days ensuring her that I m well and in best of health. The weather is mild like it was in South Africa and this time I had come packed with woollens so all was well. Just the day before the conference is to end, I call up mum and she tells about a specific hotel/hostel which I should check out. I am somewhat surprised that she knows of a specific hotel/hostel in a specific place but I accede to her request. I go there to find a small, quiet, quaint bed & breakfast place (dunno if Paris has such kind of places), something which my mum would like. Intuitively, I ask at the reception to look in the register. After seeing my passport, he too accedes to my request and shows me the logbook of all visitors registering to come in the last few days (for some reason privacy is not a concern then) . I am surprised to find my mother s name in the register and she had turned up just a day or two before. I again request the reception to be able to go to room abcd without being announced and have some sort of key (like for maintenance or laundry as an excuse) . The reception calls the manager and after looking copy of mother s passport and mine they somehow accede to the request with help located nearby just in case something goes wrong. I disguise my voice and announce as either Room service or Maintenance and we are both surprised and elated to see each other. After talking a while, I go back to the reception and register myself as her guest. The next week is a whirlwind as I come to know of hop-on, hop-off buses similar service in Paris as was in South Africa. I buy a small booklet and we go through all the museums. the vineyards or whatever it is that Paris has to offer. IIRC there is also a lock and key on a famous bridge. We also do that. She is constantly surprised at the different activities the city shows her and the mother-son bond becomes much better. I had shared the same dream with her and she laughed. In reality, she is happy and comfortable in the confines of her home. Still I hope some mother-daughter, son-father, son-mother or any combination of parent, sibling takes this entry and enrich each other by travelling together.
Filed under: Miscellenous Tagged: #dream, #mother, #planet-debian, travel

24 June 2017

Ingo Juergensmann: Upgrade to Debian Stretch - GlusterFS fails to mount

Before I upgrade from Jessie to Stretch everything worked as a charme with glusterfs in Debian. But after I upgraded the first VM to Debian Stretch I discovered that glusterfs-client was unable to mount the storage on Jessie servers. I got this in glusterfs log:
[2017-06-24 12:51:53.240389] I [MSGID: 100030] [glusterfsd.c:2454:main] 0-/usr/sbin/glusterfs: Started running /usr/sbin/glusterfs version 3.8.8 (args: /usr/sbin/glusterfs --read-only --fuse-mountopts=nodev,noexec --volfile-server=192.168.254.254 --volfile-id=/le --fuse-mountopts=nodev,noexec /etc/letsencrypt.sh/certs)
[2017-06-24 12:51:54.534826] E [mount.c:318:fuse_mount_sys] 0-glusterfs-fuse: ret = -1

[2017-06-24 12:51:54.534896] I [mount.c:365:gf_fuse_mount] 0-glusterfs-fuse: direct mount failed (Invalid argument) errno 22, retry to mount via fusermount
[2017-06-24 12:51:56.668254] I [MSGID: 101190] [event-epoll.c:628:event_dispatch_epoll_worker] 0-epoll: Started thread with index 1
[2017-06-24 12:51:56.671649] E [glusterfsd-mgmt.c:1590:mgmt_getspec_cbk] 0-glusterfs: failed to get the 'volume file' from server
[2017-06-24 12:51:56.671669] E [glusterfsd-mgmt.c:1690:mgmt_getspec_cbk] 0-mgmt: failed to fetch volume file (key:/le)
[2017-06-24 12:51:57.014502] W [glusterfsd.c:1327:cleanup_and_exit] (-->/usr/lib/x86_64-linux-gnu/libgfrpc.so.0(rpc_clnt_handle_reply+0x90) [0x7fbea36c4a20] -->/usr/sbin/glusterfs(mgmt_getspec_cbk+0x494) [0x55fbbaed06f4] -->/usr/sbin/glusterfs(cleanup_and_exit+0x54) [0x55fbbaeca444] ) 0-: received signum (0), shutting down
[2017-06-24 12:51:57.014564] I [fuse-bridge.c:5794:fini] 0-fuse: Unmounting '/etc/letsencrypt.sh/certs'.
[2017-06-24 16:44:45.501056] I [MSGID: 100030] [glusterfsd.c:2454:main] 0-/usr/sbin/glusterfs: Started running /usr/sbin/glusterfs version 3.8.8 (args: /usr/sbin/glusterfs --read-only --fuse-mountopts=nodev,noexec --volfile-server=192.168.254.254 --volfile-id=/le --fuse-mountopts=nodev,noexec /etc/letsencrypt.sh/certs)
[2017-06-24 16:44:45.504038] E [mount.c:318:fuse_mount_sys] 0-glusterfs-fuse: ret = -1

[2017-06-24 16:44:45.504084] I [mount.c:365:gf_fuse_mount] 0-glusterfs-fuse: direct mount failed (Invalid argument) errno 22, retry to mount via fusermount
After some searches on the Internet I found Debian #858495, but no solution for my problem. Some search results recommended to set "option rpc-auth-allow-insecure on", but this didn't help. In the end I joined #gluster on Freenode and got some hints there:
JoeJulian ij__: debian breaks apart ipv4 and ipv6. You'll need to remove the ipv6 ::1 address from localhost in /etc/hosts or recombine your ip stack (it's a sysctl thing)
JoeJulian It has to do with the decisions made by the debian distro designers. All debian versions should have that problem. (yes, server side).
Removing ::1 from /etc/hosts and from lo interface did the trick and I could mount glusterfs storage from Jessie servers in my Stretch VMs again. However, when I upgraded the glusterfs storages to Stretch as well, this "workaround" didn't work anymore. Some more searching on the Internet made me found this posting on glusterfs mailing list:
We had seen a similar issue and Rajesh has provided a detailed explanation on why at [1]. I'd suggest you to not to change glusterd.vol but execute "gluster volume set <volname> transport.address-family inet" to allow Gluster to listen on IPv4 by default.
Setting this option instantly fixed my issues with mounting glusterfs storages. So, whatever is wrong with glusterfs in Debian, it seems to have something to do with IPv4 and IPv6. When disabling IPv6 in glusterfs, it works. I added information to #858495.
Kategorie:
Debian
Tags:
Debian
GlusterFS
Software
Server

Next.

Previous.