Winning the Google Open Source Lottery

I don't know about you, but I frequently get mails announcing that I was picked as the lucky winner of a lottery, compensation program or simply as "business associate". Obvious Spam of course, that never happens in reality. Just like my personal "favorite" at the moment: Mails notifying me of inheritance from a previously (more or less) unknown relative. Its just that this is what has happend basically a few weeks ago in reality to me (over the phone through) – and I am still dealing with the bureaucracy required of teaching the legal system that I have absolutely no intention of becoming the legal successor of someone I haven't seen in 20 years, regardless of how close the family relation is on paper… but that might be the topic of another day.

On the 1st March a mail titled "Google Open Source Peer Bonus Program" looked at first as if it would fall into this lottery spam class. It didn't exactly help that the mail was multipart HTML and text, but the text really only the text, not mentioning the embedded links used in the HTML part. It even included a prominent and obvious red flag: "Please fill out the form". 20% Bayes score didn't come from nothing. Still, for better or worse the words "Open Source" made it unlikely to be spam similar to how the word PGP indicates authenticity. So it happened, another spam message became true for me. I wonder which one will be next…

You have probably figured out by now that I didn't know that program before. Kinda embarrassing for a previous Google Summer of Code student (GSoC is run by the same office), but the idea behind it is simple: Google employees can nominate contributors to open source stuff for a small monetary "thank you!" gift card. Earlier this week winners for this round were announced – 52 contributors including yours truly. You might be surprised, but the rational given behind my name is APT (I got a private mail with the full rational from my "patron", just in case you wonder if at least I would know more).

It is funny how a guy who was taken aback by the prospect of needing a package manager like YaST to use Linux contributed just months later the first patch to apt and has roughly 8 years later amassed more than 2400 commits. It's birthday season in my family with e.g. mine just a few days ago, so its seems natural that apt has its own birthday today just as if it would be part of my family: 19th years this little bundle of bugs joy is now! In more sober moments I wonder sometimes how apt and I would have turned out if we hadn't meet. Would apt have met someone else? Would I? Given that I am still the newest team member and only recently joined Debian as DD at all…

APT has some strange ways of showing that it loves you: It e.g. helps users compose mails which end in a dilemma to give a recent example. Perhaps you need to be a special kind of crazy1 to consider this good, but as I see it apt has a big enough userbase that regardless of what your patch is doing, someone will like it. That drastically increases the chances that someone will also like it enough to say so in public – offsetting complains from all those who don't like the (effects of the) patch which are omnipresent. And twice in a blue moon some of those will even step forward and thank you explicitly. Not that it would be necessary, but it is nice anyhow. So, thanks for the love supercow, Google & apt users! 🙂

Or in other words: APT might very well be one of the most friendly (package manager related) project to contribute to as the language-specific managers have smaller userbases and hence a smaller chance of having someone liking your work (in public)… so contribute a patch or two and be loved, too! 💖

Disclaimer: I get no bonus for posting this nor are any other strings attached. Birthdays are just a good time to reflect. In terms of what I do with my new found riches (in case I really receive them – I haven't yet so that could still be an elaborate scam…): APT is a very humble program, but even it is thinking about moving away from a dev-box with less than 4 GB of RAM and no SSD, so it is happily accepting the gift and expects me to upgrade sooner now. What kind of precedence this sets for the two decades milestone next year? If APT isn't obsolete by then… We will see.


  1. which even ended up topping Hacker News around New Year's Eve… who would have thought that apt and reproducibility bugs are top news ;) 

Switching from ikiwiki to staticsite

Earlier this year Enrico Zini experimented with static site generators and ended up with writing his own in python via component reuse. I was running ikiwiki until now myself, which is okay, but I never became ultra happy with it. One of the factors was that I don't speak Perl – but I don't speak Python either. The biggest annoyance of ikiwiki is that it supports so many many features which I don't want/need like online editing and other changes are very hard to do like working on the theme.

staticsite (aka ssite) on the other hand provides very little in terms of features in comparison, but that just means I had less to disable and could play a bit with python, markdown and jinja2 on my own to implement what I really wanted to have (which mostly isn't available in ikiwiki either, so I would have to anyway) and I like playing with such small features compared to rolling my own static site generator in perfect NIH fashion. So, what features? Thanks for asking!

Tag cloud

ssite supports tags just fine and clouds are a display thing, so that is a matter of the template – or so I thought at least. Counting is a bit hard as reassignments aren't easy and jinja2 tries to print what it can. So what I use at the moment looks like a scary hack, but it seems to work for me for now:

{%- for taxonomy in taxonomies() -%}
<ul class="tags">
  {%- set total_tag_number = [ 0 ] -%}
  {%- for t in taxonomy.items -%}
    {%- if total_tag_number.append(total_tag_number.pop() + 1) -%}{%- endif -%}
  {%- endfor -%}
  {%- for key in taxonomy.items.keys()|sort -%}
    {%- set t = taxonomy.items[key] -%}
<li data-rate="{{((10/total_tag_number[0])*(t.pages|length))|round(0,'ceil')|int}}"><a href="{{url_for_tags(t)}}">{{t.name}}</a></li>
  {%- endfor -%}
</ul>
{%- endfor -%}

The resulting unordered list can be styled at will with CSS, I opted for changing the font-size based on the data-rate field – manually for now as support for attr() isn't completely there yet – and making the list look less like a list.

ul li[data-rate] a { font-size: 80%; }
ul li[data-rate="1"] a { font-size: 90%; }
ul li[data-rate="2"] a { font-size: 100%; }
ul li[data-rate="3"] a { font-size: 110%; }

ul.tags, ul.tags li {
    list-style-type: none;
    display: inline;
}
ul.tags li:after { content: ", "; }
ul.tags li:last-child:after { content: ""; }

The result can be seen in the sidebar of this blog. Not completely happy yet, but a good first draft.

Smilies, Emojis, Emoticons and Unicode

ikiwiki has a plugin which uses a markdown list to define which text is mapped to other markdown text (usually an image). That is okayish, but results in a wild mixture of picture styles. It just looks strange if you have a blogpost and one of your smilies has a 3D effect and the other hasn't. Additionally, those are a bunch of small image files… for what is effectively a bit of text – or one (displayed) character: UTF-8 supports all kinds of smilies and other lovely pictures. Or, at least if the font you are using does, but that might be the topic of another post. Assuming good support you can do many cool things with UTF-8. The usual smilies like 🙂 😉 😃 😎 the absolutely needed cat variants like 🐱 😸 places on a 🗺 like the 🗽 and of course also various people like 👨 👩 💂 👧 and 👦 who can travel to those places by 🚗 or 🚂 And some of those unicodes can be Fitzpatrick-skinned so that 👍 becomes 👍‍🏻 👍‍🏼 👍‍🏽 👍‍🏾 👍‍🏿

That feature isn't really ssite specific: It is implemented as a simple python-markdown extension replacing things like :) with 🙂 – just many many more of those replaces. You would think there are many pre-existing extensions dealing with this, but I couldn't really find one to my liking. Most of them are actually doing the same as the ikiwiki plugin: Mapping text to tiny images: Honorable mention is githubemoji which hotlinks the emojis github supports (& has replacement images for). There are others which do similar (hot)linking of images, but a small supported character range is common and funky stuff like the mentioned fitzpatrick or region letters creating flags ( 🇩 + 🇪 = 🇩‍🇪 ) stuff isn't supported in any. So, you guessed it: I implemented it myself. Partly at least. I am still working on making this great while learning python with it, so that will take some time still as I have basically reimplemented it a few times already… and there is also this problem that support for this isn't even close to be universal so something needs to be done about that, too.

Theme of the site

ssite comes by default with a bootstrap-based theme. That is okay, but that also means it looks like nearly every other page on the planet in terms of colors and stuff. It also means I have to include hundreds of kilobytes of frameworks in CSS and JavaScript (preferably via some CDN) to get that. And then I have to change the HTML to drop classes everywhere which control look and feel of the elements I have styled with them. That is okayish for large projects I guess. I used it myself in the past but perhaps the conversion of bootstrap2 to 3 I did as part of a university project some time ago distorts my feeling in the negative direction. I kinda like fiddling with CSS and Javascript (after all, I created my own Firefox extension to fiddle with them on all sites I visit: dotPageMod) on the other hand this is a personal page I don't have much problem if it isn't working in IE8 or what not, so the theme is a personal creation. Very minimal as I actually liked that property in ikwiki but with less ugly changes in the ikiwiki specific template syntax and more with jinja2 which is its own template syntax, but at least an independent engine used by others as well, so I might stumble over it again and it feels overall more powerful & natural.

So, perhaps not pretty and not a maximum in browser compatibility, but mine and that makes me happy. 😃 Various things I want/might change in this section as well, but a website is never really done anyhow… 🚧 👷.

anything else?

Not much actually. Enrico implemented a markdown jinja2-filter based on a proof-of-concept patch from me and fixed some bugs I had reported really quickly. All in all the journey so far was quite enjoyable and it will be interesting to see how my impression is next year! As mentioned I have some ideas still, but I wanted to make a cut now and declare it version 1…

Also: One last far well to ikiwiki. I leave you for a younger & prettier alternative, but don't you worry: You served me well (and still do in some places) and there are many others which still depend on you and who knows, perhaps I will leap back if I ever want to get into perl. After all, one of the reasons I opted for ikiwiki back then was that I might learn some perl in the process. Didn't work, but perhaps next time. So long and thanks for all the fish, ikiwiki!

the new apt-transport-tor

It happened: Now that I am an uploading DD for a few months I finally made my first upload of a package – mind you, not of apt, but of a package I declared my intend to "steal" from another person a few weeks ago on deity@ and later also in a bugreport (#835128).

The result is that apt-transport-tor which used to be maintained by Tim Retout as a modified copy of apt code is now maintained by the APT team (with him and me as uploaders) using the apt code directly via a few symlinks.

That brings along a bunch of changes which I mentioned in the list/bug as well, but for completeness:

I had tried a few times to get people to provide feedback, but there wasn't much. I guess this is good as it means nobody has any complains about it. We will see if that will change now that it is on its way to archive, buildds, mirrors and users: Brace for impact in any case!

GSoC 2016: Summary

Intro, Outro and tl;dr

I participated again as a student in this years edition of the Google Summer of Code with Debian on the project APT↔dpkg communication rework. My initial proposal on the wiki details me and the plan, while this post serves as link hub and explanation of what I did. You can also find personal week-to-week posts starting with Day 0 right here on this blog, too.

The code for this project was already merged and uploaded to Debian unstable multiple times over the course of the summer, so everything described here later can be experienced directly. The official GSoC2016 final is 1.3~rc2, but APT always moves forward and I have no intention of leaving it alone, so this tag just marks the end of the GSoC2016 period and my return to "normal" contribution levels.

On a social front I finally applied for and shortly after received "Debian Developer, uploading" status. This is also the moment I want to thank Michael Vogt (mentor, apt), Julian Andres Klode (apt), Manuel A. Fernandez Montecelo (aptitude), Guillem Jover (dpkg), Enrico Zini (AM), the Debian Outreach team and the countless people I should have mentioned here, too, who have all helped me in many ways over the course of this GSoC and my entire Debian journey up to this point.

It was an overall great experience to work again on something as important as APT in Debian on a full-time basis. After two (very different) GSoCs in 2010 and now 2016 I can full heartily recommend to any student with a passion for open-source to apply next year. Perhaps in Debian and maybe in an APT project? We are waiting for YOU!

Statistics

My first commit as part of GSoC was made on 25. April titled edsp: ask policy engine for the pin of the version directly (minor bugfix), the last commit I will be counting on 17. August titled methods: read config in most to least specific order (regression fix). Not all of them are directly related to the GSoC project itself (the first is), but "just" in the timeframe (like the last) but were handled as part of general emergencies or for similar reasons described later and/or in the weekly reports. This timeframe of 115 days saw a total of 222 commits authored by me + 9 commits committed by me for others (translations, patches, …). The timeframe saw 336 commits as a whole making me responsible for a bit shy of ⅔ of all APT commits in this timeframe with on average of nearly 2 commits each day. A diffstat run over my commits says "322 files changed, 11171 insertions(+), 5847 deletions(-)" consisting of code, documentation and tests (this doesn't include automatic churn like regeneration of po and pot files, which deludes the global statistic). As a special mention our tests alone changed by: "109 files changed, 2759 insertions(+), 1063 deletions(-)". In my weekly reports here on this blog I used ~10574 words (not including this post), another ~23555 words in the IRC channel #debian-apt and sometimes very long mails to deity@ and bugreports (~100 mails) [Not counting private chit-chat with mentor via IRC/mail].

APT External Installation Planner Protocol (EIPP)

The meat of the GSoC project was the ability to let libapt talk to (external) executables (called planners) which are tasked with creating a plan for the installation (and removal) of packages from the system in the order required by their various dependency relations, similar to how libapt can talk to external dependency solvers like aspcud via EDSP. The protocol (current, archive) details how apt and a planner can communicate. APT ships such an external planner already in the form of 'apt' which is "just" using the internal always existing planner implementation, but reads and talks proper EIPP. The major benefit is testing here as it is now possible to generate an EIPP request, feed it to different versions and compare results to find regressions and similar. It also helps in bugreports as such a request is now auto-generated and logged so that it can be easily attached to bugreports and a triager can use that file to reproduce the problem. Previously recreating the system state a user had before the failed upgrade was a very involved, error prune and time consuming task (actually fixing the problem still is, but at least the first step got a lot easier).

APTs good old planner implementation saw also the activation (and fixing) of many previously experimental options intended to optimize the process blocked previously by items of the next paragraph, which makes it look like a new planner now. Entirely new planners exist as prototypes, but they aren't suitable for real use yet due to not handling "edgecases" and being effected by bugs in dpkg. Summary: Everyone can create and work on his own planner in the programming language of choice and run it against realworld cases directly opening a competition space for the invention of future improvements.

APT↔dpkg communication

The other major building block and donor of much of the projects name. Assuming a planner has figured out a plan there is still much left to do which is of no concern for each planner but handled centrally in libapt: The actual calling of dpkg and interpreting its replies. That sounds easy enough, but if you imagine the need of thousand of packages to be installed/configured at once you fear hitting something as barebones as the kernels maximum allowed commandline length. That happened once in a while in the past so finding better solutions to that problem within easy reach (as in: existing in dpkg already, new interfaces for possible future use are a different matter) is in order. Other problems included the overuse of --force options, not communication the purge/removal intentions to dpkg, insufficient crossgrade handling and avoiding losing user configuration on conffile moves involving packages to be purged just to name a few. But also listening to dpkg in terms of how it processes triggers and how all this should be reported in the form of progress reports to the user especially if some steps aren't explicitly planned anymore by a planner, but left to dpkg to do at some point.

The result is mostly invisible to the user, expect that it should all be now slightly faster as e.g. triggers are run less and most "strange" errors a thing of the past.

Side projects, emergency calls and random bufixes

Not actually on my plan for GSoC and at best only marginally related if at all I ended up working on these to deal with important bugs on a "as long as we have a full-time developer" basis.

This includes hunting for strange errors if rred is involved in updating indexes, further preparing for a binary-all future, fixing SRV support, being the master of time, improving security by allowing it to be sidestepped sometimes, improving security by potentially breaking backward-compatibility a bit, stumble into libstdc++6 bugs, implement SOCKS5 proxy support and generic config fallback for acquire methods to be able to propose the mergeback of apt-transport-tor among very many other things.

A complete list can be found with the previously shared git-branch browsing starting at my first commit in the GSoC timeframe (see also statistics above).

Future

I would love to keep working on APT full-time, but that seems rather unrealistic and all good things need to come to an end I guess, so the next weeks will have me adjust to a more "normal" contribution level of "just" in my (extended) free time again. I will also be casually "shopping" for a new money source in the form of a small job while returning to university which hasn't seen a lot of me the last few months and picking up some community work I had delayed for after GSoC. That means I will surely not keep my daily commit average up, but my journey here is far from over:

After many years in APT and Debian there is still something new in it to explore each week as both are evolving continuously – but most of it hidden in plain sight and unnoticed by the general public: Around the start of GSoC I was talking on #gsoc with an admin of another org who couldn't imagine that Debian participated at all as all projects Debian could offer would be bitsized in nature: It is just a distribution, right, not a real org producing value (slightly exaggerated for drama). I would like to concur with this view of course for obvious reasons.

My life would be massively different if I hadn't started to contribute to Debian and APT in particular ~7 years ago – even through I thought I wouldn't be "good enough" back then. I think its fair to say that I showed my past self that in fact I am. Now it is your turn!

Week 16: Constant Optimization

This week saw the release of 1.3~rc1 sporting my tor-changes disguised as general acquire methods changes I mentioned last week as well as the revamp of apt talking to dpkg (and back) I worked on the last couple weeks as part of GSoC. It doesn't include any new planner, a stub is still lying in a wip branch, but our good old planner looks and behaves slight different, so it feels like a new one – and surprising as it is: So far no bugreport related to this. Probably all user systems caught instantly fire! 🙂

So, the week was further used to get used to cmake, build and run apt on various porterboxes to fix testcase failures, fixing other incomings and especially pull some hair out while debugging the bug of the week which lends the title to this blogpost: A one word fix for an issues manifesting itself only in optimization level -O3 on ppc64el. Optimizations are evil…

Beside causing quite some time waste for this week as well as in previous years it is also closing a loop: I introduced this problem myself while being a GSoC student… in 2010. Time really flies. And I have no idea what I was thinking either… I could be describing more of these "tiny" bugs, but the commit messages tend to do a reasonable job and if you are really that damn interested: Feel free to ask. 🙂

This next week will be the last official in GSoC from a students POV as I am supposed to clean up all bases & submit my work for the final evaluation – this submit will be as a blogpost describing & linking to everything, which equals miles long and relatively soon, so that I purposefully have kept this one a very short one so you will have enough energy to bear with me for the next one.

Week 15: Onion ordering

The week started badly: I had for a long while now a dead 'e' key on my keyboard, but I didn't care that much… I just remapped CAPSLOCK, retrained my fingers and be done with it [I have some fucked up typing style anyhow]. All good, but at this week additional keys started to give up. You have no idea how annoying it is to not be able use the arrow keys. Many things I work with have at least the vim-keybindings, but even in vim picking an autocompletion becomes a nightmare (or navigating shell history)… So, replacement keyboard please! That took a while, especially replacing it as my laptop makes that extra hard it seems but oh well. All working again now! The c-key is actually working a bit too good (you have to only touch it now, which had me worried as it started out with producing and endless stream of 'c' out-of-the-box before I removed the cap once) but so be it for now.

As you might guess that wasn't the ideal work-environment and slowed me down (beside being annoying), so what I intended to do as a sideproject turned out to be covering most of the week. Mergeback of apt-transport-tor into apt? Yes, no, maybe? The first few responses by mail & IRC are in regards to the plan, but that still had the need for a lots of code to be written and refactored. I have to say, implementing SOCKS5 proxy support in apt was kinda fun and not nearly as hard as I had imagined. Slightly harder it was to get a setup working in which I could test it properly. Everyone knows netcat, but that really targets more text-based protocols, not binary ones like SOCKS5. Still, I managed to figure out how to do it with socat eventually, resulting in a testscript we can at least run manually (as it requires a specific port. Not every tool is as nice as our webserver which can be started on port 0 and reports the port it eventually picked for real). Playful as I am I even compared my implementation to others like curl, which our https method is using, where I ended up reporting minor bugs.

But why and why now you might ask: apt-transport-tor can be (surprise surprise) used to let apt talk to Tor network. Conceptionally that isn't incredibly hard: The Tor software provides a SOCKS5 proxy an application can connect to be done. Two years ago then apt-transport-tor was introduced only our curl-backed https method could do that & the intention was be able to make backports of that transport available, too, so even through I wasn't all that happy about it, we ended up with a modified copy of our https method named tor in the archive and as it is with most modified copies of code, they aren't really kept in sync with the original. I really want to get this resolved for stretch, so it slowly gets hightime to start this as if it turns out that I need to take over maintenance for it without previous-maintainer consent there is quiet a bit of waiting involved stuff like this should really not be changed last-minute before the freeze… you will find more details in the mentioned mail on the reasons for proposing this solution in the mail.

Beside, SOCKS support is actually a so much requested feature that the internet actually believes apt would support it already via Acquire::socks::proxy … which is and will also be in future wrong as there is no socks method we would configure a proxy for – if at all you configure a method like http to use a socks proxy…

Of course, bundled with this comes a bunch of other things like better redirection handling across methods and stuff, but that isn't really user visible, so I skip it here and instead refer you to the git branches if you are really interested. A few things I will surely also mention then the relevant code is in the archive so that interested peers can test…

On my actual battle front, the ordering progress was insignificant. I got lots of manual testing and review done, but not much new stuff. The problem is mostly that ordering is easy as long as the problem is easy, but as soon as Pre-Depends are entering the picture you suddenly have to account for all kinds of strange things like temporal removals, loops conflicting or-groups, … stuff you don't want to loose hair over while losing hair over your broken keyboard already. 😉

This week for realz, although target is now really more to merge the current stuff for apt 1.3. A new ordering algorithm is as detailed in the initial proposal buster material anyhow – and given all the changes in terms of trigger delaying and pending calls you are likely not to recognize our "old" ordering anymore, but more on this in the next two weeks as that will be the end of GSoC and hence I am going to look back at "the good old times" before GSoC compared to what we have now. 🙂

P.S.: This weeks weekend marks the start of a big wine festival in our state capital my family is one of the founding members of. I am "just" going to help building the booth through, so no giant timesink this time – just a couple hours – just in case you hear me saying something about wine again on IRC.

Week 14: This is CROSS!

Picture me as a messenger kicked into an endless pit of complexity by what was supposed to be an easy victim. It wasn't /that/ bad, but massaging apt to treat crossgrades right took some time – and then some more to request that dpkg would handle some of it, too, as it gets confused by multi-instance packages. Much like apt although that was just effecting apts progress reporting so not that bad… perhaps I am play-testing too much

In unrelated news I dealt with the two acquire bugs which started last week as such bugs are annoying & carry the risk of being security problems which would require immediate attention. Thankfully non of them seems to be one, but #831762 had me seriously worried for a while. Trivial in retrospective, but getting to a point in which you consider the possibility of that happening at all…

But back to the topic: There was one thing still needed to get our current internal planner a bit "smarter" by enabling options which existed for a while now, but were never activated by default, and that thing was simulation. While its kinda appealing to have the simulation only display what the planner explicitly told use to do, ignoring what would implicitly be done by the --pending calls we can't really do that as this would be an interface break. There are surely scripts out there doing funny things with this output so having it be incomplete is not an option, which in turn means that what I did internally for the progress reporting (and hook scripts) must also be done in the simulation. Easier said then done through as the implementation of it followed a direct approach running the simulation of each action as soon as the action was called rather than collecting all the actions first to post-process them (as I want to do it) and execute them only then. Add to this that this is a public class, so ABI is a concern… the solution I arrived at is slightly wrong, but is going to satisfy all existing callers (which is only aptitude in the archive thanks to codesearch.d.n) and reuses the "dpkg specific" code, which is a layer violation, but reuse is better than copy&paste without breaking ABI, so I am happy all things considered.

So, with that out of the way glory awaits: Changing the default of PackageManager::Configure from "all" to "smart"… and tada: It works! The simulation shows everything, the dpkg invocations are much shorter, trigger executions delayed, we rely more on --pending calls and progress reporting is properly moving forward as well! Not 100% production ready but good enough for a public wip branch for now (= wip aka: going to be rebased at will).

This also includes the barebones 'dpkg' planner I mentioned last week, based on that I was playing with ideas to find a more viable implementation (= handling Pre-Depends) but nothing of particular note produced yet. Maybe I can get something working this week – it is at least part of the plan beside polishing my wip branch – after leaving that pit that is… Hello, is anyone up there? Hello? Hello? …

Week 13: Progress reporting

On the public side of things I did a bunch of things this week which weren't exactly related to the GSoC project which were triggered by incoming mails (and IRC highlights) with bugreports and interesting whichlists, which isn't completed yet as there are two new responses with debug logs waiting for me next week.

I say that as I brushed up a smallish commit for merge this week which is supposed to deal better with triggers in progress reporting. That sounds boring – writing progress reporting stuff – but many people care deeply about it. While this one is more of a cosmetic change its conceptionally a big one: With the actions the planner proposed, apt builds for each package a list of states it will pass through while it is installed/upgraded/removed/purged. Triggers rain in this parade as we don't know beforehand that a package will be triggered. Instead, a status message from dpkg will tell us that a package was triggered, so if we don't want to end up in a state in which apt tells via progress report that it is done, but still has a gazillion triggers to run we have to notice this and add some progress states to the list of the triggered package – easy right? The "problem" starts with packages which are triggered but are destined to be upgraded to. A triggered package will loose its trigger state if it is unpacked, so our progress report has to skip the trigger states if the package is unpacked – we can't just exclude packages if they will be unpacked as it can easily be that a package is triggered, the trigger is acted upon and is upgraded "ages" later in this apt run.

My wip branch contains many more progress related commits as there is a big gotcha in the description above: I said "with the actions the planner proposed", so what about the actions the planner isn't proposing but will happen as part of dpkg --configure/--remove/--purge --pending calls? And what about hook scripts like apt-listbugs/changes which get told the actions to perform their own magic?

The solution is simple: We don't tell dpkg about this, but for our own usage we do trivial expansions of the --pending commands and use these for progress report planning as well as for telling the hookscripts about them. That sounds like a very simple and optional thing, but it was actually what blocked the activation of various config options I had implemented years ago which delay trigger execution, avoid explicit configuration of all packages at the end and all that which I could now all enable – a bit more on that after this hits the master branch. 🙂

I also looked into supporting crossgrades better. In apts conception a crossgrade is the remove of a package of arch A and the installation of a new package (with the same name) of arch B. dpkg on the other hand deals with it like a 'normal' upgrade, just that the architecture of the package changes. The issue with that isn't gigantic usually, but it becomes big with essential packages like if you try to crossgrade dpkg itself with apt: APT refuses to do that by default, but with enough force it will tell dpkg to remove dpkg:A and then it tells dpkg to unpack dpkg:B – just that there is no dpkg anymore which could unpack itself. At least in that case we can skip the remove of dpkg:A, but we can't do it unconditionally as that might very well be some part of an order requirement, so progress reporting should be prepared for either to (not) happen… That isn't finished yet and will surely leak into next week.

Next week will also see my freshly built planner 'dpkg' get a proper tour: With all the --pending calls it seems like a good idea to try to be extra dumb and have a planner just unpack everything in one go, let the rest be covered by --pending calls and see what breaks: Obviously the harder stuff, but I have two directions I would like to explore based on this minimal planner to make it viable. First I have to finish the crossgrading through, my usual self-review of commits and the bugreports I participated in this week want to trigger further actions, too… see you next week!

Week 11+12: Where did all the time go

Julian said that in his talk about the last year in APT in regards to (further) fixes to the performance of pdiff and apt in general. I want to say that about the last two week in general through. I was two days at the university (last two weeks of lectures even), a day helping moving, a day away with the young group, a combined day busy with mental and organisational buildup and teardown of that away-day, 5 days building, tearing down and in between manning our wine booth as well as other booths at a festival… Somehow that left only 4 days for day-to-day business like gsoc work… not ideal, especially if the plan isn't working out as it should either. I had to deal with a few issues uncovered by our testsuite caused (on non-amd64 architectures) more or less by the EIPP merge. Mind you, not actual hardcore bugs, but mostly: For some esoteric reason like additional lines in output the testcases are unhappy, but its not reproducible always and absolutely not on your local system.

Turns out that one of them was a deeper issue with how compression methods can be dynamically configured and how the testcases do this to force testing of certain aspects which interfered with me hardcoding xz-compression for EIPP – time-dependent of course as EIPP tends to run faster than /bin/false (no joke, as the errors were pipe write errors which only happen if the program we called closes the pipes aka exits). Sounds simple, but the fix is split over 6 logical commits (which all just change a few lines, but finding them is the trick…). Another dpkgs inability to change the architecture it believes to be native, while apt can do that easily and uses it in the testcases frequently.

Another issue was an a lot bigger bug in which apt ended up changing permissions, ownership & access/modification times on files it should actually only read through symlinks created by the file:// method. Finding and fixing this was an interesting walk in the kernel/libc API park as even if it isn't strictly needed to change the ownership of a symlink, it feels better too avoid to much of special casing if it can be helped and what we really don't want is singling out the Linux kernel against other kernels – I did that once accidentally (#738567) and try to avoid it ever since (that report is related by the way as that call would have been handy if it could have been used here…).

With the weeks so grossly derailed I purred some time into an issue with our relatively new SRV records support which was working only if the first connect would be successful, which is kinda against the point of SRV. Testing this was fun as I was actually convinced I would need a fullblown DNS server setup (much like we need a fullblown webserver setup so much that we implemented our own), but it turned out that its dead simple to add SRV records via dnsmasq, so that was easy to test (after I figured that out that is) at least interactively.

Also I implemented support for "install ./foo.changes" partly in response to the possibility of securing the download of individual debs question in the APT talk – now you can distribute a bunch of debs (and dscs) via a changes file, which can be signed (which the USER has to verify!) and includes the hashes of said files (which apt checks against). Mostly I was doing it for me through as I do local rebuilds at times (like dpkg with a fix for #830267) and picking the individual debs can be a bit annoying and with changes its slightly less bad.

Apart from that I looked into the progress reporting thing as intended and tried a few options, but that isn't all too easy given that apt is expecting to know EVERY action performed… I started with this, but I will probably tell you more about that next week as I fully intend to quickly make up for last two weeks, so I better get started right about now…

Week 10: That is plane wrong!

As a kid I liked Asterix as comic as well as in the animation films – I am not so fond of the actor films and haven't looked at the newer comics, but that is beside the point. I want to quote Obelix here: "These Brits are crazy!". Not because of the recent vote to leave the EU or because the english soccer team decided that this vote applies also to their play. No, I am thinking of the scene in the film in which the hero's walk down a street in search for a house and all of the houses in the street, the block, even the district look the same, but luckily they have the number, find the one and beat up the inhabitant only to be told that an 'I' is missing in the number…

After last weeks merge, I was told that "planer" doesn't mean what I thought it does. A planer is actually a type of machine to make stuff plane – which is again not making something into a plane to fly with it, but to make something plane so you don't get splinters (if its wood), all of this can be done according to a plan btw. What I meant is a "planner" – aka I was missing an 'n'. Perhaps only because I have light dyslexia, but I hate these language things. German isn't all around better in this: "The 'Planer' makes a 'Plan'." but the stuff can still be made 'plan' (even through 'planar' is what you usually hear and it hasn't the wood-meaning, you can just do this to the ground). But at least we don't drag planes or plants into this, the later being a masterpiece of word meaning all by itself… but enough of a "rant", I am pretty sure it all makes sense if I would look up history more than I did and in the end its just me trying to hide my embarrassment over such trivial mistakes being made by me for weeks…

Anyway, on the real topic of this post as I did more than just correcting this mistake (which did take a while through). Beside various things which are only slightly related or even not at all like: Not overriding an atomic file if the new file had failures in creation (oh my god, how did we miss that for so long?!?), various testing things, an overhaul of the autoremover code + implementing 'protect only the latest same-source provider' which has explicit benefits e.g. in terms of out-of-tree kernel modules (if built e.g. with module-assistant instead of dkms) as well as in other cases, fixing the handling of local deb files if it was previously already installed in that version as not behaving like a downgrade and finally a bunch of apt-key changes to make its badness more visible… which all went directly to git/master.

I started another of my wip branches for the things I am actually paid for to do: The plan was to tackle some "how apt invokes dpkg" things. Silly things like not setting --force-remove-essential on each and every remove/purge (if possible, there are non-default apt options which prevent apt from knowing which packages are essential in dpkgs view).

Also worked on codifying the --recursive usage for --unpack which sets up a symlink farm in a temporary directory and tells dpkg said directory instead of explicitly listing each and every package on the commandline explicitly (which can turn out to be quite long, see weeks earlier), but as mentioned back then this doesn't work yet unconditionally as dpkg has a bug in its ordering code, so for the time being apt needs to be nice and still help dpkg out here (that is the type of stuff I mentioned in my proposal as likely hindrance of using another planner for stretch already).

I also began saving, clearing and restoring dpkg selections before/after running dpkg so that a planner can eventually outsource the removal orders to dpkg. That is quite a dance as these selections are user settings "for the future" which we can't just discard, but we also can't just ignore them as they can include purge selections and if we would not unset them before calling dpkg in a new world order apt would implicitly instruct dpkg to perform removals the user hadn't agreed to… frankly, its a freaking mess, but the interface exists so I have to make due with what we have rather than what we "will like to be have had" if only there was a timemachine.

I am somewhere deep down in this clusterfuck, but I see light at the end of the tunnel – or perhaps that is just an oncoming train. Hopefully I am out of this by next week. I also want to give --no-triggers a chance again, a few years back I implemented support for it, but it never really saw the daylight thanks to bugs in dpkg and elsewhere, but perhaps now is a good moment for retrying. It does deal the final blow to sensible progress reporting through, so I would need to figure something out for that, too… we will see; planning plane plans isn't always working out for me.

(This weekend I have a daytrip with ~70 kids with the usual last minute emergencies and much needed decompress afterwards, so reports might be delayed and my replies/work even more off business hours than usual).