Older blog entries for joey (starting at number 485)

podcasts that don't suck

My public radio station is engaged in a most obnoxious spring pledge drive. Good time to listen to podcasts. Here are the ones I'm currently liking.

  • Free As In Freedom: The best informed podcast on software licensing issues, and highly idealistic. What keeps me coming back, though is that Karen and Bradley never quite agree on things, and always end up in some lawyerly minutia culdesac that is somehow interesting to listen to. They once did a whole show about a particular IRS tax form, and I listened to it all. (Granted, I often listen to this while cleaning house, but as Bradley would say, at least I'm not listening to it while driving.)

  • This Developer's Life: At least the early episodes before it got popular are a unashamed imitation of This American Life, and I have quite enjoyed them. Although I often roll my eyes at the proprietary developer mindsets on display in the show. For example, often they'll have a bug and not root cause it, because well, they don't have the source code for the Windows layers. Still, beneath that it's mostly about the parts of software development that are common to all our lives. A particular episode I can recommend is #10 "Disconnecting" -- the first 20 minutes is a perfect story.

  • Off the Hook: This is actually a live radio show, quite well done, with call-ins and everything. So much more polished than your typical podcast. It's hosted by Emmanuel Goldstein! And it's been going on for over 20 years, so why did I never hear about it before? Probably I'm not quite in the right hacker circles. Since it's out of NYC and very anti-authoritarian, I've mostly been enjoying it as a view into the Occupy protests.

  • StarShipSofa: The best science fiction podcast around. Probably not news to anyone who ever looked for such a podcast. Long, and tends to be frontloaded with a lot of administrivia, which I fast-forward to get to the stories.

  • Spider on the Web: The best music and science fiction podcast around. Mostly on hiatus since Jeanne died, but I hope Spider picks it back up. A good examplar is "Bianca's Hands"

  • Long Now Seminars: Consistently interesting. I visited their space last time I was in SF only to learn they'd had a talk the night before, which would have been a bummer, except they ran the bits of the Clock for us.

  • Linux Outlaws: After 18 years using Linux, I find the level of discourse in most Linux podcasts typically rather annoying. Including this one, but when Fab gets on a rant, it's all worth it. Sometimes some interesting guests.

  • This Week In Debian: Sadly no new episodes lately, and I've been too lame to respond to repeated interview requests. Probably it needs to move away from being an interview show if it is to continue; there are only so many DD's who can give excellent interviews like liw did.

Syndicated 2012-03-30 21:28:22 from see shy jo

case study: adding box.com support to git-annex

git-annex has special remotes that allow large files checked into git to be stored in arbitrary places, that are not proper git remotes. One key use of the special remotes is to store files in The Cloud.

Until now the flagship special remote used Amazon S3, although a few other things like Archive.org, rsync.net, and Tahoe-Laffs can be made to work too. One of my goals is to add as many cloud storage options to git-annex as possible.

Box.com came to my attention because they currently have a promotion that provides 50 gigabytes of free "lifetime" service. Which is a nice amount of cloud storage to have for free. I decided that I didn't want to spend more than 4 hours of my time to make git-annex use it though. (I probably have spent a week on the S3 support by contrast.)

So, this is a case study in quickly adding support for one cloud storage provider to git-annex.

  • First, I had to sign up to box.com. Their promotion requires an android phone be used to get the 50 gigabytres. This wasted about an hour getting my unused phone dusted off etc. This also includes time spent researching ways to access box.com's storage, including reading their API documentation. I found it has a WebDAV interface.
  • Sadly, there is not yet a native WebDAV library for haskell. This is a shame, because it would make the implementation better. But, I'm confident someone will eventually write one. My experience with haskell libraries for other web APIs (S3, GitHub) is that it's an excellent language to write them in, the code tends to be very simple, concise and clear. But I can't do it in 4 hours. So for now, the workaround is to use a WebDAV mounting tool. I picked davfs2 as it was the first one I got to work with box.com's slightly broken WebDAV. 2 hours spent now.
  • With box.com mounted, I was neary done; git-annex's directory special remote can use the mount point. But there was a catch: box.com only allows up to 100 mb large files. I spent 1 hour or so adding support to the directory special remote for chunking files into a user-specified size.
    This was a fairly complex problem -- the existing code had a ByteString that when accessed lazily read the whole large file (from disk or from gpg, depending), and just called writeFile on it.
    I needed to still consume it lazily to avoid reading the whole file into memory, but write out chunks. This gets a bit into haskell's ByteString internals, but they're very well suited to this kind of thing, and so after 15 minutes familiarizing myself with the data structures, it was actually fairly easy to write the code. patch
  • I spent my last hour testing and tuning the box.com special remote. Using davfs2 as a quick fix caused some technical debt that I had to make up for. In particular, the chunked filename retrieval code had to make sure not to open every chunk at once, because that makes davfs2 try to cache them all, instead of streaming one at a time. patch
  • Not counted toward my 4 hour limit is the ... er ... 4 hours I spent last night adding a progress bar to the directory special remote. A progress display while transferring the files makes using box.com as a special remote much nicer, but also makes using my phone's SD card as a special remote much nicer! This is why I'm a poor consultant -- when faced with something generic and generally useful like this, I have difficulty billing for it.

The end result is that there are detailed instructions for using box.com as a special remote.

And it seems to work quite well now. I just set up my production box.com special remote. All content written to it is gpg encrypted, and various of my computers have access to it, each using their own gpg key to decrypt the files uploaded by the others. (git-annex's encryption feature makes this work really well!)

There is a DropBox API for haskell. But as I'm not a customer, the 2 gb free account hardly makes it worth my while to make git-annex use it. Would someone like to fund my time to add a dropbox special remote to git-annex?

Syndicated 2012-03-04 17:28:59 from see shy jo

leap day

This leap day saw me driving along the river on a rainy, with 4 chickens in the car's trunk, and 3 terabytes of disk (and a half a bale of straw) in the back seat. I may have not been blogging much lately about life, because these situations can be hard to explain. (Or because "joined the Debian haskell team and spent two days working on rebuilds for the ghc 7.4 transition" is not thrilling reading.)

hens in a car

The Light Sussex chickens are my sister's spare flock, which are "too tame". They're now cozily installed into a coop we built last weekend. In return I gave her a 6 foot long APC power strip, which had been mounted on the wall of my office. I'm preparing my house in town to be rented, and have little need for two dozen power outlets here in solar power land.

Google <3s Your Work

Indeed, today is a gift economy day all around -- when I arrived at the cabin, there on the porch was an unexpected package from Google. Particularly surprising since I never get deliveries here, since the driveway is a mile long and often seems like it could dead-end into the woods at any moment.

The combination of technological wackiness (I also debugged a laptop whose USB hub hangs when a particular trackball is plugged in) and in your face country texture (including coal trains, being stuck behind a tractor, and miles of amazing tree-height mist) made this a memorable day.

Syndicated 2012-02-29 21:30:30 from see shy jo

addicted to $

One of the weird historical accidents of programming languages is that so many of them use $ for important things. The reason is just that out of the available punctuation, nearly all of it has a mathmatical or other predefined use that makes sense to retain in a programming language context, while $ (and also @ and #) do not. Still, $ annoys me, it's so asymetric that we use it all over our code, and never a £ or ฿ to be seen.

The one language that manages to use $ nicely, IMHO, is Haskell. Recently I noticed that it has an actual visual mnemonic in its use of $. And it's used for something I've not seen in other languages.

The visual mnemonic of $ is that it looks like an opening parenthesis, with the related closing parenthesis on a line below it.

  (something (that
    (lisp folks
        (are (very (familiar with)))

And this is also the problem that $ solves:

  something $ that $
    haskell folks $
        are $ very $ familiar with

This is a trivial feature.. but oh so useful. The implementation in Haskell of $ is simply:

  f $ x = f x
infixr 0 $

Just function application, but at a different precedence than usual.

I am now very addicted to my $. Out of 15 thousand lines of code, only 87 contain )), while 10% use $.

Syndicated 2012-02-17 16:49:54 from see shy jo

more on ghc filename encodings

My last post missed an important thing about GHC 7.4's handling of encodings for FileName. It can in fact be safe to use FilePath to write a command like rm. This is because GHC internally uses a special encoding for FilePath data, that is documented to allow "arbitrary undecodable bytes to be round-tripped through it". (It seems to do this by encoding the undecodable bytes as very high unicode code points.) So, when presented with a filename that cannot be decoded using utf-8 (or whatever the system encoding is), it still handles it, and using the resulting FilePath will in fact operate on the right file. Whew!

Moral of the story is that if you're going to be using GHC 7.4 to read or write filenames from a pipe, or a file, you need to arrange for the Handle you're reading or writing to use this special encoding too. I use this to set up my Handles:

  import System.IO
import GHC.IO.Encoding
import GHC.IO.Handle

fileEncoding :: Handle -> IO ()
fileEncoding h = hSetEncoding h =<< getFileSystemEncoding

Even if you're only going to write a FilePath to stdout, you need to do this. Otherwise, your program will crash on some filenames! This doesn't seem quite right to me, but I hesitate to file a bug report. (And this is not a new problem in GHC anyway.) If I did, it would have this testcase:

  # touch "me¡"
# LANG=C ghc
Prelude> :m System.Directory
Prelude System.Directory> mapM_ putStrLn =<< getDirectoryContents "."
me*** Exception: <stdout>: hPutChar: invalid argument (invalid character)

Since git-annex reads lots of filenames from git commands and other places, I had to deal with this extensively. Unfortunatly I have not found a way to read Text from a Handle using the fileSystemEncoding. So I'm stuck with slow Strings. But, it does seem to work now.

PS: I found a bug in GHC 7.4 today where one of those famous Haskell immutable values seems to get well, mutated. Specifically a [FilePath] that is non-empty at the top of a function ends up empty at the bottom. Unless IO is done involving it at the top. Really. Hope to develop a test case soon. Happily, the code that triggered it did so while working around a bug in GHC that is fixed in 7.4. Language bugs.. gotta love em.

Syndicated 2012-02-03 20:11:32 from see shy jo

unicode ate my homework

I've just spent several days trying to adapt git-annex to changes in ghc 4.7's handling of unicode in filenames. And by spent, I mean, time withdrawn from the bank, and frittered away.

In kindergarten, the top of the classrom wall was encircled by the aA bB cC of the alphabet. I'll bet they still put that up on the walls. And all the kids who grow up to become involved with computers learn that was a lie. The alphabet doesn't stop at zZ. It wouldn't all fit on a wall anymore.

So we're in a transition period, where we've all learnt deeply the alphabet, but the reality is much more complicated. And the collision between that intuitive sense of the world and the real world makes things more complicated still. And so, until we get much farther along in this transition period, you have to be very lucky indeed to not have wasted time dealing with that complexity, or at least having encountered Mojibake.

Most of the pain centers around programming languages, and libraries, which are all at different stages of the transition from ascii and other legacy encodings to unicode.

  • If you're using C, you likely deal with all characters as raw bytes, and rely on the backwards compatability built into UTF-8, or you go to long lengths to manually deal with wide characters, so you can intelligently manipulate strings. The transition has barely begin, and will, apparently, never end.
  • If you're using perl (at least like I do in ikiwiki), everything is (probably) unicode internally, but every time you call a library or do IO you have to manually deal with conversions, that are generally not even documented. You constantly find new encoding bugs. (If you're lucky, you don't find outright language bugs... I have.) You're at a very uncomfortable midpoint of the transition.
  • If you're using haskell, or probably lots of other languages like python and ruby, everything is unicode all the time.. except for when it's not.
  • If you're using javascript, the transition is basically complete.

My most recent pain is because the haskell GHC compiler is moving along in the transition, getting closer to the end. Or at least finishing the second 80% and moving into the third 80%. (This is not a quick transition..)

The change involves filename encodings, a situation that, at least on unix systems, is a vast mess of its own. Any filename, anywhere, can be in any encoding, and there's no way to know what's the right one, if you dislike guessing.

Haskell folk like strongly typed stuff, so this ambiguity about what type of data is contained in a FilePath type was surely anathama. So GHC is changing to always use UTF-8 for operations on FilePath. (Or whatever the system encoding is set to, but let's just assume it's UTF-8.)

Which is great and all, unless you need to write a Haskell program that can deal with arbitrary files. Let's say you want to delete a file. Just a simple rm. Now there are two problems:

  1. The input filename is assumed to be in the system encoding aka unicode. What if it cannot be validly interpreted in that encoding? Probably your rm throws an exception.
  2. Once the FilePath is loaded, it's been decoded to unicode characters. In order to call unlink, these have to be re-encoded to get a filename. Will that be the same bytes as the input filename and the filename on disk? Possibly not, and then the rm will delete the wrong thing, or fail.

But haskell people are smart, so they thought of this problem, and provided a separate type that can deal with it. RawFilePath hearks back to kindergarten; the filename is simply a series of bytes with no encoding. Which means it cannot be converted to a FilePath without encountering the above problems. But does let you write a safe rm in ghc 4.7.

So I set out to make something more complicated than a rm, that still needs to deal with arbitrary filename encodings. And I soon saw it would be problimatic. Because the things ghc can do with RawFilePaths are limited. It can't even split the directory from the filename. We often do need to manipulate filenames in such ways, even if we don't know their encoding, when we're doing something more complicated than rm.

If you use a library that does anything useful with FilePath, it's not available for RawFilePath. If you used standard haskell stuff like readFile and writeFile, it's not available for RawFilePath either. Enjoy your low-level POSIX interface!

So, I went lowlevel, and wrote my own RawFilePath versions of pretty much all of System.FilePath, and System.Directory, and parts of MissingH and other libraries. (And noticed that I can understand all this Haskell code.. yay!) And I got it close enough to working that, I'm sure, if I wanted to chase type errors for a week, I could get git-annex, with ghc 4.7, to fully work on any encoding of filenames.

But, now I'm left wondering what to do, because all this work is regressive; it's swimming against the tide of the transition. GHC's change is certainly the right change to make for most programs, that are not like rm. And so most programs and libraries won't use RawFilePath. This risks leaving a program that does a fish out of water.

At this point, I'm inclined to make git-annex support only unicode (or the system encoding). That's easy. And maybe have a branch that uses RawFilePath, in a hackish and type-unsafe way, with no guarantees of correctness, for those who really need it.

Previously: unicode eye chart wanted on a bumper sticker abc boxes unpacking boxes

Syndicated 2012-02-02 22:12:02 from see shy jo

announcing github-backup

Partly as a followup to a Github survey, and partly because I had a free evening and the need to write more haskell code, any haskell code, I present to you, github-backup.

github-backup is a simple tool you run in a git repository you cloned from Github. It backs up everything Github knows about the repository, including other forks, issues, comments, milestones, pull requests, and watchers.

This is all stored in the repository, as regular files, on a "github" branch.

Available in Cabal now, in Debian maybe if someone packages haskell-github.

Syndicated 2012-01-26 04:44:10 from see shy jo

olduse.net 1982

Hard to believe I've consumed all of 1981's Usenet posts now on olduse.net, and it's been running for 7 months already.

Last night, there was a "very long" post, describing nearly every node on usenet in 1982. There had been a warning about this post the day before, since it would take many sites half an hour to download at 300 baud. It was handily formatted as a shell script, which created per-node files.

So, I ran this code nobody has run since 1982. It worked. I got files. I tossed them on the olduse.net wiki, and used some ikiwiki code TOVA contracted me to write just a few months ago, to make clickable links on my usenet map.

usenet map

The map data was contributed in another post a while back. By 1982, usenet is getting nearly impossible to map with 1982 technology of ascii art. I enjoyed throwing graphviz, git, wikis, and the web at it.

So, we have a collaboration across time, me and "Mark" and a lot of people who described their usenet nodes and piles of technology that make creating a mashup easy. Awesome!

I blog about stuff I find on the olduse.net blog. It's an open blog; Koldfront also blogs there, and we welcome other bloggers.

Some of the highlights for me have included:

As the space shuttle program is winding down, reading the excitement about the first shuttle flights, and the play-by-play coverage of a launch, posted to net.columbia by a high school student borrowing his dad's account. (A usegroup name that's hard to read without remembering its fate).

The announcements of the Motorola M68k, the IBM PC, and the CD-ROM.

world ipv6 launch Reading the TCP-IP digest, and Postel's plans for launching IPv4 soon, while the world IPv6 launch is being planned now. (The nay-sayers are especially fun to read. Including the guy who was concerned about the address space size, in 1981!)

Learning that nethack ascention tales have a history streching back 30 years, to rogue, and that the stories back then had much the same flavor as they do today.

Various celebrity sightings. Dennis Ritchie teaching C and Unix. Bill Joy talking vi. RMS talking .. nuclear politics?

The general development of usenet. B-news being rolled out, groups proliferating, many first inklings of what will be major problems and developments in 5 or 10 years. A shift in tone is already apparent, by now usenet is not only about announcements, there are already some flames.

oldusenet in a period terminal

Still 9 years to go!

Syndicated 2012-01-21 20:58:05 from see shy jo

version numbers

Today I released two entirely different pieces of software with the identical version number 3.20120115. Debian developers also will be soon noticing a piece of software I released with the version number 9.20120115.

I expect to move more of my software to this version number scheme over time, unless I find something badly wrong with it. It reflects how I think about versions for my software; there's a kind of continual "now" that development progresses through, in which individual releases have little discrete meaning and at the same time, there can also be significant discontinuities, that require the user to do something to deal with (such as a new debhelper compat version, or a new git-annex repository format).

Those two things are really all that I need a version number for my software to communicate. I can do without the rest of the things that version numbers are used for:

  • The marketing of version 1.0 and 2.0.
  • The comparative nuances such as whether 1.0 to 1.1 is a relatively big change, and 1.0 to 1.0.1 is a relatively small change
  • The implication that 0.99 is almost 1.0 ready, and 1.1a is some kind of alpha release.

There is so much software, with so many version numbers that any signal encoded in such version numbers is swamped in the noise. Even on projects that I develop a version number like 2.88 is meaningless to me. All I care about is, how long ago was that version? Has there been a major change breaking compatibility since that version? "2.88" doesn't answer these questions well; "3.20111111" does.

It is a little wordy to have the full year in there, and it can be annoying to remember to set the version to the right date on release day (TODO: automate). This is balanced with the version not being so wordy as to include the time of day, which means I might have to do a 3.20120115.1 if I goof up. These minor problems are worth it to instantly know how old a version is when a user pastes it into a bug report.

And that is probably all I will ever have to say about version numbers. :)

Syndicated 2012-01-16 02:21:07 from see shy jo

a resolution that stuck

Last year, my new year's resolution was to write in my journal every day. That actually stuck, I wrote 262 journal entries in 2011. While I've been keeping a journal intermittently since 1998, last year I doubled the number of entries in it. And wrote a novel's worth of entries -- 53 thousand words!

Most of it is of course banal and mundane stuff. Not good compared with Lars, who does something with his journal where he goes into some detail about code he's working on, and other work. The excerpts I've seen are quite nice. But after I've written code, written a commit message, documentation, perhaps bug reports etc, I often can't find much to say about it in my journal, beyond the bare bones that I worked on $foo today or faced a particularly hard bug. I also worry that the journal, and my reluctance to repeat myself, often tips the balance away from me blogging, if I write down something in the journal first.

Here's my journal for today:

Compare what jokes are funny now with those in 1982. The 1982 ones from net.jokes on olduse.net seem juvenile. Now compare what Unix joke man pages are funny now with those I'm reading from 1982. They seem basically the same. What would Biella make of this?

Liw noticed ikiwiki OOM on pell. Tracked down to a perl markdown bug with long lines. Had quite enough of perl markdown; ikiwiki will be moving to a different engine. Added discount support to it today, still needs Debian package tho.


Really gorgeous sunset, with a high wind, moon, puffy low, fast moving clouds. Enjoyed it ecstaticly. It's going to get cold soon. Very rainy early, but then got intermittently sunny; power is holding out ok.

Was going to roast a chicken today, but got distracted and had a large lunch besides. Need to find some quick food for supper.

I need to start a new book, should it be the River Cottage book about meat that I stole from Anna, or some SF?

Blogged about journaling, and put this journal entry in it, so also journaled about blogging. Wrote it somewhat self-conciously.

The benefits for me have ranged from being able to go back and work out dates of events, to forwarding the odd excerpts to others. The best thing though is certianly having a regular time of introspection, to look back over my the day.

If you've not got a new year's resolution yet, I recommend this one. (Learning Haskell would be another good one, if you haven't yet.)

Just write something, anything, down in your journal every day.

Syndicated 2012-01-01 22:58:57 from see shy jo

476 older entries...

New Advogato Features

New HTML Parser: The long-awaited libxml2 based HTML parser code is live. It needs further work but already handles most markup better than the original parser.

Keep up with the latest Advogato features by reading the Advogato status blog.

If you're a C programmer with some spare time, take a look at the mod_virgule project page and help us with one of the tasks on the ToDo list!