In RFC 1123 it is stipulated that:

a DNS resolver or server that is sending a non-zone-transfer query MUST send a UDP query first.

However, if you are doing a DNS UPDATE you really want the reliability that TCP offers, even if you don’t expect truncation to be an issue. The update is sent to the relevant authority server, so the arguments about load on root servers in the RFC aren’t applicable.

I’ve made the UDP implementation retry by default, but I think if you need more than 2 retries, you should be considering using TCP with its (much more advanced) retransmission algorithms.

Peter also found a bug in glibc’s res_send (actually in their send_dg function) whereby the resolver interprets the lack of the DNS “recursion available” flag in the header as an error. However, that flag isn’t even meaningful for DNS UPDATE responses; according to RFC 2136, those bits:

Should be zero (0) in all requests and responses. A non-zero Z field should be ignored by implementations of this specification.

As a result, glibc was setting errno to ECONNREFUSED or ETIMEDOUT even when the update was successful. I’ve hacked dudders to double-check after res_send, but it’s making me question the wisdom of using res_send at all, given that I’m constantly working around it.

Update: submitted glibc bug report #11950

To get dudders-1.04 on OpenWRT, simply update the official package feed and select dudders from the Net > DNS > dudders menu in the buildroot config. For systems other than OpenWRT, you can grab the source from sourceforge, or even github.

The default javascript API uses document.write, which isn’t a DOM method and hence is not a method of true XML documents. It’s not a new issue either, wp-recaptcha has had a history of breaking XHTML. The thing is, the WordPress plugin (which uses the PHP library by the recaptcha people) has an option to “Be XHTML 1.0 Strict compliant”; but this only fixes the use of iframes and noscript!

Updated: pushed fork to github

Under firefox, you get an error like:

Error: uncaught exception:
[Exception... "Operation is not supported"  code: "9"
 nsresult: "0x80530009 (NS_ERROR_DOM_NOT_SUPPORTED_ERR)"
 location: "http://www.google.com/recaptcha/api/challenge?k=xxx Line: 12"]

While under Chrome it’s

Uncaught TypeError: Object #<a Document> has no method 'write'
api.recaptcha.net/challengek=xxx

The real solution is to use the reCAPTCHA AJAX API, which for whatever reason isn’t exposed in the PHP library. You can grab my xml fix for wp-recaptcha from github.

The situation is this: imagine you have a faceted plot that is tall enough that the x-axis ticks and labels become obscured (e.g. when using a clipped viewport such as a browser window). This is particularly destructive when you’re using an x-scale with manual breaks or a transformation.

library(ggplot2)
g <- ggplot(diamonds, aes(carat, ..density..)) +
   geom_histogram(aes(fill = clarity), binwidth = 0.2) +
   facet_grid(cut ~ .)
print(g)

There simply isn’t a way to repeat the x-axis labels in ggplot2 at the moment without discarding faceting and rendering each facet as a separate ggplot call. I’ve seen some examples of selective plotting used to good effect in combining multiple plots with common elements, but I can’t find anything applicable to keep consistent scales and binning without duplicating a lot of the (internal) facet and bin logic.

Instead my best shot was to clone some of the grob elements and redraw them at different locations:

grob <- ggplotGrob(g)
xtext <- getGrob(grob, "layout::axis_h::axis.text", grep = TRUE)
xtext <- editGrob(xtext, gp = gpar(fontsize = 8))
downViewport("background::panels::layout::axis_h-13-3") # ids from grid.ls()
pushViewport(viewport(y = unit(34, "npc"), name = "axis_h_rep-1"))
 grid.draw(xtext)
popViewport()

Unfortunately I couldn’t find a consistent way of querying the grid graphics internals for the measurements necessary to move the “mirrored” axis labels to the right place. The 34 there is a magic number I found with grid.locator() and trial-and-error; it changes depending on the graphics device. At one point I hoped I could clone the entire axis_h viewport, pry some vertical space from in between the facet panels, and paste the clones in between. Unfortunately grid layouts don’t seem to be very mutable once they’ve been created, and redrawing the text grob seemed like the best I could do to reuse the output.

While looking at the stackoverflow answer for the same problem, I came across Harlan’s assessment:

GGplot’s philosophy is about doing the right thing with a minimum of customization, which means, naturally, that you can’t customize things as much as other packages.

This is more significant when contrasted with the context of R itself; in R, the user retains full control. Coming up against ggplot’s choice of only exposing high-level primitives often leaves the user with the choice of:

• accepting The Way ggplot Does Things and not getting what they want
• waiting for Hadley to write a patch (next summer, if you’re lucky?)
• wading through ggplot internals so you can duplicate its functionality with plyr and grid calls
• abandoning ggplot completely

Ubuntu and Debian ran into plenty of bashisms when they tried to change, how about Mac OS X? So far I’ve found problems with /usr/libexec/path_helper (I just changed the shebang line to #!/bin/bash). There was also a problem with X11′s startx, and my patch was quickly committed.

Interestingly enough, when I went to move the sh binary, there are actually two versions of bash in /bin. Both report

GNU bash, version 3.2.17(1)-release (i386-apple-darwin9.0)

but differ at the binary level (they aren’t even the same size). I wonder if Apple tried to optimize their /bin/sh given that it gets more usage.

I built dash-0.5.5.1 from the tarball without a problem.