ROME 1.0RC2 Release

I’ve just pushed out a release of ROME core, ROME Fetcher and ROME modules.

For those who don’t know, ROME is a (the?) Java library for handling RSS and Atom. Unlike some other libraries it is pretty stable (18 months since the last release) and has a low number of dependencies (one – JDom – if all you need is parsing)

The annoucement, including links is at

The thing I’m most pleased about (and the number one source of complaints about ROME) is that I’ve pushed it to the Maven repository, so now it will be easier to use from Maven. Further details are at

Installing Java on RedHat Linux by building your own RPM

It’s pretty easy to install Java on Linux – download the RPM from sun and install it. Then if you run “java -version” you’ll suddenly discover that it doesn’t really work:

java version "1.4.2"
gij (GNU libgcj) version 4.1.2 20070626 (Red Hat 4.1.2-14)

You can get around that by setting your path and JAVA_HOME, or by only using Java version that have a matching JPackage RPM and using the alternatives command

If you want to be able to build your own RPM, here’s how to do it.


# Be sure to enable the distro specific repository for your distro below:
# - jpackage-fc for Fedora Core
# - jpackage-rhel for Red Hat Enterprise Linux and derivatives

name=JPackage (free), generic

name=JPackage (free) for Fedora Core $releasever

name=JPackage (free) for Red Hat Enterprise Linux $releasever

name=JPackage (non-free), generic
  • Become root
  • Copy this file to /etc/yum.repos.d. Edit it, and make sure that enabled=1 is set for the [jpackage-generic-nonfree] section.
  • Make directories required by the RPM process (I suspect you can do this outside the /usr/src directory, though):  
mkdir -p /usr/src/redhat/SOURCES  
mkdir -p /usr/src/redhat/RPMS/i586/
  • Copy the Java installation file you previously downloaded to /usr/src/redhat/SOURCES and make it executable (chmod +x <name of file>)
  • Install the tools you need to build an rpm: yum install yum-utils jpackage-utils rpm-build  (At the moment this seems to fail on 64bit machines because of missing dependencies)
  • cd usr/src/redhat/SOURCES
  • yumdownloader –source java-1.6.0-sun
  • At the moment, that will download a file called java-1.6.0-sun-
  • Run setarch i586 rpmbuild –rebuild java-1.6.0-sun*nosrc.rpm. At the moment that gives an error message, which seems to be able to be ignored:
sh: /usr/src/redhat/SOURCES/jdk-6u10-linux-i586.bin: No such file or directory
error: Bad exit status from /var/tmp/rpm-tmp.6041 (%prep)
RPM build errors:
    user jasonc does not exist - using root
    group jasonc does not exist - using root
    user jasonc does not exist - using root
    group jasonc does not exist - using root
    user jasonc does not exist - using root
    group jasonc does not exist - using root
    Bad exit status from /var/tmp/rpm-tmp.6041 (%prep)
  • That previous command extracted a RPM SPEC file in the /usr/src/redhat/SPECS/ directory.
  • Edit /usr/src/redhat/SPECS/java-1.6.0-sun.spec. Find the part that says %define buildver and change the value to the build for the new version of Java
  • Run rpmbuild -ba /usr/src/redhat/SPECS/java-1.6.0-sun.spec. This extracts the JDK installer you previously downloaded and builds a set of RPMs from it.
  • cd /usr/src/redhat/RPMS/i586; ls;

java-1.6.0-sun-        java-1.6.0-sun-fonts-
java-1.6.0-sun-alsa-   java-1.6.0-sun-jdbc-
java-1.6.0-sun-demo-   java-1.6.0-sun-plugin-
java-1.6.0-sun-devel-  java-1.6.0-sun-src-
  • You can now install the RPM: rpm -i java-1.6.0-sun-
  • For me that failed with a missing X dependency: is needed by java-1.6.0-sun-
  • I fixed that with yum -y install libX11-devel libXtst.
  • Use the alternatives command to set the correct version of Java: alternatives –config java
  • Finally: java -version:

java version "1.6.0_11"
Java(TM) SE Runtime Environment (build 1.6.0_11-b03)
Java HotSpot(TM) Client VM (build 11.0-b16, mixed mode, sharing)
That’s it – you finally have Java working on Linux! You also have a RPM which can be installed on other machines.

My Google Interview

Well it’s just under 5 months since I promised a post about my Google interview. Being the highly active blogger that I am, I’d say its about time..

Back in early April I got an email from a recruiter from the Google European Recruiting Centre. I was a little puzzled how she got my name, but a bit of detective work found a guy I went to school with worked for Google in the London office and he’d recommended me.

After a phone converstation with the recruiter, we decided that a position in London would suit me best (I live in Australia, and have a wife and a then-2 year old child, so this was kinda a big deal), and I was handed over to a recruiter from London.

Google’s London office mostly does mobile applications, and I wanted to do web apps, but I was assured this wouldn’t be a problem because they had positions like that available too.

So the wheels were set in motion to setup the dreaded Google phone screen, and I started studying. It’s hard to explain how difficult I found that. Not only did I have to remember a whole lot of half-remembered computer science from ten years ago, but I also had to remember the Math that went with it, which was much harder to dig up. Things like big-O notion are easy enough conceptually, but when you are actually analyzing an algorithm you need to remember the maths for dealing with logorithms (for example), which isn’t something I’ve thought about much since doing Computer Science 4 back in 1997…

Interestingly, every recruiter I spoke to referred me to Steve Yegge’s “Get that Job at Google” post which I found ironic considering the “I don’t speak for Google” disclaimers he uses.

Anyway, in early May I did the phone interview with a programmer from London. While I’m not going to go into specific questions, it did involve writing some code (in Google Docs), and some highish level problem solving. For me, I found that I’d read some of Steve Yegge’s other writing pretty valuable.

I finished the phone interview feeling pretty reasonable, but I was still pretty pleased when I got called to arrange some on-site interviews in Sydney.

We arranged to do two in-person interviews with engineers in Sydney, and then two video-conference interviews with London, in late May.

So I went back to studying. Working through the stuff on Steve Yegge’s post was actually getting me more and more worried about all the stuff I didn’t know, but what else could I do?

In my first interview, the first question was pretty much my nightmare scenario. It was a (computer) math question, a (to quote the interviewer) “easy question to start you off” and it was something I didn’t know, and even worse – it was something I’d known I didn’t know but had left in favour of other things. So I muddled though the best I could and got the answer in the end, and the subsequent questions from that interviewer were better, but I was pretty worried that I’d blown it badly.

The next interview was much better. It was pretty clear that the first interviewer had told the second one that I was pretty nervous, because he kept telling me to slow down and not to worry too much. His first question was something I was much more confident about, and I got the naive solution out pretty quickly. Even better, I was able to identify that the class of problem was the same as something I’d been asked before, so I was able to skip the obvious improvement and got straight from the naive solution to the optimal solution in one step. The interviewer was happy about that, and let me choose if I wanted a low level or high level question next.

I chose a high level question, and he gave me a “design and sketch-code an appropriate interface” problem. I was very happy with that question because it’s the kind of thing I deal with most days in my work. I have what I though was an adequate answer, although I could see a lot of problems with my implementation. the interviewer was very happy with it, though, and said it was the best answer he’d seen. That surprised me, because I could see areas to improve, but I’d run out of time, so suspect him telling me that was a technique to try and get me over my “nerves”.

The third interview was the first video-conference one. There was nothing the stood out at me in this one, except it was the only interview where there was a question that involved talking about design trade offs etc instead of coding. There was also an interesting question where I forgot a pretty basic computer science concept, but once I got a hint I solved it reasonably.

The fourth interview was the interesting one. The first question involved writing a solver for a puzzle-type game. Unfortunately, it wasn’t a game I’d played before and that really cost me because I didn’t know how I’d go about solving it. To be honest, I stuggled pretty badly with this one. I did write a checker, to determine if a given solution was valid, but it was the one question I had to give up on.

The second question from that interview was probably the best question I was given. I wish I could post it here, because the approach to solving it and the optimizations used were just so typical of all the other questions, and the optimal solution is glorious, and yet is easy to understand.

So that was it – the famous Google interview. I can’t say that there were any surprises, and I came out of it with mixed feelings.

I felt that I’d done reasonably well. I’d missed one question, and struggled in another, but I thought some of my other answers were pretty good, and I hoped my second interview might have been enough to get me over the line.

I was hoping to find out quickly how I’d gone, but that wasn’t to be. My next contact with Google was at a Developer Day here in Adelaide. I was fortunate in that the recruitement consultant from Sydney was at that event, and I’d met him at the interview. One of my interviewers was also there (the second interview – the one I’d done well at).

I spoke to them both, and both were pretty positive. The recruiter actually said he’d looked at my feedback and that I shouldn’t plan to be in my current job much longer, and both asked if I was fixed on a job in London or if I’d be interested in Sydney. They both mentioned again that I’d been very nervous, which I gladly agreed with (anything to excuse my bad answers!)

I came away from that event feeling pretty optimistic.

A couple of weeks later I finally got a response from London that the position I’d been going for had been taken by an internal applicant, but that they’d like to do more interviews with me for another postion on the mobile team. I also felt that the feedback on my interview was very mixed – some very good, and some not so good, which made them feel they wanted to do another interview. That pretty much brings me up to my last post on the topic.

Some common questions:

  • Do you get asked puzzle/brainteaser questions?
    • No – they were all algorithm and coding.
  • Was it as hard as everyone says?
    • Yes. By far the hardest 5 interviews I’ve ever done.
So would I do it again? Yes I would, but I’d probably go for a position nearer to where I live. I’d also do a few things differently WRT to studying. Instead of working my way though Steve Yegge’s study list, I think I’d probably concentrate a lot more on the TopCoder algorithm questions.

Sticky Sessions which aren’t

Exhibt A (the Apache 2.2 mod_proxy documentation): 

stickysession Balancer sticky session name. The value is usually set to something like JSESSIONID or PHPSESSIONID, and it depends on the backend application server that support sessions. If the backend application server uses different name for cookies and url encoded id (like servlet containers) use | to to separate them. The first part is for the cookie the second for the path.


Exhibit B (the Apache 2.2 mod_proxy code):

     * If we found a value for sticksession, find the first '.' within.
     * Everything after '.' (if present) is our route.
    if ((*route) && ((*route = strchr(*route, '.')) != NULL ))
    if ((*route) && (**route)) {
        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                                  "proxy: BALANCER: Found route %s", *route);
        /* We have a route in path or in cookie
         * Find the worker that has this route defined.
        worker = find_route_worker(balancer, *route, r);
        if (worker && strcmp(*route, worker->s->route)) {
             * Notice that the route of the worker chosen is different from
             * the route supplied by the client.
            apr_table_setn(r->subprocess_env, "BALANCER_ROUTE_CHANGED", "1");
            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                         "proxy: BALANCER: Route changed from %s to %s",
                         *route, worker->s->route);
        return worker;

Translation: In Apache mod_proxy_balancer, sitcky sessions need to be in the format <cookie value>.<route> where route refers to the backend server. 


There are a couple of useful docs about this: Mark Round and the Jetty Docs. Normally I’d submit a patch to the Apache docs to clear this up, but unfortunately I haven’t been able to get failover between servers working correctly, so I’m not convinved I completely understand all the issues yet.

However, once you have got this working it turns out to be a case of RTFM.

Exhibit C:

route Route of the worker when used inside load balancer. The route is a value appended to session id.

I’d argue that only makes any sense after you’ve got it working…

Modify java.library.path at runtime

Linking to native code in Java is always a hassle. JNI isn’t exactly nice, and there are some oddities around classloaders and native libraries which are annoying if you run into them.

One thing I wasn’t aware of was exactly how hard it is to load a library it isn’t already in the directories specified by the java.library.path system property. 

Initially, I thought I’d just be able to alter that property and the JVM would pick up the new locations. That turns out not to be the case, as is shown by this (closed) bug report.

However, there is a solution, outlined in this post on the Sun forums, which revolves around altering the usr_paths field stored in java classes.

	public static void addDir(String s) throws IOException {
		try {
			// This enables the java.library.path to be modified at runtime
			// From a Sun engineer at
			Field field = ClassLoader.class.getDeclaredField("usr_paths");
			String[] paths = (String[])field.get(null);
			for (int i = 0; i < paths.length; i++) {
				if (s.equals(paths[i])) {
			String[] tmp = new String[paths.length+1];
			tmp[paths.length] = s;
			System.setProperty("java.library.path", System.getProperty("java.library.path") + File.pathSeparator + s);
		} catch (IllegalAccessException e) {
			throw new IOException("Failed to get permissions to set library path");
		} catch (NoSuchFieldException e) {
			throw new IOException("Failed to get field handle to set library path");

Obviously, I don’t think that’s portable across JVMs, though.


For the last I’ve been doing webdesign (yeah, that actual visual UI stuff, not just AJAX or something) at work, and – remakably – for the first time since 1997 (yes – 1997!) I’ve enjoyed it.

Generally speaking my design tastes are different – or perhaps I could better say they reflect my unique sense of humour. For example, the orginal – and best – design for featured a colour scheme generated from converting universal constants (the speed of light, e, etc etc to hex values). It was unique, and is still yet to be duplicated (!!).

But doing serious webdesign led me to dig out an old, old review for the first website I ever built and maintained. This, was when the web was young, CSS didn’t really work, Netscape 4 (!) was my browser of choice and I think I was running a pre-Slackware 1.0 Linux install, which I’d downloaded onto 12 floppies.

Website review, 1997 (actually, the article is from the May 1998 edition of Adelaide Review but I did the site in ’97)


Website review
Website review

Nick’s Two Laws of Software Engineering

So I’ve been working in software for over 10 years, and so I figured its about time I came out with some highly scientific principles of software engineering. Follow these, and I personally guarantee success…

  1. Don’t try and do too much at once.
  2. Hire smart people.
It’s important that you do both of these – leave either out and you’ll probably fail. 

Firstly, software is too hard to try and get too much of it done at once. Don’t bother trying – no matter how smart your team is you’ll fail – or have to redefine success to something less than 100% satisfactory. If you’ve got a big project to do, then incrememental delivery is the only way forward.

Secondly, no matter how small the project is you need smart people. Software is too hard, and it has an amplifying effect on stupidity. Since the smallest bug can cause big problems, and the number of bugs decreases expoentially with smartness you just can’t afford to have less than the smartest people available (I’ve got no evidence this bug vs smartness relationship is true, but it sounds kinda scientific & shit, so I’ll leave it in). However, if you have smart people, you have to stop them trying to do too much at once. See rule one.

That’s it. I now declare software development to be a solved field.


So Android is out (a couple of months after I got a Nokia E71 – which is great BTW). People seem to think it will succeed mearly on the basis of having an open platform. I’m sure that will help, but the real issue holding back mobile is the carriers, not the software platform. Getting a decent deal out of carriers was Apple’s biggest move with the iPhone, and Android phones will need to get similar deals. Ask a mobile developer about how to get “on deck” on most carriers, and how much money they get from that (usually around 20%!) and compare that to the AppStore deal.

On not going to Google

So contrary to some self-inflicted rumors, I’m not off to Google London or Sydney. My wife has taken a new contract here in Adelaide so we’ll be staying here for at least another 12 months.

It is kind of disappointing, but I’ve been doing the Google recruiting process for a week short of 3 months now, been though 5 interviews (with somewhat mixed results – yes, I’ll do a post about that), turned down the opportunity to do more interviews for some position I had no interest in and the last message I had from Google HR was that they would have “concrete clarification” about other positions for me on Wednesday. That was Wednesday three weeks ago.

So apparently Google have done studies which show that slowing page load times from 0.5 to 0.9 seconds cuts traffic by 20% – people just don’t wait around. Perhaps I might recommend a similar study for the recruitment process?

OTOH, all the Google engineering staff I met or talked to were great. So all in all it was a mixed experience – if you are thinking about trying it I’d recommend it, but I’d also recommend not trying anything too complicated (like saying yes to a recruiter from another continent..)

FriendFeed – 6 likes, 3 don’t likes and 2 requests.

I’m a huge fan of FriendFeed.

I think that too many internet pundits see it as competition for Twitter, which is distracting from the real innovations it has provided. FriendFeed is the first real new way of reading rss feeds since the distinction between river-of-news and source-centric emerged.

The addition of a social layer which allows people to define who they are (by what data they produce) makes the subscription process much easier. I could see myself suggesting to family members to sign up to it so they’ll see what I’ve been doing – rather than the alternative of them having to remember to visit Flickr, and my 4 blogs etc, etc, or use a traditional blog reader wich will just confuse them.

At work, we started building a similar service for a vertical market group (educators in Australia) in roughly the same time frame as FriendFeed. There are a number of differences (we’ve only had 1.5 developers working on it over that time, for a start!), but the one thing FriendFeed has which I want is the commenting on items.

We actually built a proof-of-concept for a social-bookmarking service which would allow commentry on posted items (as well as on tags), but that hasn’t been incorparated into our service yet. However, we didn’t think of building that directly into the newsfeed, which is such a small thing, but makes such a difference.

Apart from that, here’s some things which I love about FriendFeed but most people probably don’t think about:

  1. The way your profile shows who you follow, not who follows you. Showing the number of people who follow you turns it into a popularity contest, which is kind of silly.
  2. The subtle influence of “Like” by your friends on what shows in your feed. If one of your friends “Likes” something then it will show up in your feed as posted by a friend-of-your-friend.
  3. The ordering of who liked something by how far away they are from you in the social graph (or showing your friends first, anyway)
  4. The search. The fact that it is easier to find one of my own posts on FriendFeed than in itself is scary.
  5. Imaginary Friends is a brilliant idea, which solves a really big problem. Whoever thought of that – in particular the name! – deserves lots of “Like”s
  6. The “multi-level” nature of it. You can start with using it just as a way of following people, then discover features just as you think “wouldn’t it be great if I could….”

Things I don’t like:

  1. “Like”. The meaning of the word makes it difficult to use in some circumstances (eg, reading about something bad which you want to remember). In our social bookmarking prototype we used a system very much like the “Rating an Object” pattern from the Yahoo design pattern library (which is a great resource for social software patterns, BTW). I think that actually rating an object may not quite have the correct social connotations for FriendFeed, but perhaps a “Star” (like in GMail) might be appropriate?
  2. I don’t think FriendFeed rooms work, yet. Maybe it is that I don’t quite get them, but firstly I can’t see a good way to find them, and secondly the fact that items need to be specifically re-shared into them is confusing. (OTOH, I’m probably wrong here, and they are probably already heavily used. We built a similar feature called communities (eg), and they have worked pretty well. We do have a discovery mechanism, though (as well as a more subtle recommendation thing when a person edits their profile)).
  3. Sometime a friend will share an item, and because people keep commenting it will remain towards the top of my feed for a long time. I know I can hide it, but I’d prefer the reverse – if I don’t “Like” it of comment on it then it should go away quicker.

Feature requests (some of these are things we’ll probably build into our system anyway):

  1. Tagging. I want to use FriendFeed as a social bookmark system.
  2. Direct messages, or a “@”-like syntax which will make sure a message is recived by the target.

Anyway, like I said: I’m a big fan. I think FriendFeed is already beautiful software, and it’s a joy to see the subtle, continuous refinement and evolution it goes though.