http://www.hietavirta.net/blog/ J2EE software engineer writing about working abroad, cultures and insights en-us Nucleus CMS v3.32 © Weblog http://backend.userland.com/rss http://www.hietavirta.net/blog//nucleus/nucleus2.gif http://www.hietavirta.net/blog/ http://feedproxy.google.com/~r/hietavirta/ptHE/~3/7IkZM4Ydt-g/index.php DevDays in London and it was pretty good event. Most of the speakers were good and I think I learnt something new from every one of them. Unfortunately there was not too much time to network with other developers as the breaks were short and the catering was failing. I am look forward to attending it next year.

Some photos of the event]]> General http://www.hietavirta.net/blog/index.php?itemid=327 Thu, 29 Oct 2009 23:40:27 +0200 http://www.hietavirta.net/blog/index.php?itemid=327 http://www.hietavirta.net/blog/index.php?itemid=327 http://feedproxy.google.com/~r/hietavirta/ptHE/~3/2RpmHN0rXqc/index.php Bits and Bytes http://www.hietavirta.net/blog/index.php?itemid=326 Sun, 25 Oct 2009 00:22:46 +0300 http://www.hietavirta.net/blog/index.php?itemid=326 http://www.hietavirta.net/blog/index.php?itemid=326 http://feedproxy.google.com/~r/hietavirta/ptHE/~3/Sz5x7U6P4V0/index.php Twitter accounts have received regular updates. This seems to be common among bloggers as it is so much easier to blurp couple lines for an update. But blogging is not dead because it is a medium for longer articles.

So, to summarise past month I could mention couple highlights. We made a trekking trip to Kingussie which was fun but we did not reach our goal. The route to the munro was way too muddy for our shoes. A pair of rubber boots would have been better.

Then we had an autumn holiday. I visited Finland and Dóra visited Hungary. My trip was mostly about hunting with very modest results. I did not have time to visit friends but I met my brothers and their families.

Among other things I have been dreaming about buying Canon 7D but I think it is a bit too expensive. And our Canon 450D is still doing pretty fine after 10K shots so there is no good excuse to spend around 1700 GBP... ]]> General http://www.hietavirta.net/blog/index.php?itemid=325 Tue, 22 Sep 2009 21:59:13 +0300 http://www.hietavirta.net/blog/index.php?itemid=325 http://www.hietavirta.net/blog/index.php?itemid=325 http://feedproxy.google.com/~r/hietavirta/ptHE/~3/z781vsiLIJw/index.php
I think there are two things contributing to this. First of all, I do much more workout and outdoor activity than in Hungary. Visiting then gym with sauna two or three times a week keeps neck and back muscles fit. It also helps to relax after work and allows me to get rid of some code originated frustrations. The monthly fee of the gym is not too bad and I see it as investing in myself.

Getting a new computer to replace 12" PowerBook has helped as well. 20" iMac results in a much more ergonomic home setup and I think the bigger screen is better for my eyes as well. I picked a nice mesh back computer chair from a local store couple weeks ago so things have improved even more. I think the next step would be buying a bigger table with more space for all these items.]]> General http://www.hietavirta.net/blog/index.php?itemid=324 Sun, 9 Aug 2009 21:45:49 +0300 http://www.hietavirta.net/blog/index.php?itemid=324 http://www.hietavirta.net/blog/index.php?itemid=324 http://feedproxy.google.com/~r/hietavirta/ptHE/~3/e9NXeMtGejM/index.php ]]> Culture http://www.hietavirta.net/blog/index.php?itemid=323 Sun, 2 Aug 2009 18:43:34 +0300 http://www.hietavirta.net/blog/index.php?itemid=323 http://www.hietavirta.net/blog/index.php?itemid=323 http://feedproxy.google.com/~r/hietavirta/ptHE/~3/3pzYRg9F_Iw/index.php
To investigate this I installed Fiddler to check responses sent by the server. It turned out that our JSON collections had an extra comma after the last item. This trailing comma caused IE to expect yet another item.

Such a small and easy to fix problem but rather tricky to find - but that is life of a programmer.]]> Bits and Bytes http://www.hietavirta.net/blog/index.php?itemid=322 Wed, 29 Jul 2009 20:30:14 +0300 http://www.hietavirta.net/blog/index.php?itemid=322 http://www.hietavirta.net/blog/index.php?itemid=322 http://feedproxy.google.com/~r/hietavirta/ptHE/~3/OJa88A11nsI/index.php
I also had bad luck with cash ISA (tax free savings account) as I applied for higher rate account but First Direct introduced new lower rates while they were processing my application. I did not like that so I cancelled the opening - luckily I did not send transfer order before that.

But at least now GBP seems to get stronger against Euro. That is good because our trip to Finland is approaching... holiday I say!]]> General http://www.hietavirta.net/blog/index.php?itemid=321 Mon, 15 Jun 2009 17:42:05 +0300 http://www.hietavirta.net/blog/index.php?itemid=321 http://www.hietavirta.net/blog/index.php?itemid=321 http://feedproxy.google.com/~r/hietavirta/ptHE/~3/iwkYSzsqGuo/index.php Apache HTTP for proxying and load balancing.

I started up JBoss on both machines with -c all. This setup has clustering turned on as a default so instances found each other and established JGroup communication channels. Then I deployed the .ear file directly to the deploy directory on each server as the farm deployment did not look too promising. The Apache proxy and balancer were already correctly configured so cookies and sticky sessions worked fine.

The big question is naturally how the performance improved. First I ran a load test without second level caching or query caching in order to have a baseline for comparisons. Then I turned Hibernate second level cache on and executed the same load test. The results were showing around twofold throughput as the average response times halved. I also tried turning on query caching but I did not experience any significant difference with it. Maybe I did not have proper configurations.

I also learned that it is not a good idea to modify data on the DB used by the cluster with Hibernate second level caching on. The nodes communicate sending invalidate messages to each other when data is changed and needs to be refreshed. Modifications outside the cluster mean that the cached data is stale but nodes do not know about it and resulting various errors...]]> Bits and Bytes http://www.hietavirta.net/blog/index.php?itemid=320 Thu, 28 May 2009 21:49:11 +0300 http://www.hietavirta.net/blog/index.php?itemid=320 http://www.hietavirta.net/blog/index.php?itemid=320 http://feedproxy.google.com/~r/hietavirta/ptHE/~3/dNMifji0qKI/index.php
Our persistence layer is using Hibernate so the next step in caching was to enable Hibernate's second level cache. There are various options but in our clustered environment JBoss Cache was the choice. But getting started with it took some time.

The easiest way is to use 'all' server setup from the JBoss 5 and enable second level cache in Hibernate settings. The JBoss community wiki page provides an example for the setup. Also your JPA entity annotations or mappings need some changes as well because you need to define caching strategy for them.

Taking a look at the documentation of JBoss Cache reveals huge amount of configuration options. Luckily only some of them are relevant for Hiberante second level caching. Be aware that JBoss Cache has been around for some time so some of the older tutorials and blog posts are outdated. At the moment JBoss Cache version 3.x is the recommended one.

In case of caching it is very important to run proper load tests after each configuration modification to verify the performance gain or loss. At the moment I have my test setup running on Apache JMeter. It creates similar load to the server based on historical usage data. Another area of testing is to verify that cluster's caches are having their state updated properly.

I have been experimenting with JBoss Cache only for a day so it will take a bit more time before I can give my opinion or better advices. So, follow my RSS feed to learn more - hopefully soon there will be an update.]]> Bits and Bytes http://www.hietavirta.net/blog/index.php?itemid=319 Mon, 25 May 2009 22:00:38 +0300 http://www.hietavirta.net/blog/index.php?itemid=319 http://www.hietavirta.net/blog/index.php?itemid=319 http://feedproxy.google.com/~r/hietavirta/ptHE/~3/CO4GF-HtRiE/index.php
The sauna in the topic has nothing to do with helicopters. Instead, we found a nice gym in Kirkcaldy and it has a proper sauna. I would pay the membership fee almost just for sauna usage but being able to do some work out is a big plus.

]]> General http://www.hietavirta.net/blog/index.php?itemid=318 Tue, 19 May 2009 22:45:24 +0300 http://www.hietavirta.net/blog/index.php?itemid=318 http://www.hietavirta.net/blog/index.php?itemid=318