I really love Gnome 3 and its Shell, but I almost went nuts on this. It really took me a while to finally figure this out. To make a really short blog post even shorter: Use dconf-editor (from package dconf-tools) and go to org.gnome.desktop.wm.keybindings. There you have it. Why would I want to change keyboard […]
After a few sudden server deaths, this blog is back online. Which does not necessarily mean that I am back online writing new posts. That said, there is a lot in my mind that might be worth blogging about, so stay tuned.
There are several extension to JUnit that provide means to test performance like JUnitPerf or p-unit. But it is hard to formulate the right assertions. What if the test runs on a beefier machine or in another environment? Did performance degrade? I just want to answer a simple question: Did performance degrade? (And if, when?) […]
We use both MySQL and Hadoop a lot. If you utilize each system to its strengths then this is a powerful combination. One problem we are constantly facing is to make data extracted from our Hadoop cluster available in MySQL. The problem Look at this simple example: Let’s say we have a table customer: CREATE […]
In the past months we struggled with large SELECT queries just get stuck at: java.net.SocketInputStream.socketRead0(Native Method) java.net.SocketInputStream.read(SocketInputStream.java:129) com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113) com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160) com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188) – locked com.mysql.jdbc.util.ReadAheadInputStream@cb9a81c com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2494) com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2949) com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2938) com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3481) com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959) com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2109) com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2642) – locked java.lang.Object@70cbccca com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2571) com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:782) – locked java.lang.Object@70cbccca com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:625) org.apache.commons.dbcp.DelegatingStatement.execute(DelegatingStatement.java:260) org.apache.commons.dbcp.DelegatingStatement.execute(DelegatingStatement.java:260) Whenever this happened we just restarted the Tomcat server and everything was fine again […]
Hadoop is designed to run on huge clusters containing several hundred machines. But some people just don’t need such a big cluster and are able to use the benefits of HDFS and MapReduce on a smaller scale. We managed to improve performance of our 10-node-test-cluster by almost 100% by adjusting the heartbeat intervals. Namenode and […]
“Internet slow” means actually “DNS slow”. After upgrading to Ubuntu 9.10 I experienced a strange and very annoying lag in DNS resolution. Running dig in a shell worked like a charm. But Firefox, Synaptic and everything else was hanging at DNS resolution. To make a long story short (you probably read a lot of forum […]
I fell in love with collectd and drraw.cgi (a front-end to collectd). This combination is great: Fast, simple and yet sufficient. But there was one thing I missed in drraw that I loved in cacti: Zooming. (This is how it looks like in cacti) So I went on and hacked it into drraw.cgi using jQuery. […]
Just a quick note: Don’t mount a cifs share with flag directio if you want to execute binaries that reside on that share. Otherwise you will get the following error: <command>: cannot execute binary file Took me 2 hours to find out.
You should not try to use Hadoop as a “drop-in” replacement of your current (R)DBMS. That said it is still possible to utilize the power of cluster computing while circumventing its weaknesses when it comes to ad-hoc or real-time queries. We use Hadoop as an on-line system tightly integrated with our application and use it […]