Happy Coding

Jenkins, github and Host key verification failed.

Daniel — Fri, 27 Apr 2012 10:34:46 +0000

I have just switched a Jenkins project from Svn to git (hosted on GitHub). When I wanted to build the project I experienced the following error:

Host key verification failed

The first issue was, that Jenkins didn’t run with the normal user, but it’s own Jenkins user. So I switched to this user

su jenkins

and created an own private/public key using

ssh-keygen

After this I tried to ssh into git

ssh git@github.com

and got a welcome message:

You’ve successfully authenticated, but GitHub does not provide shell access.

After this I tried to clone the repository to the Jenkins machine and got

hudson.plugins.git.GitException: Could not apply tag …

This problem could be fixed by adding git name and email via

git config --global user.email "email@yourdomain.com"
git config --global user.name "Jenkins"

Get sizes of directories in Debian

Daniel — Fri, 20 Apr 2012 10:48:09 +0000

Get the sizes of directories nicely formated via the following command. This can take some while to execute, because it sums up the file sizes in the directories.

du --max-depth=1 -h

log parsing with Grok

Daniel — Fri, 20 Apr 2012 08:30:06 +0000

Just discovered Grok while listening to the logstash talk of the logstash developer. Seems pretty neat to me, especially if you are not willing to write always ugly regular expressions by hand, when you want to parse your logs.

Grok is simple software that allows you to easily parse logs and other files. With grok, you can turn unstructured log and event data into structured data.

Error when trying to deploy Rails 3 application with ActiveAdmin

Daniel — Thu, 22 Mar 2012 19:16:33 +0000

I have just tried to deploy my Rails 3 application which uses ActiveAdmin and I’ve gotten the following error:

File to import not found or unreadable: active_admin/mixins

The solution was to add the following line into my capistrano configuration file config/deploy.rb:

load "deploy/assets"

After a new

cap deploy

the error was gone.

Better Builds with Maven

Daniel — Fri, 16 Mar 2012 09:55:52 +0000

I think a lot of people who are working with Maven know this already. But I have never wrote about it here at Happy-Coding:

Better Builds with Maven is a freely available book, which contains lot’s of best practice information about the work with Maven.
Available to download at MaestroDev.

Social Graph API retiring…

Daniel — Thu, 15 Mar 2012 15:34:28 +0000

Oh, I didn’t recognize that Google is retiring his Social Graph API in 2012:

This API makes information about the public connections between people on the web available for developers. The API isn’t experiencing the kind of adoption we’d like, and is being deprecated as of today. It will be fully retired on April 20, 2012. (via Google)

Resetting Java formatting options in Netbeans

Daniel — Wed, 14 Mar 2012 18:41:28 +0000

I’ve just searched for a way to reset the Java Formatting Options in Netbeans 7.1.1. And I didn’t find a convenient way to do this. The only way I found was to directly delete the .xml file (org-netbeans-modules-editor-settings-CustomPreferences.xml) which is responsible for storing the Java settings:

USER_DIR/.netbeans/7.1/config/Editors/text/x-java/Preferences

quick coding info: order of Java modifiers

Daniel — Fri, 09 Mar 2012 10:34:55 +0000

How you should order Java mofifiers so that you conform to the Java specs.

public
protected
private
abstract
static
final
transient
volatile
synchronized
native
strictfp

SSH to a cluster

Daniel — Tue, 06 Mar 2012 09:33:42 +0000

Nowadays it is pretty normal if you are a Linux administrator or a happy coder with a passion for servers, that you have a cluster of machines at your fingertips. And a normal task is to execute the same commands on multiple machines. One way is to log into every machine and enter the commands multiple times. An easier way is to use cluster ssh tools. For me as a Mac user I am using csshX, which gives you the opportunity to execute simultaneously one command on multiple machines.

If you have for example 4 servers (server1, server2, server3, server4) and your user on every server is happycoder, then you can log into all machines via

csshX --login happycoder server1 server2 server3 server4

This will open 4 terminal slave windows and one master window, which receives your input and sends it to all slave windows:

There is this nice screencast, where the guy also uses csshX for setting up an Apache Cassandra cluster in 2 minutes. For other platforms there are also tools like e.g. clusterSSH.

Testing Javascript with JSFIDDLE

Daniel — Wed, 22 Feb 2012 09:51:21 +0000

Just stumbled over jsfiddle.net a nice tool for testing Javascript on the fly. You can also include the different Javascript frameworks like Jquery, Mootools, YUI etc.