Say you’re running a load test (with a predefined duration) and want to monitor I/O on the system under test (a Linux machine).

First install the sysstat package and then, as you start the load test, run:

# iostat -N <test duration in seconds> 2

on the machine whose I/O you want to monitor. For NFS statistics, apply the -n switch.

The first report will display cumulative statistics since last reboot (which may or may not be useful), whereas the second report (that appears exactly <test duration in seconds> later) will display cumulative statistics for the duration of your test.

HTH,
Jukka

If you ever need to run automated WebDriver (Selenium 2) tests with Jenkins on a headless CI machine running RHEL 6, with a recent version of Firefox, here’s how:

1. Make yourself root
   $ su -
2. Install JDK 6 and use it
   # yum -y install java-1.6.0-openjdk-devel
# alternatives --config java
# alternatives --config javac
   
3. Install Jenkins CI server
   # wget -O /etc/yum.repos.d/jenkins.repo http://pkg.jenkins-ci.org/redhat/jenkins.repo
# rpm --import http://pkg.jenkins-ci.org/redhat/jenkins-ci.org.key
# yum -y install jenkins
4. Install Xvfb (via the RHEL Server Optional repository)
   # yum -y install xorg-x11-server-Xvfb
# yum -y install mesa-dri-drivers
# yum -y install dbus-x11
# dbus-uuidgen --ensure
5. Setup Xvfb as a service
   # useradd xvfb
# vim /etc/init.d/xvfb
# chkconfig --add xvfb
# chkconfig xvfb on
6. Install Firefox 10
   # wget http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-5.noarch.rpm
# yum -y install epel-release-6-5.noarch.rpm
# wget http://rpms.famillecollet.com/enterprise/remi-release-6.rpm
# yum -y install remi-release-6.rpm
# yum -y --enablerepo=remi install firefox
7. Configure Jenkins to use the appropriate virtual display
   # echo "export DISPLAY=:99" >> /etc/sysconfig/jenkins
8. Start Xvfb and Jenkins
   # service xvfb start
# service jenkins start
9. Setup a test Maven project
   • Test dependencies in pom.xml

     <dependencies>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <version>4.9</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.seleniumhq.selenium</groupId>
             <artifactId>selenium-firefox-driver</artifactId>
             <version>2.19.0</version>
             <scope>test</scope>
         </dependency>
     </dependencies>
     

   • Create a test class

     package test;
     import org.junit.*;
     import org.openqa.selenium.WebDriver;
     import org.openqa.selenium.firefox.FirefoxDriver;
     public final class Test {
     
         private WebDriver driver;
     
         @Before
         public void before() {
             driver = new FirefoxDriver();
         }
     
         @Test
         public void test() {
             driver.get("http://www.google.fi");
         }
     
         @After
         public void after() {
             driver.close();
         }
     }
     

10. Build the project on Jenkins with goals clean test

HTH,
Jukka

Say you’re building a WAR with Maven, and need to do automated deployment via SSH.

Here’s a working Maven antrun plugin def to get you going:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-antrun-plugin</artifactId>
    <version>1.6</version>
    <configuration>
        <target>
            <echo message="Stopping test server ..." />
            <sshexec trust="true" host="test.example.com"
                username="root" keyfile="${user.home}/.ssh/id_rsa"
                command="service tomcat6 stop" />
            <sleep seconds="10" />
            <echo message="Copying WAR to test server ..." />
            <scp trust="yes"
                file="${project.build.directory}/${project.build.finalName}.war"
                keyfile="${user.home}/.ssh/id_rsa"
                remoteTofile="root@test.example.com:/usr/share/tomcat6/webapps/app.war" />
            <echo message="Starting test server ..." />
            <sshexec trust="true" host="test.example.com" username="root"
                keyfile="${user.home}/.ssh/id_rsa" command="service tomcat6 start" />
            <echo message="Waiting for app to get deployed ..." />
            <waitfor maxwait="1" maxwaitunit="minute" checkevery="10" checkeveryunit="second">
                <http url="http://test.example.com/app" />
            </waitfor>
        </target>
    </configuration>
    <dependencies>
        <dependency>
            <groupId>org.apache.ant</groupId>
            <artifactId>ant-jsch</artifactId>
            <version>1.8.2</version>
        </dependency>
        <dependency>
            <groupId>com.jcraft</groupId>
            <artifactId>jsch</artifactId>
            <version>0.1.44-1</version>
        </dependency>
    </dependencies>
</plugin>

This example uses SSH public key authentication (be sure to add the SSH public key of the user running the build, e.g. Jenkins, to the SSH authorized_keys file on the test server).

Tomcat (or whatever servlet container you’re using) is restarted to avoid perm gen errors (here we use an /etc/init.d script).

Now just run mvn clean package antrun:run as part of your CI (e.g. Jenkins) build to deploy.

HTH,
Jukka

Though I’m generally more aligned to writing backend code, sometimes it’s nice to write code that you can actually click. Here’s a simple email form template with attachment support. The form uses JQuery, which is referenced via Google’s CDN.

Feel free to use and/or modify the template as you see fit.

Regards,
Jukka

If you’re doing Java web application development and are sick and tired of restarting your app server whenever making changes to classes / configuration, check out JRebel.

JRebel reloads modified classes and resources automatically upon save. It also works nicely with Spring, among other things. And it’s really easy to use (through an Eclipse plugin).

- Jukka

Coming from a Java background, Scala looks real nice. So does Buildr. So I just had to try them out with Spring and JPA. Here’s a sample CRUD project that exercises basic JPA features with the aforementioned technologies. Have a look at the README for more information.

You may also find http://buildr.apache.org/languages.html#scala useful.