In my last post about setting up Jenkins I looked at how to do a basic Jenkins setup on an Ubuntu machine. In my case I set it up on an old machine which is fine when I’m working at home but if I make changes when I’m not at home or when my build machine isn’t running the changes are not built and tested. If you hadn’t worked it out, in a proper continuous integration environment you should be running your builds continuously. So this morning I set out to get an EC2 instance running Jenkins.
The other reason I wanted to have the build server running continually is that I need to start scheduling some jobs for Knowsis to do the NLP part of our process., which I could do with Cron, but buildservers liike Jenkins and Teamcity offer really flexible scheduling and a nice interface for feedback so I don’t need to worry about building one myself, for now.
Setting up an EC2 instance
The first step in the process is to set up your EC2 instance. Amazon kindly provide a free tier so you can get a free micro instance for a year. This should work for you initially if your builds aren’t overly complex.
I won’t run through exactly how to get your instance running as you can find plenty of guides online, if you are completely new to EC2 I would recommend this guide provided by Amazon.
One thing to note is that you should make sure you set up the security group for your image to allow all traffic on port 80 so you can actually see Jenkins.
In my previous post I mentioned setting up nginx to route requests to Jenkins but didn’t cover it. So we’ll go though it here as we need a webserver running to host the requests coming through.
We’ll need to use YUM here as apt-get and aptitude aren’t installed. Thankfully the Amazon package index includes a version of nginx.
yum install nginx
Once installed we should start the nginx server to make sure that we can see our new EC2 instance before proceeding.
sudo /etc/rc.d/init.d/nginx start
You should be be able to hit your instance in a web browser. You can get the public hostname of your instance from the AWS management console, but it should look something like this:
In my previous post we used aptitude to install Jenkins but the Amazon Linux AMI doesn’t have the aptitude package manager, s owe have to use YUM instead.
First we need to add the repository to the list of YUM repos:
sudo wget -O /etc/yum.repos.d/jenkins.repo http://pkg.jenkins-ci.org/redhat/jenkins.repo
and then get the GPG key:
sudo rpm --import http://pkg.jenkins-ci.org/redhat/jenkins-ci.org.key
then we can install Jenkins:
yum install jenkins
The installer will install the server as well as create jenkins user under which the service will run. You can now start the jenkins service:
sudo /etc/init.d/jenkins start
As Jenkins runs on port 8080 by default, the next step is to get nginx to proxy all requests on port 80 to port 8080. You could probably just change Jenkins to run on port 80 by default if you wanted. Anyway, just change your nginx config (/etc/nginx/nginx.conf) so that the server section reads as follows:
listen 80 default;
I won’t go into the details of nginx setup, but this is the minimum required to get you to a point of having Jenkins working.
Make sure you restart nginx to take account of the config changes,
sudo /etc/rc.d/init.d/nginx restart
You should be be able to view the jenkins homepage in a web browser using the same url as before:
One of the topics mentioned but not covered previously was security. As your build server is now visible publicly, you will want to set up some sort of security to prevent people from doing bad things. The simplest way is to use Jenkins own user database, but there are other options to use an LDAP server or the underlying OS users. A few points to make sure that the server is secure:
- Disable the option to allow new users to sign up (unless you actually want people to be able to signup)
- Change the authorisation section to either allow logged in users to do anything or use matrix based security and make sure anonymous users have no permissions
Setting up builds
You should refer back to my previous post on how to get your builds set up.7
Let me know how you get on
After beavering away at some ideas for Knowsis over the last 3 weeks and admittedly not really doing it test first , I spent this weekend finally getting round to setting up a CI server and some builds to run the pitiful number of tests that I have actually written to try and make me write more. It’s been bugging me all along but as the only developer at the moment it’s not been at the top of the priority list. However, my previous experience of setting this kind of thing up for legacy projects tells me that if I don’t get round to it soon, it will be infinitely more painful in the long run.
At 7digital we used Teamcity as our CI build server, but knowing how much their build agent licensing can cost I thought I would look at the open source alternatives seeing as we’re bootstrapping. After some research a nailed it down to the either BuildBot or Jenkins (formerly Hudson) and digging a bit deeper it seems that people with experience of both would suggest using Jenkins first until you realise it can’t do something that you really need BB for as it can be quite painful to get set up; Jenkins on the other hand is very simple to get set up.
One of my favourite things about using Ubuntu, coming from a Windows background, is the ease of installing things using apt-get. These instructions are taken from the Jenkins site:
wget -q -O - http://pkg.jenkins-ci.org/debian/jenkins-ci.org.key | sudo apt-key add - sudo sh -c 'echo deb http://pkg.jenkins-ci.org/debian binary/ > /etc/apt/sources.list.d/jenkins.list' sudo aptitude update sudo aptitude install jenkins
Jenkins gets installed and set up to run as a daemon at startup under a newly created user Jenkins. It’s now usable at http://127.0.0.1:8080, however I wanted to be able to skip the need for a port number so set up nginx to proxy requests for me. This isn’t a necessary step so I won’t go into it here but there are some simple guides available on line if you haven’t used nginx before (just remember to restart nginx after you change the config, it’ll save you hours of head scratching!).
Setting up Jenkins to work with git
This step isn’t necessary if you don’t use git, but i’ll go into it as I do and it took me a bit of figuring out, plus there wasn’t a huge amount of info out there on how to do it.
From the home screen of Jenkins go to the plugins section:
Manage Jenkins -> Manage Plugins
In the Available tab find the “Jenkins GIT plugin” and check the install checkbox. If you use github you can also install the “GitHub plugin” which creates a link from your project page to your github repository and also allows you to use GitHub’s post receive hooks to notuify Jenkins when code has been committed (not necessary as you can use polling to check for changes). Your Jenkins instance will need to be exposed publicly for this to work, so make sure you set up user authentication properly; there’s also a plugin to allow you to use your GitHub logins as authentication if you want to use that.
Once you have selected the required plugins click ‘Download now and install after restart’ which will install the plugins and restart Jenkins, should take no more than a minute to complete.
Create SSH keys for Jenkins
You now need to set up your ssh keys for the Jenkins user. Open up a terminal window and switch to the Jenkins user
sudo -su jenkins
You can run through the creation of your public private key pairs as normal which will be created in the Jenkins user home directory (/var/lib/jenkins). If you want a guide for this, I have always found the one on the GitHub site help pages to be the easiest to follow.
Now set up a user with your git repository for your build slaves to run as and copy the contents of the public key to it. You can use your own account if you wish but I would recommend using a separate one.
Creating a Job in Jenkins is really simple. From the Jenkins dasboard click “New Job”. Enter the name of your job and select “Build a freestyle software project“. Click Ok.
For now you can ignore the options at the top of the next screen, head down to the source control section.
Source Code Management
If you installed the git plugin you should see git as an option here. Select the option that’s relevant and point it to the location of your repository.
Further down is the “Build Triggers” section, you should select the option ‘Poll SCM‘ option, this will then present you with a schedule box that will allow you to enter the frequency to poll your SCM, it uses the cron format. A few examples
* * * * *
Every 10 minutes:
*/10 * * * *
Every hour :
At 15 mins past every hour:
15 * * * *
So far the job will just checkout when there are any changes to your code, so now you need to make the job actually do something interesting. You can set up one of more build steps to run for your unit tests, tp deploy your code to a test environment, run your system tests, deploy your code to live etc.
At this point i’ll just run the unit tests. If you have written some tests using unitest syntax you can use the nose test runner (nosetests) to automatically discover and run these tests. You can also get it to output the test results in Junit report format so that Jenkins can display your test results. You will need to make sure that nose is installed on your build server and slaves for this to work.
Select “Excute Shell” in the “Add Build Step” dropdown and add the following line:
The shell script will run from the top level of your project (known as the workspace root) so if nose cannot auto discover your tests because they are buried in a folder tree structure you can always add a cd command to switch to that directory first. The –with-xunit switch will output an xml report in the Junit format called nosetests.xml into the folder under which nosetests ran.
In the Jenkins set up there is a “Post-build Actions” section under which you should select “Publish Junit test report results” and enter nosetests.xml
If you use some other test format or want to use another test runner enter the shell command that would execute those tests remembering to install anything required onto your build server as well.
Now Go And Write Some Tests
That’s it, you now have a build set up to run your tests every time you check in changes, so there is no excuse not to write any. This is only a start and there a plenty of other things you might want to set up like failure notifications, test reports, dashboards etc so the best thing to do is explore the Jenkins site.