Introduction
In the previous blog post I described how you could create
Web Applications using JSF and CDI that are running in the cloud with Google
App Engine.
Using a database is also possible but is not available for
free on AppEngine and that was the reason I didn’t go into detail about it.
But there exists another possibility to host your Java EE application
in the cloud, and it has even more possibilities and is much easier, OpenShift
of JBoss.
And best of all, you can run them for free if your requirements
are not too high.
What is it?
OpenShift is a so-called PaaS, platform as a service. So it is not only limited to a server that
you can use or a program, like a web server that is available, it is the
complete stack.
With OpenShift you can use for example a WildFly application
server and a database instance to deliver you an environment for the execution
of your web application. It has also a unique way of deploying you app using a
GIT repository.
In this text I’ll describe the Java EE solution that you can
use, but there exists also other possibilities like PHP, Tomcat with Spring,
Continuous integration server, and many others.
Have a look on their site about the supported environments.
Creating an application
You first start by creating a domain. The domain will hold one or more of your
applications. The domain name is also
reflected in the URL. The structure is as follows
%application%-%domain%.rhcloud.com
You can assign it an alias if you supply this URL to your
DNS provider.
Creating a domain is nothing spectacular, you just have to
specify the name for it.
Once you have the domain, you can create the web application
in it.
And the first thing you have to do when you create an
application is to specify which type of application you want.
In my case, I want to have a Java EE environment in the
cloud, so I took the WildFly 8 possibility.
As said there are a lot of possibilities and maybe one that I want to
mention here also is CapeDwarf. It implements fully the Google AppEngine API’s
so that you can migrate easily from Google to the JBoss cloud.
In the next step you have to give some configuration
options, like the application name, as said part of the URL, and if you want to
have scaling and thus a load balancer for your application.
The creation of the application takes some time, as it is
preparing a machine for you with all the software you need.
But when it is finished, you can already go the to URL and
see the welcome page of your application, which you want to customise of
course.
The overview page also gives some very important information
that you need to be able to deploy and use the application.
In the case of WildFly, it gives the username and password
you need to be able to log on in the console of the application server.
It also states the GIT URL that you can use to clone the
source of the application locally and start developing your application.
More on those later.
Database
Since my test application needs some database to store
information, I can create it also on the OpenShift platform.
The idea is that you can add additional ‘cartridges’ that
have certain functionality and allows you to create the ideal server for your
application.
A database is the most common cartridge, but there exists
also others like for example a cartridge to execute some scheduled jobs (CRON
like)
Regarding the databases, you can choose between MySQL and
PostGreSQL but you have also the possibility of using MongoDB.
Configuration is not needed, you add the cartridge and you
receive the URL, username and password for the database to access it.
In case of MySQL, the access is through phpMyAdmin that
needs to be added if you want console access directly to your database.
Web application
I talked a lot about setting everything up, because creating
your web application is very easy.
If you clone the GIT repository that was indicated on the
site, you see that it is maven based. So any maven based Java EE application
can be used.
No special configuration needed, no adjustments like with
AppEngine. If it runs on your machine, it runs on OpenShift.
Database access
The only thing that took a little bit of research was the
URL to my MySQL database that was created.
I found this knowledge base article, where it is clearly described.
You first have to create a datasource for WildFly in the
configuration files. You can find the
standalone.xml file in the .openshift/config/ directory when you
have checkout the GIT repository.
You have to leave the placeholders,
like ${env.OPENSHIFT_MYSQL_DB_HOST} in the configuration file so that it can
properly be resolved at deployment time.
Once you have defined it there, you can
define the datasource in your persistence XML file and the application is able to
connect to it.
java:jboss/datasources/MySQLDS
Deploy
When you push the changes to the remote
GIT repository, a lot of things are happening.
First your application and WildFly
server are stopped. Then it is running
the mvn package on your new code. And then the server is started again with
your new version of the application deployed.
So it can take a minute or more before your push ends due to these
tasks.
Client tool
Besides the option to push the code,
you also have the RHC client tools. It is a ruby based tool that allows you to
connect to your server. You can perform various operations which this tool
which are also possible online.
These include things like
Getting started, like creating domain,
applications and adding cartridges.
Working with your app as looking at
your log, port forwarding so that you can open the WildFly console from your
browser, etc
Account management like setting up ssh
connections, authorisation, key generation etc..
Cost
OpenShift can be used free of
charge. They work with the concept of
gears. Each feature uses one or more gears, categorised in small, medium and
large size.
A WildFly instance takes only 1 small
gear and you get 1 GB of space with it. The space calculation takes into
account the code and log size and also the database size.
So the database isn’t taking up any
additional gear, a load balancer counts also for 1 small gear.
Since you have 3 small gears for free,
you can run up to 3 applications with a database on their platform.
Conclusion
With OpenShift it becomes very easily
to deploy your Java EE application in the cloud. JBoss made it possible to use
a Maven based application that runs on WildFly to deploy it on their cloud
infrastructure. No changes needed, only some slight modification for the
datasource to access your database also hosted on their PaaS.
