Companies are often wary of booking external cloud services that involve storage of data on servers abroad, either because of compliance requirements or because of concern about the safety of data sent off-site. The Prism surveillance program and programs like it certainly have not done anything to dispel this skepticism.

Meanwhile, the number of as-a-service offerings by local service providers continues to grow, including some by smaller providers with smart ideas. For example, Jelastic, a platform-as-a-service (PaaS) solution [1], hosts the entire infrastructure users need to run PHP and Java applications.

Testing of the Jelastic service for this article was hosted by dogado GmbH [2]. The public Jelastic cloud resides in a TÜV-certified data center operated by Host Europe [3] in Cologne, Germany, and it was designed to counter increasing concerns among corporate users in Germany regarding data protection, in that the jurisdiction of the Federal Republic of Germany applies exclusively.

When you use the Jelastic service, you will note that the manufacturer understands customer expectations for public cloud computing: After you create an account on the Jelastic site, access credentials are mailed, and you can pay by bank transfer or credit card before using the service. Self-service obviously plays a major role in Jelastic. After unlocking your account, you are given access to the Jelastic dashboard that controls the services you use within the Jelastic cloud.

Understanding Cloudlets

The service is based on technology from Parallels [4], which calls appliances "containers" ("cloudlets" in Jelastic parlance), which are separate areas on the host system provided with their own, limited resources.

A Jelastic appliance is therefore not a genuine virtual machine, but rather an encapsulated application that cannot independently access the resources of another cloudlet. This arrangement keeps applications from influencing each other, contending over resources, or stealing data.

Scalability as a Core Function

A service can scale in two ways: horizontally and vertically. Vertical scaling extends or removes existing systems to create additional resources or replaces them with either more-powerful or less-powerful systems. The number of systems does not change. In contrast, horizontal scaling involves matching the number of available systems to the workload. Vertical scaling naturally reaches its limits when a computer can no longer be extended. Horizontal scaling works fine until the entire computer pool is overloaded.

According to dogado [5], the Jelastic platform scales both vertically and horizontally. Either a cloudlet is provided with extra cloudlets on the fly or the host-side hypervisor adapts the quantity of available resources, or both.

The difference for the customer is noticeably reflected in billing; the customer typically pays for the PaaS performance used. Cloudlets at Jelastic are charged a base fee once an instance starts. The customer thus determines how many virtual servers an appliance should include.

Horizontal scaling is handled by the platform itself at run time: If an appliance notices that its resources are scarce, it automatically requests more power from the hypervisor. In practical terms, customers do not have to worry about performance, as long as they have not undersized the maximum number of cloudlets. The platform automatically absorbs peak loads with the described horizontal scaling method.

In our lab, the provisioning and scaling operations worked well, as a test in which several parallel wget processes in an infinite loop served to prove. As the load increased, the number of cloudlets in use rose to the limit previously selected in the dashboard.

Hello World

During the first login after registering with Jelastic, the user is given access to a wizard on the dashboard (Figure 1); the wizard in turn offers more or less useful tips. During initial setup and during normal work, the wizard is backed up by detailed documentation of a remarkably good quality.

Figure 1: The bespectacled wizard guides you through the setup. The classical documentation is complete and useful.

To begin, the customer must decide what type of appliance is desired: Java or PHP. For both variants, the admin can also request an SQL or a NoSQL database. A single cloudlet with a MySQL database and Tomcat comes for a basic fee of around EUR 28.50 (EUR 24 without tax) per month (Figure 2). At the end of the setup process, which takes less than two minutes, the customer receives a complete MySQL Tomcat VM in which the sample project "Hello World" is already deployed.

Figure 2: The Jelastic wizard in the dashboard guides you through the task of setting up an initial environment, including a database.