Together with growing demand in PaaS and DevOps solutions, we can notice a set of adoption barriers for the owners of legacy applications hosted inside VMs or just on top of bare metal servers. The complexity of decomposition and migration processes is often very high. Usually, application owners have to redesign their application architecture in order to benefit from the modern PaaS and CaaS solutions.
In this article, we will analyze the specific challenges of migrating Java legacy applications that are running inside VMs to container based platforms. And using the example of Oracle WebLogic Server, we’ll show the exact steps of decomposition process and the outcome of this migration.
Hardware virtualization was a great step forward in the hosting of Java EE applications compared to the era of Bare Metal. It gave us the ability to isolate multiple applications from each other and utilize hardware more efficiently. However, with Hypervisors, each VM requires its own full OS, TCP and file system stacks, which uses significant processing power and memory of the host machine.
Each VM has a fixed amount of RAM and only some hypervisors can resize VMs while running with a help of memory ballooning that is not a trivial task. As a result, usually we reserve resources in each VM for the further scaling of the application. These resources are not fully utilized and, at the same time, they cannot be shared with other applications due to the lack of proper instances isolation inside a VM.
Containers take performance and resource utilization a step further by sharing the OS kernel, TCP stack, file system and other system resources of the host machine while using less memory and CPU overhead. Read the complete article here.
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