![]() ![]() Spring Boot uses a “fat JAR” as its default packaging format. ![]() When we pull the Docker image from the registry, it is pulled by layers and cached in the host. Each layer is a delta of the changes over the underlying layer. Security: large-sized images also have a greater surface area for vulnerabilities.Ī Docker image is composed of a stack of layers each representing an instruction in our Dockerfile.Pulling large-sized images from the registry result in long scheduling times in container orchestration systems and long build times in CI pipelines. Performance: in a container orchestration system, the container image is pulled from the image registry to a host running a container engine. ![]() We have two main motivations for optimization: Motivations and Techniques for Building Optimized Images The output shows that the container image is built and pushed to the registry. Container entrypoint set to Built and pushed image as pratikdas/usersignup:v1 Containerizing application to pratikdas/usersignup:v1. We can customize the name of the image required for pushing to the Docker Registry by specifying the name in the image tag: Images are built using the bootBuildImage task (Gradle) or the spring-boot:build-image goal (Maven) and a local Docker installation. The Spring Boot plugin creates OCI images from the source code using a Buildpack. Cloud-Native Buildpacks bring standardization across platforms by supporting the OCI image format which ensures the image can be run by a Docker engine. One main advantage of using Buildpack for building images is that changes to the image configuration can be managed in a centralized place (the builder) and propagated to all applications which are using the builder.īuildpacks were tightly coupled to the platform. It was started by Heroku in 2011 and has since been adopted by Cloud Foundry, Google App Engine, Gitlab, Knative, and some others. Building a Container Image with Buildpackīuildpacks is a generic term used by various Platform as a Service(PAAS) offerings to build a container image from source code. We will aim to reduce the size of this layer in the following sections as part of our optimization. Here is part of the output from running the Dive command:Īs we can see the application layer forms a significant part of the image size. ![]() Next, we containerize this application by adding a Dockerfile: We also add a rest controller to expose an API with the GET method. Let us create our Spring Boot application from Spring Initializr with dependencies for web, lombok, and actuator. We first build an executable JAR and as part of the Docker file instructions, copy the executable JAR over a base JRE image after applying necessary customizations. It is very easy to create Docker images of Spring Boot applications by adding a few instructions to a Docker file. Building a Container Image the Conventional Way The 2.3 release of Spring Boot provides plugins for building OCI images.ĭocker happens to be the most commonly used container implementation and we are using Docker in our examples, so all subsequent reference to a container in this article will mean Docker. The container runtime pulls this image from the registry, unpacks the image, and runs the application inside it. To containerize an application, we enclose our application inside a container image and publish that image to a shared registry. The OCI Image Specification defines industry standards for container image formats and runtimes to ensure that all container engines can run container images produced by any build tool. OCI Standard: the Open Container Initiative (OCI) is a lightweight, open governance structure formed under the Linux Foundation. We convert our application into a container image by running a build tool.Ĭontainer: the runtime instance of a container image.Ĭontainer engine: the daemon process responsible for running the Container.Ĭontainer host: the host machine on which the container engine runs.Ĭontainer registry: the shared location that is used for publishing and distributing the container image. We will start with the container terminologies used throughout the article:Ĭontainer image: a file with a specific format. This article is accompanied by a working code example on GitHub.
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