Docker

Writing our manifest files for Kubernetes / Openshift often forces us to edit xml, json and yml files by hand. A new library, ap4k allows to specify metadata for these manifest files directly in our Java code using annotations. In the following short example I am going to demonstrate how to generate manifest files using Maven and ap4k. Figure 1. ap4k Tutorial Dependencies Using Maven we just need to add the following one dependency to our project’s pom.xml ...

A lot of boilerplate code is written when developers need to test their applications with different connected systems like databases, stream platforms and other collaborators. Docker allows to handle those dependencies but there is still some glue code required to bind the container’s lifecycle and the configuration to the concrete integration test. Testcontainers is a testing library that offers lightweight throwaway instances of anything able to run in a Docker container, with bindings to configure the specific containers and also provides wrappers to manage our own custom containers. ...

When implementing distributed systems, client-server architectures and simple applications with network related functionalities, everything is fine when we’re in the development or in the testing stage because the network is reliable and the communicating systems are not as stressed as they are in production. But to sleep well we want to validate how resilient we have implemented our systems, how they behave when the network fails, the latency rises, the bandwidth is limited, connections time out and so on. ...

When writing test for applications that interact with Kafka brokers we often need to setup a decent environment including an instance of Kafka and ZooKeeper. Though Kafka ships with some classes for testing, setting up a simple testing environment is quite easier with the kafka-unit library that offers JUnit test rule support or a fast programmatic setup within no time. In the following short example, I’d like to show how create a simple setup using Maven, Surefire and kafka-unit. ...

Communicating with identity and access management systems is a common task for many web-applications exposing secured resources. Keycloak is an open source software that provides not also such authorization services but also offers a lot of features from Single-Sign-On, Identity-Brokering, Social-Login, User-Federation, multiple client-adapters up to the administration console or support for protocols like OpenID, SAML, OAuth2, Kerberos and more. I will demonstrate how to integrate a Spring Boot web application with Keycloak and configure an authentication flow that requires a two-factor-authentication with user credentials and also one-time-passwords. ...

Atlassian has added a continuous integration service as a new feature to their GitHub Cloud product. It’s called GitHub Pipelines and it is similar to Travis CI for GitHub offering a nice integration for continuous integration/delivery pipelines for projects hosted on GitHub. It’s still in the beta phase and requires a sign-up but nevertheless I’d like to demonstrate the current state of this service and how easy it is to add scripted pipelines to a project. ...

Inspect Docker Image with dive Install dive brew install dive Now we can run dive against any Docker image we wish to inspect…​ Run dive dive confluentinc/cp-kafka:5.4.3 Figure 1. Screenshot of dive analyzing the Kafka Docker image Resources: dive on GitHub Introspect Private Docker Registry List images: curl -s https://the-registry-url/v2/_catalog Get tags for an image curl -s https://the-registry-url/v2/the-image-name/tags/list An example: curl -s https://registry.local/v2/alpine/rabbitmq/tags/list {"name":"alpine/rabbitmq","tags":["3.9.17"]} Run Trivy Scan for Docker Image docker run aquasec/trivy image IMAGE:TAG ...

Common operations Add Helm Repository helm repo add NAME URL e.g. for the Bitnami repository: helm repo add bitnami https://charts.bitnami.com/bitnami 1 ↵ "bitnami" has been added to your repositories List Repositories helm repo list 130 ↵ NAME URL bitnami https://charts.bitnami.com/bitnami Searching in a Helm Repository helm search repo wordpress NAME CHART VERSION APP VERSION DESCRIPTION bitnami/wordpress 15.2.30 6.1.1 WordPress is the world's most popular blogging ... bitnami/wordpress-intel 2.1.31 6.1.1 DEPRECATED WordPress for Intel is the most popu... ...

Remote Debug a Pod’s Java Process Simple steps for remote debugging a Java process running on a k8 pod: Edit deployment and add the following parameters to the Java start line: -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=127.0.0.1:5005 Also add the following port mapping at the section container → ports in the deployment: - containerPort: 5005 protocol: TCP Safe, wait for the new pods and then add a port forward for port 5005 for this pod: kubectl port-forward podname 5005 ...

These are not only linux snippets but also bash snippets and snippets using tools that run under Linux, *nix or sometimes even MacOSX, I should reorder this article someday ;) Settings for more reliable bash scripts set -euo pipefail this gives us …​ -e: exit script if a single command fails -u: exit script if an unset variable is used -o pipefail: return value of a pipeline is the status of the last command to exit with a non-zero status, or zero if no command exited with a non-zero status ...