Tech

Reactive design or reactive architecture has an impact on how modern software systems are implemented. RSocket is a project that aims to adapt the benefits of the patterns described in the Reactive Manifesto and resulting tools like Reactive Streams or Reactive Extensions to a formal new communication protocol. RSocket works with TCP, WebSockets and Aeron transport layers and offers additional features like session resumption. In the following tutorial I’m going to demonstrate how to implement simple client-server communication over TCP and Websockets for different interaction models like request-response, request-stream, fire-and-forget and event subscription. ...

Whitesource Configuration for GitLab Pipeline The following configuration derives values from predefined GitLab Variables whitesource.conf # Providing project information from GitLab CI wss_project_name="$CI_PROJECT_NAME" wss_project_version="$CI_JOB_ID" wss_project_tag="$CI_COMMIT_TAG" # Providing product information wss_product_name="The Product Name" wss_product_version="$POM_VERSION" # Analyze the Maven POM and its transitive dependencies only, no file-system check # Use this only if you don't have any extra checked in jar-files or stuff like that! fileSystemScan=false includes=pom.xml # Only scanning the Maven project resolveAllDependencies=false maven.resolveDependencies=true ...

Arthas created by Alibaba is a tool that allows developers to connect to running Java applications without stopping them or suspending threads for debugging the application from the console. It offers features like monitoring invocation statistics, searching for classes and methods in the classloaders, view method invocation details (like parameters), show the stack trace of a method invocation, monitor system metrics and others. In the following examples I’m going to demonstrate some of these features applied to a running web application. ...

Capacity planning is an important task when trying to anticipate resources and scaling factors for our applications. The usl4j library offers us an easy abstraction for Neil J. Gunther’s Universal Scalability Law and allows us to build up a predictive model based on the parameters throughput, latency and concurrent operations. With a basic input set of two of these parameters, we are able to predict how these values change if we change one input parameter so that we can build our infrastructure or systems according to our SLAs. ...

The OpenAPI and Swagger API description format are becoming important standards to specify API contracts for RESTful web services and the Microservices trend pushes the need for such contracts even further. Therefore arises the need for software architects, testers and developers to write tests to verify if an exposed API follows such a specified contract. In the following tutorial I will demonstrate a setup with Java, Maven, JUnit and the designated contract-testing-library, assertj-swagger that verifies the validity of such a contract exposed by a Spring Boot application against a local stored definition. ...

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. ...

JetstreamDB is a in-memory database engine for Java that claims to be built for ultra-high speed and the ability of managing complex data structures by storing real Java objects instead of serializing data structures to other database specific formats. In the following short example I would like to demonstrate how to create and read items from such a database by building a small article management sample app. ...

Every software project includes a set of architecture decisions defining boundaries and constraints for further design and implementation. It’s important to document those decisions somehow or else a development team might not know which decisions where made and with which assumptions. Or they know the decision but are missing the context and the consequences and therefore decisions are blindly accepted or blindly changed. In the following short tutorial I will show how to structure architecture decisions in so called Architecture Decision Records and how to manage them with a simple tool named ADR-Tools. ...

When we need to investigate the cause for a dysfunctional Java application we have a plethora of tools available that on the one hand help us in gathering information, artifacts and statistics and on the other hand help us in processing this information and identifying possible problems. The following list of tools, snippets, workflows and information about specific artifacts could provide a starting point for analyzing such problems and covers topics like heap-dumps, thread-dumps, heap-histograms, heap-regions, garbage-collection-logs, hotspot-compiler/codecache-logs, debugging native-memory, tools for heap-dump-analysis, JVM unified logging and more.. ...

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. ...