The struggle with Hazelcast queue persistence
In this blog I will outline why we used Hazelcast for queueing messages in-memory distributed over a cluster and how we achieved higher resilience by persisting the queue’s content. I will explain the pitfalls and difficulties that we encountered and how I constantly switched between praising and condemning Hazelcast.
The problem to solve I’m currently working in a project for a large customer data backend. The prod system consists of a load balanced cluster of five VMs each running two Tomcat instances hosting our application.
Karlsruher Entwicklertage 2017 - Conference Day
Am 22.5. habe ich zum ersten Mal die Karlsruher Entwicklertage besucht.
Insgesamt war die Veranstaltung gut organisiert, man bekam schnell und unkompliziert seine Badge und die obligatorische Info-Tüte. Es gab eine große Auswahl an verschiedenen Talks, die auf 6 parallele Tracks aufgeteilt waren. Die einzelnen Tracks wurden unter anderem von einigen Usergroups wie z.B. der Java Usergroup, der .NET-Usergroup und dem lokalen OWASP-Chapter organisiert. Danke an die ehrenamtlichen Helfer für das Engageme
Validating internal structure / dependencies using IntelliJ IDEA
There are several different tools to maintain the internal structure of a java application available. The tools range from simple open source software like jdepend and degraph to full fledged architecture tooling like Structure101 or Sonargraph Architect. All these provide methods to define the internal structure of an application and validate it somehow.
Visualising sensors and coffee machines with ESP8266, MQTT, InfluxDB and Grafana
A few months ago, here at the synyx office we started out with a simple idea: hook up a couple of sensors to an ESP8266 module (or twenty) and have it write its data somewhere for visualisation purposes. Then we got creative.
Our current setup consists out of a number of ESP8266 (currently NodeMCU) boards, featuring humidity (DHT-22, BME280) as well as CO2 (MH-Z14) sensors which publish their data over MQTT.
Axon 3: Event Replaying
Axon is a lightweight framework that supports the implemenation of CQRS patterns by providing commonly used building blocks. One of those patterns is an event sourced application architecture. Even though Event Sourcing and CQRS are orthogonal concepts they fit together very well and are often used together. Event sourcing in an ES/CQRS architecture means that all changes to the application state are done via domain events and the current state can always be rebuilt from the series of events available in a persistent event store.