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Getting Started with Heron on Apache Mesos and Apache Kafka

Heron has been Open Sourced, woo! Heron is Twitter’s  distributed stream computation system for running Apache Storm compatible topologies in production. A Heron topology is a directed acyclic graph used to process streams of data. Heron topologies consist of three basic components: spouts and bolts, which are connected via streams of tuples. Below is a visual illustration of a simple topology: Spouts are ...

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Scala Notes – Futures – 1

Almost all modern programming languages have a Future-Promise idiom for concurrent programming. I don’t intend to bore you with why we need higher level of concurrency abstractions. Instead, in this post, we’ll cut to the chase and discuss only about Scala’s approach to Futures. A scala.concurrent.Future is a representation of a value that is yet to be realized. This value ...

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The Building Blocks of Your First Bot

The world of bots who can intelligently converse continues to build momentum. We’ve seen the opening up of the Facebook Messenger and LINE platforms, as well as improvements to the existing Telegram platform. In addition to new and improved platforms, the Kik bot store has opened, and Slack is making submission to their app store a product priority. While messaging ...

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Why Microservices Should Be Event Driven: Autonomy vs Authority

I’ve been working on a series of articles showing how to build microservices using an event-driven approach (which IMHO is the only real way to build microservices :) or… any complex distributed architecture). I’ll explore DDD, CQRS, Event-sourcing, event streaming, complex-event processing and more. I’m using a reference monolith application based on Java EE that uses all the typical Java ...

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Aspect Oriented Programming with Spring Boot


On a previous post I provided a simple example on how to achieve aspect orientation in spring by using a ProxyFactoryBean and implementing the MethodBeforeAdvice interface. On this example we will learn how to achieve aspect orientation by using Spring boot and Aspect4j annotations. Let’s start with our gradle file. group 'com.gkatzioura' version '1.0-SNAPSHOT' apply plugin: 'java' apply plugin: 'idea' ...

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Couchbase XDCR using Docker Swarm, Machine and Compose

Cross Datacenter Replication (XDCR) in Couchbase provides an easy way to replicate data from one cluster to another. The clusters are typically set in geographically diverse data centers. This enables for disaster recovery or to bring data closer to users for faster data access. This blog will show: Setup two data centers using Docker Swarm Run Couchbase containers on each node of Docker Swarm ...

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Cloud Foundry Java Client – Streaming events


Cloud Foundry Java Client provides Java based bindings for interacting with a running Cloud Foundry instance. One of the neat things about this project is that it has embraced the Reactive Stream based API’s for its method signatures, specifically using the Reactor implementation, this is especially useful when consuming streaming data. In this post I want to demonstrate a specific use case where ...

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Scalable Microservices through Messaging

Microservices are everywhere nowadays, and so is the idea of using service choreography (instead of service orchestration) for microservices interactions. In this article I describe how to set up service choreography using ActiveMQ virtual topics, which also enables scalable event based service interactions. Service Interaction Styles There are two main types of service interaction: synchronous and asynchronous. With synchronous interactions, the service consumer makes a request ...

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