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Spark Streaming Example – How to Stream from Slack

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Let’s write a Spark Streaming example in Scala, which streams from Slack. This post will show how to write, configure and execute the code, first. Then, the source code will be examined in detail. If you don’t have a Slack team, you can set one up for free. We’ll cover that too. Let’s start with a big picture overview of ...

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Spark Data Source API: Extending Our Spark SQL Query Engine

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In my last post, Apache Spark as a Distributed SQL Engine, we explained how we could use SQL to query our data stored within Hadoop. Our engine is capable of reading CSV files from a distributed file system, auto discovering the schema from the files and exposing them as tables through the Hive meta store. All this was done to ...

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Introducing The Delegate Pattern

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Delegate: a person who is chosen or elected to vote or act for others – Merriam-Webster. Delegate pattern: In software engineering, the delegation pattern is a design pattern in object-oriented programming where an object, instead of performing one of its stated tasks, delegates that task to an associated helper object – Wikipedia. Make things as simple as possible, but not simpler – Albert ...

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Improve Your JUnit Experience with this Annotation

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JUnit is probably part of 90% of all Java projects. And the exciting thing is, we’ll soon have JUnit 5 with Java 8 support. We’ve blogged about an improvement recently. Back in JUnit 4 land, there’s this little trick that I can only recommend you put in all of your unit tests. Just add this little annotation here and you’ll ...

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Keycloak SSO Integration into jBPM and Drools Workbench

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Introduction Single Sign On (SSO) and related token exchange mechanisms are becoming the most common scenario for the authentication and authorization in different environments on the web, specially when moving into the cloud. This article talks about the integration of Keycloak with jBPM or Drools applications in order to use all the features provided on Keycloak. Keycloak is an integrated SSO ...

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Java Remote Debug for Applications Running in Kubernetes

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Kubernetes 1.2 was just released and is quickly becooming the defacto cluster management solution for containers (Docker, Rocket, Hyper, etc). Check it out if you haven’t already – here are some interesting tidbits about the 1.2 release: Cluster can now scale to 30,000 containers per cluster Graceful shutdown of nodes, transitioning to other running nodes in the cluster Custom defined ...

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Logging Requests to Elasticsearch

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This is something I wanted to write down for years but never got down to completing the post. It can help you a lot with certain Elasticsearch setups by answering two questions using the slow log. Is my application talking to Elasticsearch? What kind of queries are being built by my application? A while ago I helped a colleague on ...

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Micro-services for performance

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Overview Microservices is a buzz word at the moment. Is it really something original or based on established best practices. There are some disadvantages to the way micro-services have been implemented, but can these be solved? Component testability and consistency Once you have assembled a large system, it can be hard to impossible to profile where the highest delays come ...

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Building GORM Criteria Queries Dynamically

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I originally wrote most of the queries in the spring-security-ui plugin using HQL because I find it more intuitive than criteria queries, but HQL only works with Hibernate and relational databases. A pull request updated the queries to use criteria queries to allow the plugin to be used with NoSQL datastores, but one query didn’t fit the programming style that ...

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