Author Archives: Jan Sipke

Installing a Storm cluster on CentOS hosts

Storm is a distributed, realtime computation system to reliably process unbounded streams of data. The following picture shows how data is processed in Storm: This tutorial will show you how to install Storm on a cluster of CentOS hosts. A … Continue reading

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Installing Apache Libcloud on CentOS

Apache Libcloud is a standard Python library that abstracts away differences among multiple cloud provider APIs. At the moment it can be used to manage four different kinds of cloud services: servers, storage, loadbalancers and DNS. Here are the steps … Continue reading

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Creating a Java WebStart (JNLP) application

Java WebStart, also called Java Network Launching Protocol (JNLP), allows you to launch Java applications directly from the internet using a webbrowser. In this article we will create a simple application and all configuration files necessary to launch it through … Continue reading

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Creating network diagrams with D3.js

D3.js is a JavaScript library for manipulating documents based on data. It can be used for all sorts of visualizations including network diagrams. In this article we will create a network diagram with nodes and directed links between them, visualized … Continue reading

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Grep lines before and after matched line

The command grep is really useful for finding matches of a certain word in files or streams. However, until recently I didn’t know how to display lines before and after the matched line(s). Let’s say we have a file named … Continue reading

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Temperature graphs

In a previous article we looked at remote measurement of temperature and humidity. Now it is time to show the results of the temperature measurements. First a recap of the setup: Three remote temperature and humidity sensors are located in … Continue reading

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Measuring temperature and humidity with a JeeNode

In a previous article we looked at the Arduino. Now we will look at an (almost) Arduino compatible clone, the JeeNode. It is a bit smaller and cheaper than the original version and operates at 3.3V instead of 5V. This … Continue reading

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