Posts Tagged ‘Technology’

Spring into kotlin: A short video presentation

December 15, 2018

If you heard about kotlin and have some knowledge about the spring framework you might enjoy this 30 min video presentation on infoq.com.

Mark Heckler discusses how Kotlin can be used to reduce boilerplate and increase code quality, showing how to begin incorporating Kotlin into an existing Spring application.

Springing into Kotlin: How to Make the Magic Even More Magical

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Why should I care about Progressive Web Apps?

February 25, 2018

If you are interested in web development you may have heard the term Progressive Web Apps. If you are not sure what the hype is all about or you know some things but want to get an easy transition into how to use some them, then I recommend you the InfoQ.com presentation called Up and Running with Progressive Web Apps. You will learn how the install, push notifications and offline functionality looks like and works.

Usefull resources/links presented in the presentation:

Check if port on remote server is open without using telnet

June 13, 2017

If you want to check if a given port is open on a given remote server, you can use telnet. More and more telnet disappears on server. So the question arises: What can we use instead of telnet? Short answer: netcat. For example:

nc -zv 192.168.1.15 22

Which checks if the port 22 (SSH) is open on the server 192.168.1.115

Debugging scalability issues in action: Twitch Plays Pokémon

December 28, 2016

On Infoq.com you can wath a presentation about that:

John Rizzo introduces Twitch’s chat’s architecture, telling how their engineers investigated and worked through the issues in what turned out to be a make-or-break situation for the company.

 

Where Has the Java PermGen in Java8 Gone?

November 30, 2016

Java 8 is released since 2014. If you are working in an enterprise oriented company, chances are you are only now getting experience with usage of Java 8. You may ask yourself what this warning is telling you.

VM warning: ignoring option MaxPermSize=128M; support was removed in 8.0

Why is PermGen gone? An article of infoq.com tells you something of the reasoning behind this change.

Howto access git via ssh behind a corporate proxy

November 22, 2016

If you are working behind a proxy and have to access git repositories on the internet via ssh (e.g. github), then you sooner or later (probably sooner) find out that this will not work out of the box. This is because you need to proxy your ssh connection. This summary on stackoverflow explains how to do this in a short but comprehensible manner.

 

Hardware based exploit: Rowhammer

November 10, 2016

The Rowhammer exploit is at least known since 2014 but only in the last months it seems that this exploit may be found out in the wild.

Row hammer (also written as rowhammer) is an unintended side effect in dynamic random-access memory (DRAM) that causes memory cells to leak their charges and interact electrically between themselves, possibly altering the contents of nearby memory rows that were not addressed in the original memory access. This circumvention of the isolation between DRAM memory cells results from the high cell density in modern DRAM, and can be triggered by specially crafted memory access patterns that rapidly activate the same memory rows numerous times.
[…]
Memory protection, as a way of preventing processes from accessing memory that has not been assigned to each of them, is one of the concepts behind most modern operating systems. By using memory protection in combination with other security-related mechanisms such as protection rings, it is possible to achieve privilege separation between processes, in which programs and computer systems in general are divided into parts limited to the specific privileges they require to perform a particular task. Using privilege separation can also reduce the extent of potential damage caused by computer security attacks by restricting their effects to specific parts of the system. [wikipedia]

In other words: Switching to another operating system or patching it may not solve the problem, because the root of the problem lies in the memory chips every which computer contain. An article on wired.com describes it like this

Both of those new attacks use a technique Google researchers first demonstrated last March called “Rowhammer.” The trick works by running a program on the target computer, which repeatedly overwrites a certain row of transistors in its DRAM flash memory, “hammering” it until a rare glitch occurs: Electric charge leaks from the hammered row of transistors into an adjacent row. The leaked charge then causes a certain bit in that adjacent row of the computer’s memory to flip from one to zero or vice versa. That bit flip gives you access to a privileged level of the computer’s operating system.

lwn.net is reporting that linux kernel developers are trying to mitigate the exploit.

An intriguing alternative turned up on the linux-kernel list, though its nature wasn’t immediately clear. Pavel Machek asked a question that raised some eyebrows: “I’d like to get an interrupt every million cache misses… to do a printk() or something like that.” Developers naturally wondered what he was up to. The answer turns out to be an in-kernel Rowhammer defense.

Intro to Reactive Programming in Java

September 27, 2016

Infoq.com has  a nice little intro and tutorial to reactive programming in Java with the RxJava library.

Key takeaways

  • Reactive programming is a specification for dealing with asynchronous streams of data
  • Reactive provides tools for transforming and combining streams and for managing flow-control
  • Marble diagrams provide an interactive canvas for visualizing reactive constructs
  • Resembles Java Streams API but the resemblance is purely superficial
  • Attach to hot streams to attenuate and process asynchronous data feeds

Also you should checkout the RxMarbles website which interactivly visualizes the reactive functions.

Mozilla Flyweb: How to get rid of custom apps to communicate with IOT devices…

September 8, 2016

Mozilla has an interesting project called flyweb. If you want to know what it is about and why you should have a look at it watch this video.

https://air.mozilla.org/friday-plenary-flyweb/video/

This specification aims to allow web applications to connect with and communicate to each other over local-area transport protocols. In particular, this specification aims to bring the web’s client/server application model to inter-device communication. The web’s application architecture enables an application running on a server to dynamically and incrementally send application state and logic to an intermittently connected client. This model enables a powerful multi-homed application architecture.

Git Staging: Video about what it is, how it is used and why we need it

August 29, 2016