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Load test of WebRTC recording on AWS

Flashphoner corporate blogSystem administration*Working with video*IT Infrastructure*DevOps*

Do you remember how just a few years ago it was a disaster to lose a camera at the end of a vacation? All memorable pictures and videos then disappeared along with the lost device. Probably, this fact prompted the great minds to invent cloud storage, so that the safety of records no longer depends on the presence of the devices on which these records are made.

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Rating0
Views26
Comments 0

WebRTC face to face video chat. Load test

Flashphoner corporate blogSystem administration*Working with video*IT Infrastructure*DevOps*

We continue to review variants of load tests. In this article we will go over the testing methodology and conduct a load test that we will use to try and determine the number of users that could watch and stream at the same time, meaning the users will simultaneously publish and view the streams.

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Rating0
Views161
Comments 0

Linux kernel turns 30: congratulations from PVS-Studio

PVS-Studio corporate blogOpen source*C++*C*Development for Linux*

On August 25th, 2021, the Linux kernel celebrated its 30th anniversary. Since then, it's changed a lot. We changed too. Nowadays, the Linux kernel is a huge project used by millions. We checked the kernel 5 years ago. So, we can't miss this event and want to look at the code of this epic project again.

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Total votes 2: ↑2 and ↓0+2
Views421
Comments 0

XSS: attack, defense — and C# programming

PVS-Studio corporate blogInformation Security*Programming*.NET*C#*

XSS - or cross-site scripting - is one of the most common vulnerabilities in web applications. It has been on the OWASP Top 10 list (the list of the most critical security risks to web applications) for a while now. So let's figure out together how your browser can acquire and execute a script from a third-party website, and what this may lead to (spoiler: your cookies could get stolen, for example). And while we're at it, we'll talk about ways you can protect yourself from XSS.

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Total votes 1: ↑1 and ↓0+1
Views434
Comments 1

Load testing for WebRTC mixer

Flashphoner corporate blogSystem administration*Working with video*IT Infrastructure*DevOps*

This article is a continuation of our series of write-ups about load tests for our server. We have already discussed how to compile metrics and how to use them to choose the equipment, and we also provided an overview of various load testing methods. Today we shall look at how the server handles stream mixing.

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Total votes 1: ↑1 and ↓0+1
Views160
Comments 0

How to create a custom Scrollbar in Flutter using RenderShiftedBox

Flutter*
Sandbox

In my project, I was faced with the need to implement a scroll bar. The standard approaches didn't fully satisfy what designers wanted to see. Here is an example, it is slightly different in appearance from what I needed, but the essence is approximately the same: the scroll bar should be on the right side of the list and take into account the padding of the scroll bar, with the slider displaying the percentage of the scrolled part of the list.

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Total votes 3: ↑3 and ↓0+3
Views342
Comments 0

One does not simply calculate the absolute value

Programming*Java*Mathematics*
Translation

It seems that the problem of calculating the absolute value of a number is completely trivial. If the number is negative, change the sign. Otherwise, just leave it as it is. In Java, it may look something like this:


public static double abs(double value) {
  if (value < 0) {
    return -value;
  }
  return value;
}

It seems to be too easy even for a junior interview question. Are there any pitfalls here?

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Total votes 11: ↑10 and ↓1+9
Views22K
Comments 4

How to setup TON (The Open Network) validator

Cryptocurrencies
Tutorial
The The Open Network (TON) is a fast, secure and scalable blockchain and network project, capable of handling millions of transactions per second.

It was originally introduced by Telegram and called Telegram Open Network. Unfortunately, in May 2020, they announced the closure of the project due to the US court decision. Right after that, three different organizations announced their intentions to continue work on the blockchain: TON Labs, NewTON (TON Foundation), and the Chinese TON community.


In early August, the Telegram team transferred the original repository on GitHub, as well as the ton.org domain, to the open developer community of the TON Foundation.


You can read more about it here.


Introduction


In this tutorial, you will learn how to set up & run a TON validator using mytonctrl on Ubuntu. Note that, it is only dedicated to validators on the NewTON (TON Foundation) blockchain.

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Total votes 5: ↑5 and ↓0+5
Views715
Comments 0

New features of the hybrid monitoring AIOps system Monq

Gals Software corporate blogIT systems testing*System administration*IT Infrastructure*Software


In one of the previous articles, I’ve already written about the hybrid monitoring system from Monq. Almost two years have passed since then. During this time, Monq has significantly updated its functionality, a free version has appeared, and the licensing policy has been updated. If monitoring systems in your company start to get out of control, and their number rushes somewhere beyond the horizon, we suggest you take a look at Monq to take control of monitoring. Welcome under the cut.
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Total votes 9: ↑9 and ↓0+9
Views235
Comments 0

Десятка лучших frontend-сообществ и каналов

Конференции Олега Бунина (Онтико) corporate blogJavaScript*ConferencesDesign

Что может быть ценнее новых идей и нового опыта? Только возможность обсудить их вместе с людьми, которые в теме. 

Мы решили сделать для вас подборку самых интересных frontend-сообществ и полезных каналов на YouTube для разработчиков JavaScript и веб-дизайнеров.

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Total votes 24: ↑23 and ↓1+22
Views1.4K
Comments 0

Quantitative‌ ‌Funds:‌ ‌What’s‌ ‌Interesting‌ ‌for‌ ‌Coders?

Luxoft corporate blogBig Data*Machine learning*IT careerFinance in IT

Hello, Habr! Not only traders but also mathematicians and programmers work with stock markets. Director of Engineering at Luxoft Artem Sosulnikov tells about data, which specialists of quantitative hedge funds work with, things they pay attention to, and conditions in such companies.

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Total votes 1: ↑1 and ↓0+1
Views403
Comments 0

Tutorial: how to port a project from Interop Word API to Open XML SDK

PVS-Studio corporate blogProgramming*.NET*C#*Development for Office 365*
Tutorial

With the .NET5 release further development of some projects was questionable due to the complexity of porting. One can abandon small outdated libraries or find a replacement. But it's hard to throw away Microsoft.Office.Interop.Word.dll. Microsoft doesn't plan to add compatibility with .NET Core/5+, so in this article we focus on creating Word files with Open XML SDK.

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Total votes 4: ↑3 and ↓1+2
Views420
Comments 0

Controlling Brushless Motors using a Linux computer or a PLC

*nix*SCADA*Computer hardwareDIYElectronics for beginners
Tutorial

In this video, we will look at how to connect brushless motor controllers to a Linux computer. Specifically, we will use a computer running Debian. The same steps would work for Ubuntu Linux and other Linux distributions derived from Debian.

I've got a small sensorless brushless motor, and a bigger brushless motor with a built-in absolute encoder. Lets look at how to control those from my Debian Linux computer. Servosila brushless motor controllers come in several form factors with either a circular or a rectangular shape. The controllers come with a set of connectors for motors and encoders as well as for USB or CANbus networks.

The controllers can be powered by a power supply unit or by a battery. To spice up my setup, I am going to use a battery to power the controllers and thus their motors. The controllers need 7 to 60 volts DC of voltage input. If I connect the battery, the controllers get powered up. The small LED lights tells us that the controllers are happy with the power supply.

We need to connect the brushless motor controllers to the Linux computer. There are two ways to do that - via CANbus or via USB. Lets look at the USB option first. A regular USB cable is used. Only one of the controllers needs to be connected to a computer or a PLC.

Next, we need to build an internal CANbus network between the controllers. We are going to use a CANbus cross-cable to interconnect the controllers. Each controller comes with two identical CANbus ports that help chain multiple controllers together in a network. If one of the interconnected brushless motor controllers is connected to a computer via USB, then that particular controller becomes a USB-to-CANbus gateway for the rest of the network. Up to 16 controllers can be connected this way via a single USB cable to the same control computer or a PLC. The limit is due to finite throughput of the USB interface.

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Total votes 4: ↑3 and ↓1+2
Views555
Comments 0

Шпаргалка по CSS свойству display

CSS*
Привет, Хабр. Я часто вижу, что разработчики плохо знают, как работает свойство display. Это приводит к разного рода ошибкам. Чтобы побороть это, я собрал наиболее популярные значения и описал, как они влияют на элемент. Все эксперименты я выложил в виде шпаргалки на Codepen, чтобы вы могли проинспектировать их и изучить.



P.S. Если я что-то пропустил, то поправляйте меня в комментариях. Спасибо!
Total votes 3: ↑3 and ↓0+3
Views879
Comments 0

CodeIgniter 4. Prelude to PHPUnit

PHP*CodeIgniter*
Tutorial

Thanks for your feedbacks

I thank the members of the Habr community for their benevolent attitude to the article by the author «Speed Dating with the CodeIgniter 4 on GitHub» in the form of votes and comments.

The friendly attitude to the author prompted him to continue developing a topic dedicated to PHPUnit as part of CodeIgniter 4.

Install Xdebug on XAMPP (Windows 32-bit (x86))

1. Why Xdebug? In file «appstarter/tests/README.md» in the «Requirements» section explicitly states: «You also need to install XDebug to successfully calculate code coverage».

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Total votes 1: ↑0 and ↓1-1
Views347
Comments 0

Using a headless browser for WebRTC load tests

Flashphoner corporate blogSystem administration*Working with video*IT Infrastructure*DevOps*

In the previous article we went over a load test whose data could be used to choose a load-appropriate server. In the course of the testing, we would publish a stream on one WCS, and we would pick up that stream several times using a second WCS. The acquired results could be used as a basis for decisions on server operability.

Some would (justly) have concerns regarding the possible biases in such a test — after all, one of our servers was used to test another one of our servers. Could it be that we were using a specially optimized code that skewed the results in our favor?

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Total votes 1: ↑1 and ↓0+1
Views385
Comments 0

Controlling Brushless Motors from Windows

Robotics development*Development for IOT*Development for Windows*RoboticsIOT
Tutorial

In this video, we will look at how to connect brushless motors to a Windows computer via USB. We are going to connect a network of Servosila brushless motor controllers to the computer. The other option is CANbus interface, but we will look at CANbus in a dedicated video. A regular USB cable is used. Note that the USB cable is not used to power the controller and its motor.

The first brushless motor controller in network appears to Windows as a Virtual COM port. Once connected via USB, it can be found in a general list of devices in the Window's "Settings" window. Up to 16 controllers can be connected this way via a single USB cable to the same control computer or a PLC. If one of the interconnected brushless motor controllers is connected to a computer via USB, then that particular controller becomes a USB-to-CANbus gateway for the rest of the network.

If your computer happens to have more that one serial port, you may wish to check a COM port's number assigned by Windows to the controller. Then, you pick this COM port in a drop down menu in the Servoscope software, and click Connect. If the COM port is not listed in the drop-down menu, click the Refresh button. If everything is good, the controller appears in a list of devices. Double-click to open up a control and configuration window.

Video & Read more
Total votes 5: ↑3 and ↓2+1
Views431
Comments 0