Developers Club geek daily blog

Yandex. The browser for transparency of mobile subscriptions

1 year, 1 month ago
How most quicker to subscribe for paid service from the phone? It is enough to click once the button on the accidental website, without having read a condition in the bottom of the page. Today I will tell you about a problem of paid mobile subscriptions and about that technology in Yandex. The browser which protects people from unconscious expenditure.



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Evolution of data structures in Yandex. To a metrics

1 year, 1 month ago
Yandex. A metrics today it not only system of web analytics, but also AppMetrica — system of analytics for applications. On an input in the Metrics we have a data stream — the events which are taking place on the websites or in applications. Our task — to process these data and to present them in the form, suitable for the analysis.



But data handling is not a problem. The problem is in that as well as in what type to save results of processing that it was possible to work with them conveniently. In development process we had to change approach to the organization of data storage several times completely. We began with the tables MyISAM, used LSM trees and eventually came to column-oriented to the database. In this article I want to tell what us forced to do it.

Yandex. The metrics works since 2008 — more than seven years. Every time change of approach to data storage was caused by the fact that this or that solution worked too badly — with an insufficient stock on performance, it is insufficiently reliable also with a large number of problems at operation, used too many computing resources, or just did not allow us to implement that we want.

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Yandex Meteum announces own technology of forecasting of weather. To within the house

1 year, 1 month ago
Today we announce new technology Meteum — now with its help to Yandex. Weather will build own weather forecast, but not to rely only on data of partners as it was earlier.

And the forecast will be separately calculated for each point from which you request it and to be recalculated every time when you look at it to be the most actual.



In this post I want to tell a little about how presently the world of weather models is arranged, than our approach differs from normal why we decided to build own forecast and why we believe what at us will turn out better, than at all others.

We constructed own forecast with use of traditional model of the atmosphere and the most detailed grid, but also tried to collect all possible sources of data on atmospheric conditions, statistics on how weather in practice behaves, and applied machine learning to these data to reduce error probability.

Now in the world there are several main models on which forecast the weather. For example, model open source WRF, the GFS model which initially were the American development. Now the NOAA agency is engaged in its development.

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As people with sight violation use the Internet and modern technologies. Research of Yandex

1 year, 2 months ago
Today, on November 13, International day of blind people. It is dated for birthday of the teacher Valentin Gayui which in 1784 opened on personal means the first-ever school for blind children. It is not a holiday, but the memorial urged to remind society of existence by a number of people with sight violations. In the modern world the most part of life of people moved to on-line that opened before people with restrictions of health new opportunities, but also generated new challenges.

Диаграмма по данным таблицы 5

To work with computer devices and to use the Internet, people with violations of sight apply auxiliary technologies which actually are their white cane in digital space. However work of such users with the computer equipment has the specifics in comparison with ordinary able to see people. In particular, among them a few other devices, operating systems and browsers, than in the market in general are most popular. It means that thinking of availability of the services to blind persons, it is necessary to consider these features.

The problem is that to take information on technical preferences blind and visually impaired often just there is no place. There are corresponding researches of English-speaking audience, but on the RuNet such information is absent. Therefore we decided to conduct research of technical preferences of users of the RuNet with violations of sight which most important results we want to share with all.

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Theory of a sound. What it is necessary to know about a sound that to work with it. Experience of Yandex. Music

1 year, 2 months ago
The sound, as well as color, people perceive differently. For example, the fact that it seems too loud or low-quality to one can be normal for others.

For work on Yandex. Music it is always important to us to remember different subtleties which are concealed in itself by a sound. What is volume as it changes and what depends on? How sound filters work? What noise happen? How the sound changes? As people perceive it.



We learned about all this very much, working on our project, and today I will try to describe on fingers some basic concepts which are required to be known if you deal with digital sound processing. In this article there is no serious mathematics like fast Fourier transforms and other — it is simple to find these formulas in a network. I will describe an essence and sense of things which it is necessary to face.

As reason for this post you can consider that we added to applications of Yandex. Music an opportunity to listen to tracks in high quality (320kbps). And you can not consider. So.

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As we looked for a bug in search Balansere, and found in Chromium

1 year, 2 months ago
Some time ago colleagues began to receive from users complaints that sometimes when using Search and Yandex. The browser they see the error SSL connection error. Investigation of why it occurred, in my opinion, turned out interesting therefore I want to share it with you. In the course of analysis of a situation we several times changed the "suspected" software, studied a set of dump, remembered the device of the machine of statuses of TLS and as a result even understood Hromium's code. I hope, it will be interesting to you to read it not less, than to us was to investigate. So.



After a while we had records of logs of errors and pcap-files with similar contents:



All look like the server answered incorrectly and the client stopped handshake. Having analyzed "correct" (accepted by the client) and "incorrect" answers of the server, we understood that they are identical.

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Course on machine learning on Coursera from Yandex and HSE

1 year, 3 months ago
Once we published on Habré course on machine learning from Konstantin Vorontsov from School of data analysis. To us then suggested to make from this full-fledged course with homeworks and to place it on Kurser.

And today we want to tell that at last we can execute all these wishes. In January on Kurser will complete the course organized jointly by Yandex (School of data analysis) and HSE. It is possible to register in it already now: www .coursera.org/learn/introduction-machine-learning.


The co-founder of Coursera Dafna Koller at office of Yandex

The course will last seven weeks. It means that in comparison with the Shadovsky two-semestrial course it will be considerably simplified. However these seven weeks we have tried to contain only that precisely is useful in practice, and some basic things which should be known. As a result the ideal Russian-speaking course for the first acquaintance to machine learning has turned out.

Besides, we believe that after passing of course with the person has to remain not only the theory in the head, but also skill "in fingers". Therefore all practical tasks are constructed round use of scikit-learn (Python) library. It turns out that after passing of our course of people will be able to solve itself data analysis problems, and it will be simpler to it to develop further.

Under cat it is possible to read in more detail about all authors of course and to learn its approximate contents.

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Testing in Yandex. How to make fault-tolerant grid of one thousand browsers

1 year, 3 months ago
Any specialist involved in testing of web applications knows that the majority of routine actions on services is able to do Selenium framework. In Yandex in day millions of autotests using Selenium for work with browsers therefore we need thousands of the different browsers available at the same time and 24/7 are executed. And here the most interesting begins.



Selenium with large number of browsers has many problems with scaling and fault tolerance. After several attempts at us the elegant and simple solution in service has turned out, and we want to share it with you. Fault-tolerant Selenium-grid from any number of browsers allows to organize our gridrouter project. The code is laid out in open-source and is available on Github. Under cat I will tell, to what shortcomings of Selenium we paid attention as have come to our decision, and I will explain how to configure it.

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19 principles of development on BEM or that each developer of libraries has to know

1 year, 3 months ago
BEM gains popularity and becomes more actual — for example, recently Google has let out the new library of blocks under the name Material Design Lite implemented on BEM-methodology. The BEM team too did not do nothing — we have issued the new version of bem-components library on the basis of which the sites and projects not only Yandex, but also other developers are constructed.

These events have suggested to us idea once again to remember and tell you as the principles of development of libraries in BEM-methodology were created. We hope that it will be interesting to much and it is useful. So, have gone.

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Long time we created libraries of blocks, using generally intuition and as then it seemed to us, sense of beauty. On this thorny road many cones have been typed and many lessons are learned. As a result we gave rise the new document containing the principles of development of libraries which we use now as cheklist when developing each new block. In our opinion, these simple and obvious principles give us the chance to receive the thought over, convenient, scalable and easy code in support.

If you want to learn on examples as we have come to our principles of development, welcome under kat.

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As we did Conversation: from prototype on the hakatena to Yandex application

1 year, 4 months ago
Recently Yandex has released the experimental Conversation application which helps to communicate to deafs and people hard of hearing. Now there passes the international week of deafs, and we have decided that it is very good occasion to tell about our application, about that, why we did it and as it has turned out so that Yandex has supported our idea. And also how process of work on prototype for hakaton differs from release of full-fledged product.

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Last fall in MFTI where I studied, on basic chair of Yandex to us gave the course "Creation of New Internet Products". He reflected as certain startapersky practical work within which it was necessary to think up something that successfully would solve the existing problem by means of technologies of Yandex. We with several of my classmates have thought that communication of the people who are switched off from usual communication by voice with other hearing world – task which approaches under such criteria. According to World Health Organization, 10% of inhabitants of Earth have problems with hearing, 1,5-2% from them suffer from heavy violations. In their Russia — something Would be healthy to make 2,2 million that could help these people with everyday life.

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