Developers Club geek daily blog

Under Redis cowl: Hash table (part 1)

1 year, 9 months ago
If you know why after execution of 'hset mySey foo bar' we will spend not less than 296 bytes of random access memory why engineers of instagramm do not use line keys why it is always worth changing hash-max-ziplist-entries/hash-max-ziplist-val and why the data type which is the cornerstone of hash it and part of list, sorted set, set — do not read. For the others I will try to tell about it. The understanding of the device and work a hash of tables in Redis is crucial when writing systems where the economy of memory is important.

About what this article — what expenses incurs Redis on storages of the key that such ziplist and dict when and for what they are used how many borrow in memory. When hash is stored in ziplist when in dicth and that it gives us. What councils from fashionable articles about optimization of Redis you should not perceive seriously and why.

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How to send IDOC from SAP MII to SAP ERP

1 year, 9 months ago
Once, we faced a problem of implementation of transaction in SAP MII for the mechanism of creation of correct IDOC and sending it in SAP MDG (this instruction is applicable to all SAP ERP to systems).

The task was following: to implement regular sending necessary data on partners from not - SAP of systems in SAP MDG using SAP MII.

First, we began search of the mechanism of sending IDOC'OV from SAP MII to SAP MDG. After short searches RFC the IDOC_INBOUND_ASYNCHRONOUS function on the party of SAP MDG was found.

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Example of express performance review of SHD by means of the free Mitrend service

1 year, 9 months ago


Studying of a problem with performance and search of solutions are familiar to much not by hearsay. There is a large number of instruments of visualization and parsing of statistics of input-output. Now automation of the intellectual analysis based on Internet services gains steam.

In this post I want to share an example of the analysis of a problem with SHD performance based on one of such services (Mitrend) and I will offer ways of its solution. In my opinion, this example represents the interesting etude which as I think, can be useful to a wide range of IT readers.

So, the customer asked EMC to look at performance unrolled at it in SAN of hybrid storage system VNX5500. The VMware servers on which all turns "in general" are connected to SHD: from infrastructure tasks to file a sphere and the DB servers. Complaints to podvisaniye of the applications unrolled on connected to VNX servers were the cause of carrying out this express assessment.

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RDMA: look from within

1 year, 9 months ago
Growth of popularity of cluster systems as environments for high-performance calculations or HPC (High Performance Computing) brings a problem of ensuring effective interaction of the platforms forming a cluster to the forefront.

Картинка для привлечения внимания

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Inconvenient questions of architecture of RDMA

1 year, 9 months ago
We saved up an array of the materials connected with studying of architecture of Remote Direct Memory Access. During its forming a number of the moments became more clear, but mechanisms of some implementations still remained only in the form of assumptions. Unfortunately, the existing perspective of remote access directly to memory is reduced to a reduced model of failure from excess transfers. It is obvious that in a case with RDMA we deal with the entity generating new quality of cross-platform interaction which basis is mortgaged by such corner concepts as IfiniBand and NUMA.

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Method of fast performance measurement of the accidental server

1 year, 10 months ago
In the world of web development often there is a problem of selection of the server according to a web application, or on - analogies check of performance of the available server. Perhaps, we need to purchase the new server that it maintained estimated loading. Perhaps, the customer gives us for deploya the available server. Anyway, if after expansion and an application launch it shows poor performance, then will ask from command.

The main problem is that it is necessary to expedite a server performance assessment, without use special (read, difficult) tools and, certainly, to release. We have to be able to remove certain metrics from the server and, having increased them by the known indicators of the application, to receive application performance assessment on this server.

In life not each developer can carry out this task, and from remained not everyone wants to execute it.

In this article I want to tell about those acceptances and tools which we use for a server performance assessment.

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Under Redis cowl: Lines

1 year, 10 months ago
If you know why the simple line 'strings' in Redis will borrow in random access memory of 56 bytes — to you, I think, article will not be interesting. I will try to tell all rest what is lines in Redis and why it is important to the developer using this database to understand how they are arranged and work. This knowledge is especially important if you try to calculate the actual consumption of memory your application or are going to build highly loaded systems of statistics or accounting of data. Or, as often happens, you try to understand urgently why suddenly your copy redis began to consume unexpectedly a lot of memory.

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Whether can replace nanoCAD the western CAD solutions? Let's look for the answer …

1 year, 10 months ago

At implementation of our CAD platform we often face that very few people in our country can adequately evaluate functionality of such difficult and multi-faceted tool as a CAD, full to compare the competing solutions and to make an impartial assessment. Most often such work is charged to local "CAD guru" — the specialist - "fan" who can be (and, most likely, will be) it is prejudiced since loves the solution used by him at the moment. As a result we receive the list of the "tasty", but low-used functions which "you have to make differently any implementation!", and the import substitution subject smoothly fades. In reply we thought of the tool which will allow to make an independent assessment, implemented it and now are ready to share it with you.

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Non-paid, that is for nothing: a free ERP solution for modest e-commerce of business on the Ultima Businessware platform

1 year, 10 months ago
All hi.

We present habrakolleg the closed beta community - release of a new product: the ERP system free (almost) for business e-commerce small (almost):



  • to 12 simultaneous users — it is free
  • open configuration with zero license restrictions for modification and use
  • as a web component for the full-function integrated online store Bitriks is used (instead of Ultima eStore)
  • integration with 1C: Accounts department 3.0 through REST API
  • to services of developers all opportunities of the Ultima Businessware platform without restrictions

In addition to distribution kits, the unrolled full-function demoversion in the form of an image of the virtual computer — including is available to first attempts at writing of developers.

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Forecasting in the game industry. Part 3: Forecasts for the forecast industry

1 year, 10 months ago
By this moment you already had to have a quite good understanding of forecast modeling and its application to games. If is not present, you look: part 1 and part 2 of this article. We created good base, and in final part we will try to predict forecasting and we will look what future waits for promptly developing industry.


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