Users sometimes ask how new diagnostics appear in the PVS-Studio static analyzer. We answer that we draw inspiration from a variety of sources: books, coding standards, our own mistakes, our users' emails, and others. Recently we came up with an interesting idea of a new diagnostic. Today we decided to tell the story of how it happened.
The step has been made. Not sure where to, but for sure from the point of no return. Keep calm and keep walking. It is about time to look around and understand the smelly and slippery route before you. And what are those noisy creatures swarming around our fishy “innovative” design we called Mandelbrot blueprint? You don't get a buzzing noise like that, just buzzing and buzzing, without its meaning something.
In microservice world the problem of high load is exteremely big especially when we have a REST API which is accessed quite extensively. Why do we need throttling? The main answer is to decrease the load of the service at the moment.
Different frameworks have different solutions, mostly some additional libraries. Also there is a Guava RateLimiter and Bucket4J . What is interesting Spring MVC being one of the most popular solutions for building REST APIs (thank you Spring Boot) doesn't have any built in rate limiter. As for external solutions there not that many ways around.
Today, I would like to present a tiny experimental library specific for Spring MVC. It is called SpringRateLimitter. The library is very tiny ,works in runtime. The idea is to annotate entire rest controller or specific method , than count the number of incoming requests for the annotated URI and based on the values check if we exceed the allowed number of calls. In case of exceeding an HTTP error code 429 is thrown and after the throttling period is over , the endpoint is available again.
So How does it look like. As first step Maven dependency must be added
Here I am going to cover my own approach to compilation of mathematical functions into Linq.Expression. What we are going to have implemented at the end:
1. Arithmetical operations, trigonometry, and other numerical functions
2. Boolean algebra (logic), less/greater and other operators
3. Arbitrary types as the function's input, output, and those intermediate
Hope it's going to be interesting!
Architect. This word sounds so mysterious. So mysterious that to understand it you are almost forced to add something. Like “System Architect” or “Program Architect”. Such an addition does not make it clearer, but for sure adds weight to the title. Now you know – that’s some serious guy! I prefer to make undoubtful and around 10 years ago added to my email signature “Enterprise Architect of Information Systems”. It’s a powerful perk. Like “Chosen One”. With architects it is always the matter of naming, you know. Maybe that is why the only way to become an architect is to be named as one by others. Like with vampires. One of them has to byte you! That is probably the easiest way to earn the title as there is no degree or school to grant you one. And if there’s a troubling title, somebody’s making a trouble, and the only reason for making a trouble that I know of is because you’re an Enterprise. Huge old and complex multinational corporation. Like a one-legged pirate. Strong and scary, but not a good runner. You own your ship, you had good days, you have some gold, you need new ways.
To get to new treasures and avoid losing the second leg to piranha regulators and local business sharks swarming waters near every enterprise ship – every pirate has a map. A map is a list of major features and requirements in desired order and priority.
The DHT system has existed for many years now, and torrents along with it, which we successfully use to get any information we want.
Together with this system, there are commands to interact with it. There are not many of them, but only two are needed to create a decentralized database: put and get.
Security. What does this word mean to you? Nowadays, companies spare no effort to ensure that their product is secured from hacking and all sorts of information leaks. PVS-Studio decided to help its users and expand the functionality in this area. Therefore, one of the main innovations of the upcoming release will be the introduction of analyzer new features which will ensure code safety and security. This article aims to present these features.
We work using Agile: Scrum, or Kanban, or any other extended project management way. Agile appeared in 2001 as a result of a long discussion between really smart guys. They just formed best practices of management into the shape of short documents - the Agile Manifesto. But what did they want to replace by the Agile way? Most of you may say that they wanted the Waterfall to go to the past. But what would you think if I tell you that the “classical” Waterfall had been a really rare thing even for those days?
Some of the features of your website require message queue integration. It is not a complex task for most developers. If you work with Azure infrastructure, you are able to choose Azure Service Bus as a queue engine. It sounds quite simple: just create Azure Resource, write some code and then be happy! But what would you say if the resources are limited? What will you do if there are several teammates in your team, and all of you have to debug queues at the same time? I try to give you a simple solution.
Most solutions to algorithmic problems can be grouped into a rather small number of patterns. When we start to solve some problem, we need to think about how we would classify them. For example, can we apply fast and slow аlgorithmic pattern or do we need to use cyclic sortpattern? Some of the problems have several solutions based on different patterns. In this series, we discuss the most popular algorithmic patterns that cover more than 90% of the usual problems.
It is different from High-School Algorithms 101 Course, as it is not intended to cover things like Karatsuba algorithm (fast multiplication algorithm) or prove different methods of sorting. Instead, Algorithmic Patterns focused on practical skills needed for the solution of common problems. For example, when we set up a Prometheus alert for high request latency we are dealing with Sliding Window Pattern. Or let say, we organize a team event and need to find an available time slot for every participant. At the first glance, it is not obvious that in this case, we are actually solving an algorithmic problem. Actually, during our day we usually solve a bunch of algorithmic problems without realizing that we dealing with algorithms.
The knowledge about Algorithmic Patterns helps one to classify a problem and then apply the appropriate method.
But probably most importantly learning algorithmic patterns boost general programming skills. It is especially helpful when you are debugging some production code, as it trains you to understand the execution flow.
Patterns covered so far:
Stay tuned :)
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In this article, we discuss the postorder traversal of a binary tree. What does postorder traversal mean? It means that at first, we process the left subtree of the node, then the right subtree of the node, and only after that we process the node itself.
Why would we need to do it in this order? This approach solves an entire class of algorithmic problems related to the binary trees. For example, to find the longest path between two nodes we need to traverse the tree in a postorder manner. In general, postorder traversal is needed when we cannot process the node without processing its children first. In this manner, for example, we can calculate the height of the tree. To know the height of a node, we need to calculate the height of its children and increment it by one.
Let's start with a recursive approach. We need to process the left child, then the right child and finally we can process the node itself. For simplicity, let's just save the values into slice out.