Part of my daily routine is to consume, design and deliver services built for HTTP clients. This might manifest in something special like WebSocket, Protobuf but most often a plain JSON REST API. In any case, the performance is key, and an Undertow REST API with JAX-RS can deliver a stable performance under consistent load. In this article, I will cover some basics for setting up and deploying a REST API with Undertow, in Docker.

The flyweight pattern is a design pattern I am not seeing that often in code bases but can be a good design pattern to reduce memory. The core idea is to initialize objects an share them as often as possible for reuse. Mostly the flyweight pattern can be seen in desktop UI implementation (GUI). In Java Swing, for instance, the JTable rendering uses this pattern, to reduce the computation needed for painting.

There are a number of design patterns I am using on daily bases, and one of them is the Singleton pattern. In Golang penalties in performance are not so harsh as in other languages, if the application is not designed and written to perform with minimal CPU and memory footprint. I’m trying to keep my implementations as performing as possible, but sometimes explicit benchmarks can revile the details. The singleton pattern is widely used in Object Oriented languages, and it is well worth to use it in golang.

This post is a walkthrough on my approach to develop and deploy Golang web service in Docker container. There are many reasons for integrating Docker into the daily routine as a developer, one being the simplification of setting up a separated runtime environment. Using containers in production has, even more, advantages from simplified release to better performance. Kubernetes and Docker Swarm is gaining more and more space, which I think is partly because of the simplified management on IBM Cloud and Google Cloud Platform.

In most cases web applications are well covered with unit tests, to covert a functional requirements and acceptance tests. Unit tests combined with Continuous Integration can improve the deviling rate of a team/company. At the same time it can remove the need of manual testing, which is error prone. Tools for CI are widely available in self hosted solutions like Jenkins or cloud based like CircleCi or Travis, if the project source does not need to be secured as much. In any case these tools offer a wide variety of build and test scheduling to automated deployment and configuration. I think for most Software Engineers these are familiar concepts and possible part of daily work routines.

One important part of most web based application is not covered with these tools, the benchmark or load test of new features and the application in general. It is obvious that CI tools are not meant for this task, but to have good understanding where the application bottlenecks and limitations are is crucial. In most cases this is an SRE or DevOps task clearly, but I think it is good for all Engineers to understand they changes and the consequences of them (if any). There is also another important factor which is the price of keeping one system up. Many times I heard, read that “…the application is not busy, so it does not matter…”. I believe that it does, even in not busy apps, because the development time/cost is a small percentage of the system all over lifetime cost. There is a really good breakdown of this idea in the Site Reliability Engineering – How Google Runs Production Systems.

For a developer there are many tools to benchmark new features, in a standalone setup in most modern stacks. The tricky part I think is to being able to measure and understand the capabilities of an application as a whole. For this post I will stick to the HTTP load testing tools I found useful and use on regular bases.

Heapsort algorithm details: Worst-case Time Complexity: O(n log(n)) Space Complexity: O(1) The algorithm The heapsort algorithm is an in-place, comparison based sorting algorithm. In the core of the algorithm (as the name suggest), the use of the heap data structure is improving the time complexity. In a nutshell, heap is a special type of tree, where the elements in the tree are in a certain order to each other. This allows to find the minimum or maximum of binary heap in O(1) and insertion/deletion in O(log(n)).

Merge sort algorithm details: Worst-case Time Complexity: O(n log(n)) Space Complexity: O() The algorithm Merge sort is comparison based algorithm, from the efficient sorting category. The algorithm is based on “Divide and conquer” (John Van Neumann), which means in this case, that the original collection is divided into smaller chunks. This idea can be implemented in a recursive fashion, so that the collection is divided into single elements and then re-constructed into a sorted collection.

Algorithm details: Worst-case Time Complexity: O(n^2) Space Complexity: O(1) The algorithm Bubble sort is a very simple sorting algorithm, with straight forward implementation. The algorithm is based on comparison of all elements to each other. The compared element positions are switched on the comparison result, and the element is shifted to the correct location. This implies, that each element has to be checked against each other. This results in n*n comparisons, even if the collection is in order.

I upgraded my Ubuntu 14.04 development system to 16.04 in August with the first point release. I have to say the upgrade process when really smooth. There where small issues with PHP and Python. The only painful issue I had was with Cassandra and CqlSh. The python version which is shipped with Ubuntu 16.04 is 2.7.12 and the version CqlSh is targeted is 2.7.11. When I tried to connect to CqlSh I got the following error:

I am always really excited reading peoples notes about new languages and technologies, and this was not different with Golang. I read about the language and an implementation roughly 4 years ago. After reading the article I looked around to find more details about the background of the language, and I was quiet surprised how much effort Google did put into this language. For this very reason the language was always on my “look into if I can” list.