{"id":9663,"date":"2020-02-24T16:56:59","date_gmt":"2020-02-24T15:56:59","guid":{"rendered":"https:\/\/blog.mi.hdm-stuttgart.de\/?p=9663"},"modified":"2023-06-18T18:20:04","modified_gmt":"2023-06-18T16:20:04","slug":"how-to-increase-robustness-of-a-large-scale-system-by-testing","status":"publish","type":"post","link":"https:\/\/blog.mi.hdm-stuttgart.de\/index.php\/2020\/02\/24\/how-to-increase-robustness-of-a-large-scale-system-by-testing\/","title":{"rendered":"How to increase robustness of a large scale system by testing"},"content":{"rendered":"\n

When a distributed software system grows bigger and bigger, one will end up with a big amount of various components which all need to scale independently. In order to achieve these components working smooth together, it is necessary to figure out at which time a component needs to be scaled, to avoid having one component as a bottleneck.<\/p>\n\n\n\n

This blog post focuses on the possibility to test the behaviour of a large scale system under extreme load in order to discover vulnerabilities. Therefore I will provide an overview of scalability testing and a more specific variant, which has already proven itself as a successful testing variant for such systems, called Chaos Engineering.
<\/p>\n\n\n\n\n\n\n\n

Scalability testing<\/h2>\n\n\n\n

Scalability testing is a testing method that is assigned to non-functional testing, which means it checks non-functional aspects of a system, like performance, reliability or usability.
The main aspect behind testing scalability is to measure an application\u2019s performance based on its ability to perform up – and downscaling during different amount of load. [1]<\/p>\n\n\n\n

Scalability Testing vs Load Testing
<\/h3>\n\n\n\n

The term \u201cLoad Testing\u201d might be better known for some people. Performing load tests on an application means, that the entire system is tested under maximum load, to figure out the point at that the application is not usable anymore. [2]
This point indicates how much load the application can just about handle before the response times become too long or the system even crashes.
<\/p>\n\n\n\n

So what\u2019s the difference to Scalability Testing?<\/p>\n\n\n\n

When testing for scale, unlike load tests, now the minimum and maximum load for all levels of a system is measured, which includes software, hardware and database levels.
When there is more traffic, the system should scale up the specific layer in order to prevent large response times. The goal of scalability testing is to ensure that the application performs these scaling functions correctly. Measuring performance always means defining metrics or parameters to be able to produce results which can be compared later on. [3]
These parameters can be different, depending on the type of the application. For example in a web frontend application one would most likely measure the number of users or the network usage, while when testing a web server, the amount of processed requests is more important.
<\/p>\n\n\n\n

As you might have seen, testing in general is closely linked to another topic when dealing with large scale systems, which is monitoring<\/strong>.
You can get a good introduction into this topic by reading this blog post: https:\/\/blog.mi.hdm-stuttgart.de\/index.php\/2019\/02\/26\/end-to-end-monitoring-of-modern-cloud-applications\/<\/a>.<\/p>\n\n\n\n

For the purpose of testing it is important to know, that results can only be compared, if a correct monitoring environment is set up, on which the specific parameters can be can be viewed independently.
I have talked a lot about different parameters for different types of applications, so let\u2019s take a look at some examples: [4], [5]
<\/p>\n\n\n\n