This article was written in 2021. Versions, tools and recommendations may have changed since then. Newer posts are collected under .NET.
While analyzing nearly 120 million requests, we noticed that one thing was dragging down our performance: parsing user agents for detecting bots and search engines.
For this task, we used the UA Parser library, which is quite widely used. Unfortunately, it is quite outdated, generates a lot of allocations and lowers our performance in its implementation.
1| Method | Mean | Error | StdDev | Gen 0 | Gen 1 | Gen 2 | Allocated |
2|-------------------- |-------------|-----------|-----------|---------|--------|-------|-----------|
3| 'UA Parser' | 3,238.59 us | 27.435 us | 25.663 us | 7.8125 | - | - | 168225 B |Since the alternatives are not really better, we decided to build our own parser: mycsharp/HttpUserAgentParser
During implementation, we paid special attention to the fact that this component could be part of a hot path of the application and therefore invested a lot in optimized performance. And our implementation lives up to this expectation in comparison!
1| Method | Mean | Error | StdDev | Gen 0 | Gen 1 | Gen 2 | Allocated |
2|-------------------- |-------------|-----------|-----------|---------|--------|-------|-----------|
3| 'UA Parser' | 3,238.59 us | 27.435 us | 25.663 us | 7.8125 | - | - | 168225 B |
4| UserAgentService | 391.11 us | 5.126 us | 4.795 us | 35.1563 | 3.4180 | - | 589664 B |
5| HttpUserAgentParser | 67.07 us | 0.740 us | 0.693 us | - | - | - | 848 B |As can be seen, we generate minimal allocations, but as the only implementation no GenX load at all!
Besides the implementation itself, we also created a caching component that checks respective browser agent strings for equality and thus very widely used agents only need to be parsed once.
We also provide a Dependency Injection registration for ASP.NET Core directly.
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BEN ABT
Ben is Chief Engineering Officer and Principal Software Engineer at Medialesson.de, with a strong focus on .NET and Microsoft Azure. In his professional role, he designs and builds highly scalable platforms for hybrid and cloud-based scenarios. He also advises companies and C-levels on migrating to the sovereign cloud.
He runs myCSharp.de, the largest and most active German-speaking C# community forum, actively contributes to both his own and external open-source projects and regularly shares his knowledge through his blog, at community events, conferences and as a writer for technical magazines.
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