AUTHOR: Marin Bratanov
DATE POSTED: July 27, 2018
When generating the RadCaptcha audio, the server CPU usage goes high and does not come back down. The RadCaptcha audio does not work and the request for it does not return.
The CPU usage may go up to 50% on the first request and then to 100%, or to 100% directly.
The issue seems related to the Microsoft Speech Synthesizer that is used by default to generate the audio for the captcha code in-memory.
According to client reports, the following configuration is more likely to cause this:
There are two known solutions to this issue that can allow you to keep using the audio code:
You can also disable the audio code generation for your entire application. This can alleviate performance issues, but will effectively disable the audio code for your end users.