Revolving around the core of technology
It is very common to see following message in the log file that looks like:
2019-05-26 15:16:59,163 ERROR loader.WebappClassLoader - The web application [/] appears to have started a thread named [Thread-21] but has failed to stop it. This is very likely to create a memory leak. 2019-05-26 15:16:59,164 ERROR loader.WebappClassLoader - The web application [/] appears to have started a thread named [Tomcat-startStop-2] but has failed to stop it. This is very likely to create a memory leak.
This is a false alarm and you should ignore it.
The HTTP server continuously receives messages from client. The server does not respond to any HTTP requests received after it receives a signal to shutdown and logs this error message. Additionally, the process terminates with the next few milliseconds and therefore, even if this were a real memory leak, the operating system would have reclaimed all the memory.
Therefore, please ignore this message. It has no affect on your system or the running process.