FIN_WAIT_2 is TCP socket status which is waiting for final FIN from the peer. This is the status of whom completes its job and just waits job completion of the other side.

However, we usually observe many FIN_WAIT_2 sockets drain file descriptors and it consequently causes troubles due to lack of resources. What is the problem? Out of running of resources caused by too many FIN_WAIT_2 sockets or not coming FIN from the peer side?

It is not only about network stuff. In computer area, there are so many similar symptoms and reasons like too many FIN_WAIT_2 sockets we can not understand unless we understand under the hood of the knowledges. I would like to discuss these stories.