BUG: possible TCP connection/file descriptor leak by calling HTTP probes

[dinoallo]

Version

• image-cri-shim v0.0.8 with endpoints-operator v0.1.1 as the library

Description

Currently, doing an HTTP probe requiring allocating a new http.Client and http.Transport, and the underlying connections managed by http.Transport might be ESTABLISHED indefinitely if no parties (client or server) directly close them. As a result, if the probes continuously happen, we can see TCP connections opened by one process
(e.g. image-cri-shim) drastically increase.

How to reproduce the bug?

1. Deploy image-cri-shim
2. Deploy several containers with invalid image names and wait for a couple of hours
3. Check the host node of the containers
4. Use ss or netstat to inspect connection

[dinoallo]

Directly close idle connections like this commit: 0e6deb6 can fix this issue.