CentOS release 6.9 (Final)
First used the Version 1.8.3 epel package.
Then tried compiling from Version 1.10.0 source code.

After some time, all result in "Waiting servers (0) is less than MinSpareServers (5). Creating new child. "
Then the client has no internet connection any more, and wait a long time to timeout.

But while check processes, there are enough processes (maybe 100) shows:
/usr/sbin/tinyproxy -c /etc/tinyproxy/tinyproxy.conf

After a service restart everything back to normal. Now I put service tinyproxy restart in crontab to run every hour to deal with this problem.