28/Dec 2019
2 min. read
1. OpenVPN & MFA There are few tutorials about setting up OpenVPN and multi-factor authentication. For MFA, Google Authenticator is used here.
To setup OpenVPN server, I use OpenVPN road warrior installer. For MFA config, the script from egonbraun is forked and modified to work with road warrior setup: https://gist.github.com/carsonip/b02eecf9f7d036555a53fea6f516ced8
Also, the default OVPN server will renegotiate every 1 hour, but this will fail the MFA authentication, effectively disconnecting the OVPN connection periodically.20/Feb 2019
2 min. read
Update 21 Mar 2019 There’s a new post Fixing ProxySQL Idle Threads Epoll Hang Heisenbug about fixing a bug of ProxySQL when --idle-threads is enabled.
Problem ProxySQL does not scale with high numbers of connections by default. When there are tens of thousands of client connection to ProxySQL, the CPU usage of ProxySQL may go up to 300%+ because by default it uses 4 threads. Even with 3000 mostly idle connections, it hits ~70% CPU usage.4/Nov 2018
1 min. read
parallel-ssh has a -I option to feed in a shell script file such that quotes escaping is not needed. On Ubuntu 14.04, the HAProxy may have 2 pids after sudo service haproxy restart. I suspect one of them is a zombie since the new open file limit does not apply. The safer way is to killall haproxy then sudo service haproxy start. HAProxy has a maxconn globally and maxconn for each frontend.