Step 1: Verify that HAProxy is running
On ubuntu, run the following command:
sudo service haproxy status
You should see output like below if it is running:
haproxy is running.
Step 2: Verify only one HAProxy process is running:
sudo ps ax | grep haproxy
This should result in output similar to:
590 ? Ss 0:00 /usr/sbin/haproxy -f /etc/haproxy/haproxy.cfg -p /var/run/haproxy.pid -D -sf 334 602 pts/0 S+ 0:00 grep --color=auto haproxy
This indicates only one HAProxy process is currently running. If you see more than one of the first line-you have launched multiple instances of HAProxy which can cause a lot of unexpected behavior.
To fix this condition, use
kill PID where PID represents the process identifier (which is the first column in the output of the above command).