I upgraded to haproxy 2.6.6-1, it looks good
# echo 'show proc' | socat - /run/haproxy-master.sock
#<PID> <type> <reloads> <uptime> <version>
1590727 master 1 [failed: 0] 0d00h08m11s 2.6.6-1~bpo11+1
# workers
1590983 worker 0 0d00h06m29s 2.6.6-1~bpo11+1
# programs
# echo '@!1590983 show stat' | socat - /run/haproxy-master.sock | grep ^10_0_55_192-22,10_0_55_192-22 | cut -d "," -f5
2
# echo 'reload' | socat - /run/haproxy-master.sock
# echo 'show proc' | socat - /run/haproxy-master.sock
#<PID> <type> <reloads> <uptime> <version>
1590727 master 2 [failed: 0] 0d00h08m28s 2.6.6-1~bpo11+1
# workers
1592078 worker 0 0d00h00m03s 2.6.6-1~bpo11+1
# old workers
1590983 worker 1 0d00h06m46s 2.6.6-1~bpo11+1
# programs
# echo '@!1590983 show stat' | socat - /run/haproxy-master.sock | grep ^10_0_55_192-22,10_0_55_192-22 | cut -d "," -f5
2
Thanks @lukastribus
Hope this thread can help who want to get accurate counters after haproxy reload.