BASIC CONCEPTS
External Link

/etc/haproxy/haproxy.cfg

We define acl and backends. Then acl define what backend we use.

use_backend blog-backend if acl_url_blog

OPERATION:
Restart:

/etc/rc.d/init.d/haproxy restart

MONITORING
From the cli, this command gives us a csv, dump in Calc. Check max connections and current connections.

echo "show info;show stat" | nc -U /var/lib/haproxy/stats  # Also | grep DOWN to see what is not working atm
ssh -o  UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -n ha1.dc "echo "show stat" | nc -U /var/lib/haproxy/stats" > file1 ; csvtool readable file1 | view -
ssh -o  UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -n ha1.dc "echo "show info" | nc -U /var/lib/haproxy/stats" 

External Link There's GUI available as well as interacetive commands accessible with:

nc -U /var/run/haproxy.sock

Also non-interactive commands for automated based operations.

From the stats page:

• Session rate : number of new sessions per second. A session is a connection that was accepted by the layer 4 rules.
• Connection: Note that a session can have one or more connections. “With the introduction of SSL, proxy protocol and layer4 ACLs, it was needed to cut the end-to-end sessions in smaller parts, hence the introduction of “connections””

PROTECT AGAINST DDOS:

• haproxy-first-row-of-defense-against-ddos
• Block by source IP based on different criteria. Stick tables. Some examples here:

SPECIAL FEATURES
Enable slow start: https://cbonte.github.io/haproxy-dconv/1.7/configuration.html#5.2-slowstart

• Conceptual difference between a proxy and a 'reverse proxy': Proxy is a client proxy; reverse proxy is ~load balancer.
  • Proxy hides clients identity to the server. This is for client to server connections.
  • Proxy hides servers identity to the client. This is for client to server connections as well.

TODO:

• Block by source IP based on different criteria. Stick tables:
• Some examples here: http://blog.exceliance.fr/2012/02/27/use-a-load-balancer-as-a-first-row-of-defense-against-ddos/