This section describes how to configure HAProxy to work in front of the cluster.
Here is the simple configuration file example for HAProxy
# this config needs haproxy-1.4.20
global
log 127.0.0.1 local0
log 127.0.0.1 local1 notice
maxconn 4096
uid 99
gid 99
daemon
#debug
#quiet
defaults
log global
mode http
option tcplog
option dontlognull
retries 3
redispatch
maxconn 2000
contimeout 5000
clitimeout 50000
srvtimeout 50000
listen mysql-cluster 0.0.0.0:3306
mode tcp
balance roundrobin
option mysql-check user root
server db01 10.4.29.100:3306 check
server db02 10.4.29.99:3306 check
server db03 10.4.29.98:3306 check
With this configuration HAProxy will load balance between three nodes. In this case it only checks if mysqld listens on port 3306, but it doesn’t take into an account state of the node. So it could be sending queries to the node that has mysqld running even if it’s in “JOINING” or “DISCONNECTED” state.
To check the current status of a node we need a more complex checks. This idea was taken from codership-team google groups.
To implement this setup you will need two scripts:
- clustercheck (place to /usr/local/bin) and a config for xinetd and
- mysqlchk (place to /etc/xinetd.d) on each node.
Both scripts are available in binaries and source distributions of Percona XtraDB Cluster.
You’ll need to change /etc/services file by adding the following line on each node:
mysqlchk 9200/tcp # mysqlchk
The configuration file for HAProxy in this case may look like this:
# this config needs haproxy-1.4.20
global
log 127.0.0.1 local0
log 127.0.0.1 local1 notice
maxconn 4096
uid 99
gid 99
#daemon
debug
#quiet
defaults
log global
mode http
option tcplog
option dontlognull
retries 3
redispatch
maxconn 2000
contimeout 5000
clitimeout 50000
srvtimeout 50000
listen mysql-cluster 0.0.0.0:3306
mode tcp
balance roundrobin
option httpchk
server db01 10.4.29.100:3306 check port 9200 inter 12000 rise 3 fall 3
server db02 10.4.29.99:3306 check port 9200 inter 12000 rise 3 fall 3
server db03 10.4.29.98:3306 check port 9200 inter 12000 rise 3 fall 3
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