Load balancing MySql with HAProxy on EC2 Servers - mysql

Question

For our application, setup on the Amazon EC2 instances, we are using MySQL databases, installed on 2 EC2 instances, in master-master replication mode. To load balance these DB Servers I am using an HAProxy deployed on another EC2 instance with configuration
listen mysql <public dns of haproxy>:<port>
mode tcp
balance roundrobin
server mysql-db-s1 <elastic ip of db server1>:<port> maxconn 2000
server mysql-db-s2 <elastic ip of db server2>:<port> maxconn 2000
All three instances are assigned elastic ip's and I use the public dns of haproxy to connect from my application. But at times I get the error
`com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: C
ommunications link failure The last packet successfully received from the server was 58,085 milliseconds ago.
The last packet sent successfully to the server was 0 milliseconds ago.`
Has this anything to do with the configuration I have given here? Is it better to use the elastic ip's instead of Public DNS ?

Answer 1

This was not essentially an HAProxy issue, as I got the same error after I connected directly to one of the databases. Tuned the database a little and fixed some code in my application, and now I am not getting this atleast for the past 12 hours. Thanks for the suggestions. I would be moving one of the DB to another availability zone.

Answer 2

Web servers and databases load balancing concepts because of the request for the websites in large number. So we need to know how to handle this large number of requests through load balancing.
In this article, we are going to discuss this MySQL load balancing concepts using HAProxy. Let's consider the MySQL node 1 ip address is 192.168.1.172 and MySQL node 2 ip address is 192.168.2.82.
Step 1: Create MySQL Users And Install MySQL Client The first thing we need to make sure MySQL servers have to be configured to perform Master-Master replication as load balancing involves both reading and writing to all the backends. The initial thing we need to create a MySQL users for HAPorxy. The first user will be used by HAProxy to check the status of a server
$ mysql -u root -p -e "INSERT INTO mysql.user (Host,User) values ('192.168.1.172','haproxy_check'); FLUSH PRIVILEGES;"
$ mysql -u root -p -e "GRANT ALL PRIVILEGES ON *.* TO 'haproxy_root'#'192.168.1.172' IDENTIFIED BY 'password' WITH GRANT OPTION; FLUSH PRIVILEGES"
$ sudo apt-get install mysql-client
$ sudo apt-get install haproxy
$ sed -i "s/ENABLED=0/ENABLED=1/" /etc/default/haproxy
$ sudo nano /etc/haproxy/haproxy.cfg
and add this content to that new configuration file
global
log 127.0.0.1 local0 notice
user haproxy
group haproxy
defaults
log global
retries 2
timeout connect 3000
timeout server 5000
timeout client 5000
listen mysql-cluster
bind 127.0.0.1:3306
mode tcp
option mysql-check user haproxy_check
balance roundrobin
server mysql-1 192.168.1.172:3306 check
server mysql-2 192.168.2.82:3306 check
Step 3: Test Load Balancing
$ mysql -u haproxy_root -p -e "show variables like 'server_id'"