Adding One More MySQL Slave to Cloud Based System (Amazon AWS)

MySQL Replication tends to be complex.

Creating a new slave to support your system expansion is not easier: coping large data files over the LAN, recovering replication, etc.

Fortunately, virtualization and SAN help us do it easier and faster.

Lucky us, Cloud Computing make it even easier.

Adding a New Slave is Easier than Ever

1. Select an existing slave that can be reboot w/o affecting the service.
1. Take the slave out of the production environment.
2. Stop the MySQL slave and perform a read lock: SLAVE STOP;FLUSH TABLES WITH READ LOCK;
3. Create an AMI based on this instance using AWS console or API.
4. Recover the instance upon AMI creation completion and get the slave back to production: UNLOCK TABLES;SLAVE START;SHOW SLAVE STATUS\G
2. Create a new slave based on the AMI
1. Launch a new slave using the AWS console or API.
2. Change the server's /etc/my.cnf file to fit a new slave instance:
1. Change the server-id=N value to a new numeric value.
2. Set relay-log='server-relay-bin' to the original slave server relay log name. (if you want to make it even easier, configure in the first slave's my.cnf relay-log=mysqld-relay-bin, and you'll be able to avoid this step).
3. Restart the MySQL instance: sudo /etc/init.d/mysql restart
4. Recover the MySQL: UNLOCK TABLES;SLAVE START;SHOW SLAVE STATUS\G
5. Add this new slave to the production environment.

Bottom Line

Expanding your business today is easier w/o the need for file copy or any other tedious action.

Keep Performing,

Moshe Kaplan 

Blocked Sessions In the Cloud

When you test you new software (or feature) in a new environment (e.g installing your system in cloud environment) you may face errors when you'll try to connect your newly deployed service. What happened?
There are two options:

1. You did not install correctly your system. You can verify it by connecting the service from within the server (using Terminal Services in Windows case). If it fails you should start exploring the event log and your application log.
2. Someone is blocking your sessions (probably it is a firewall). You can verify it by running netstat -na from you client command line, and check for SYN_SENT lines in the output. If it's attached to the server IP and port that your service uses, you definitely have firewall in you way. There are several options who is the blocker and how to solve it:
1. Your computer personal firewall. Probability: Low; Verification: try connecting from another computer.
2. Your company firewall. Probability: Medium-Low; Verification: try connecting from another computer which is outside your company network (your favorite neighborhood cafe can be great).
3. Your cloud provider firewall. Probability: High; Verification: if it's Amazon AWS, login to the AWS Management Console, verify the Security Group that your instance is linked to, and verify the Security Group rules.
4. Your server firewall: Probability: High (if you are using Windows); Verification: check the server firewall configuration that it allows incoming connections in the relevant ports.

Keep Performing
Moshe Kaplan