I installed Wordpress using EC2. I created a Load Balancer by creating image (AMI) then adding both Wordpress1 and Wordpress2 on Load Balancer. But I'm still getting database error and have to restart the instances. If I'd like to make 4 instances as Load balancer, are the steps the same? because I saw a "Number of Instances" option when I launched an AMI. Default value is 1. I'm not sure if I should enter 3 or 4 to create multiple instances in one click.
Also, if I update on Wordpress1 instance, will the updates show if the domain will load Wordpress2 instance?
If you want to launch multiple instances and a database etc, you should consider using AWS CloudFormation. CloudFormation is just a big json string that contains the configuration of your environment, including the servers, autoscaling, access, register with the loadbalancer, etc.
See http://aws.amazon.com/en/cloudformation/ for more details.
There is already an example template for wordpress including a database and autoscaling groups (example wordpress template)
However like datasage mentioned you will need to make adjustments to wordpress to make it working in a multiserver environment.
The "problem" with multiserver environments is that if you upload a file or in your case upgrade wordpress, it will only happen on one server, which could be terminated at any point. Furthermore the upgrade could contain changes in the database structure and then its getting complicated.
If you are building something in the cloud you should always keep in mind that every service you build, in you case the frontend webservers and the database should be allowed to fail without interrupting your service.
Another point is, that you should avoid doing stuff by hand, automation is the key. An environment where you need to link your server by hand to a loadbalancer is not very useful in the cloud where servers are continuously terminated, rebooted and exchanged.
For you webservers you can use "autoscaling groups" to get this behavior. If you are using autoscaling groups and a server is terminated or considered unhealthy, a new one will be started automatically and registered with the loadbalancer as soon as it is considered as healthy.
For your database amazon offers for rds multi AZ environments which provide a automatic failover.
Applying upgrades in the cloud can be a tricky and there are different ways to do this. for example using a shared NFS mount with the code base, git deployments or the way you already started: creating a new AMI for every upgrade and then replacing the servers. There are a lot options and they all have their benefits and drawbacks.
As far as i understand you use-case the cloud is maybe not the right choice at the moment.
Normally hosting a small business in the cloud is much more expensive than using a single server. You will only save money if you need like 20 servers in the evening and only 2 or 3 for the rest of the day. Of course there are a lot more points to consider but that would be to much.
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