Do I need to duplicate code on every EC2 instance running behind an ELB?

Question

Hi this is a very noob question, but I am trying to deply my Node JS API server on AWS. Everything is working fine with one m1.large instance that my Front End running on S3 connects to. Now I want to Scale and put my EC2 instance and possibly many more behing and ELB and an Auto Scaling Group. Do I need to duplicate my server code on every EC2 instance? If so , I assume I'll have to create a seperate DB server which all of the EC2 instances will connect to. Am I right,anyone experienced in Amazon AWS can answer this, I tried googling but most of the links point to detailed tutorials which however don't answer my question. Any help would be much appreciated. Thanks

Answer 1

yep. that's basically correct. the code needs to be on all instances fronted by the load balancer. for the database you may want to look into RDS.

Answer 2

Of course NOT.. But sure you can do.. That's why there are EFS volumes, which are shared volumes to more than one EC2 instance, but you have to choose a region that support them since they are available on certain regions. As a candidate AWS certified architect I would recommend you more than two options.

• You can follow your first approach and create an EC2 instance put your code inside and then create an AMI and use this AMI to launch your upcoming EC2s through autoscaling group. In my opinion bad decision since on any code change you have to go on each one and put the new code and then create a new AMI and a new Auto scaling configuration..Lot's of stuff to do, but it will work.
• Second approach, following the first approach but do not create an AMI, instead upload your code on a private (I suppose) Repo like github, bitbucket, install SSM and the appropriate roles for managing EC2 and on every code changes push them to repo and pull them on your EC2, using SSM. Of course you may write a webhook to bitbucket to call an api and run the git pull command on each EC2. Probably the last sentence could be a third approach but needs more coding!!!
• Last but not least!! Use an EFS volume put your code there, mount this volume on your EC2, add a auto mount command on every boot, alter your apache httpd main document to point on this EFS/folder and create an AMI with this configuration. Voila! every new EC2 will use the same code which located on this shared/network volume. Whenever you need to change something you have to log in on a third instance outside of your autoscaling group for a certain amount of time upload your changes and then turn it off and all of your EC2 will take immediately the new code. Of course you may pull the changes from a repo following the third approach.

Maybe there are more approaches, I'm using the third one with private repos of course and until now I haven't faced any problem (Fingers crossed)!

Answer 3

One other option is to use Elastic Beanstalk to Deploy NodeJs applications. Here is the guide specific to NodeJs. This will take care of most of the stuff which you would need to do otherwise if you only use EC2 For example: ELB, Autoscaling Cloudwatch etc.

For Database, you may want to use the Master Slave with Read Replicas. Another option is to evaluate NoSql Databases like DynamoDB if it fits your use case. The scalability of DynamoDB tables is managed by AWS so you dont need to worry about it.