AWS EC2 infrastructure

amazon ec2awsdockerMySQLtomcat

I was on a job interview today and one question I faced was:

I have my application running within a docker container on an EC2 instance (AWS Linux 64bit). The docker containers we use for the application (one application per container) connects to an RDS instance and we have the containers set up to auto-scale. What do you think of that set up?

I advised him that a better way may be to have on EC2 instance based on size of customers as he can use AWS's scalable feature to auto scale as needed. He mentioned he tried it this way but yielded slower networking for customers when auto-scaling.

My question is this: Is it more efficient from an architectural point of view, to run scalable EC2 instances running Docker that connect to an RDS? Or is the current setup better?

My reasoning behind using EC2 scalability is because he has auto scalable containers running and that if his EC2 may eventually run out of resources and may cause high CPU utilization from auto scaling too many containers.

He is using Tomcat as his web/application server if that bit of info is useful to this question.

Best Answer

slower networking for customers when auto-scaling

That statement is a bit confusing... but I will assume he meant that scaling events are slower when using EC2 Instances compared to scaling containers.

Launching an EC2 instance is faster than launching a docker container, therefore, it is faster to scale the containers within the OS itself than to scale EC2 instances. If you have to scale up EC2 instances, that means you have to launch a new instance and this takes time depending on the startup process of your system.

But if you are scaling docker containers instead, if you need to scale up, it means launching a new docker container on that same instance and this is way faster than launching a new EC2 instance. This allows applications to respond to quickly respond to scaling events.

I understand your concern about running out of resources on the instance if you scale the containers but... there's nothing stopping you from scaling your EC2 instances too. If you are interested you should check out AWS ECS and how it handles auto-scaling

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AWS EC2 Apache – Apache Server Not Reachable on New Instance

The web server seems to be listening to the actual port and running, accordingly to your netstat.

You have got to open the firewall rule in the AWS console.

Have a look at this: Authorizing Inbound Traffic for Your Linux Instances

Change SSH from the quoted test to HTTP.

To enable network access to your instance, you must allow inbound traffic to your instance. To open a port for inbound traffic, add a rule to a security group that you associated with your instance when you launched it.

To add a rule to a security group for inbound SSH traffic using the console

In the navigation pane of the Amazon EC2 console, choose Instances. Select your instance and look at the Description tab; Security groups lists the security groups that are associated with the instance. Choose view rules to display a list of the rules that are in effect for the instance.

In the navigation pane, choose Security Groups. Select one of the security groups associated with your instance.

In the details pane, on the Inbound tab, choose Edit. In the dialog, choose Add Rule, and then select SSH from the Type list.

In the Source field, specify the public IP address of your computer, in CIDR notation. For example, if your IP address is 203.0.113.25, specify 203.0.113.25/32 to list this single IP address in CIDR notation. If your company allocates addresses from a range, specify the entire range, such as 203.0.113.0/24.

Choose Save.

Ssh – iptables is preventing ssh to aws ec2 instance

You need to change this line

sudo iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

sudo iptables -A INPUT -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

Because your rule matches only established (syn-ack) and related connections, not new ones (syn)

So complete rule should look like:

sudo iptables -A INPUT -i lo -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 22 -d 34.195.109.193 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
sudo iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
sudo iptables -A INPUT -j DROP

sudo iptables -A OUTPUT -p tcp -m state --state ESTABLISHED,RELATED -j ACCEPT
sudo iptables -A OUTPUT -p tcp -j DROP

The last output rule, will allow established connections to your host.

Best Answer

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AWS EC2 Apache – Apache Server Not Reachable on New Instance

Ssh – iptables is preventing ssh to aws ec2 instance

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