EC2: Virtual Machines

EC2 User Data
EC2 Meta Data
EC2 Instance Launch Types
EC2 Pricing
AMIs
EC2 Instances Overview
By default, your EC2 machine comes with:
- A private IP for the internal AWS Network
- A public IP for the WWW
When you SSH into your EC2 machine:
- We can’t use a private IP, because we are not in the same network
- We can only use the public IP

If your machine is stopped and then restarted, the public IP will change

EC2 User Data

It is possible to bootstrap our instances using an EC2 User data script
Bootstrapping means launching commands when a machine starts
That script is only run once at the instance first start
Purpose: Ec2 data is used to automated boot tasks such as:
- Installing updates
- Installing software
- Downloading common files from the internet
The EC2 User Data Script runs with the root user

Information about your EC2 instance
It allows EC2 isntances to “learn” about themselves without having to use an IAM role for that purpose
Powerful but one of the least known features to developers
You can retrieve IAM roles from the metadata but not IAM policies
URL: {ec2-ip-address}/latest/meta-data

Pay for what you use
Has the highest cost but no upfront payment
No long term commitment
Recommended for short-term and un-interrupted workloads, where you can’t predict how the application will behave

Can get a discount of up to 90% compared to On-demand
You bid a price and get the instance as long as its under the price
Price varies based on offer and demand
Spot instances are reclaimed within a 2 minute notification warning when the spot price goes above your bid
Used for batch jobs, Big Data analysis, or workloads that are resilient to failures
Not great for critical jobs or databases

Physical dedicated Ec2 server for your use
Full control of Ec2 Instance placement
Visibility into the underlying sockets / physical cores of the hardware
Allocated for your account for a 3 year period reservation
More expensive
Useful for software that have a complicated licensing model (Bring your own License)
Or for a companies that have strong regulatory or compliance needs

On demand: coming and staying in resort whenever we like, we pay the full price
Reserved: like planning ahead and if we plan to stay for a long time, we may get a good discount.
Spot instances: the hotel allows people to bid for the empty rooms and the highest bidder keeps the rooms.You can get kicked out at any time
Dedicated Hosts: We book an entire building of the resort

Instances have 5 distinct characteristics advertised on the website:
- The RAM(type,amount,generation)
- The CPU(type,make,frequency,generation,number of cores)
- The I/O (disk performance, EBS optimizations)
- The Network (network bandwidth, network latency
- The Graphical Processing Unit (GPU)
It may be daunting to choose the right instance type (there are over 50 of them) - https://aws.amazon.com/ec2/instance-types/
https://ec2instances.info/ can help with summarizing the types of instances
R/C/P/G/H/X/I/F/Z/CR are specialized in RAM, CPU, I/O, Network, GPU
M instance types are balanced
T2/T3 instance types are “burstable” Burstable Instances (T2)
AWS has the concept of burstable instances (T2 machines)
Burst means that overall, the instance has OK CPU performance.
When the machine needs to process something unexpected (a spike in load for example), it can burst, and CPU can be VERY good.
If the machine bursts, it utilizes “burst credits”
If all the credits are gone, the CPU becomes BAD
If the machine stops bursting, credits are accumulated over time
Burstable instances can be amazing to handle unexpected traffic and getting the insurance that it will be handled correctly
If your instance consistently runs low on credit, you need to move to a different kind of non-burstable instance (all the ones described before).

Nov 2017: It is possible to have an “unlimited burst credit balance
You pay extra money if you go over your credit balance, but you don’t lose in performance
Overall, it is a new offering, so be careful, costs could go high if you’re not monitoring the health of your instances