Monitoring and Managing EC2 Instance State with the AWS CLI

Amazon EC2 instances power countless mission-critical workloads. Their state directly impacts application availability and business productivity. Although the AWS Management Console provides an intuitive interface for basic status checks, utilizing the AWS Command Line Interface (CLI) unlocks more advanced server health automation at scale.

In this comprehensive guide, we’ll explore the fundamentals of tracking EC2 state before digging into automation best practices. By the end, you’ll understand exactly how instance monitoring connects to larger cloud reliability challenges while gaining applicable skills along the way.

Why Care About EC2 Instance State?

In 2021 alone, over 28% of organizations faced publicly disclosed cloud outages. Yet 80% of cloud costs stem from keeping instances continually running. So both excessive downtime and overprovisioning resources carry financial impacts.

Understanding EC2 state allows you to:

Table 1 – Benefits of Monitoring EC2 Instance State

Business Benefit	Technical Perk
Optimize costs by right-sizing instance types	Identify impaired instances causing errors
Justify moving workloads to cloud	Automate healing, scaling, and retry processes
Limit revenue losses from outages	Gain cloud architecture visibility

Without state insights, you operate partially blind.delicate transitional periods like deployments or traffic surges. Broad outages spread unless impaired servers are promptly identified and recovered.

Both user experience and engineering productivity depend deeply on instance health. Memorizing a few CLI commands paves the way to unlocking all of those benefits.

Prerequisites – Configuring the AWS Command Line

Since we’ll primarily use the interactive CLI, first install and configure it:

Detailed AWS CLI installation guide

The CLI transparently handles API authorization behind the scenes. Once set up, no further coding is required to manage AWS infrastructure.

Authentication and AWS Credentials

Next, configure programmatic access credentials through IAM so that the CLI can securely interact with your account’s resources.

This quickstart guide covers creating CLI profiles to manage multiple sets of account keys.

With credentials populated in the AWS Config file (~/.aws/config), we can start running commands. Confirm everything works by listing S3 buckets in your account:

aws s3 ls

Now that preliminary CLI access is functioning, we can focus specifically on EC2 instances.

Understanding EC2 Instance Lifecycle and States

EC2 instances transition through various transient states reflected by underlying hardware activity. Let’s briefly review what causes common state changes.

Diagram 1 – Simplified EC2 Instance State Flows

• Pending (0) – After an instance launches, the EC2 service prepares deployment on physical servers

• Running (16) – Fully provisioned/initialized and able to receive requests

• Stopping (64) – In the process of shutting down, analogous to ACPI shutdown

• Stopped (80) – Powered off, but resources still allocated. No charges accrue unlike terminated state.

• Terminated (48) – Permanently deleted along with the filesystem disk data

For brevity, additional states like rebooting or impaired cover scenarios like instance storage drive failures.

The full state breakdown in the EC2 documentation provides those specifics.

Generally, aim to keep productive instances in the running state as much as possible to minimize downtime. But occasionally stopping them saves costs for infrequent workloads.

Later sections show how the CLI helps track state fluctuations expected during normal operations. First, though, let’s cover the fundamental commands.

AWS CLI Commands for Checking EC2 Status

While the Console presents state visually, the CLI requires translating raw API output.

The workhorse command for querying current EC2 state is:

aws ec2 describe-instances

With no parameters, this lists metadata for all running instances under your account.


Screenshot 1 – Example summarize-instances output

Even with a modest cluster, this quickly becomes verbose. Instead, target specific instances using the --instance-id parameter.

aws ec2 describe-instances --instance-ids i-01234567890abcdef

For our example, this particular instance has status:

"State": {
  "Code": 16,
  "Name": "running"
},

The friendly Name property represents the human readable value like running. Meanwhile, Code returns a numeric constant mapped to internal EC2 logic.

While naming varies slightly across API calls, codes persist as a stable indicator. Common codes include:

State Name	Code
Pending	0
Running	16
Shutting-down	32
Terminated	48

So if checking state across different tools, rely on codes rather than naming.

Interpreting EC2 State Meanings

Let‘s discuss an example workflow to demonstrate incorporating state monitoring:

1. Developer commits application update
2. CI/CD pipeline deploys changes
3. Old container instances transition stopping → terminated
4. Replacement revised containers become pending → running

Watching this lifecycle unfold provides critical uptime insights even without directly observing the application itself yet.

If new instances stayed pending indefinitely, something clearly blocked completion. The CLI separates infrastructure health factors from front-end code errors.

Expanding Beyond Instance Basics

So far we’ve focused on fundamentals – the what and why of checking state. Now let’s tackle more advanced usage patterns to make retrieving status operationally impactful.

Automating CLI Commands

hardcoded parameters becomes limiting fast. Here are two common ways to script state interrogations dynamically:

Cron

Schedule cron jobs (or CloudWatch Events) to run describe-instances across the infrastructure automatically:

/5 * aws ec2 describe-instances –query ‘Reservations[].Instances[].State‘

This polls every 5 minutes, outputting any detected not-running instances.

AWS CLI + AWS SDK

For more programmatic workflows, AWS software development kits (SDKs) integrate easily with existing CLI profiles.

This Python snippet using Boto3 handles authentication implicitly while adding state logic:

import boto3

ec2 = boto3.session.Session().client(‘ec2‘)

instances = ec2.describe_instances()[‘Reservations‘]

for i in instances:
   state = i[‘Instances‘][0][‘State‘][‘Name‘]
   if state != ‘running‘:
      print(f‘Issue - {i["InstanceId"]} is `{state}`!‘)

Processing directly in code unlocks leveraging conditionals, data structures, external integrations etc.

Additional Related CLI Commands

While describe-instances retrieves status, other EC2 CLI options can prove useful:

• stop-instances/start-instances – Stopping and starting instances on demand
• terminate-instances – Permanently shutting down instances
• reboot-instances – Rebooting an instance if impaired

Diagram 2 – AWS CLI commands relating to instance state

The best way to understand these is to test manually. Fore example, try:

aws ec2 stop-instances --instance-ids i-01234567890abcdef

Then check back with describe-instances until the state updates to stopped.

Combining these instance management actions expands the types of automation you can script:

• Schedule start/stop across development stacks to cut weekend costs
• Restart UAT instances nightly to test latest AMI builds
• Retry failed tasks by rebooting associated containers

So don’t just passively check state; control it using the CLI!

Moving Beyond the CLI

While indispensable, CLI instance queries represent just one approach for cloud engineers. Be sure to also consider:

CloudWatch Dashboards – Surface key metrics/graphs without parsing text CLI output

AWS SDKs – Check status directly from code for greater logic customization

Third Party Tools – Specialized solutions providing turnkey dashboards, historical trends, forecasting etc.

Evaluating alternate interfaces allows selecting the optimal method depending on use case. Just remember the CLI underlies all infrastructure regardless of higher abstractions.

Relating State to Broader System Health

So far our focus rested solely on EC2. But instance health bleeds into all aspects of cloud native solution monitoring:

Reliability – unregistering diving containers from load balancers

Performance – plotting latency spikes against instance teardowns

Cost – right-sizing instance types and families based on actual usage not guesses

Business Continuity – modeling recovery time objective (RTO) impacts from region wide AWS outages

The importance of accurate systems status monitoring is a recurring DevOps theme. Do not overlook the foundation EC2 provides.

Key Takeaways and Putting Knowledge Into Practice

If managing EC2 infrastructure is new, this covered expansive ground. Before wrapping up, let‘s review the key lessons:

• Check state often to catch issues early
• Use CLI scripts to automate at scale
• Integrate with SDKs and existent toolchains
• Relate state to broader cloud reliability practices

Monitoring instance health teaches foundational skills applicable across cloud engineering:

• Optimizing uptime and performance
• Weighing provisioning trade-offs
• Building robust automation
• Streamlining maintenance workflows

So put that knowledge to work:

• Set up Cron to email regular status reports – Pipe describe-instances into an email summary

• Graph state codes not names – Plot Code values over time rather than strings

• Correlate deployments with pending counts – Catch faulty images failing to start

• *ReviewSTOPPED reports before down-sizing** – Ensure unused instances for safe removal

Both your users and future self will thank you for the insight and reduced headaches!

Conclusion

I hope mapping EC2 concepts to immediately useful CLI commands demystified the critical task of cloud instance monitoring. Reliability starts from fundamental infrastructure visibility.

Now fully equipped to track instance state, the only limit is your imagination. Build something awesome! Then let me know what EC2 learnings you’d like us to unravel next.