Table of Contents
CloudWatch Alarms are the silent watchdogs of your AWS environment, always ready to act when things go wrong. Arjun, like many AWS beginners, once wondered: “Okay, CloudWatch collects metrics… but how do I actually respond when an issue happens?” That’s when he discovered the power of CloudWatch Alarms — the feature that not only monitors thresholds but also takes action to keep your cloud safe and reliable.
🎯 What Are CloudWatch Alarms?
CloudWatch Alarms monitor metrics and take action when thresholds are crossed.
Think of it like this:
“If CPU usage is over 80% for 5 minutes, alert me!”
“If disk space drops below 10%, reboot the instance!”
Simple rules, powerful outcomes.
🚦 Alarms Have 3 States
| State | Meaning |
✅ OK | All is well. |
⏳ INSUFFICIENT_DATA | Not enough data to decide. |
🔴 ALARM | Threshold crossed. Take action! |
⏱️ The Heartbeat: Period
Period = how often you check the metric.
- Can be as short as 10 seconds (high-resolution metric)
- Or as long as 5 minutes, depending on what you need
Arjun set his alarm to check CPU every 60 seconds. That was enough for his use case.
🛠️ What Can an Alarm Do?
An alarm isn’t just about shouting.
It can actually do things:
- Take action on EC2 instances
- Stop, terminate, reboot, recover
- Trigger Auto Scaling
- Add/remove EC2s based on load
- Send notifications
- 🔔 Push to SNS topic
- 📩 Notify email/SMS
- 🤖 Call Lambda for custom logic
When Arjun’s app went down once due to a full disk, he set up an alarm that automatically notified him AND triggered a Lambda to clean up logs. Crisis avoided.
🤹♂️ Composite Alarms — The Smart Combo
Arjun noticed a problem: too many alarms were firing. He needed to get smart.
So he used Composite Alarms.
Here’s how they work:
- Combine multiple alarms using
AND/ORlogic. - Get notified only when multiple conditions are true.
Example:
✅ CPU > 80% AND Disk I/O high → Trigger alert
❌ CPU > 80% but Disk I/O normal → Ignore it
This helped Arjun reduce alarm noise and focus only on real issues.
🛡️ EC2 Instance Recovery with Alarms
Arjun wanted peace of mind in case EC2 failed. So he used CloudWatch Alarms to trigger EC2 recovery based on status checks:
| Check Type | What It Monitors |
| Instance Status | EC2 OS health (like kernel panic) |
| System Status | Host hardware issues |
| EBS Status | Attached disk health |
If the host failed, the alarm automatically moved his instance to a healthy host.
Same IP. Same data. No stress.
🧠 Bonus: Log-Based Alarms
Arjun was monitoring an app log file for the word ERROR. He created a CloudWatch Log Metric Filter, and tied that to an alarm.
Now if ERROR appears more than 10 times in 5 minutes, he gets an alert.
Simple setup. High confidence.
🧪 Test Before You Trust
Before going live, Arjun tested everything using this CLI command:CopyCopy
aws cloudwatch set-alarm-state \
--alarm-name "CPUHigh" \
--state-value ALARM \
--state-reason "Testing alarm action"
This simulated a breach and confirmed SNS and Lambda triggers were working.
📌 SAA-Certified Knowledge
If you’re prepping for the AWS SAA exam, remember:
✅ CloudWatch Alarms monitor metrics
✅ Can trigger EC2 actions, SNS, Auto Scaling
✅ Composite Alarms = Combine logic across alarms
✅ Can be tied to Log Metric Filters
✅ Support EC2 recovery actions
✅ Use IAM roles properly when needed
✅ CLI command: set-alarm-state for testing
🧘 Arjun’s Takeaway
“CloudWatch collects data.
Alarms give it a voice.”
He now sleeps peacefully, knowing CloudWatch is watching over his infrastructure — and will shout (or act) if anything goes wrong.
FAQ
Q1: What are CloudWatch Alarms in AWS?
CloudWatch Alarms let you monitor metrics and trigger actions such as notifications, EC2 recovery, or Auto Scaling when thresholds are breached.
Q2: What are the three states of a CloudWatch Alarm?
A CloudWatch Alarm can be in one of three states: OK, INSUFFICIENT_DATA, or ALARM, depending on the metric’s threshold evaluation.
Q3: Can CloudWatch Alarms automatically recover EC2 instances?
Yes. CloudWatch Alarms can trigger EC2 recovery actions when instance or system status checks fail, ensuring uptime with minimal manual effort.
Q4: What is a Composite Alarm in CloudWatch?
A Composite Alarm combines multiple CloudWatch Alarms with AND/OR logic, helping reduce noise by alerting only when multiple conditions are true.
Q5: Can CloudWatch Alarms be tied to CloudWatch Logs?
Yes. You can create a Log Metric Filter and connect it to a CloudWatch Alarm to trigger alerts when log events (like “ERROR”) appear frequently.
Read More on AWS Monitoring
- Amazon CloudWatch Logs Insights: A Beginner’s Guide
- Difference between AWS CloudWatch, CloudTrail and Config
- Understanding AWS EventBridge: The Automation Service Explained
- Understanding AWS CloudWatch Alarms: Listen to Your Cloud Signals
- How CloudWatch Agent Completes EC2 Monitoring: A Comprehensive Guide
- Understanding Live Tail in Amazon CloudWatch Logs
- Master AWS Resource Monitoring with CloudWatch Metrics
- An Introduction to CloudWatch Logs: What You Need to Know
- Understanding Amazon CloudWatch: A Comprehensive Guide
I loved as much as youll receive carried out right here The sketch is attractive your authored material stylish nonetheless you command get bought an nervousness over that you wish be delivering the following unwell unquestionably come more formerly again as exactly the same nearly a lot often inside case you shield this hike
Thank you so much for your thoughtful words and encouragement! I’m really glad you enjoyed the style and presentation.