Monitoring: Is My Server Healthy?
If you cannot measure it, you cannot fix it
If you cannot measure it, you cannot fix it
Watch a simulated server's vital signs in real time. CPU, memory, requests per second, and error rate update continuously. Click "Add Load" to stress the server and watch metrics respond.
Google's Site Reliability Engineering team identified four metrics that tell you everything about system health.
How long requests take. Track the median AND the 99th percentile. 99% of users may be fast, but 1% experiencing 10-second loads will leave and never come back.
How many requests per second. A sudden spike could mean viral growth (good) or a DDoS attack (bad). A sudden drop could mean your DNS is broken.
What percentage of requests fail. Even 0.1% errors at high traffic = thousands of affected users. Track 4xx (client errors) and 5xx (server errors) separately.
How full your resources are. CPU at 95% means the next traffic spike will cause failures. Disk at 99% means your database will crash when it tries to write.
Real stories where monitoring prevented or shortened outages.
RAM usage climbs 1% per hour. Without monitoring, the server crashes at 3am. With monitoring, an alert fires at 80% and the team deploys a fix during business hours.
Log files grow until the disk is 100% full. The database cannot write and the entire app crashes. A simple disk space alert at 85% prevents this entirely.
A post goes viral. Traffic 10x in minutes. Auto-scaling spins up new servers. The load balancer distributes. Users never notice. Without monitoring, the single server would have crashed.
Netflix has a tool called "Chaos Monkey" that randomly kills production servers during business hours. The idea: if your monitoring and recovery are good enough to handle random failures gracefully, you will survive any real outage.
You've learned what to monitor, how health checks catch failures, and why alerts prevent outages. Monitoring is not glamorous, but it is the difference between finding problems yourself and hearing about them from angry users.
Latency (how fast), traffic (how much), errors (how often things fail), saturation (how full). These four metrics tell you if your system is healthy.
A health check pings your server every few seconds: "Are you alive? Can you reach the database?" If the answer is no, alerts fire and traffic is rerouted.
When metrics cross thresholds (CPU > 90%, error rate > 5%), alerts notify the team via Slack, email, or PagerDuty. The goal: know before your users do.
Metrics tell you WHAT is wrong. Logs tell you WHY. Every request, error, and event is recorded. When something breaks, logs are where you find the cause.
Put your new knowledge into practice!