Doors to Software System

Monitoring

The four golden signals of monitoring are latency, traffic, errors, and saturation. If you can only measure four metrics of your user-facing system, focus on these four.

Latency - The time it takes to service a request. It is important to seperate latency of successful request from the failed ones. Consider using percentiles p50, p90, p99 & sum, avg

Traffic - A measure of how much demand is being placed on your system, measured in a high-level system-specific metric. (ex. For aweb service, this measurement is usually requests per second)

Errors - The rate of requests that fail, either explicitly (ex. HTTP 500s), implicitly (ex. HTTP 200, but with the wrong content), or by policy policy (ex. If you committed to one-second response times, any request over one second is an error)

Saturation - How "full" your service is. Consumption of your resources

Monitoring vs Observing ?

Monitoring is the process of collecting data and generating reports on different metrics that define system health.

Observability is a more investigative approach. It looks closely at distributed system component interactions and data collected by monitoring to find the root cause of issues.

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