What are the four golden signals of monitoring? [Basic]
Answer
The four golden signals are latency, traffic, errors, and saturation. They are a strong starting point for service monitoring because they map closely to user experience and system limits.
Technical explanation
Latency measures how long requests take, usually with percentiles such as p50, p95, and p99.
Traffic measures demand, such as requests per second, messages per second, or bytes per second.
Errors measure failed work, and saturation measures how close a resource is to exhaustion, such as CPU, memory, thread pools, queues, or connection pools.
Hands-on example
PromQL examples: rate(http_requests_total[5m]) for traffic, sum(rate(http_requests_total{status=~'5..'}[5m])) / sum(rate(http_requests_total[5m])) for error rate, histogram_quantile(0.95, sum(rate(http_request_duration_seconds_bucket[5m])) by (le)) for latency, and node_cpu_seconds_total or queue_depth for saturation.
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