Observability
Definition
Observability is the ability to understand a system’s internal state from the telemetry it emits. Its four core data types are captured by the acronym MELT: Metrics, Events, Logs, and Traces. New Relic’s model is a concrete reference implementation of these ideas.
Core Ideas
MELT data types
- Metrics — aggregated numeric measurements over time.
- Events — discrete occurrences with arbitrary attributes; you can report custom events, and turn high-cardinality events into metrics to make them cheaper to query and chart at scale.
- Logs — timestamped text records.
- Traces — the path of a request across services.
Distributed tracing
A trace follows one request across service boundaries. It’s composed of spans — each span represents one operation within the trace. Agents emit span events; the backend stores contextual metadata describing the relationships and timing calculations between spans. Make a high-value transaction a key transaction to monitor/alert on it differently.
Alerting model
A layered vocabulary:
- Threshold — defines what counts as a violation.
- Condition — a monitored data source plus its thresholds.
- Policy — a group of one or more conditions.
- Violation — occurs when a data source crosses a condition’s threshold.
- Incident / Issue — an issue is a collection of one or more incidents.
Infrastructure & real-user monitoring
- Infrastructure — CPU, memory, disk, network sampled (e.g. every 5s) into
SystemSampleevents;InfrastructureEventrecords state deltas. - Browser / RUM — tracks Core Web Vitals: LCP (loading, target <2.5s), FID (interactivity, <100ms), CLS (visual stability, <0.1). JS error tracking also matters for SEO, since crawlers increasingly run JavaScript.
Relationships
- Cloud & AWS Infrastructure — monitoring cloud workloads
- System Design — observability is a reliability pillar
- Microservices — distributed tracing is essential once calls span services
- Software Engineering Practices
References
- New Relic — MELT data types
- New Relic — Alerts concepts and workflow
- New Relic — Distributed tracing details
- New Relic — PageViewTiming / Core Web Vitals