Best Open-Source Monitoring and Observability Tools
Metrics, logs, and traces — the strongest open-source monitoring stacks and how to choose between them.
The three pillars
Observability rests on three signals: metrics (numbers over time), logs (discrete events), and traces (request paths through a system). The best open-source stacks cover at least one pillar deeply and integrate with the others.
Metrics: the Prometheus + Grafana pair
Prometheus is the dominant metrics database; Grafana is the dominant visualization layer. Together they form the default metrics stack. Both are fiercely active, CNCF-graduated projects with excellent health scores.
Logs and traces
Beyond metrics, the open-source landscape offers log aggregation and distributed tracing systems. Match the tool to your scale: single-service setups can run lean; microservice fleets need a tracing backend that survives high cardinality.
Choosing as a stack
Monitoring tools are chosen as a stack, not in isolation. Search 'monitoring observability metrics' and look at which projects share integrations and a common query language — that interoperability is worth more than any single project's star count.