Grafana Loki

Grafana Loki is a horizontally scalable, highly available, multi-tenant log aggregation system inspired by Prometheus, designed and developed by Grafana Labs. First released in 2018 and now with over 24,000 stars as of 2026, Loki takes a unique approach to log aggregation: unlike ELK (Elasticsearch/Logstash/Kibana) which indexes the full text of every log line, Loki only indexes metadata (labels) associated with log streams, keeping the log content unindexed and compressed in object storage. This dramatically reduces storage costs (typically 10-100x cheaper than full-text indexing) while maintaining fast query performance for label-based filtering. Key features include: log collection via Promtail (the default agent for Kubernetes, systemd, and file-based log collection), Alloy (Grafana's newer universal telemetry collector), Fluentd/Fluent Bit plugins, and direct API pushes, LogQL query language (combining Prometheus-like label selectors with full-text search, regex matching, JSON/logfmt parsing, and metrics queries derived from logs), microservices architecture with separate components for ingestion (distributor and ingester), querying (querier, query-frontend, query-scheduler), and compaction (compactor), single binary deployment mode for simpler setups, horizontal scalability for both ingestion and querying, multi-tenancy via X-Scope-OrgID header, object storage backends including S3, GCS, Azure Blob, and local filesystem, chunk-based storage format with configurable compression (snappy, gzip, zstd), retention policies, and seamless integration with Grafana dashboards for unified metrics, logs, and traces visualization.