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Promtail lost support on 2 March 2026 and its replacement is Grafana Alloy. The alloy convert command translates the configuration and inherits the positions file, but it silently changes multiline and rereads the history of Docker containers. Here I migrate a real setup and check with LogQL that no line is lost or duplicated.
After a decade of Prometheus, three years of consolidation around OpenTelemetry, and the open stack now mature with Grafana, Loki, and Tempo, concrete recommendations for teams starting or reviewing their observability layer: what fits, what is excess, and what to avoid.
Loki indexes only labels, not log content, which cuts storage costs dramatically compared to Elasticsearch. The main production risk is cardinality explosion each unique label-value combination generates a stream that inflates the index and slows queries. Separating read and write paths ensures a heavy query cannot saturate ingestion.
The Grafana stack combines three open source projects: Loki for logs, Tempo for traces, and Mimir for metrics. All three keep data in object storage (S3/GCS) with a minimal index instead of indexing everything like Elasticsearch, which cuts cost sharply at high volume and lets you correlate metric, log, and trace from a single Grafana panel.
