samber-slog

Use slogmulti.Router with predicates like LevelIs to send errors to Sentry and info logs to Loki. Always add a predicate-less catch-all handler so unmatched records are not silently dropped.

Order the pipeline as sampling, then formatting, then routing, then sinks. Sampling first avoids wasting CPU formatting records that get dropped, and formatting before routing ensures every sink receives clean attributes.

Fanout broadcasts sequentially so latency equals the sum of all handler latencies, while Pool dispatches concurrently so latency equals the slowest handler. Use Pool for multiple slow sinks and Fanout only when sequential delivery is acceptable.

Batch handlers like slog-datadog, slog-loki, slog-kafka, and slog-parquet buffer records internally. You must call Stop, Close, or Flush on shutdown via defer, or pending buffered logs are discarded.

AttrFromContext only works when an HTTP middleware such as slog-gin, slog-echo, slog-fiber, or slog-chi has populated the request context first. Install the framework middleware with router.Use before any handler reads context attributes.

Combine a FirstMatch Router with sampling: add the error handler as the first route without sampling, then route everything else through a sampling middleware. Threshold sampling preserves the first N records per interval before rate-based sampling.