Configure Firecracker metrics to a file or FIFO and tag lines with instance id and custom properties
domain: firecracker-microvm.github.io · 5 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Create the destination: mkfifo metrics.fifo or touch metrics.file
Configure via API: curl --unix-socket /tmp/firecracker.socket -X PUT http://localhost/metrics -d '{"metrics_path":"metrics.fifo","emit_id":true,"properties":{"customer_id":"1234","bundle_id":"fn-abc"}}'
Or set just the path on the CLI: firecracker --metrics-path metrics.fifo
Metrics are written as JSON, one object per line, with a utc_timestamp_ms plus named counter groups
Enable emit_id to add a top-level 'id' field (the --id, default 'anonymous-instance') and properties to add operator-defined key-value tags so lines from many microVMs can be attributed to a source
Known gotchas
Metrics config is set once before boot and fixed for the lifetime of the microVM
emit_id and properties are opt-in and OFF by default; the default line carries only utc_timestamp_ms and counters
Metrics configuration is NOT part of guest config and is NOT restored from a snapshot — reconfigure on a restored microVM
The metrics destination must be able to keep up with the configured flush cadence or lines are dropped
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