Logger formatter that emits one JSON object per line in the shape Lambda's advanced logging controls expect, so CloudWatch parses level, request id and tenant id:
{"timestamp":"2026-09-27T07:00:00.123Z","level":"INFO","requestId":"…","tenantId":"…","message":"…"}Mayfly.Boot installs it when AWS_LAMBDA_LOG_FORMAT=JSON. To use it
yourself:
config :logger, :default_formatter, {Mayfly.LogFormatter, []}All Logger metadata except internal keys is included; values that are not
JSON-encodable are inspected.