LogRecord

A LogRecord is one log entry as a value — everything a single log.info(...) call captured, bundled together: the message, its severity, when it happened, the key/value fields attached to it, and which request it belongs to.

The type exists because a log entry has to travel. From the call site it may go to your console, to a file, and to a backend that indexes it, and each of those destinations needs the whole story in one self-contained package — a bare string wouldn't carry the severity or the trace it came from. Because a record is immutable, every destination can read the same one safely.

You never build a LogRecord in normal use; the global log (or a Logger) builds one for you on every call. You meet it when you extend the pipeline: it's the value handed to a LogRecordProcessor's onEmit and to a LogFormatter, so writing either means reading fields off a record.

final case class LogRecord(
  timestampNanos:         Long,
  observedTimestampNanos: Long,
  severity:               Severity,
  severityText:           String,
  body:                   LogMessage,           // LogMessage.Simple(text), or a lazy template
  attributes:             Attributes,           // code.* source location + caller-supplied attrs
  traceIdHi:              Long,                 // 0L when no span is active
  traceIdLo:              Long,                 // 0L when no span is active
  spanId:                 Long,                 // 0L when no span is active
  traceFlags:             Byte,                 // 0x00 when not sampled
  resource:               Resource,
  instrumentationScope:   InstrumentationScope,
  throwable:              Option[Throwable] = None
) {
  def hasTraceId: Boolean  // traceIdHi != 0L || traceIdLo != 0L
  def hasSpanId:  Boolean  // spanId != 0L
}

object LogRecord {
  def builder: LogRecordBuilder
}

Each field mirrors what the emission recorded. The source location the macro captured arrives inside attributes, as the code.filepath, code.namespace, code.function, and code.lineno keys. The trace and span IDs are what tie this entry back to the request that produced it: they're filled in when the call ran inside an active span, and left as 0 when it didn't — so check hasTraceId/hasSpanId rather than comparing to zero yourself.