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Colotok keeps context-wide attributes and MDC values separate:

context attributes are defaults attached to every record created by a logger;
MDC values are ambient values attached to records created while they are present.

Logger name and default attributes

Use getLogger(name) to give records a logger name. Use withAttrs() to replace the context's default attributes, or putAttrs() to merge additional attributes into them.

val context = ColotokLoggerContext()
    .withAttrs(mapOf("service" to "checkout"))
    .putAttrs(mapOf("environment" to "production"))
    .addProvider(ConsoleProvider(ConsoleProviderConfig()))

val logger = context.getLogger("order-api")
logger.info("order accepted", mapOf("orderId" to "A-123"))

The per-call attributes override a context attribute with the same key. Attributes are copied when the log call creates its record, so changing the original map later does not change the queued log.

Mapped Diagnostic Context (MDC)

MDC is useful for request or operation values that should be available to subsequent log calls. Values are captured in each record and can be read or removed through the common API:

MDC.put("requestId", "req-123")
logger.info("request started")

MDC.remove("requestId")
MDC.clear()

MDC is thread-local on JVM, Android, and Native targets. On JS/Node it follows AsyncLocalStorage resources. Logging-call snapshots remain isolated from later MDC mutations. The built-in formatters do not include MDC by default; a custom formatter can select a %{key} text placeholder or an Element.CUSTOM structured field.

Context lifecycle

Providers process records asynchronously. Call context.shutdown() from a suspend context at the end of the application to drain records and release provider resources. Use forceShutdown() only when queued records may be discarded.

Last modified: 07 September 2026