Metrics

Colotok can collect metrics about its operation, such as the number of logs output, the number of errors, and the time taken to write logs.

MetricsCollector

MetricsCollector is an interface to collect metrics. You can implement this interface to send metrics to your monitoring system like Prometheus, InfluxDB, etc.

interface MetricsCollector {
    /**
     * Increment log count.
     * @param level log level
     * @param providerName provider name
     */
    fun incrementLogCount(level: Level, providerName: String)

    /**
     * Increment error count.
     * @param providerName provider name
     * @param errorType error type
     */
    fun incrementErrorCount(providerName: String, errorType: String)

    /**
     * Update buffer size.
     * @param providerName provider name
     * @param size current buffer size
     */
    fun updateBufferSize(providerName: String, size: Int)

    /**
     * Record write duration.
     * @param providerName provider name
     * @param durationMs duration in milliseconds
     */
    fun recordWriteDuration(providerName: String, durationMs: Long)
}

Metrics Selection Strategy

You can specify how to collect metrics for each provider using MetricsCollectorSpec.

Inherit

The provider inherits the global collector configured in ColotokLoggerContext. This is the default.

val logger = ColotokLoggerContext()
    .withMetrics(globalCollector)
    .addProvider(ConsoleProvider {
        metricsSpec = MetricsCollectorSpec.Inherit
    })
    .getLogger()

Explicit

The provider uses a specific collector. You can choose whether to also report to the global collector using the inheritParent flag.

val logger = ColotokLoggerContext()
    .withMetrics(globalCollector)
    .addProvider(LokiProvider {
        // Only report to lokiCollector
        metricsSpec = MetricsCollectorSpec.Explicit(lokiCollector, inheritParent = false)
    })
    .addProvider(FileProvider(...) {
        // Report to both fileCollector AND globalCollector
        metricsSpec = MetricsCollectorSpec.Explicit(fileCollector, inheritParent = true)
    })
    .getLogger()

NoOp

Metrics collection is disabled for the provider.

.addProvider(ConsoleProvider {
    metricsSpec = MetricsCollectorSpec.NoOp
})

Internal Metrics Logging

By setting enableInternalMetricsLogging = true, you can output metrics events as LogRecord.Metrics to the provider itself. This is useful for debugging or monitoring without external infrastructure.

.addProvider(LokiProvider {
    enableInternalMetricsLogging = true
})

Internal metrics logging can be used alongside MetricsCollectorSpec. For example, you can report to a global Prometheus collector while also logging metrics events to a local file.

Last modified: 19 May 2026