first tmp version for Promviz

VisualisationMetricHandler.kt

const val UPSTREAM_SERVICE_NAME_HEADER = "x-client-name"

class VisualisationMetricHandler : Handler<RoutingContext> {

    val httpGauge = Gauge.build()
            .name("status:http_requests_total:rate5m")
            .help("Requests per 5m")
            .labelNames("service", "client", "status")
            .register()

    var lastTickInstant = Instant.now()

    override fun handle(ctx: RoutingContext) {
        ctx.addBodyEndHandler {
            val fiveMinutesAgo = Instant.now().minus(Duration.ofMinutes(5))

            val clientName = ctx.request().getHeader(UPSTREAM_SERVICE_NAME_HEADER) ?: "unknown"

            if (lastTickInstant.isBefore(fiveMinutesAgo)) {
                httpGauge.labels(SERVICE_NAME, clientName, "OK").set(0.0)
                httpGauge.labels(SERVICE_NAME, clientName, "WARN").set(0.0)
                httpGauge.labels(SERVICE_NAME, clientName, "ERROR").set(0.0)
                lastTickInstant = Instant.now()
            }

            val status = when (ctx.response().statusCode) {
                in 200 until 400 -> "OK"
                in 400 until 500 -> "WARN"
                else -> "ERROR"
            }

            httpGauge.labels(SERVICE_NAME, clientName, status).inc()
        }

        ctx.next()
    }
}