find-slow-lines-in-log

import java.io.File
import java.time.Duration
import java.time.LocalDateTime
import java.time.format.DateTimeFormatter

val formatter: DateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS")

fun main() {
    File("log.txt")
        .readLines()
        .asSequence()
        .withIndex()
        .filter { it.value.startsWith('[') }
        .map { Pair(it.index + 1, LocalDateTime.parse(it.value.substring(1, 24), formatter)) }
        .windowed(6, 2)
        .map { Pair(lineSet(it), Duration.between(it.last().second, it.first().second)) }
        .sortedBy { it.second }
        .take(25)
        .toList()
        .forEach { println(it) }
}

private fun lineSet(it: List<Pair<Int, LocalDateTime>>) =
    "" + it.first().first + "-" + it.last().first