ChromeTraceEventReporter.scala

package sbt // package privateなclassを参照したいので

import java.nio.file.Files
import sbt.internal.AbstractTaskExecuteProgress
import sbt.internal.ShutdownHooks
import scala.concurrent.duration._
import sjsonnew.shaded.scalajson.ast.unsafe.JString
import sjsonnew.support.scalajson.unsafe.CompactPrinter

/**
  * 本来sbtの起動時の引数に `-Dsbt.traces=true` だけ指定すれば、大体同等のことが可能だが、
  * デフォルトだと全てのtaskが記録されて大きなファイルになるので、多少改変したもの
  * [[https://github.com/sbt/sbt/blob/eec3c32cc841365799eaa5460272e8287b975f10/main/src/main/scala/sbt/internal/TaskTraceEvent.scala]]
  * [[https://github.com/sbt/sbt/pull/4576]]
  */
class ChromeTraceEventReporter extends AbstractTaskExecuteProgress with ExecuteProgress[Task] {
  import AbstractTaskExecuteProgress.Timer
  private[this] val start = System.nanoTime

  override def initial(): Unit = ()
  override def afterReady(task: Task[_]): Unit = ()
  override def afterCompleted[T](task: Task[T], result: Result[T]): Unit = ()
  override def afterAllCompleted(results: RMap[Task, Result]): Unit = ()
  override def stop(): Unit = ()

  ShutdownHooks.add(() => report())

  private[this] def report() = {
    if (anyTimings) {
      writeTraceEvent()
    }
  }

  def taskFilter(name: String, durationMicros: Long): Boolean = {
    // 一定以上時間がかかったものだけを記録
    durationMicros > 1.seconds.toMicros
  }

  private[this] def writeTraceEvent(): Unit = {
    val fileName = "trace.json"
    val tracesDirectory = (new File("target").getAbsoluteFile) / "traces"
    if (!tracesDirectory.exists) IO.createDirectory(tracesDirectory)
    else ()
    val outFile = tracesDirectory / fileName
    val trace = Files.newBufferedWriter(outFile.toPath)
    try {
      trace.append("""{"traceEvents":[""")
      trace.append("\n")
      def durationEvent(name: String, t: Timer): String = {
        val sb = new java.lang.StringBuilder(name.length + 2)
        CompactPrinter.print(new JString(name), sb)
        s"""{"name":${sb.toString},"cat":"","ph":"X","ts":${(t.startMicros)},"dur":${(t.durationMicros)},"pid":0,"tid":${t.threadId}}"""
      }
      val entryIterator = currentTimings
      var first = true
      while (entryIterator.hasNext) {
        val (key, value) = entryIterator.next()
        val n = taskName(key)
        if (taskFilter(n, value.durationMicros)) {
          if (first) {
            first = false
          } else {
            trace.append(",\n")
          }
          trace.append(durationEvent(n, value))
        }
      }
      trace.append("\n]}\n")
      ()
    } finally {
      trace.close()
      try println(s"wrote $outFile")
      catch { case _: java.nio.channels.ClosedChannelException => }
    }
  }
}