* application. The tuning parameters in this pool are subject to change in future OkHttp releases.
 * Currently this pool holds up to 5 idle connections which will be evicted after 5 minutes of
 * inactivity.
 */
class ConnectionPool internal constructor(
  internal val delegate: RealConnectionPool,
) {
  internal constructor(
    maxIdleConnections: Int = 5,
    keepAliveDuration: Long = 5,
    timeUnit: TimeUnit = TimeUnit.MINUTES,

    val queue: TaskQueue,
    var policy: ConnectionPool.AddressPolicy,
  ) {
    /**
     * How many calls the pool can carry without opening new connections. This field must only be
     * accessed by the connection closer task.
     */
    var concurrentCallCapacity: Int = 0
  }

  companion object {
    fun get(connectionPool: ConnectionPool): RealConnectionPool = connectionPool.delegate

internal fun OkHttpClient.Builder.taskRunnerInternal(taskRunner: TaskRunner) = this.taskRunner(taskRunner)

internal fun buildConnectionPool(
  connectionListener: ConnectionListener,
  taskRunner: TaskRunner,
): ConnectionPool =
  ConnectionPool(
    connectionListener = connectionListener,
    taskRunner = taskRunner,

This logs task enqueues, starts, and finishes.

```
[2020-01-01 00:00:00] Q10000 scheduled after   0 µs: OkHttp ConnectionPool
[2020-01-01 00:00:00] Q10000 starting              : OkHttp ConnectionPool
[2020-01-01 00:00:00] Q10000 run again after 300 s : OkHttp ConnectionPool
[2020-01-01 00:00:00] Q10000 finished run in   1 ms: OkHttp ConnectionPool
[2020-01-01 00:00:00] Q10001 scheduled after   0 µs: OkHttp squareup.com applyAndAckSettings

          taskRunner = taskRunner,
          connectionPool = connectionPool,
          route = route,
          rawSocket = rawSocket,
          socket = socket,
          handshake = handshake,
          protocol = protocol,
          source = source,
          sink = sink,
          pingIntervalMillis = pingIntervalMillis,
          connectionListener = connectionPool.connectionListener,
        )

  val originalRequest: Request,
  val forWebSocket: Boolean,
) : Call, Cloneable {
  internal val lock: ReentrantLock = ReentrantLock()

  private val connectionPool: RealConnectionPool = client.connectionPool.delegate

  internal val eventListener: EventListener = client.eventListenerFactory.create(this)

  private val timeout =
    object : AsyncTimeout() {
      override fun timedOut() {

    if (uncaughtException == null) {
      uncaughtException = throwable
    }
  }

  fun ensureAllConnectionsReleased() {
    testClient?.let {
      val connectionPool = it.connectionPool

      connectionPool.evictAll()
      if (connectionPool.connectionCount() > 0) {
        // Minimise test flakiness due to possible race conditions with connections closing.

  }

  @Test fun inUseConnectionsNotEvicted() {
    val pool = factory.newConnectionPool()
    val poolApi = ConnectionPool(pool)
    val c1 = factory.newConnection(pool, routeA1, 50L)
    val client =
      OkHttpClient.Builder()
        .connectionPool(poolApi)
        .build()
    val call = client.newCall(Request(addressA.url)) as RealCall

    assertConnectionNotReused(request, request)
  }

  @Test
  fun connectionsAreNotReusedIfPoolIsSizeZero() {
    client =
      client.newBuilder()
        .connectionPool(ConnectionPool(0, 5, TimeUnit.SECONDS))
        .build()
    server.enqueue(MockResponse(body = "a"))
    server.enqueue(MockResponse(body = "b"))
    val request = Request(server.url("/"))

    val tunnelRequest =
      when {
        route.requiresTunnel() -> createTunnelRequest(route)
        else -> null
      }

    return ConnectPlan(
      taskRunner = taskRunner,
      connectionPool = connectionPool,
      readTimeoutMillis = readTimeoutMillis,
      writeTimeoutMillis = writeTimeoutMillis,
      socketConnectTimeoutMillis = socketConnectTimeoutMillis,
      socketReadTimeoutMillis = socketReadTimeoutMillis,