result.withLock { pool.put(result) }
    return result
  }

  fun newConnectionPool(
    taskRunner: TaskRunner = this.taskRunner,
    maxIdleConnections: Int = Int.MAX_VALUE,
  ): RealConnectionPool =
    RealConnectionPool(
      taskRunner = taskRunner,
      maxIdleConnections = maxIdleConnections,
      keepAliveDuration = 100L,
      timeUnit = TimeUnit.NANOSECONDS,

class ConnectionPool internal constructor(
  internal val delegate: RealConnectionPool,
) {
  internal constructor(
    maxIdleConnections: Int = 5,
    keepAliveDuration: Long = 5,
    timeUnit: TimeUnit = TimeUnit.MINUTES,
    taskRunner: TaskRunner = TaskRunner.INSTANCE,
    connectionListener: ConnectionListener = ConnectionListener.NONE,
  ) : this(
    RealConnectionPool(
      taskRunner = taskRunner,

Since HTTP requests frequently happen in parallel, connection pooling must be thread-safe.

These are the primary classes involved with establishing, sharing, and terminating connections:

 * **RealConnectionPool** manages reuse of HTTP and HTTP/2 connections for reduced latency. Every OkHttpClient has one, and its lifetime spans the lifetime of the OkHttpClient.

import mockwebserver3.MockWebServer
import mockwebserver3.junit5.StartStop
import okhttp3.Headers.Companion.headersOf
import okhttp3.internal.DoubleInetAddressDns
import okhttp3.internal.connection.RealConnectionPool.Companion.get
import okhttp3.testing.Flaky
import okhttp3.testing.PlatformRule
import okhttp3.tls.internal.TlsUtil.localhost
import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.Tag