*
   * @param eventClass a class to assert that the returned event is an instance of, or null to
   *     take any event class.
   * @param elapsedMs the time in milliseconds elapsed since the immediately-preceding event, or
   *     -1L to take any duration.
   */
  fun takeEvent(
    eventClass: Class<out ConnectionEvent>? = null,
    elapsedMs: Long = -1L,
  ): ConnectionEvent {

   * requires us to have a DNS address for both hosts, which only happens after route planning. We
   * can't coalesce connections that use a proxy, since proxies don't tell us the origin server's IP
   * address.
   */
  private fun routeMatchesAny(candidates: List<Route>): Boolean {
    return candidates.any {
      it.proxy.type() == Proxy.Type.DIRECT &&

    // Check that a fresh connection was created, either immediately or after attempting reuse.
    // We know that a fresh connection was created if the server recorded a request with sequence
    // number 0. Since the client may have attempted to reuse the broken connection just before
    // creating a fresh connection, the server may have recorded 2 requests at this point. The order
    // of recording is non-deterministic.

    assertThat(source1.readUtf8(10)).isEqualTo("abcdefghij")
    assertThat(source1.exhausted()).isTrue()
    source1.close()
    assertThat(relay1.isClosed).isTrue()

    // Since relay1 is closed, new sources cannot be created.
    assertThat(relay1.newSource()).isNull()
    val relay2 = read(file)
    assertThat(relay2.metadata()).isEqualTo(metadata)
    val source2 = relay2.newSource()!!.buffer()

  val bodySize: Long,
  /** The body of this POST request. This may be truncated. */
  val body: Buffer,
  /**
   * The index of this request on its HTTP connection. Since a single HTTP connection may serve
   * multiple requests, each request is assigned its own sequence number.
   */
  val sequenceNumber: Int,
  socket: Socket,
  /**

 * may cause corruption or runtime errors if not. It may however be shared amongst multiple OkHttpClient
 * instances.
 *
 * ## Cache Optimization
 *
 * To measure cache effectiveness, this class tracks three statistics:
 *
 *  * **[Request Count:][requestCount]** the number of HTTP requests issued since this cache was
 *    created.

            try {
              plan.connectTcp()
            } catch (e: Throwable) {
              ConnectResult(plan, throwable = e)
            }
          // Only post a result if this hasn't since been canceled.
          if (plan in tcpConnectsInFlight) {
            connectResults.put(connectResult)
          }
          return -1L
        }
      },
    )
    return null
  }

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:

  override fun hashCode(): Int = commonHashCode()

  /**
   * Returns header names and values. The names and values are separated by `: ` and each pair is
   * followed by a newline character `\n`.
   *
   * Since OkHttp 5 this redacts these sensitive headers:
   *
   *  * `Authorization`
   *  * `Cookie`
   *  * `Proxy-Authorization`
   *  * `Set-Cookie`
   */
  override fun toString(): String = commonToString()

Some requests will have a cached response. When this cached response isn’t fresh, OkHttp can do a _conditional GET_ to download an updated response if it’s newer than what’s cached. This requires headers like `If-Modified-Since` and `If-None-Match` to be added.

## Rewriting Responses