If there's a problem with the connection, OkHttp will select another route and try again. This allows OkHttp to recover when a subset of a server's addresses are unreachable. It's also useful when a pooled connection is stale or if the attempted TLS version is unsupported.

    "X-Amz-Request-Id": "17CDC1F4D7E69123",
    "X-Content-Type-Options": "nosniff",
    "X-Xss-Protection": "1; mode=block"
  },
  "tags": {
    "objectLocation": {
      "name": "hosts",
      "poolId": 1,
      "setId": 1,
      "drives": [
        "/mnt/data1",
        "/mnt/data2",
        "/mnt/data3",
        "/mnt/data4"
      ]
    }
  },
  "accessKey": "minioadmin"
}
```

	m.Set(erasureSetOverallWriteQuorum, float64(result.WriteQuorum))
	m.Set(erasureSetOverallHealth, b2f(result.Healthy))

	for _, h := range result.ESHealth {
		poolLV := strconv.Itoa(h.PoolID)
		setLV := strconv.Itoa(h.SetID)
		labels := []string{poolIDL, poolLV, setIDL, setLV}
		m.Set(erasureSetReadQuorum, float64(h.ReadQuorum), labels...)
		m.Set(erasureSetWriteQuorum, float64(h.WriteQuorum), labels...)

        when {
          client.fastFallback -> FastFallbackExchangeFinder(routePlanner, client.taskRunner)
          else -> SequentialExchangeFinder(routePlanner)
        }
    }
  }

  /** Finds a new or pooled connection to carry a forthcoming request and response. */
  internal fun initExchange(chain: RealInterceptorChain): Exchange {
    this.withLock {
      check(expectMoreExchanges) { "released" }

    };
  }

  /**
   * Combines two iterators into a single iterator. The returned iterator iterates across the
   * elements in {@code a}, followed by the elements in {@code b}. The source iterators are not
   * polled until necessary.
   *
   * <p>The returned iterator supports {@code remove()} when the corresponding input iterator
   * supports it.
   */
  public static <T extends @Nullable Object> Iterator<T> concat(

    // Second call attempts the pooled connection, and it fails. Then it retries a new route which
    // succeeds.
    val response2 = client.newCall(request).execute()
    assertThat(response2.body.string()).isEqualTo("abc")
    assertThat(server.takeRequest().sequenceNumber).isEqualTo(1) // Pooled connection.
    assertThat(server.takeRequest().sequenceNumber).isEqualTo(0) // New connection.

 * **Exchange** carries a single HTTP request/response pair.

 * **ExchangeFinder** chooses which connection carries each exchange. Where possible it will use the same connection for all exchanges in a single call. It prefers reusing pooled connections over establishing new connections.      

#### Per-Connection Locks

      expected.assertSuppressed { throwables: List<Throwable>? ->
        assertThat(throwables!!.size).isEqualTo(1)
      }
    }
  }

  /**
   * When a pooled connection fails, don't blame the route. Otherwise pooled connection failures can
   * cause unnecessary SSL fallbacks.
   *
   * https://github.com/square/okhttp/issues/515
   */
  @Test
  fun sslFallbackNotUsedWhenRecycledConnectionFails() {

    different cipher suite than before! OkHttp's defaults cipher suites are selected for good
    security and performance.

 *  New: `ConnectionListener` publishes events for connects, disconnects, and use of pooled
    connections.

 *  Fix: Immediately update the connection's flow control window instead of waiting for the
    receiving stream to process it.

Finally, we SHOULD tell our (HBONE) peers we are shutting down.
This can help ensure that clients do not hold onto pooled connections for too long.