### Events with Failures

When an operation fails, a failure method is called. This is `connectFailed()` for failures while building a connection to the server, and `callFailed()` when the HTTP call fails permanently. When a failure happens it is possible that a `start` event won’t have a corresponding `end` event.

![Events Diagram](../assets/images/******@****.***)

### Events with Retries and Follow-Ups

  }

  /**
   * Returns true if this connection's route has the same address as any of [candidates]. This
   * 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 tunnelResult
        }
      }

      if (route.address.sslSocketFactory != null) {
        // Assume the server won't send a TLS ServerHello until we send a TLS ClientHello. If
        // that happens, then we will have buffered bytes that are needed by the SSLSocket!
        // This check is imperfect: it doesn't tell us whether a handshake will succeed, just

     *
     * If the server does not respond to each ping with a pong within `interval`, this client will
     * assume that connectivity has been lost. When this happens on a web socket the connection is
     * canceled and its listener is [notified][WebSocketListener.onFailure]. When it happens on an
     * HTTP/2 connection the connection is closed and any calls it is carrying
     * [will fail with an IOException][java.io.IOException].
     *

    return response;
  }
}
```

A call to `chain.proceed(request)` is a critical part of each interceptor’s implementation. This simple-looking method is where all the HTTP work happens, producing a response to satisfy the request. If `chain.proceed(request)` is being called more than once previous response bodies must be closed.