1、调用流程图

connection的erase.jpg

2、关键方法分析

主要方法是Connection::UpdateState()，该方法

• 更新了connection的状态
• 实现了哪些connection要从可用集合中删除

代码(port.cc 1042L)：

void Connection::UpdateState(int64_t now) {
  int rtt = ConservativeRTTEstimate(rtt_);

  if (LOG_CHECK_LEVEL(LS_VERBOSE)) {
    std::string pings;
    PrintPingsSinceLastResponse(&pings, 5);
    LOG_J(LS_VERBOSE, this) << "UpdateState()"
                            << ", ms since last received response="
                            << now - last_ping_response_received_
                            << ", ms since last received data="
                            << now - last_data_received_
                            << ", rtt=" << rtt
                            << ", pings_since_last_response=" << pings;
  }

  // Check the writable state.  (The order of these checks is important.)
  //
  // Before becoming unwritable, we allow for a fixed number of pings to fail
  // (i.e., receive no response).  We also have to give the response time to
  // get back, so we include a conservative estimate of this.
  //
  // Before timing out writability, we give a fixed amount of time.  This is to
  // allow for changes in network conditions.

  if ((write_state_ == STATE_WRITABLE) &&
      TooManyFailures(pings_since_last_response_,
                      CONNECTION_WRITE_CONNECT_FAILURES,
                      rtt,
                      now) &&
      TooLongWithoutResponse(pings_since_last_response_,
                             CONNECTION_WRITE_CONNECT_TIMEOUT,
                             now)) {
    uint32_t max_pings = CONNECTION_WRITE_CONNECT_FAILURES;
    LOG_J(LS_INFO, this) << "Unwritable after " << max_pings
                         << " ping failures and "
                         << now - pings_since_last_response_[0].sent_time
                         << " ms without a response,"
                         << " ms since last received ping="
                         << now - last_ping_received_
                         << " ms since last received data="
                         << now - last_data_received_
                         << " rtt=" << rtt;
    set_write_state(STATE_WRITE_UNRELIABLE);
  }
  if ((write_state_ == STATE_WRITE_UNRELIABLE ||
       write_state_ == STATE_WRITE_INIT) &&
      TooLongWithoutResponse(pings_since_last_response_,
                             CONNECTION_WRITE_TIMEOUT,
                             now)) {
    LOG_J(LS_INFO, this) << "Timed out after "
                         << now - pings_since_last_response_[0].sent_time
                         << " ms without a response"
                         << ", rtt=" << rtt;
    set_write_state(STATE_WRITE_TIMEOUT);
  }

  // Check the receiving state.
  int64_t last_recv_time = last_received();
  bool receiving = now <= last_recv_time + receiving_timeout_;
  set_receiving(receiving);
  if (dead(now)) {
    Destroy();
  }
}

从上述删除中可以看出connection的删除条件如下图：

connection的erase的条件.jpg