import {getConnection} from "typeorm";

await getConnection()
    .createQueryBuilder()
    .insert()
    .into(User)
    .values([
        { firstName: "Timber", lastName: "Saw" }, 
        { firstName: "Phantom", lastName: "Lancer" }
     ])
    .execute();

const posts = await manager.createQueryBuilder(Post, "post")
    .where("post.authorId IN (:...authors)", { authors: [3, 7, 9] })
    .orderBy("post.createDate")
    .getMany();

return await getConnection()
  .createQueryBuilder()
  .select(['post_tag.tagId'])
  .from(PostTag, 'post_tag')
  .where('post_tag.postId = :pid', {pid: pid})
  .getMany()

await getManager().query('SET FOREIGN_KEY_CHECKS = 0;')

await getRepository('Post').clear()
await getRepository('User').clear()
await getRepository('Tag').clear()

await getManager().query('SET FOREIGN_KEY_CHECKS = 1;')

tcp_keepalive_time

 the interval between the last data packet sent (simple ACKs are not considered data) and the first keepalive probe; after the connection is marked to need keepalive, this counter is not used any further

tcp_keepalive_intvl

 the interval between subsequential keepalive probes, regardless of what the connection has exchanged in the meantime

tcp_keepalive_probes

 the number of unacknowledged probes to send before considering the connection dead and notifying the application layer

tcp_keepalive_time

当一台机器在 N 秒内，还没有收到对方的任何数据时，开始 keepalive 探测对方是否正常

tcp_keepalive_intvl

keepalive报文发送的间隔，单位秒

tcp_keepalive_probes

keepalive报文探测次数

[root@localhost ~]# cat /proc/sys/net/ipv4/ 
1800
[root@localhost ~]# cat /proc/sys/net/ipv4/tcp_keepalive_probes 
9
[root@localhost ~]# cat /proc/sys/net/ipv4/tcp_keepalive_intvl  
75

int on = 1;
if (setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on))) {
	// log
    return -1;
}

int idle = 10;
if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &idle, sizeof(int)) < 0) {
  // log
  return -1;
}

int probes = 4;
if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &probes, sizeof(int)) < 0) {
  // log
  return -1;
}

int intvl = 1;
if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &intvl, sizeof(int)) < 0) {
  // log
  return -1;
}

int uv_tcp_keepalive(uv_tcp_t* handle, int enable, unsigned int delay)
   Enable / disable TCP keep-alive. delay is the initial delay in seconds, ignored when enable is zero.

int uv__tcp_keepalive(int fd, int on, unsigned int delay) {
  if (setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)))
    return -errno;

#ifdef TCP_KEEPIDLE
  if (on && setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &delay, sizeof(delay)))
    return -errno;
#endif

  /* Solaris/SmartOS, if you don't support keep-alive,
   * then don't advertise it in your system headers...
   */
  /* FIXME(bnoordhuis) That's possibly because sizeof(delay) should be 1. */
#if defined(TCP_KEEPALIVE) && !defined(__sun)
  if (on && setsockopt(fd, IPPROTO_TCP, TCP_KEEPALIVE, &delay, sizeof(delay)))
    return -errno;
#endif

  return 0;
}

int uv_tcp_keepalive(uv_tcp_t* handle, int on, unsigned int delay) {
  int err;

  if (uv__stream_fd(handle) != -1) {
    err =uv__tcp_keepalive(uv__stream_fd(handle), on, delay);
    if (err)
      return err;
  }

  if (on)
    handle->flags |= UV_TCP_KEEPALIVE;
  else
    handle->flags &= ~UV_TCP_KEEPALIVE;

  /* TODO Store delay if uv__stream_fd(handle) == -1 but don't want to enlarge
   *      uv_tcp_t with an int that's almost never used...
   */

  return 0;
}

//
// 设置 keepalive 相关的2个参数
// probes: 对应内核 tcp_keepalive_probes, 发送多少次keepalive报文还未收到回应时, close该连接
// intvl:  对应内核 tcp_keepalive_intvl, 发送keepalive报文的间隔时间
// idle:   对应内核 tcp_keepalive_time
int set_keep_alive(const uv_handle_t* handle, int probes, int intvl, int idle) {
    int ret;
    uv_os_fd_t fd;

    ret = uv_fileno(handle, &fd);
    if (ret < 0) {
        return ret;
    }

    if (idle > 0) {
        if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &idle, sizeof(idle)))
            return -1;
    }
    // 设置 tcp_keepalive_intvl
    if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPINTVL,
                (const void *) &intvl, sizeof(int)) < 0 ) {
        return -1;
    }

    // 设置 tcp_keepalive_probes
    if ( setsockopt(fd, IPPROTO_TCP, TCP_KEEPCNT,
                (const void *) &probes, sizeof(int)) < 0) {
        return -1;
    }

    return 0;
}