我们有 MySQL 5.7 主从复制，在从服务器端，我们的应用程序监控工具(Tideways 和 PHP7.0)不时报告

MySQL has gone away.

show global status like '%Connection%';

+-----------------------------------+----------+
| Variable_name                     | Value    |
+-----------------------------------+----------+
| Connection_errors_accept          | 0        |
| Connection_errors_internal        | 0        |
| Connection_errors_max_connections | 0        |
| Connection_errors_peer_address    | 323      |
| Connection_errors_select          | 0        |
| Connection_errors_tcpwrap         | 0        |
| Connections                       | 55210496 |
| Max_used_connections              | 387      |
| Slave_connections                 | 0        |
+-----------------------------------+----------+

MySQL has gone away

Connection_errors_peer_address

net_retry_count = 10 
net_read_timeout = 120 
net_write_timeout = 120 
skip_networking = OFF
Aborted_clients = 151650

net_retry_count = 10
net_read_timeout = 30 
net_write_timeout = 60 
skip_networking = OFF
Aborted_clients = 3

net_retry_count = 10
net_read_timeout = 30 
net_write_timeout = 60 
skip_networking = OFF
Aborted_clients = 3

最佳答案

在 MySQL 5.7 中，当新的 TCP/IP 连接到达服务器时，服务器执行多项检查，在 sql/sql_connect.cc 中实现在函数中 check_connection()
其中一项检查是获取客户端连接的 IP 地址，如下所示:

static int check_connection(THD *thd)
{
...
  if (!thd->m_main_security_ctx.host().length)     // If TCP/IP connection
  {
...
    peer_rc= vio_peer_addr(net->vio, ip, &thd->peer_port, NI_MAXHOST);
    if (peer_rc)
    {
      /*
        Since we can not even get the peer IP address,
        there is nothing to show in the host_cache,
        so increment the global status variable for peer address errors.
      */
      connection_errors_peer_addr++;
      my_error(ER_BAD_HOST_ERROR, MYF(0));
      return 1;
    }
...
}

my_bool vio_peer_addr(Vio *vio, char *ip_buffer, uint16 *port,
                      size_t ip_buffer_size)
{
  if (vio->localhost)
  {
...
  }
  else
  {
    /* Get sockaddr by socked fd. */

    err_code= mysql_socket_getpeername(vio->mysql_socket, addr, &addr_length);

    if (err_code)
    {
      DBUG_PRINT("exit", ("getpeername() gave error: %d", socket_errno));
      DBUG_RETURN(TRUE);
    }

    /* Normalize IP address. */

    vio_get_normalized_ip(addr, addr_length,
                          (struct sockaddr *) &vio->remote, &vio->addrLen);

    /* Get IP address & port number. */

    err_code= vio_getnameinfo((struct sockaddr *) &vio->remote,
                              ip_buffer, ip_buffer_size,
                              port_buffer, NI_MAXSERV,
                              NI_NUMERICHOST | NI_NUMERICSERV);

    if (err_code)
    {
      DBUG_PRINT("exit", ("getnameinfo() gave error: %s",
                          gai_strerror(err_code)));
      DBUG_RETURN(TRUE);
    }
...
  }
...
}

NAME

   getpeername - get name of connected peer socket

ERRORS

   EBADF  The argument sockfd is not a valid descriptor.

   EFAULT The addr argument points to memory not in a valid part of the process address space.

   EINVAL addrlen is invalid (e.g., is negative).

   ENOBUFS
          Insufficient resources were available in the system to perform the operation.

   ENOTCONN
          The socket is not connected.

   ENOTSOCK
          The argument sockfd is a file, not a socket.

NAME

   getnameinfo - address-to-name translation in protocol-independent manner

RETURN VALUE

   EAI_AGAIN
          The name could not be resolved at this time.  Try again later.

   EAI_BADFLAGS
          The flags argument has an invalid value.

   EAI_FAIL
          A nonrecoverable error occurred.

   EAI_FAMILY
          The address family was not recognized, or the address length was invalid for the specified family.

   EAI_MEMORY
          Out of memory.

   EAI_NONAME
          The name does not resolve for the supplied arguments.  NI_NAMEREQD is set and the host's name cannot be located, or neither 

hostname nor service name were requested.

   EAI_OVERFLOW
          The buffer pointed to by host or serv was too small.

   EAI_SYSTEM
          A system error occurred.  The error code can be found in errno.

   The gai_strerror(3) function translates these error codes to a human readable string, suitable for error reporting.

关于MySQL 已经消失 : Connection_errors_peer_address with high numbers，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52496902/