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为了方便，使用python测试连接mysql容器

脚本内容非常简单

#!/usr/bin/python3
import pymysql

conn=pymysql.connect(host="localhost",user="root",port=3306,password="12345",database="mydb")
cursor=conn.cursor()
cursor.execute("select count(*) from mydb.t")
cursor.close()
conn.close()

执行上述脚本后，发生以下异常

Traceback (most recent call last):
  File "./p.py", line 6, in <module>
    conn=pymysql.connect(host="localhost",user="root",port=3306,password="12345",database="mydb")
  File "/usr/local/lib64/python3.6/site-packages/pymysql/__init__.py", line 94, in Connect
    return Connection(*args, **kwargs)
  File "/usr/local/lib64/python3.6/site-packages/pymysql/connections.py", line 325, in __init__
    self.connect()
  File "/usr/local/lib64/python3.6/site-packages/pymysql/connections.py", line 598, in connect
    self._get_server_information()
  File "/usr/local/lib64/python3.6/site-packages/pymysql/connections.py", line 975, in _get_server_information
    packet = self._read_packet()
  File "/usr/local/lib64/python3.6/site-packages/pymysql/connections.py", line 657, in _read_packet
    packet_header = self._read_bytes(4)
  File "/usr/local/lib64/python3.6/site-packages/pymysql/connections.py", line 707, in _read_bytes
    CR.CR_SERVER_LOST, "Lost connection to MySQL server during query")
pymysql.err.OperationalError: (2013, 'Lost connection to MySQL server during query')

从错误信息看，是不能够正常连接到OMC，刚开始怀疑是pymysql.connect方法中传递的参数不正确，但无论怎么修改，始终出现2013的异常，后来查看mysql配置文件，发现存在一条配置

bind_address=127.0.0.1

改参数限制了mysql不能被远程访问，所以在容器外部没法访问到容器内部的mysql，造成2013异常，注释掉改配置，重启mysql docker容器，访问正常

另外如果将改配置对应的ip地址改为宿主机地址，还会出现如下异常

Traceback (most recent call last):
  File "./p.py", line 6, in <module>
    conn=pymysql.connect(host="localhost",user="root",port=3306,password="12345",database="mydb")
  File "/usr/local/lib64/python3.6/site-packages/pymysql/__init__.py", line 94, in Connect
    return Connection(*args, **kwargs)
  File "/usr/local/lib64/python3.6/site-packages/pymysql/connections.py", line 325, in __init__
    self.connect()
  File "/usr/local/lib64/python3.6/site-packages/pymysql/connections.py", line 630, in connect
    raise exc
pymysql.err.OperationalError: (2003, "Can't connect to MySQL server on 'localhost' ([Errno 111] Connection refused)")

且mysql未正常启动，错误日志中有如下信息

2019-10-15T02:27:03.769286Z 0 [Warning] [MY-010068] [Server] CA certificate ca.pem is self signed.
2019-10-15T02:27:03.791952Z 0 [ERROR] [MY-010262] [Server] Can't start server: Bind on TCP/IP port: Cannot assign requested address
2019-10-15T02:27:03.791960Z 0 [ERROR] [MY-010257] [Server] Do you already have another mysqld server running on port: 3306 ?
2019-10-15T02:27:03.792191Z 0 [ERROR] [MY-010119] [Server] Aborting
2019-10-15T02:27:04.855205Z 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 8.0.17)  MySQL Community Server - GPL.