给Python中的MySQLdb模块添加超时功能的教程

使用Python操作MySQL数据库的时候常使用MySQLdb这个模块。
今天在开发的过程发现MySQLdb.connect有些参数没法设置。通过这个页面我们可以看到在connect的时候，可以设置的option和client_flags和MySQL c api相比差不少。
一个很重要的参数 MYSQL_OPT_READ_TIMEOUT没法设置，这个参数如果不设置，极致状况MySQL处于hang住，自动切换IP漂移，客户端无法重连到新MySQL。
给MySQLdb加Option很简单，只要修改_mysql.c这个把Python对象映射到MySQL操作的文件，添加参数，再加一段mysql_option即可。
下面是修改后的git diff 文件    
?View Code BASH
 
diff --git a/_mysql.c b/_mysql.c
index d42cc54..61a9b34 100644
--- a/_mysql.c
+++ b/_mysql.c
@@ -489,9 +489,10 @@ _mysql_ConnectionObject_Initialize(
"named_pipe", "init_command",
"read_default_file", "read_default_group",
"client_flag", "ssl",
-                 "local_infile",
+                 "local_infile", "read_timeout",
NULL } ;
int connect_timeout = 0;
+    int read_timeout = 0;
int compress = -1, named_pipe = -1, local_infile = -1;
char *init_command=NULL,
*read_default_file=NULL,
@@ -500,7 +501,7 @@ _mysql_ConnectionObject_Initialize(
self->converter = NULL;
self->open = 0;
check_server_init(-1);
-    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|ssssisOiiisssiOi:connect",
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|ssssisOiiisssiOii:connect",
kwlist,
&host, &user, &passwd, &db,
&port, &unix_socket, &conv,
@@ -509,7 +510,8 @@ _mysql_ConnectionObject_Initialize(
&init_command, &read_default_file,
&read_default_group,
&client_flag, &ssl,
-                    &local_infile /* DO NOT PATCH FOR RECONNECT, IDIOTS
+                    &local_infile, &read_timeout
+                    /* DO NOT PATCH FOR RECONNECT, IDIOTS
IF YOU DO THIS, I WILL NOT SUPPORT YOUR PACKAGES. */
))
return -1;
@@ -540,6 +542,12 @@ _mysql_ConnectionObject_Initialize(
mysql_options(&(self->connection), MYSQL_OPT_CONNECT_TIMEOUT,
(char *)&timeout);
}
+
+    if (read_timeout) {
+        unsigned int timeout = read_timeout;
+        mysql_options(&(self->connection), MYSQL_OPT_READ_TIMEOUT, (char *)&timeout);
+    }
+
if (compress != -1) {
mysql_options(&(self->connection), MYSQL_OPT_COMPRESS, 0);
client_flag |= CLIENT_COMPRESS;

代码修改完毕，python setup.py install 即可，如果出现mysql_config找不到的问题。你还要修改setup_posix.py文件。    
hoterran@hoterran-laptop:~/Projects/MySQL-python-1.2.3$ git diff setup_posix.py
diff --git a/setup_posix.py b/setup_posix.py
index 86432f5..f4f08f1 100644
--- a/setup_posix.py
+++ b/setup_posix.py
@@ -23,7 +23,7 @@ def mysql_config(what):
     if ret/256 > 1:
       raise EnvironmentError("%s not found" % (mysql_config.path,))
   return data
-mysql_config.path = "mysql_config"
+mysql_config.path = "/usr/local/mysql/bin/mysql_config"
 
 def get_config():
   import os, sys

编译通过，我们来试试添加的read_timeout这个参数。    
conn = MySQLdb.connect(host = DB_SERVER,user = DB_USERNAME,passwd = DB_PASSWORD,db = DB_NAME, port=int(DB_PORT), client_flag = 2, read_timeout = 10)

然后执行语句前，你试着把mysql用gdb hang住10s后，python就会异常抛错    
OperationalError: (2013, 'Lost connection to MySQL server during query')
 >/home/hoterran/Projects/dbaas/trunk/dbtest.py(18)()
 >mydb.execute_sql(conn, sql)
(Pdb)
--Return--
> /home/hoterran/Projects/dbaas/trunk/dbtest.py(18)()->None
> mydb.execute_sql(conn, sql)
(Pdb)
OperationalError: (2013, 'Lost connection to MySQL server during query')
> <string>(1)<module>()->None