給Python中的MySQLdb模塊添加超時功能的教程

使用Python操作MySQL數據庫的時候常使用MySQLdb這個模塊。
今天在開發的過程發現MySQLdb.connect有些參數沒法設置。通過這個頁面我們可以看到在connect的時候，可以設置的option和client_flags和MySQL c api相比差不少。
一個很重要的參數 MYSQL_OPT_READ_TIMEOUT沒法設置，這個參數如果不設置，極致狀況MySQL處于hang住，自動切換IP漂移，客戶端無法重連到新MySQL。
給MySQLdb加Option很簡單，只要修改_mysql.c這個把Python對象映射到MySQL操作的文件，添加參數，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;

代碼修改完畢，python setup.py install 即可，如果出現mysql_config找不到的問題。你還要修改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

編譯通過，我們來試試添加的read_timeout這個參數。    
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)

然后執行語句前，你試著把mysql用gdb hang住10s后，python就會異常拋錯    
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