Python中MySQLdb和torndb模塊對MySQL的斷連問題處理

在使用python 對wordpress tag 進(jìn)行細(xì)化代碼處理時，遇到了調(diào)用MySQLdb模塊時的出錯，由于錯誤提示和問題原因相差甚遠(yuǎn)，查看了N久代碼也未發(fā)現(xiàn)代碼有問題。后來問了下師傅，被告知MySQLdb里有一個斷接的坑 ，需要進(jìn)行數(shù)據(jù)庫重連解決。
一、報(bào)錯代碼及提示
運(yùn)行出錯的代碼如下：    
import MySQLdb
def getTerm(db,tag):
    cursor = db.cursor()
    query = "SELECT term_id FROM wp_terms where name=%s "
    count = cursor.execute(query,tag)
    rows = cursor.fetchall()
    db.commit()
    #db.close()
    if count:
        term_id = [int(rows[id][0]) for id in range(count)]
        return term_id
    else:return None
def addTerm(db,tag):
    cursor = db.cursor()
    query = "INSERT into wp_terms (name,slug,term_group) values (%s,%s,0)"
    data = (tag,tag)
    cursor.execute(query,data)
    db.commit()
    term_id = cursor.lastrowid
    sql = "INSERT into wp_term_taxonomy (term_id,taxonomy,description) values (%s,'post_tag',%s) "
    value = (term_id,tag)
    cursor.execute(sql,value)
    db.commit()
    db.close()
    return int(term_id)
dbconn = MySQLdb.connect(host='localhost', user='root', passwd='123456', db='361way', port=3306, charset='utf8', init_command='set names utf8')
tags = ['mysql','1111','aaaa','bbbb','ccccc','php','abc','python','java']
tagids = []
for tag in tags:
    termid = getTerm(dbconn,tag)
    if termid:
        print tag, 'tag id is ',termid
        tagids.extend(termid)
    else:
        termid = addTerm(dbconn,tag)
        print 'add tag',tag,'id is ' ,termid
        tagids.append(termid)
print 'tag id is ',tagids

直接可以執(zhí)行，在第for循環(huán)里第二次調(diào)用getTerm函數(shù)時，報(bào)錯如下：    
Traceback (most recent call last):
 File "a.py", line 40, in <module>
  termid = getTerm(dbconn,tag)
 File "a.py", line 11, in getTerm
  count = cursor.execute(query,tag)
 File "/usr/lib64/python2.6/site-packages/MySQLdb/cursors.py", line 154, in execute
  charset = db.character_set_name()
_mysql_exceptions.InterfaceError: (0, '')

二、解決方法

初始時以為是編碼問題了，又細(xì)核對了幾遍未發(fā)現(xiàn)編碼有問題，在python代碼里也未發(fā)現(xiàn)異常。后來問過師傅后，師傅來了句提示：

只看代碼有啥用，mysql 的超時時間調(diào)長點(diǎn)或捕獲異常從連，原因是
cursor. connection 沒有關(guān)閉
但是socket已經(jīng)斷了
cursor 這個行為不會再建立一次socket的
重新執(zhí)行一次MysqlDB.connect()
看的有點(diǎn)懵懂，先從mysql 里查看了所有timeout相關(guān)的變量
?
1
    
mysql> show GLOBAL VARIABLES like "%timeout%";
    
+----------------------------+-------+
| Variable_name       | Value |
+----------------------------+-------+
| connect_timeout      | 10  |
| delayed_insert_timeout   | 300  |
| innodb_lock_wait_timeout  | 50  |
| innodb_rollback_on_timeout | OFF  |
| interactive_timeout    | 28800 |
| net_read_timeout      | 30  |
| net_write_timeout     | 60  |
| slave_net_timeout     | 3600 |
| table_lock_wait_timeout  | 50  |
| wait_timeout        | 28800 |
+----------------------------+-------+
10 rows in set (0.00 sec)

發(fā)現(xiàn)最小的超時時間是10s ，而我的程序執(zhí)行起來顯然就不了10s 。因?yàn)橹安檫^相關(guān)的報(bào)錯，這里估計(jì)這個很可能是另外一個報(bào)錯：2006，MySQL server has gone away  。即然和這個超時時間應(yīng)該沒關(guān)系，那就嘗試通過MySQLdb ping測試，如果捕獲異常，就再進(jìn)行重連，修改后的代碼為：    
#!/usr/bin/python
#coding=utf-8
import MySQLdb
def getTerm(db,tag):
 cursor = db.cursor()
 query = "SELECT term_id FROM wp_terms where name=%s "
 count = cursor.execute(query,tag)
 rows = cursor.fetchall()
 db.commit()
 #db.close()
 if count:
 term_id = [int(rows[id][0]) for id in range(count)]
 print term_id
 return term_id
 else:return None
def addTerm(db,tag):
 cursor = db.cursor()
 query = "INSERT into wp_terms (name,slug,term_group) values (%s,%s,0)"
 data = (tag,tag)
 cursor.execute(query,data)
 db.commit()
 term_id = cursor.lastrowid
 sql = "INSERT into wp_term_taxonomy (term_id,taxonomy,description) values (%s,'post_tag',%s) "
 value = (term_id,tag)
 cursor.execute(sql,value)
 db.commit()
 db.close()
 return int(term_id)
dbconn = MySQLdb.connect(host='localhost', user='root', passwd='123456', db='361way', port=3306, charset='utf8', init_command='set names utf8')
tags = ['mysql','1111','aaaa','bbbb','ccccc','php','abc','python','java']
if __name__ == "__main__":
 tagids = []
 for tag in tags:
 try:
   dbconn.ping()
 except:
  print 'mysql connect have been close'
   dbconn = MySQLdb.connect(host='localhost', user='root', passwd='123456', db='361way', port=3306, charset='utf8', init_command='set names utf8')
 termid = getTerm(dbconn,tag)
 if termid:
  print tag, 'tag id is ',termid
  tagids.extend(termid)
 else:
  termid = addTerm(dbconn,tag)
  print 'add tag',tag,'id is ' ,termid
  tagids.append(termid)
 print 'All tags id is ',tagids

再執(zhí)行發(fā)現(xiàn)竟然OK了，而細(xì)看下結(jié)果，發(fā)現(xiàn)基本上每1－2次getTerm或addTerm函數(shù)調(diào)用就會打印一次'mysql connect have been close' 。

三、使用torndb模塊解決mysql斷連問題
1.MySQLdb和torndb的代碼樣例對比
torndb是facebook開源的一個基于MySQLdb二次封裝的一個mysql模塊，新封裝的這個模塊比較小，是一個只有2百多行代碼的py文件。雖然代碼短，功能確相較MySQLdb簡便不少，并且該模塊由于增加了reconnect方法和max_idel_time參數(shù)，解決了mysql的斷連問題。比較下使用原生MySQLdb模塊和使用torndb模塊的代碼：
使用MySQLdb模塊的代碼    
import MySQLdb
def getTerm(db,tag):
    cursor = db.cursor()
    query = "SELECT term_id FROM wp_terms where name=%s "
    count = cursor.execute(query,tag)
    rows = cursor.fetchall()
    db.commit()
    #db.close()
    if count:
        term_id = [int(rows[id][0]) for id in range(count)]
        return term_id
    else:return None
def addTerm(db,tag):
    cursor = db.cursor()
    query = "INSERT into wp_terms (name,slug,term_group) values (%s,%s,0)"
    data = (tag,tag)
    cursor.execute(query,data)
    db.commit()
    term_id = cursor.lastrowid
    sql = "INSERT into wp_term_taxonomy (term_id,taxonomy,description) values (%s,'post_tag',%s) "
    value = (term_id,tag)
    cursor.execute(sql,value)
    db.commit()
    db.close()
    return int(term_id)
def addCTag(db,data):
    cursor = db.cursor()
    query = '''INSERT INTO `wp_term_relationships` (
      `object_id` ,
      `term_taxonomy_id`
      )
      VALUES (
      %s, %s) '''
    cursor.executemany(query,data)
    db.commit()
    db.close()
dbconn = MySQLdb.connect(host='localhost', user='root', passwd='123456', db='361way', port=3306, charset='utf8', init_command='set names utf8')
tags = ['mysql','1111','aaaa','bbbb','ccccc','php','abc','python','java']
tagids = []
for tag in tags:
    if termid:
        try:
         dbconn.ping()
        except:
         dbconn = MySQLdb.connect(host='localhost', user='root', passwd='123456', db='361way', port=3306, charset='utf8', init_command='set names utf8')
         print tag, 'tag id is ',termid
        termid = getTerm(dbconn,tag)
        tagids.extend(termid)
    else:
        try:
         dbconn.ping()
        except:
         dbconn = MySQLdb.connect(host='localhost', user='root', passwd='123456', db='361way', port=3306, charset='utf8', init_command='set names utf8')
        termid = addTerm(dbconn,tag)
        print 'add tag',tag,'id is ' ,termid
        tagids.append(termid)
print 'tag id is ',tagids
postid = '35'
tagids = list(set(tagids))
ctagdata = []
for tagid in tagids:
  ctagdata.append((postid,tagid))
try:
  dbconn.ping()
except:
  dbconn = MySQLdb.connect(host='localhost', user='root', passwd='123456', db='361way', port=3306, charset='utf8', init_command='set names utf8')
  addCTag(dbconn,ctagdata)

使用torndb的代碼    
#!/usr/bin/python
#coding=utf-8
import torndb
def getTerm(db,tag):
    query = "SELECT term_id FROM wp_terms where name=%s "
    rows = db.query(query,tag)
    termid = []
    for row in rows:
      termid.extend(row.values())
    return termid
def addTerm(db,tag):
    query = "INSERT into wp_terms (name,slug,term_group) values (%s,%s,0)"
    term_id = db.execute_lastrowid(query,tag,tag)
    sql = "INSERT into wp_term_taxonomy (term_id,taxonomy,description) values (%s,'post_tag',%s) "
    db.execute(sql,term_id,tag)
    return term_id
def addCTag(db,data):
    query = "INSERT INTO wp_term_relationships (object_id,term_taxonomy_id) VALUES (%s, %s) "
    db.executemany(query,data)
dbconn = torndb.Connection('localhost:3306','361way',user='root',password='123456')
tags = ['mysql','1111','aaaa','bbbb','ccccc','php','abc','python','java']
tagids = []
for tag in tags:
  termid = getTerm(dbconn,tag)
  if termid:
    print tag, 'tag id is ',termid
    tagids.extend(termid)
  else:
    termid = addTerm(dbconn,tag)
    print 'add tag',tag,'id is ' ,termid
    tagids.append(termid)
print 'All tags id is ',tagids
postid = '35'
tagids = list(set(tagids))
ctagdata = []
for tagid in tagids:
  ctagdata.append((postid,tagid))
addCTag(dbconn,ctagdata)

從兩者的代碼上來看，使用torndb模塊和原生相比，發(fā)現(xiàn)可以省略如下兩部分：

torndb模塊不需要db.cursor進(jìn)行處理，無不需要db.comment提交，torndb是自動提交的；

torndb不需要在每次調(diào)用時，進(jìn)行db.ping()判斷數(shù)據(jù)庫socket連接是否斷開，因?yàn)閠orndb增加了reconnect方法，支持自動重連。

2.torndb的方法

torndb提供的參數(shù)和方法有：

execute                      執(zhí)行語句不需要返回值的操作。
execute_lastrowid            執(zhí)行后獲得表id，一般用于插入后獲取返回值。
executemany                  可以執(zhí)行批量插入。返回值為第一次請求的表id。
executemany_rowcount         批量執(zhí)行。返回值為第一次請求的表id。
get                          執(zhí)行后獲取一行數(shù)據(jù)，返回dict。
iter                         執(zhí)行查詢后，返回迭代的字段和數(shù)據(jù)。
query                        執(zhí)行后獲取多行數(shù)據(jù)，返回是List。
close                        關(guān)閉
max_idle_time                最大連接時間
reconnect                    關(guān)閉后再連接
使用示例：    
mysql> CREATE TABLE `ceshi` (`id` int(1) NULL AUTO_INCREMENT ,`num` int(1) NULL ,PRIMARY KEY (`id`));

>>> import torndb
>>> db = torndb.Connection("127.0.0.1","數(shù)據(jù)庫名","用戶名", "密碼", 24*3600)  # 24*3600為超時時間
>>> get_id1 = db.execute_lastrowid("insert ceshi(num) values('1')")
>>> print get_id1
1
>>> args1 = [('2'),('3'),('4')]
>>> get1 = db.executemany("insert ceshi(num) values(%s)", args1)
>>> print get1
2
>>> rows = db.iter("select * from ceshi")
>>> for i in rows:
… print i
3.報(bào)錯

在使用過程中可能遇到的錯誤：    
File "/home/361way/database.py", line 145, in execute_lastrowid
  self._execute(cursor, query, parameters)
 File "/home/361way/database.py", line 207, in _execute
  return cursor.execute(query, parameters)
 File "/usr/lib/pymodules/python2.7/MySQLdb/cursors.py", line 159, in execute
  query = query % db.literal(args)
TypeError: not enough arguments for format string

寫上面的代碼時，我剛開始還是試著使用MySQLdb模塊的方式引用數(shù)據(jù)，結(jié)果發(fā)現(xiàn)報(bào)參數(shù)的錯誤 ，經(jīng)查看代碼發(fā)現(xiàn) ，torndb在使用幾個sql方法時較MySQLdb精簡過了。具體各個方法的傳參方法如下（注意參數(shù)個數(shù)）：    
close()
reconnect()
iter(query, *parameters, **kwparameters)
query(query, *parameters, **kwparameters)
get(query, *parameters, **kwparameters)
execute(query, *parameters, **kwparameters)
execute_lastrowid(query, *parameters, **kwparameters)
execute_rowcount(query, *parameters, **kwparameters)
executemany(query, parameters)
executemany_lastrowid(query, parameters)
executemany_rowcount(query, parameters)
update(query, *parameters, **kwparameters)
updatemany(query, parameters)
insert(query, *parameters, **kwparameters)
insertmany(query, parameters)