我們?cè)谑褂胢ysql服務(wù)的時(shí)候，正常情況下，mysql的設(shè)置的timeout是8個(gè)小時(shí)(28800秒)，也就是說(shuō)，如果一個(gè)連接8個(gè)小時(shí)都沒(méi)有操作，那么mysql會(huì)主動(dòng)的斷開(kāi)連接，當(dāng)這個(gè)連接再次嘗試查詢的時(shí)候就會(huì)報(bào)個(gè)”MySQL server has gone away”的誤，但是有時(shí)候，由于mysql服務(wù)器那邊做了一些設(shè)置，很多情況下會(huì)縮短這個(gè)連接timeout時(shí)長(zhǎng)以保證更多的連接可用。有時(shí)候設(shè)置得比較變態(tài)，很短，30秒，這樣就需要客戶端這邊做一些操作來(lái)保證不要讓mysql主動(dòng)來(lái)斷開(kāi)。

查看mysql的timeout

使用客戶端工具或者M(jìn)ysql命令行工具輸入show global variables like ’%timeout%’;就會(huì)顯示與timeout相關(guān)的屬性，這里我用docker模擬了一個(gè)測(cè)試環(huán)境。

mysql> show variables like ’%timeout%’; +-----------------------------+----------+| Variable_name| Value |+-----------------------------+----------+| connect_timeout | 10 || delayed_insert_timeout | 300 || have_statement_timeout | YES || innodb_flush_log_at_timeout | 1 || innodb_lock_wait_timeout | 50 || innodb_rollback_on_timeout | OFF || interactive_timeout | 30 || lock_wait_timeout | 31536000 || net_read_timeout | 30 || net_write_timeout | 60 || rpl_stop_slave_timeout | 31536000 || slave_net_timeout | 60 || wait_timeout| 30 |+-----------------------------+----------+13 rows in set

wait_timeout:服務(wù)器關(guān)閉非交互連接之前等待活動(dòng)的秒數(shù)，就是你在你的項(xiàng)目中進(jìn)行程序調(diào)用

interactive_timeout: 服務(wù)器關(guān)閉交互式連接前等待活動(dòng)的秒數(shù),就是你在你的本機(jī)上打開(kāi)mysql的客戶端,cmd的那種

使用pymysql進(jìn)行查詢

我在數(shù)據(jù)庫(kù)里隨便創(chuàng)建了一個(gè)表，插入兩條數(shù)據(jù)

mysql> select * from person;+----+------+-----+| id | name | age |+----+------+-----+| 1 | yang | 18 || 2 | fan | 16 |+----+------+-----+2 rows in set

我使用pymysql這個(gè)庫(kù)對(duì)其進(jìn)行查詢操作，很簡(jiǎn)單

#coding:utf-8import pymysqldef mytest(): connection = pymysql.connect( host=’localhost’, port=3306, user=’root’, password=’123456’, db=’mytest’, charset=’utf8’) cursor = connection.cursor() cursor.execute('select * from person') data = cursor.fetchall() cursor.close() for i in data: print(i) cursor.close() connection.close()if __name__ == ’__main__’: mytest()

可以正確的得到結(jié)果

(1, ’yang’, 18)

(2, ’fan’, 16)

連接超時(shí)以后的查詢

上面可以正常得到結(jié)果是由于當(dāng)創(chuàng)建好一個(gè)鏈接以后，就立刻進(jìn)行了查詢，此時(shí)還沒(méi)有超過(guò)它的超時(shí)時(shí)間，如果我sleep一段時(shí)間，看看什么效果。

#coding:utf-8import pymysqlimport timedef mytest(): connection = pymysql.connect( host=’localhost’, port=3306, user=’root’, password=’123456’, db=’mytest’, charset=’utf8’) cursor = connection.cursor() cursor.execute('select * from person') data = cursor.fetchall() for i in data: print(i) cursor.close() time.sleep(31) cursor = connection.cursor() cursor.execute('select * from person') data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close()if __name__ == ’__main__’: mytest()

這里進(jìn)行了兩次查詢，因?yàn)槲野裮ysql的wait_timeout設(shè)置了30秒，所以我在第一次查詢之后停了31秒，目的讓mysql服務(wù)主動(dòng)的和我剛才創(chuàng)建的連接斷開(kāi)，得到的結(jié)果是

(1, ’yang’, 18)(2, ’fan’, 16)Traceback (most recent call last): File 'F:/python/python3Test/mysqltest.py', line 29, in <module> mytest() File 'F:/python/python3Test/mysqltest.py', line 22, in mytest cursor.execute('select * from person') ... ... File 'C:Python35libsite-packagespymysqlconnections.py', line 702, 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’)Process finished with exit code 1

可以看到在停了31秒鐘以后，再次使用該連接進(jìn)行查詢將拋出2013, ’Lost connection to MySQL server during query’錯(cuò)誤。

解決辦法

解決的方法有兩種，既然這里的超時(shí)是由于在規(guī)定時(shí)間內(nèi)沒(méi)有任何操作導(dǎo)致mysql主動(dòng)的將鏈接關(guān)閉，pymysql的connection對(duì)象有一個(gè)ping()方法，可以檢查連接是否有效，在每次執(zhí)行查詢操作之前先執(zhí)行一下ping()方法,該方法默認(rèn)的有個(gè)reconnect參數(shù)，默認(rèn)是True，如果失去連接了會(huì)重連。

#coding:utf-8import pymysqlimport timedef mytest(): connection = pymysql.connect( host=’localhost’, port=3306, user=’root’, password=’123456’, db=’mytest’, charset=’utf8’) connection.ping() cursor = connection.cursor() cursor.execute('select * from person') data = cursor.fetchall() for i in data: print(i) cursor.close() time.sleep(31) connection.ping() cursor = connection.cursor() cursor.execute('select * from person') data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close()if __name__ == ’__main__’: mytest()

我曾嘗試使用另外一個(gè)線程不停來(lái)執(zhí)行ping()操作，但是當(dāng)我這樣做以后連接就會(huì)丟失，之后的操作就不能進(jìn)行了。這個(gè)問(wèn)題我再研究研究。

#coding:utf-8import pymysqlimport timeimport threadingimport tracebackdef ping(conn): while True: try: conn.ping() except: print(traceback.format_exc()) finally: time.sleep(1)def mytest(): connection = pymysql.connect( host=’localhost’, port=3306, user=’root’, password=’123456’, db=’mytest’, charset=’utf8’) cursor = connection.cursor() # 放在此處不行，必須等待cursor的一個(gè)execute之后再運(yùn)行才可以 # th = threading.Thread(target=ping, args=(connection,)) # th.setDaemon(True) # th.start() cursor.execute('select * from person') data = cursor.fetchall() for i in data: print(i) cursor.close() # 線程放在此處啟動(dòng)可以 th = threading.Thread(target=ping, args=(connection,)) th.setDaemon(True) th.start() time.sleep(31) cursor = connection.cursor() cursor.execute('select * from person') data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close()if __name__ == ’__main__’: mytest()

還有一種方法是使用連接池，連接池中保持著指定數(shù)量的可用連接，每次重新獲取一個(gè)有效的連接進(jìn)行查詢操作,pymysql本身不具有連接池功能，需要借住DBUtils

#coding:utf-8import pymysqlimport timefrom DBUtils.PooledDB import PooledDB, SharedDBConnectiondef mytest(): pool = PooledDB( creator=pymysql, # 初始化時(shí),連接池至少創(chuàng)建的空閑連接,0表示不創(chuàng)建 maxconnections=3, # 連接池中空閑的最多連接數(shù),0和None表示沒(méi)有限制mincached=2, # 連接池中最多共享的連接數(shù)量,0和None表示全部共享(其實(shí)沒(méi)什么卵用) maxcached=5,maxshared=3, host=’localhost’, port=3306, user=’root’, password=’123456’, db=’mytest’, charset=’utf8’ ) connection = pool.connection() cursor = connection.cursor() cursor.execute('select * from person') data = cursor.fetchall() for i in data: print(i) time.sleep(40) cursor.execute('select * from person') data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close()if __name__ == ’__main__’: mytest()

這種方式雖然可以正確的獲取結(jié)果，但是實(shí)際的項(xiàng)目中并不會(huì)這么使用，而是在執(zhí)行完查詢語(yǔ)句以后要將connection關(guān)閉，注意這里的關(guān)閉并不是真正的關(guān)閉，而只是將連接返回給連接池讓其它人使用.

#coding:utf-8import pymysqlimport timefrom DBUtils.PooledDB import PooledDB, SharedDBConnectiondef mytest(): pool = PooledDB( creator=pymysql, maxconnections=3, # 初始化時(shí),連接池至少創(chuàng)建的空閑連接,0表示不創(chuàng)建 mincached=2, # 連接池中空閑的最多連接數(shù),0和None表示沒(méi)有限制 maxcached=5, # 連接池中最多共享的連接數(shù)量,0和None表示全部共享(其實(shí)沒(méi)什么卵用) maxshared=3, host=’localhost’, port=3306, user=’root’, password=’123456’, db=’mytest’, charset=’utf8’ ) connection = pool.connection() cursor = connection.cursor() cursor.execute('select * from person') data = cursor.fetchall() for i in data: print(i) cursor.close() # 關(guān)閉連接，其實(shí)并沒(méi)有真正關(guān)閉，只是將連接返回給連接池 connection.close() time.sleep(40) connection = pool.connection() cursor = connection.cursor() cursor.execute('select * from person') data2 = cursor.fetchall() for i in data2: print(i) cursor.close() connection.close()if __name__ == ’__main__’: mytest()

以上這篇解決mysql服務(wù)器在無(wú)操作超時(shí)主動(dòng)斷開(kāi)連接的情況就是小編分享給大家的全部?jī)?nèi)容了，希望能給大家一個(gè)參考，也希望大家多多支持好吧啦網(wǎng)。