我們在使用mysql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，如果一個(gè)連接8個(gè)小時(shí)都沒有操作，那么mysql會(huì)主動(dòng)的斷開連接，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保證不要讓mysql主動(dòng)來斷開。
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mysql的客戶端,cmd的那種
使用pymysql進(jìn)行查詢
我在數(shù)據(jù)庫里隨便創(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)庫對(duì)其進(jìn)行查詢操作，很簡單
#coding:utf-8
import pymysql
def 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)還沒有超過它的超時(shí)時(shí)間，如果我sleep一段時(shí)間，看看什么效果。
#coding:utf-8
import pymysql
import time
def 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，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:\Python35\lib\site-packages\pymysql\connections.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-8
import pymysql
import time
def 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)問題我再研究研究。
#coding:utf-8
import pymysql
import time
import threading
import traceback
def 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-8
import pymysql
import time
from DBUtils.PooledDB import PooledDB, SharedDBConnection
def 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-8
import pymysql
import time
from DBUtils.PooledDB import PooledDB, SharedDBConnection
def 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)器在無操作超時(shí)主動(dòng)斷開連接的情況就是小編分享給大家的全部內(nèi)容了，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。
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