pymysql 多執行緒報錯問題:Packet sequence number wrong - got 1 expected 2'NoneType' object has no attribute 'read'
阿新 • • 發佈:2021-06-28
import time import requests from concurrent.futures import ThreadPoolExecutor import pymysql import threading import json def get_info(item): try: id,url=item content=json.dumps(requests.get(url,timeout=5).text,ensure_ascii=False) update_sql='update talent_info_3 set content=%s where id= %s'%(content,id) # lock.acquire() cur.execute(update_sql) conn.commit() # lock.release() # time.sleep(2) except Exception as e: print(e,url) if __name__ == '__main__': conn=pymysql.connect(host='127.0.0.1', user='root', password="xxxxxx", database='work', port=3306 ) cur=conn.cursor() # lock = threading.Lock() sql='select id,mainurl from talent_info_3 where content is null and mainurl is not null and school="馬薩諸塞大學,阿默斯特"' res1=cur.execute(sql) print(res1) res=cur.fetchall() with ThreadPoolExecutor(max_workers=3) as p: futures=[p.submit(get_info,item) for item in res] result=[task.result() for task in futures] print(result)
異常原因:
使用了多執行緒,多執行緒使用了同一個資料庫連線,但每個execute前沒有加上互斥鎖
方法:
方法一:每個execute前加上互斥鎖
import threading
lock=threading.lock()
lock.acquire()
cursor.execute(command)
lock.release()
方法二:
每個執行緒擁有自己的資料庫連線,即線上程呼叫函式中加上資料庫連線程式碼
方法三:
所有執行緒共用一個連線池,需要考慮執行緒總數和連線池連線數上限的問題