實例分析python3實現(xiàn)并發(fā)訪問水平切分表

更新時間：2018年09月29日 10:54:20 投稿：laozhang

在本文中小編給大家整理了關于python3實現(xiàn)并發(fā)訪問水平切分表的相關知識點以及實例代碼，有興趣的朋友們參考下。

場景說明

假設有一個mysql表被水平切分，分散到多個host中，每個host擁有n個切分表。

如果需要并發(fā)去訪問這些表，快速得到查詢結果，應該怎么做呢？

這里提供一種方案，利用python3的asyncio異步io庫及aiomysql異步庫去實現(xiàn)這個需求。

代碼演示

import logging
import random
import asynciofrom aiomysql 
import create_pool
# 假設mysql表分散在8個host, 每個host有16張子表
TBLES = {  "192.168.1.01": "table_000-015",
# 000-015表示該ip下的表明從table_000一直連續(xù)到table_015
  "192.168.1.02": "table_016-031", 
   "192.168.1.03": "table_032-047",  
    "192.168.1.04": "table_048-063", 
     "192.168.1.05": "table_064-079",  
     "192.168.1.06": "table_080-095", 
      "192.168.1.07": "table_096-0111", 
       "192.168.1.08": "table_112-0127",
}
USER = "xxx"PASSWD = "xxxx"# wrapper函數(shù)，用于捕捉異常def query_wrapper(func):
  async def wrapper(*args, **kwargs):
    try:
      await func(*args, **kwargs)    except Exception as e:
      print(e)  return wrapper
      # 實際的sql訪問處理函數(shù)，通過aiomysql實現(xiàn)異步非阻塞請求@
      query_wrapperasync def query_do_something(ip, db, table):
  async with create_pool(host=ip, db=db, user=USER, password=PASSWD) as pool:
    async with pool.get() as conn:
      async with conn.cursor() as cur:
        sql = ("select xxx from {} where xxxx")
        await cur.execute(sql.format(table))
        res = await cur.fetchall()    
 # then do something...# 生成sql訪問隊列, 隊列的每個元素包含要對某個表進行訪問的函數(shù)及參數(shù)def gen_tasks():
  tasks = []  for ip, tbls in TBLES.items():
    cols = re.split('_|-', tbls)
    tblpre = "_".join(cols[:-2])
    min_num = int(cols[-2])
    max_num = int(cols[-1])   
      for num in range(min_num, max_num+1):
      tasks.append(
        (query_do_something, ip, 'your_dbname', '{}_{}'.format(tblpre, num))
      )
 
  random.shuffle(tasks)  
   return tasks# 按批量運行sql訪問請求隊列def run_tasks(tasks, batch_len):
  try:  
    for idx in range(0, len(tasks), batch_len):
      batch_tasks = tasks[idx:idx+batch_len]
      logging.info("current batch, start_idx:%s len:%s" % (idx, len(batch_tasks))) 
            for i in range(0, len(batch_tasks)):
        l = batch_tasks[i]
        batch_tasks[i] = asyncio.ensure_future(
          l[0](*l[1:])
        )
      loop.run_until_complete(asyncio.gather(*batch_tasks)) 
       except Exception as e:
    logging.warn(e)# main方法, 通過asyncio實現(xiàn)函數(shù)異步調用def main():
  loop = asyncio.get_event_loop()
 
  tasks = gen_tasks()
  batch_len = len(TBLES.keys()) * 5  # all up to you
  run_tasks(tasks, batch_len)
 
  loop.close()

以上就是本次相關內容的全部實例代碼，大家可以本地測試以下，感謝你對腳本之家的支持。

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