AWS Lambda RDS MySQL数据库连接InterfaceError

Question

当我尝试连接到AWS RDS(MySQL)时,我收到的大部分时间都是InterfaceError.当我编辑Lambda代码并重新运行时,它将在第一次正常工作,但随后会出现相同的错误.

我的代码:

import sys
import logging
import pymysql
import json
import traceback
rds_host  = "*****.rds.amazonaws.com"
name = "*****"
password = "****"
db_name = "myDB"
logger = logging.getLogger()
logger.setLevel(logging.INFO)
try:
    conn = pymysql.connect(rds_host, user=name, passwd=password, db=db_name, connect_timeout=5)
except:
    logger.error("ERROR: Unexpected error: Could not connect to MySql instance.")
    sys.exit()
logger.info("SUCCESS: Connection to RDS mysql instance succeeded")
def handler(event, context):
    sub = event['sub']
    username = event['username']
    givenname = event['givenname']
    isAdmin = event['isAdmin']
    print (sub)
    print (username)
    print (givenname)
    print (isAdmin)
    data = {}

    cur = conn.cursor()
    try:
        cmd = "SELECT AuthState FROM UserInfo WHERE UserName=" + "\'" + username + "\'"
        rowCnt = cur.execute(cmd)
        print (cmd)
    except:
        print("ERROR: DB Query Execution failed.")
        traceback.print_exc()
        data['errorMessage'] = 'Internal server error'
        response = {}
        response['statusCode'] = 500
        response['body'] =  data
        return response
    if rowCnt <= 0:
        print (username)
        data['errorMessage'] = 'No User Name Found'
        response = {}
        response['statusCode'] = 400
        response['body'] =  data
        conn.close()
        return response
    for row in cur:
        print row[0]
        if int(row[0]) == 0:#NOT_AUTHORIZED
            ret = "NOT_AUTHORIZED"
        elif int(row[0]) == 1:#PENDING
             ret = "PENDING"
        elif int(row[0]) == 2:#AUTHORIZED
            ret = "AUTHORIZED"
        else:#BLOCKED
            ret = "BLOCKED"
    data['state'] = ret
    response = {}
    response['statusCode'] = 200
    response['body'] =  data
    conn.close()
    return response

堆栈跟踪:

Traceback (most recent call last):
  File "/var/task/app.py", line 37, in handler
  File "/var/task/pymysql/connections.py", line 851, in query
    self._execute_command(COMMAND.COM_QUERY, sql)
  File "/var/task/pymysql/connections.py", line 1067, in _execute_command
    raise err.InterfaceError("(0, '')")
InterfaceError: (0, '')

Answer 1

阅读了解Lambda中的容器重用.

它是关于Node编写的,但对Python来说同样准确.

每次调用时,您的代码都不会从顶部运行.有时它始于handler.

为什么？它更快.

你怎么知道这会发生什么？你没有...除了每次重新部署函数时,当然,你总是会在第一次调用时得到一个新的容器,因为旧的容器会被重新部署放弃.

如果要在处理程序之外进行数据库连接,请不要调用conn.close(),因为在下次调用函数时,您可能会发现容器仍处于活动状态,并且使用已关闭的数据库句柄调用处理程序.

您必须编写Lambda函数,以便在重用容器时它们既不会失败,也不会在不重用容器时失败.

更简单的解决方案是在处理程序内打开数据库连接.更复杂但也更优化的解决方案(在运行时方面)是永远不会关闭它,以便它可以被重用.