来自Python的SSH正在自动关闭隧道

Question

我需要一些关于我计划结构的建议。我正在使用sshtunnel连接到外部MySQL数据库。它现在可以正常工作了（我可以发出SQL命令并获得结果），但前提是这些命令与打开连接的功能相同。如果他们在不同的功能，隧道自动关闭之前，我可以使用它。（参见下面的代码-它在两个检查点之间关闭。）所以我的问题是：

1. 每次我想使用连接时都要检查连接是否打开？我该怎么做？在
2. 如何使用来自不同函数的连接？我在sstunnel中看到了一个名为“keepalive”的属性（它将在指定的时间长度内保持连接打开）-这就是我需要的吗？如何使用它？在
3. 我能忘记手动关闭隧道吗？在
4. 还有什么能帮我搞定的吗？你可能会说，我在这个问题上是个新手！在

谢谢。在

Python脚本：

import pymysql, shlex, shutil, subprocess
import logging
import sshtunnel
from sshtunnel import SSHTunnelForwarder
import iot_config as cfg

def OpenRemoteDB():
    global remotecur, remotedb
    sshtunnel.DEFAULT_LOGLEVEL = logging.DEBUG
    with SSHTunnelForwarder(
            (cfg.sshconn['host'], cfg.sshconn['port']),
            ssh_username = cfg.sshconn['user'],
            ssh_private_key = cfg.sshconn['private_key_loc'],
            ssh_private_key_password = cfg.sshconn['private_key_passwd'],
            remote_bind_address = ('127.0.0.1', 3306)) as server:
        remotedb = None
        remotedb = pymysql.connect(host='127.0.0.1', user=cfg.remotedbconn['user'], passwd=cfg.remotedbconn['passwd'], db=cfg.remotedbconn['db'], port=server.local_bind_port)
        remotecur = remotedb.cursor()
        print("Checkpoint 1")
        #The next three lines work fine
#        remotecur.execute("SELECT ActionID, Description FROM cmAction")
#        for r in remotecur:
#            print(r)

def SyncActions():
    print("Checkpoint 2")
    #the next three lines don't work (because the connection has closed)
    remotecur.execute("SELECT ActionID, Description FROM cmAction")
    for r in remotecur:
        print(r)

# Main program starts here
OpenRemoteDB()
SyncActions()

输出：

^{pr2}$

Answer 1

根据steven-rumbalski的评论：

替换：with SSHTunnelForwarder(...) as server
使用：server = SSHTunnelForwarder(...)
然后包装：server.start()...server.stop()
关于您希望通过SSH隧道发送的代码。在

以下是转换后的代码：

import pymysql, shlex, shutil, subprocess
import logging
import sshtunnel
from sshtunnel import SSHTunnelForwarder
import iot_config as cfg

def OpenSSHTunnel():
    global server
    sshtunnel.DEFAULT_LOGLEVEL = logging.DEBUG
    server = SSHTunnelForwarder(
        (cfg.sshconn['host'], cfg.sshconn['port']),
        ssh_username = cfg.sshconn['user'],
        ssh_private_key = cfg.sshconn['private_key_loc'],
        ssh_private_key_password = cfg.sshconn['private_key_passwd'],
        remote_bind_address = ('127.0.0.1', 3306)
    )

def OpenRemoteDB():
    global remotecur, remotedb
    remotedb = None
    remotedb = pymysql.connect(
        host='127.0.0.1',
        user=cfg.remotedbconn['user'],
        passwd=cfg.remotedbconn['passwd'],
        db=cfg.remotedbconn['db'],
        port=server.local_bind_port
    )
    remotecur = remotedb.cursor()
    print("Checkpoint 1")

def SyncActions():
    print("Checkpoint 2")
    # this should now work as expected
    remotecur.execute("SELECT ActionID, Description FROM cmAction")
    for r in remotecur:
        print(r)

# Main program starts here
OpenSSHTunnel()
server.start()
OpenRemoteDB()
SyncActions()
server.stop()