使用 python 3 通过 SSH（通过跳转主机）连接到 MySQL 数据库

Question

I am trying to build a connection between python and my MySQL-Database (which is in AWS).

The SSH tunnel works fine, the matters happens if its about starting the connection to the database afterwards. Here is my code:

from sqlalchemy import create_engine from sshtunnel import SSHTunnelForwarder

Here is my code:

tunnel = SSHTunnelForwarder(
    ('ssh-host', 22),
    ssh_pkey="my-keypair",
    ssh_username="my-user",
    ssh_password="my-pw",
    remote_bind_address=('database-host', db-port)
    )

tunnel.start()
print("SSH connection created..")   #until here it works fine.
port = str(tunnel.local_bind_port)
engine = create_engine("mysql+pymysql://db-username:db-pw@db-url"+port+"/dbname",encoding='latin1', echo=True, pool_recycle=280)
connection = engine.connect()

After I try to connect to the database it shows following error:

sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on db-url

Before I created a jump host, the connection string worked fine.

Answer 1

With this statement:

tunnel = SSHTunnelForwarder(
    ('ssh-host', 22),
    ssh_pkey="my-keypair",
    ssh_username="my-user",
    ssh_password="my-pw",
    remote_bind_address=('database-host', db-port)
    )

An SSH tunnel is established to the ssh server at ssh-host on port 22 and the remote tunnel endpoint is instructed to connect to the database server running on database-host on port db-port (eg 3306). But the essential point to note is that this tunnel is only established once the client makes the connection.

But how does the client make the connection, you may ask? Well, part of the functionality of the SSHTunnelForwarder is that it listens for connections on a random port on the localhost. So when you connect to localhost using your client application (this is what happens in the create_engine() and engine.connect() calls), the SSH tunnel will read data from that connection, push it across the tunnel and deliver it to the remote endpoint on that side of the tunnel (ie the database server at database-host:db-port).

So what you are missing in your code is that the database connection should be targeting localhost, as in the following (you should be able to use the IP address 127.0.0.1 or the hostname localhost ):

engine = create_engine("mysql+pymysql://db-username:db-pw@127.0.0.1:"+port+"/dbname",encoding='latin1', echo=True, pool_recycle=280)