How to connect MySQL database using Python+SQLAlchemy remotely?

Question

I am having difficulty accessing MySQL remotely. I use SSH tunnel and want to connect the database MySQL using Python+SQLALchemy.

When i use MySQL-client in my console and specify “ptotocol=TCP“, then everything is fine!
I use command:

mysql -h localhost —protocol=TCP -u USER -p

I get access to remote database through SSH-tunnel.

However, when I want to connect to the database using the Python+SQLAchemy I can’t find such option like —protocol=TCP
Otherwise, i have only connect to local MySQL Databases.
Tell me please, is there a way to do it using SQLAlchemy.

Asked By: strevg

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Source

Answer 1

The classic answer to this issue is to use 127.0.0.1 or the IP of the host or the host name instead of the “special name” localhost. From the documentation:

[…] connections on Unix to localhost are made using a Unix socket file by default

And later:

On Unix, MySQL programs treat the host name localhost specially, in a way that is likely different from what you expect compared to other network-based programs. For connections to localhost, MySQL programs attempt to connect to the local server by using a Unix socket file. This occurs even if a –port or -P option is given to specify a port number. To ensure that the client makes a TCP/IP connection to the local server, use –host or -h to specify a host name value of 127.0.0.1, or the IP address or name of the local server.

However, this simple trick doesn’t appear to work in your case, so you have to somehow force the use of a TCP socket. As you explained it yourself, when invoking mysql on the command line, you use the --protocol tcp option.

As explained here, from SQLAlchemy, you can pass the relevant options (if any) to your driver either as URL options or using the connect_args keyword argument.

For example using PyMySQL, on a test system I’ve setup for that purpose (MariaDB 10.0.12, SQLAlchemy 0.9.8 and PyMySQL 0.6.2) I got the following results:

>>> engine = create_engine(
      "mysql+pymysql://sylvain:passwd@localhost/db?host=localhost?port=3306")
#                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
#                               Force TCP socket. Notice the two uses of `?`
#                               Normally URL options should use `?` and `&`  
#                               after that. But that doesn't work here (bug?)
>>> conn = engine.connect()
>>> conn.execute("SELECT host FROM INFORMATION_SCHEMA.PROCESSLIST WHERE ID = CONNECTION_ID()").fetchall()
[('localhost:54164',)]

# Same result by using 127.0.0.1 instead of localhost: 
>>> engine = create_engine(
      "mysql+pymysql://sylvain:[email protected]/db?host=localhost?port=3306")
>>> conn = engine.connect()
>>> conn.execute("SELECT host FROM INFORMATION_SCHEMA.PROCESSLIST WHERE ID = CONNECTION_ID()").fetchall()
[('localhost:54164',)]

# Alternatively, using connect_args:
>>> engine = create_engine("mysql+pymysql://sylvain:passwd@localhost/db",
                       connect_args= dict(host='localhost', port=3306))
>>> conn = engine.connect()
>>> conn.execute("SELECT host FROM INFORMATION_SCHEMA.PROCESSLIST WHERE ID = CONNECTION_ID()").fetchall()
[('localhost:54353',)]

As you noticed, both will use a TCP connection (I know that because of the port number after the hostname). On the other hand:

>>> engine = create_engine(
      "mysql+pymysql://sylvain:passwd@localhost/db?unix_socket=/path/to/mysql.sock")
#                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#                               Specify the path to mysql.sock in
#                               the `unix_socket` option will force
#                               usage of a UNIX socket

>>> conn = engine.connect()
>>> conn.execute("SELECT host FROM INFORMATION_SCHEMA.PROCESSLIST WHERE ID = CONNECTION_ID()").fetchall()
[('localhost',)]

# Same result by using 127.0.0.1 instead of localhost: 
>>> engine = create_engine(
      "mysql+pymysql://sylvain:[email protected]/db?unix_socket=/path/to/mysql.sock")
>>> conn = engine.connect()
>>> conn.execute("SELECT host FROM INFORMATION_SCHEMA.PROCESSLIST WHERE ID = CONNECTION_ID()").fetchall()
[('localhost',)]

# Alternatively, using connect_args:
>>> engine = create_engine("mysql+pymysql://sylvain:passwd@localhost/db",
                       connect_args= dict(unix_socket="/path/to/mysql.sock"))
>>> conn = engine.connect()
>>> conn.execute("SELECT host FROM INFORMATION_SCHEMA.PROCESSLIST WHERE ID = CONNECTION_ID()").fetchall()
[('localhost',)]

No port after the hostname: this is an UNIX socket.

Answered By: Sylvain Leroux

Answer 2

In my setup (I’m using mysql-python) just using 127.0.0.1 instead of localhost in the MySQL SQLAlchemy url works. The complete url I’m using exactly for that scenario (tunnel with local port 3307) is:

mysql:/user:[email protected]:3307/

I’m using SQLAlchemy 1.0.5, but I guess that doesn’t matter too much…

Answered By: jgbarah

Answer 3

This worked for me:

import pandas as pd
import pymysql
from sqlalchemy import create_engine

cnx = create_engine('mysql+pymysql://<username>:<password>@<host>/<dbname>')    
df = pd.read_sql('SELECT * FROM <table_name>', cnx) #read the entire table

Where credentials are added to mysql database like this:

CREATE USER '<username>' IDENTIFIED BY '<password>';
GRANT ALL PRIVILEGES ON *.* TO '<username>' WITH GRANT OPTION;
FLUSH PRIVILEGES;

Answered By: sparrow

Answer 4

I Tried this to connect with mysql db of xampp server

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://usrnme:passwd@hstnme/dbname")

Answered By: Ankur prajapati

Answer 5

If you are using Python 3.x you can use:

pip install mysql-connector-python

Then:

import sqlalchemy as db
engine = db.create_engine("mysql+mysqlconnector://username:password@hostname:port/dbname")

Answered By: Hassan A

How to connect MySQL database using Python+SQLAlchemy remotely?

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