Geert JM Vanderkelen

There have been some request to have some reconnect possibilities in Connector/Python. I’m wondering now whether there should be some automatic reconnect on certain errors within the database driver.

My personal feeling is to have no automatic reconnect within Connector/Python and the programmer has to come up with retrying transactions herself.

For example:

	cnx.disconnect() # For testing..
	tries = 2
	while tries > 0:
		tries -= 1
		try:
			cursor.execute("INSERT INTO t1 (c1) VALUES ('ham')")
			cnx.commit()
		except mysql.connector.InterfaceError:
			if tries == 0:
				print "Failed inserting data after retrying"
				break
			else:
				print "Reconnecting.."
				cnx.reconnect()
		else:
			break

The above mimics how you would handle transactions and trying them reconnecting. I have ideas how to get this into Connector/Python, but it would not really fit PEP-249.

Would the above use case of reconnecting be enough?

Today we registered MySQL Connector/Python with the Python Package Index (PyPI). It makes installing your favorite connector even easier (provided you first install setuptools or pip):

shell> easy_install mysql-connector
shell> pip install mysql-connector

Please report problems either using Launchpad or MySQL Bugs website.

In addition to reporting MySQL Connector/Python bugs on Launchpad, it is now also possible to enter them using http://bugs.mysql.com.

After more than 6 years doing MySQL Support for MySQL AB, Sun Microsystems, and Oracle, it’s time for a change. Time to get back to development!

As of November 2011 I’ll be working full-time on MySQL Connector/Python and other goodies within the MySQL development team at Oracle. Before, this was more or less a pet project done after working hours. However, with the birth of our son Tomas more than a year ago, I’ve been slacking and family got priority.

The idea is to make MySQL Connector/Python the best choice for connecting to MySQL from within your Python code. We still got a long road ahead of us, but I’m confident that we are on the right track.

This is a reply to the blog post Poor man’s MySQL replication monitoring. Haidong Ji had a few problems using MySQLdb (could use the ‘dict’ cursor) and apparently he doesn’t want to much dependencies. I agree that using the mysql client tool is a nice alternative if you don’t want to use any 3rd party Python modules. And the MySQL client tools are usually and should be installed with the server.

However, since MySQL Connector/Python only needs itself and Python, dependencies are reduced to a minimum. Here you’ll find a refactored version of Haidong’s version (can of course be made much more sophisticated) using the connector:

import sys
from socket import gethostname
import smtplib
import mysql.connector

emailSubject = "Replication problem on slave %s"
emailTo = "recipient@example.com"
emailFrom = "monitor-tool@example.com"

def runCmd(cmd):
    cnx = mysql.connector.connect(user='root',
                                  unix_socket='/path/to/mysql.sock')
    cur = cnx.cursor(buffered=True)
    cur.execute(cmd)
    columns = tuple( [d[0].decode('utf8') for d in cur.description] )
    row = cur.fetchone()
    if row is None:
        raise StandardError("MySQL Server not configured as Slave")
    result = dict(zip(columns, row))
    cur.close()
    cnx.close()
    return result

try:
    slave_status = runCmd("SHOW SLAVE STATUS")
except mysql.connector.Error, e:
    print >> sys.stderr, "There was a MySQL error:", e
    sys.exit(1)
except StandardError, e:
    print >> sys.stderr, "There was an error:", e
    sys.exit(1)

if (slave_status['Slave_IO_Running'] == 'Yes' and
    slave_status['Slave_SQL_Running'] == 'Yes' and
    slave_status['Last_Errno'] == 0):
    print "Cool"
else:
    emailBody = [
        "From: %s" % emailFrom,
        "To: %s" % emailTo,
        "Subject: %s" % (emailSubject %  gethostname()),
        "",
        '\n'.join([ k + ' : ' + str(v) for k,v in slave_status.iteritems()]),
        "\r\n",
        ]
    server = smtplib.SMTP("localhost")
    server.sendmail(emailFrom, [emailTo], '\r\n'.join(emailBody))
    server.quit()

MySQL Connector/Python 0.3.2, a development release, is available for download:
https://launchpad.net/myconnpy/+download

Disclaimer: Since version 0.3 is still a development release, or ‘alpha’, it is not
recommended to run this in production.

MySQL Connector/Python 0.3.2-devel is a maintenance release fixing following bugs:

• lp:701081 -Doesn’t install with Python 2.4

About MySQL Connector/Python: MySQL Connector/Python is implementing the
MySQL Client/Server protocol completely in Python. No MySQL libraries
are needed, and no compilation is necessary to run this Python DB API v2.0
compliant driver. It is compatible with Python v2.4 and later as well as
Python v3.1 and later.

MySQL Connector/Python 0.3.1, a development release, is available for download:
https://launchpad.net/myconnpy/+download

Disclaimer: Since version 0.3.1 is still a development release, or ‘alpha’, it is not
recommended to run this in production.

MySQL Connector/Python 0.3.1-devel is a maintenance release fixing following bugs:

• lp:695514 – Infinite recursion when setting connection client_flags
• lp:691836 – Incorrect substitution by cursor.execute when tuple args contains ‘%s’

About MySQL Connector/Python: MySQL Connector/Python is implementing the
MySQL Client/Server protocol completely in Python. No MySQL libraries
are needed, and no compilation is necessary to run this Python DB API v2.0
compliant driver. It is compatible with Python v2.4 and later as well as
Python v3.1 and later.

Setting client flags with MySQL Connector/Python works a bit differently than the other MySQL Python drivers. This blog post describes how to set and unset flags, like the CLIENT_FOUND_ROWS.

The default client flags for the MySQL Client/Server protocol can be retrieved using the constants.ClientFlag class:

>>> from mysql.connector.constants import ClientFlag
>>> defaults = ClientFlag.get_default()
>>> print ClientFlag.get_bit_info(defaults)
['SECURE_CONNECTION', 'TRANSACTIONS', 'CONNECT_WITH_DB',
 'PROTOCOL_41', 'LONG_FLAG', 'MULTI_RESULTS',
 'MULTI_STATEMENTS', 'LONG_PASSWD']

To set an extra flag when connecting to MySQL you use the client_flags argument of connect()-method. For example, you’d like to have the CLIENT_FOUND_ROWS set:

import mysql.connector
from mysql.connector.constants import ClientFlag
extra_flags = [ClientFlag.FOUND_ROWS]
cnx = mysql.connector.connect(client_flags=extra_flags)

Similar, you can unset a flag passing a list of negative values, or all at the same time. For example, you’d like the CLIENT_FOUND_ROWS set, but you don’t want CLIENT_MULTI_STATEMENTS:

import mysql.connector
from mysql.connector.constants import ClientFlag
extra_flags = [ClientFlag.FOUND_ROWS, -ClientFlag.MULTI_STATEMENTS]
cnx = mysql.connector.connect(client_flags=extra_flags)

It is also possible to pass the client_flags an integer, but you need to get first the defaults, and do bitwise operations to set/unset flags yourself. At the moment of writing, there is a bug about this, see lp:695514, but I recommend using the list-method.

MySQL v5.5 is GA, but is it working with Python? Yes, it does. Below you’ll find some quick, small tests I did with MySQLdb, oursql and our own MySQL Connector/Python.

My desktop is a Mac, but when it works on that, I’m sure it works elsewhere too. If not, just let us know!

MySQL for Python (aka MySQLdb)

Installing MySQL v5.5.8 64-bit from tar ball on MacOS X 10.6, it compiled fine and the module loaded giving me the expected result:

>>> import MySQLdb
>>> cnx = MySQLdb.connect(user='root')
>>> cur = cnx.cursor()
>>> cur.execute("SELECT VERSION()")
1L
>>> print cur.fetchall()
(('5.5.8',),)

oursql

oursql is an alternative for MySQLdb. Both are using the MySQL C API and thus need to be compiled from source (if you don’t find binaries of course).

>>> import oursql
>>> cnx = oursql.connect(user='root')
>>> cur = cnx.cursor()
>>> cur.execute("SELECT VERSION()")
>>> print cur.fetchall()
[(u'5.5.8',)]

MySQL Connector/Python

Our own MySQL Connector/Python doesn’t need compiling and doesn’t need any MySQL software installed to be able to connect to a MySQL server. Current unittests run fine against MySQL v5.5.8.

>>> cnx = mysql.connector.connect(user='root')
>>> cur = cnx.cursor()
>>> cur.execute("SELECT VERSION()")
-1
>>> print cur.fetchall()
[(u'5.5.8',)]

Conclusion

One can’t really conclude anything with the simple tests above, but it looks like MySQL v5.5 will work fine with Python.

MySQL Connector/Python 0.3.0, a development release, is available for download:
https://launchpad.net/myconnpy/+download

Since version 0.3.0 is still a development release, or ‘alpha’, it is not
recommended to run this in production.

MySQL Connector/Python 0.3.0 adds following features:

• Python v2.4 support is back.
• Support for compressed protocol.
• Support for SSL connections (when Python’s ssl module is available).
• Support for packets which are bigger than 16MB.
• Max allowed packetsize defaults to 1GB.
• Some performance improvements.

See the ChangeLog for extra details.

Please report bugs and comments using the bug tracker on Launchpad:
https://bugs.launchpad.net/myconnpy

About MySQL Connector/Python: MySQL Connector/Python is implementing the
MySQL Client/Server protocol completely in Python. No MySQL libraries
are needed, and no compilation is necessary to run this Python DB API v2.0
compliant driver. It is compatible with Python v2.4 and later as well as
Python v3.1 and later.