mysql_pool.py

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"""\
@file mysql_pool.py
@brief Thin wrapper around eventlet.db_pool that chooses MySQLdb and Tpool.

$LicenseInfo:firstyear=2007&license=mit$

Copyright (c) 2007-2008, Linden Research, Inc.

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"""

import MySQLdb
from eventlet import db_pool

class DatabaseConnector(db_pool.DatabaseConnector):
    def __init__(self, credentials, min_size = 0, max_size = 4, *args, **kwargs):
        super(DatabaseConnector, self).__init__(MySQLdb, credentials, min_size, max_size, conn_pool=db_pool.ConnectionPool, *args, **kwargs)

    # get is extended relative to eventlet.db_pool to accept a port argument
    def get(self, host, dbname, port=3306):
        key = (host, dbname, port)
        if key not in self._databases:
            new_kwargs = self._kwargs.copy()
            new_kwargs['db'] = dbname
            new_kwargs['host'] = host
            new_kwargs['port'] = port
            new_kwargs.update(self.credentials_for(host))
            dbpool = ConnectionPool(self._min_size, self._max_size, *self._args, **new_kwargs)
            self._databases[key] = dbpool

        return self._databases[key]

class ConnectionPool(db_pool.TpooledConnectionPool):
    """A pool which gives out saranwrapped MySQLdb connections from a pool
    """

    def __init__(self, min_size = 0, max_size = 4, *args, **kwargs):
        super(ConnectionPool, self).__init__(MySQLdb, min_size, max_size, *args, **kwargs)

    def get(self):
        conn = super(ConnectionPool, self).get()
        # annotate the connection object with the details on the
        # connection; this is used elsewhere to check that you haven't
        # suddenly changed databases in midstream while making a
        # series of queries on a connection.
        arg_names = ['host','user','passwd','db','port','unix_socket','conv','connect_timeout',
         'compress', 'named_pipe', 'init_command', 'read_default_file', 'read_default_group',
         'cursorclass', 'use_unicode', 'charset', 'sql_mode', 'client_flag', 'ssl',
         'local_infile']
        # you could have constructed this connectionpool with a mix of
        # keyword and non-keyword arguments, but we want to annotate
        # the connection object with a dict so it's easy to check
        # against so here we are converting the list of non-keyword
        # arguments (in self._args) into a dict of keyword arguments,
        # and merging that with the actual keyword arguments
        # (self._kwargs).  The arg_names variable lists the
        # constructor arguments for MySQLdb Connection objects.
        converted_kwargs = dict([ (arg_names[i], arg) for i, arg in enumerate(self._args) ])
        converted_kwargs.update(self._kwargs)
        conn.connection_parameters = converted_kwargs
        return conn

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