定向塔和Memcached [英] Pylons and Memcached

问题描述

有人碰巧在他们的Web应用程序中使用这种组合吗?我在寻找某种用于配置此功能的教程或指南时遇到了一些麻烦.还看到最近我是如何开始使用Pylons的，所以我并不熟悉，所以请保持建议非常友好(我什至没有使用过像Beaker这样的模块).

Anyone happen to use this combination in their web application? I'm having a bit of trouble finding some sort of tutorial or guideline for configuring this. Also seeing as how I started using Pylons recently I'm not familiar so please keep the advice very newbie friendly ( I haven't even used modules like Beaker all that much ).

我正在使用MySQL，运行Pastie HTTP服务器，刚刚在Debian上安装了memcached软件包，使用SQLAlchemy ORM与我在Pylons应用程序中的数据库进行交互，现在我不确定该怎么做.

I'm using MySQL, running pastie HTTP server, just installed memcached package on Debian, using SQLAlchemy ORM to interact with my DB in my Pylons app, now I'm not sure what to do.

推荐答案

memcached很好，并且与框架无关，您只需要编写一些代码即可与之交互. memcached的一般想法是:

memcached is nice and framework-agnostic, and you just have to write a bit of code to interact with it. The general idea of memcached is:

object = try_memcached()
if not object:
    object = real_query()
    put_in_memcached(object)

根据您的情况，这很可能会在您的SQLAlchemy抽象中完成.由于我不熟悉您的整个平台(只有memcached)，因此我做了一些谷歌搜索.

That will likely be done in your SQLAlchemy abstraction, in your case. Since I'm unfamiliar with your entire platform (and only memcached), I did a bit of Googling.

此博客似乎已一起实施，并且有用地提供了他使用的代码的链接.相关的代码似乎是这样，这对您可能有意义:

This blogger appears to have implemented them together, and has helpfully provided a link to the code he uses. The relevant code appears to be this, which might make sense to you:

#!/usr/bin/python
"""
memcached objects for use with SQLAlchemy
"""
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.

import memcache
import sqlalchemy
import sqlalchemy.orm

SQLA_SESSION = sqlalchemy.orm.sessionmaker()

MEMCACHED_CLIENT = memcache.Client(['127.0.0.1:11211'])

class DetachedORMObject(object):
    """
    Session-detached object for use with ORM Mapping.  As the SQLAlchemy
    documentation indicates, creating and closing a session is not analogous
    to creating and closing a database connection.  Connections are pooled by
    the database engine by default.  Creating new sessions is of a minimal
    cost.  Also, objects using this wrapper will not likely interact in with
    the database through the full power of SQLAlchemy queries.

    """
    @classmethod
    def fetch_by_field(cls, field, value):
        """Fetch a mapped orm object with the give field and value"""
        session = SQLA_SESSION()
        try:
            class_object = session.query(cls).filter(field == value).one()
        except sqlalchemy.orm.exc.NoResultFound:
            class_object = None
        finally:
            session.close()
        return class_object

    def update(self):
        """Update the database with the values of the object"""
        session = SQLA_SESSION()
        session.add(self)
        session.commit()
        session.refresh(self)
        session.close()

    def refresh(self):
        """Refresh the object with the values of the database"""
        session = SQLA_SESSION()
        session.add(self)
        session.refresh(self)
        session.close()

    def delete(self):
        """Delete the object from the database"""
        session = SQLA_SESSION()
        session.add(self)
        session.delete(self)
        session.commit()
        session.close()


class MemcachedObject(object):
    """
    Object Wrapper for serializing objects in memcached. Utilizes an abstract
    method, get_isntance_key, to understand how to get and set objects that
    impliment this class.
    """
    @classmethod
    def get_cached_instance(cls, instance_key):
        """Retrieve and return the object matching the instance_key"""
        key = str(cls.__module__ + '.' + cls.__name__ + ':' \
           + str(instance_key))
        print "Memcached Getting:", key
        return MEMCACHED_CLIENT.get(key)

    def set_cached_instance(self, time=0, min_compress_len=0):
        """Set the cached instance of an object"""
        print "Memcached Setting:", self.get_cache_key()
        return MEMCACHED_CLIENT.set(self.get_cache_key(), self, time, \
            min_compress_len)

    def delete_cached_instance(self, time=0):
        """Wrapper for the memcached delete method"""
        print "Memcached Deleting:", self.get_cache_key()
        return MEMCACHED_CLIENT.delete(self.get_cache_key(), time)

    def get_cache_key(self):
        """Prepends the full class path of the object to the instance key"""
        return self.__class__.__module__ + '.' + \
            self.__class__.__name__ + ':' + self.get_instance_key()

    def get_instance_key(self):
        """Get the instance key, must be implemented by child objects"""
        raise NotImplementedError \
            ("'GetInstanceKey' method has not been defined.")


class MemcachedORMObject(DetachedORMObject, MemcachedObject):
    """
    Putting it all together now.  Implements both of the above classes. Worth
    noting is the method for checking to see if the fetch_by_field method is
    invoked using a primary key of the class.  The same technique is used to
    generate an instance key for an instance of the class.
    """
    @classmethod
    def fetch_by_field(cls, field, value):
        """Fetch the requested object from the cache and database"""
        orm_object = None
        matched_primary_key = True
        for key in cls._sa_class_manager.mapper.primary_key:
            if field.key != key.key:
                matched_primary_key = False
        if matched_primary_key:
            orm_object = cls.get_cached_instance('(' + str(value) + ')')
        if orm_object is None:
            orm_object = super(MemcachedORMObject, cls). \
                fetch_by_field(field, value)
            if orm_object is not None:
                orm_object.set_cached_instance()
        return orm_object

    def update(self):
        """Update the object in the database and memcached"""
        DetachedORMObject.update(self)
        self.set_cached_instance()

    def refresh(self):
        """Refresh the object from the database and memcached"""
        DetachedORMObject.refresh(self)
        self.set_cached_instance()

    def delete(self):
        """Delete the object from the database and memcached"""
        DetachedORMObject.delete(self)
        self.delete_cached_instance()

    def get_instance_key(self):
        """Get the instance key, implimenting abstract method in base"""
        key = []
        for column in self._sa_instance_state.manager.mapper.primary_key:
            key.append('(' + str(getattr(self, column.key)) + ')')
        return ''.join(key)

不确定是否有帮助，但是在那里.您可以看到正在使用memcached习惯用法:

Not sure if that helps, but there you have it. You can see that memcached idiom in use:

    if matched_primary_key:
        orm_object = cls.get_cached_instance('(' + str(value) + ')')
    if orm_object is None:
        orm_object = super(MemcachedORMObject, cls). \
            fetch_by_field(field, value)

这篇关于定向塔和Memcached的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！