img = img.transform((r,r), Image.EXTENT, area)

#ERROR
File "/usr/local/lib/python2.7/dist-packages/PIL/ImageFile.py", line 231, in load_prepare
    self.im = Image.core.new(self.mode, self.size)
MemoryError

google PIL+MemoryError，主要提到2个可能错误。一个是PIL库本身ctype代码问题，一个是传递裁减范围为负值导致内存问题。仔细检查了一下，都没有异常。后来考虑到上面的代码为创建新图像时内存错误，直接调整了uwsgi参数。

-M -p 2 --no-orphans --logdate --chmod-socket=666 --uid admin --gid admin --limit-as 384 --harakiri 60 --max-requests 2000

[--limit-as]参数从256调整到384，系统恢复正常。

反思查找原因，发现图片文件虽然不大仅3M+，但是该图片像素巨大为4096*5210，将该图片转换为BMP，有60M+。估计库在处理图片裁减时会将jpg文件重新读取为完整位图，再考虑到操作位图消耗和程序本身需要的内存空间，原设定256M限制肯定不足了，需要设定更大。

目前程序运行在一个虚拟机上，内存2G……看来需要尽快切换主机了……

sudo pip install gevent

出错提示

command ‘gcc-4.2′ failed with exit status 1 

下载源代码包安装

wget http://pypi.python.org/packages/source/g/gevent/gevent-0.13.6.tar.gz
tar -zxvf gevent-0.13.6.tar.gz
cd gevent-0.13.6
sudo python setup.py install -I /opt/local/include -L /opt/local/lib #指定默认的macport路径

这里和大家分享2个简单的decorator，分别用于session认证和响应头cache设置

# -*- coding: utf-8 -*-
"""
    lib/decorator.py
    ~~~~~~~~~~~~~~

    some decorator defined 

    :author: linnchord@gmail.com
    :date:2011-8-4

"""
from functools import wraps
from flask import session, redirect, url_for, flash, request, make_response
from models.user import User
from util import helper

def login_required(f):

    @wraps(f)
    def do(*args, **kwargs):
        if 'userId' not in session:
            #cookie自动登录机制
            token=request.cookies.get('auto_login')
            if token:
                userId, token = token.split('_')
                user = User.get_user_by_id(userId)
                from matrix import app
                if user and helper.md5(str(user.id) + user.password + app.config['SECURIY_KEY'])==token:
                    session['userId']=user.id
                    session['phone']=user.phone
                    session['nickName']=user.nickName
                else:
                    return redirect('/logout')
            else:
                return redirect('/')

        return f(*args, **kwargs)

    return do

def no_cache_header(f):

    @wraps(f)
    def do(*args, **kwargs):
        response = make_response(f(*args, **kwargs))
        response.headers['pragma'] = 'no-cache'
        response.headers['Cache-Control'] = 'no-cache, must-revalidate'
        return response
    return do

使用很简单方便

@app.route('/user/follow/', methods=['GET'])
@login_required
@no_cache_header
def follow_user(userId,appId):
    pass

需要注意的是@no_cache_header修饰应该放在最后，否则逻辑无法正确完成。这个修饰经常用于ajax响应，因为……坑爹的IE总是要缓存第一次请求结果。

这个session auto login机制有个问题，他的auto login cookie始终是不变的，长期使用会有一定安全隐患。更安全的方法是用户每次登录生成一个security key来进行hash，不过这样对于经常换浏览器甚至操作系统的人会造成一定障碍。例如我……经常使用chrome/firefox/ie，还在mac/win下切来切去，某个小说网站每次切了就得重新登录，让我很蛋疼……

过程如下

#清除系统上现有库 python版本自行替换
sudo rm -rf /usr/lib/python2.7/site-packages/PIL
sudo rm /usr/lib/python2.7/site-packages/PIL.pth

#安装依赖包
sudo apt-get install libjpeg8 libjpeg8-dev libfreetype6 libfreetype6-dev liblcms1-dev

#下载
wget http://effbot.org/downloads/Imaging-1.1.7.tar.gz
tar -zxvf Imaging-1.1.7.tar.gz
cd Imaging-1.1.7/
python setup.py build_ext -i
sudo python setup.py install

#安装后如果发现安装的包没有正确支持可进行如下操作
sudo ln -s /usr/lib/x86_64-linux-gnu/libfreetype.so /usr/lib/
sudo ln -s /usr/lib/x86_64-linux-gnu/libz.so /usr/lib/
sudo ln -s /usr/lib/x86_64-linux-gnu/libjpeg.so /usr/lib/

# -*- coding:utf-8 -*-
"""

lib/RedisSessionStore.py
~~~~~~~~~~~~~~

Flask, session store in redis

ref by https://gist.github.com/994937

:author: linnchord@gmail.com
:date:2011-08-04

"""
import redis
from flask import Flask, request, session, json
from werkzeug.contrib.sessions import Session, SessionStore
import msgpack

class RedisSessionStore(SessionStore):

    def __init__(self, key_prefix=None, host='127.0.0.1', port=6379, dbindex=1, expire=1800):
        SessionStore.__init__(self)

        self.redis = redis.Redis(host,port,dbindex)
        self.key_prefix = key_prefix
        self.expire = expire

    def save(self,session):
        key = self._get_session_key(session.sid)
        data = msgpack.Packer().pack(dict(session))
        #print "set session {0}:{1}".format(key, data)
        self.redis.setex(key, data, self.expire)

    def delete(self, session):
        key = self._get_session_key(session.sid)
        self.redis.delete(key)

    def get(self, sid):
        key = self._get_session_key(sid)
        data = self.redis.get(key)
        if data is not None:
            self.redis.setex(key, data, self.expire)
            un = msgpack.Unpacker()
            un.feed(data)
            data = un.unpack()
        else:
            data = {}

        return self.session_class(data, sid, False)

    def _get_session_key(self,sid):
        key = self.key_prefix + sid
        if isinstance(key, unicode):
          key = key.encode('utf-8')
        return key

    @staticmethod
    def init_app(app):
        app.session_store = RedisSessionStore(
            app.config['SESSION_KEY_PREFIX'],
            app.config['SESSION_REDIS_HOST'],
            app.config['SESSION_REDIS_PORT'],
            app.config['SESSION_REDIS_DB'],
            app.config['SESSION_LIFETIME']
        )
        app.session_key = app.config['SESSION_KEY']

class SessionMixin(object):

  __slots__ = ('session_key', 'session_store')

  def open_session(self, request):
    sid = request.cookies.get(self.session_key, None)
    if sid is None:
        return self.session_store.new()
    else:
        return self.session_store.get(sid)

  def save_session(self, session, response):
    if session.should_save:
        self.session_store.save(session)
        response.set_cookie(self.session_key, session.sid)
    return response

class MyFlask(SessionMixin, Flask): pass

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

HOW TO USE

app = MyFlask(__name__)
RedisSessionStore.init_app(app)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

APP CONFIG:

SESSION_REDIS_HOST = '127.0.0.1'
SE