Google App Engine 不支持直接下载代码文件，所以我们无法直接将服务器上的代码进行备份。如果本地的代码一旦丢失，就很难找回，这点对GAE的用户来说，是相当麻烦的。

好在有人编写了一个工具，用于将GAE站点的代码打包成zip格式并下载。

步骤如下：

1.在根目录下根据manatlan的代码建立zipme.py

2.在app.yaml中加入

- url: /zipme
script: zipme.py3.访问youapp.appspot.com/zipme

zipme.py脚本

#!/usr/bin/env python
# -*- coding: UTF-8 -*-
"""
##########################################################################
ZipMe : GAE Content Downloader
##########################################################################
Just add this lines in your app.yaml :

- url: /zipme
script: zipme.py

##########################################################################
""" # manatlan

from google.appengine.ext import webapp
from google.appengine.api import users

import wsgiref.handlers
import zipfile
import os,re,sys,stat
from cStringIO import StringIO

def createZip(path):

def walktree (top = ".", depthfirst = True):
names = os.listdir(top)
if not depthfirst:
yield top, names
for name in names:
try:
st = os.lstat(os.path.join(top, name))
except os.error:
continue
if stat.S_ISDIR(st.st_mode):
for (newtop, children) in walktree (os.path.join(top, name),
depthfirst):
yield newtop, children
if depthfirst:
yield top, names

list=[]
for (basepath, children) in walktree(path,False):
for child in children:
f=os.path.join(basepath,child)
if os.path.isfile(f):
f = f.encode(sys.getfilesystemencoding())
list.append( f )

f=StringIO()
file = zipfile.ZipFile(f, "w")
for fname in list:
nfname=os.path.join(os.path.basename(path),fname[len(path)+1:])
file.write(fname, nfname , zipfile.ZIP_DEFLATED)
file.close()

f.seek(0)
return f

class ZipMaker(webapp.RequestHandler):
def get(self):
if users.is_current_user_admin():
folder = os.path.dirname(__file__)
self.response.headers['Content-Type'] = 'application/zip'
self.response.headers['Content-Disposition'] = \
'attachment; filename="%s.zip"' % os.path.basename(folder)
fid=createZip(folder)
while True:
buf=fid.read(2048)
if buf=="": break
self.response.out.write(buf)
fid.close()
else:
self.response.headers['Content-Type'] = 'text/html'
self.response.out.write("<a href=\"%s\">You must be admin</a>." %
users.create_login_url("/zipme"))

def main():
application = webapp.WSGIApplication(
[('/zipme', ZipMaker)],
debug=False)
wsgiref.handlers.CGIHandler().run(application)

if __name__ == "__main__":
main()
这段代码会通过google的身份认证来判断访问者是否可以下载代码，所以不用担心代码泄漏。不过还是希望Google可以提供代码备份和数据库备份的功能。