/usr/share/pyshared/paste/cascade.py is in python-paste 1.7.5.1-4ubuntu2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 | # (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
"""
Cascades through several applications, so long as applications
return ``404 Not Found``.
"""
from paste import httpexceptions
from paste.util import converters
import tempfile
from cStringIO import StringIO
__all__ = ['Cascade']
def make_cascade(loader, global_conf, catch='404', **local_conf):
"""
Entry point for Paste Deploy configuration
Expects configuration like::
[composit:cascade]
use = egg:Paste#cascade
# all start with 'app' and are sorted alphabetically
app1 = foo
app2 = bar
...
catch = 404 500 ...
"""
catch = map(int, converters.aslist(catch))
apps = []
for name, value in local_conf.items():
if not name.startswith('app'):
raise ValueError(
"Bad configuration key %r (=%r); all configuration keys "
"must start with 'app'"
% (name, value))
app = loader.get_app(value, global_conf=global_conf)
apps.append((name, app))
apps.sort()
apps = [app for name, app in apps]
return Cascade(apps, catch=catch)
class Cascade(object):
"""
Passed a list of applications, ``Cascade`` will try each of them
in turn. If one returns a status code listed in ``catch`` (by
default just ``404 Not Found``) then the next application is
tried.
If all applications fail, then the last application's failure
response is used.
Instances of this class are WSGI applications.
"""
def __init__(self, applications, catch=(404,)):
self.apps = applications
self.catch_codes = {}
self.catch_exceptions = []
for error in catch:
if isinstance(error, str):
error = int(error.split(None, 1)[0])
if isinstance(error, httpexceptions.HTTPException):
exc = error
code = error.code
else:
exc = httpexceptions.get_exception(error)
code = error
self.catch_codes[code] = exc
self.catch_exceptions.append(exc)
self.catch_exceptions = tuple(self.catch_exceptions)
def __call__(self, environ, start_response):
"""
WSGI application interface
"""
failed = []
def repl_start_response(status, headers, exc_info=None):
code = int(status.split(None, 1)[0])
if code in self.catch_codes:
failed.append(None)
return _consuming_writer
return start_response(status, headers, exc_info)
try:
length = int(environ.get('CONTENT_LENGTH', 0) or 0)
except ValueError:
length = 0
if length > 0:
# We have to copy wsgi.input
copy_wsgi_input = True
if length > 4096 or length < 0:
f = tempfile.TemporaryFile()
if length < 0:
f.write(environ['wsgi.input'].read())
else:
copy_len = length
while copy_len > 0:
chunk = environ['wsgi.input'].read(min(copy_len, 4096))
if not chunk:
raise IOError("Request body truncated")
f.write(chunk)
copy_len -= len(chunk)
f.seek(0)
else:
f = StringIO(environ['wsgi.input'].read(length))
environ['wsgi.input'] = f
else:
copy_wsgi_input = False
for app in self.apps[:-1]:
environ_copy = environ.copy()
if copy_wsgi_input:
environ_copy['wsgi.input'].seek(0)
failed = []
try:
v = app(environ_copy, repl_start_response)
if not failed:
return v
else:
if hasattr(v, 'close'):
# Exhaust the iterator first:
list(v)
# then close:
v.close()
except self.catch_exceptions, e:
pass
if copy_wsgi_input:
environ['wsgi.input'].seek(0)
return self.apps[-1](environ, start_response)
def _consuming_writer(s):
pass
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