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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
|
#!/usr/bin/env python3
# Arch Linux packages proxy
#
# Proxies requests, caching files with ".pkg.tar.xz" suffix.
# If the cached file exists, serve that file.
# Otherwise, try to download file (as normally) and optionally cache it with
# ".download" extension. If the file exists and the file is not being
# downloaded, resume the download (Range requests).
import argparse
import http.server
import os
import re
import socket
from datetime import datetime
import requests
from contextlib import closing, contextmanager
import fcntl
DATE_FORMAT = '%a, %d %b %Y %H:%M:%S GMT'
def text_to_epoch(text):
return datetime.strptime(text, DATE_FORMAT).timestamp()
def epoch_to_text(epoch):
return datetime.fromtimestamp(epoch).strftime(DATE_FORMAT)
class BadRequest(Exception):
pass
class RequestHandler(http.server.BaseHTTPRequestHandler):
def send_ok(self, size, headers={}, cached=False, range_offset=None):
if range_offset is None:
code = 200
else:
if range_offset >= size:
# TODO need different status code
raise BadRequest("416 Requested Range Not Satisfiable")
code = 206
content_range = "bytes %d-%d/%d" % (range_offset, size - 1, size)
headers["Content-Range"] = content_range
size -= range_offset
self.log_message('"%s" %d %s %s', self.requestline, code, size,
"HIT" if cached else "MISS")
self.send_response_only(code)
self.send_header('Content-Length', size)
for k, v in headers.items():
self.send_header(k, v)
self.end_headers()
def request_data(self, head_only=False, mtime_out=None, range_offset=None):
method = "HEAD" if head_only else "GET"
url = self.get_upstream_url()
with closing(requests.request(method, url, stream=not head_only)) as r:
if r.status_code != 200:
self.log_request(r.status_code)
self.send_response_only(r.status_code)
self.end_headers()
return
response_headers = {}
if 'Last-Modified' in r.headers:
try:
mtime = text_to_epoch(r.headers['Last-Modified'])
response_headers['Last-Modified'] = epoch_to_text(mtime)
if mtime_out:
mtime_out[0] = mtime
except ValueError:
self.log_error("Unable to parse Last-Modified header")
self.send_ok(int(r.headers['Content-Length']), response_headers,
range_offset=range_offset)
if not head_only:
yield from r.iter_content(4096)
@contextmanager
def open_write_cache(self, path):
if self.server.is_readonly:
yield None
return
temp_path = path + ".download"
try:
with open(temp_path, 'wb') as f:
# Prevent concurrent writers
fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
yield f
except OSError as e:
self.log_error("Failed to create cache file %s: %s", temp_path, e)
yield None
def finish_cache(self, mtime):
path = self.get_local_path()
temp_path = path + ".download"
if mtime:
os.utime(temp_path, times=(mtime, mtime))
try:
os.rename(temp_path, path)
except OSError as e:
self.log_error("Failed to rename %s", temp_path)
try:
os.unlink(temp_path)
except OSError as e:
self.log_error("Failed to remove %s", temp_path)
def parse_range(self):
value = self.headers.get('Range')
if value is not None:
# Only support "continue" range requests, resuming previous
# download. Anything more complex is not needed at the moment.
m = re.match(r'bytes=(?P<from>\d+)-$', value)
if not m:
raise BadRequest("Unsupported range request: %s" % value)
return int(m.group("from"))
@staticmethod
def skip_range_chunk(chunk, skip_bytes):
if skip_bytes:
chunksize = len(chunk)
if chunksize > skip_bytes:
chunk = chunk[skip_bytes:]
skip_bytes = None
else:
chunk = b''
skip_bytes -= chunksize
return chunk, (skip_bytes or None)
@classmethod
def skip_range(cls, it, skip_bytes):
for chunk in it:
chunk, skip_bytes = cls.skip_range_chunk(chunk, skip_bytes)
if chunk:
yield chunk
def request_data_with_cache(self, head_only=False):
range_offset = self.parse_range()
if not self.is_cacheable():
# Not cacheable, directly obtain data and bypass cache
remote_data = self.request_data(range_offset=range_offset)
yield from self.skip_range(remote_data, range_offset)
return
path = self.get_local_path()
try:
# Try to open cached file and yield data from it
stat_info = os.stat(path)
response_headers = {'Last-Modified':
epoch_to_text(stat_info.st_mtime)}
self.send_ok(stat_info.st_size, response_headers, cached=True,
range_offset=range_offset)
if not head_only:
with open(path, 'rb') as f:
if range_offset:
f.seek(range_offset)
yield from f
except FileNotFoundError:
# File does not exist, so try to pipe upstream
# (optionally writing to cache file)
mtime_pointer = [None]
remote_data = self.request_data(head_only=head_only,
mtime_out=mtime_pointer, range_offset=range_offset)
if head_only:
list(remote_data) # consume yield and StopIteration
if not head_only and remote_data:
cache_ok = False
with self.open_write_cache(path) as cache_file:
cache_ok = cache_file is not None
if cache_ok:
skip = range_offset
for chunk in remote_data:
cache_file.write(chunk)
chunk, skip = self.skip_range_chunk(chunk, skip)
if chunk:
yield chunk
if cache_ok:
# Write was successful, now fix mtime and rename
self.finish_cache(mtime_pointer[0])
else:
# Cache file unavailable, just pass all data
yield from self.skip_range(remote_data, range_offset)
def do_GET(self):
try:
data = self.request_data_with_cache()
if data:
for chunk in data:
self.wfile.write(chunk)
except BadRequest as e:
self.log_error("GET %s - Bad Request: %s", self.path, e)
self.send_response(400)
except Exception as e:
self.log_error("GET %s failed: %s", self.path, e)
import traceback; traceback.print_exc()
self.send_response(502)
def do_HEAD(self):
try:
list(self.request_data_with_cache(True))
except BadRequest as e:
self.log_error("GET %s - Bad Request: %s", self.path, e)
self.send_response(400)
except Exception as e:
self.log_error("HEAD %s failed: %s", self.path, e)
import traceback; traceback.print_exc()
self.send_response(502)
def get_upstream_url(self):
prefix = "http://mirror.nl.leaseweb.net/archlinux/"
return prefix + self.path
def get_local_path(self):
filename = os.path.basename(self.path)
return os.path.join(self.server.cachedir, filename)
def is_cacheable(self):
"""Whether the requested file should be cached."""
return self.path.endswith(".pkg.tar.xz")
class SomeServer(http.server.HTTPServer):
def __init__(self, addr, handler, args):
self.allow_reuse_address = True
if ':' in addr[0]:
self.address_family = socket.AF_INET6
super().__init__(addr, handler)
self.cachedir = args.cachedir
self.is_readonly = args.readonly
parser = argparse.ArgumentParser()
parser.add_argument("--readonly", action="store_true")
parser.add_argument("--cachedir", default=os.getcwd())
parser.add_argument("--port", type=int, default=8001)
if __name__ == '__main__':
args = parser.parse_args()
addr = ('', args.port)
server = SomeServer(addr, RequestHandler, args)
server.serve_forever()
|
