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#!/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 http.server
import os
import socket
from datetime import datetime
import requests
from contextlib import closing, contextmanager
import fcntl
addr = ('', 8001)
cache_dir = os.getcwd()
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 RequestHandler(http.server.BaseHTTPRequestHandler):
def send_ok(self, size, headers={}, cached=False):
self.log_message('"%s" %d %s %s', self.requestline, 200, size,
"HIT" if cached else "MISS")
self.send_response_only(200)
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):
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)
if not head_only:
yield from r.iter_content(4096)
@contextmanager
def open_write_cache(self, path):
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 request_data_with_cache(self, head_only=False):
if not self.is_cacheable():
# Not cacheable, directly obtain data and bypass cache
yield from self.request_data()
return
path = self.get_local_path()
try:
# Try to open cached file and yield data from it
self.send_ok(os.path.getsize(path),
{'Last-Modified': epoch_to_text(os.stat(path).st_mtime)},
cached=True)
if not head_only:
with open(path, 'rb') as f:
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)
if head_only:
list(remote_data) # consume yield and StopIteration
if not head_only and remote_data:
with self.open_write_cache(path) as cache_file:
if cache_file:
for chunk in remote_data:
cache_file.write(chunk)
yield chunk
else:
# Cache file unavailable, just pass all data
yield from remote_data
return
# Write was successful, now fix mtime and rename
self.finish_cache(mtime_pointer[0])
def do_GET(self):
try:
data = self.request_data_with_cache()
if data:
for chunk in data:
self.wfile.write(chunk)
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 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(cache_dir, 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):
self.allow_reuse_address = True
if ':' in addr[0]:
self.address_family = socket.AF_INET6
super().__init__(addr, handler)
if __name__ == '__main__':
server = SomeServer(addr, RequestHandler)
server.serve_forever()
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