1 files changed, 105 insertions, 0 deletions
diff --git a/taskcluster/docker/debian-raw/snapshot-hack.py b/taskcluster/docker/debian-raw/snapshot-hack.py
new file mode 100755
index 0000000000..6e880f0a74
--- /dev/null
+++ b/taskcluster/docker/debian-raw/snapshot-hack.py
@@ -0,0 +1,105 @@
+#!/usr/bin/python3
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import subprocess
+import sys
+import threading
+import urllib.request
+from urllib.parse import urlparse, urlunparse
+
+# This script interposes between APT and its HTTP method. APT sends queries on
+# stdin, and expect responses on stdout. We intercept those and change the
+# snapshot.debian.org URLs it requests on the fly, if the equivalent URLs
+# exist on deb.debian.org.
+
+URI_HEADER = "URI: "
+
+
+def url_exists(url):
+    try:
+        req = urllib.request.Request(url, method="HEAD")
+        response = urllib.request.urlopen(req)
+        return response.getcode() == 200
+    except Exception:
+        return False
+
+
+def write_and_flush(fh, data):
+    fh.write(data)
+    fh.flush()
+
+
+def output_handler(proc, url_mapping, lock):
+    for line in proc.stdout:
+        if line.startswith(URI_HEADER):
+            url = line[len(URI_HEADER) :].rstrip()
+            # APT expects back the original url it requested.
+            with lock:
+                original_url = url_mapping.get(url, None)
+            if original_url:
+                write_and_flush(sys.stdout, line.replace(url, original_url))
+                continue
+        write_and_flush(sys.stdout, line)
+
+
+def main():
+    proc = subprocess.Popen(
+        ["/usr/lib/apt/methods/http"],
+        stdin=subprocess.PIPE,
+        stdout=subprocess.PIPE,
+        text=True,
+    )
+    url_mapping = {}
+    lock = threading.Lock()
+    output_thread = threading.Thread(
+        target=output_handler, args=(proc, url_mapping, lock), daemon=True
+    )
+    output_thread.start()
+
+    while True:
+        try:
+            line = sys.stdin.readline()
+        except KeyboardInterrupt:
+            # When apt cuts the connection, we receive a KeyboardInterrupt.
+            break
+        if not line:
+            break
+
+        if line.startswith(URI_HEADER):
+            url = line[len(URI_HEADER) :].rstrip()
+            url_parts = urlparse(url)
+            # For .deb packages, if we can find the file on deb.debian.org, take it
+            # from there instead of snapshot.debian.org, because deb.debian.org will
+            # be much faster. Hopefully, most files will be available on deb.debian.org.
+            if url_parts.hostname == "snapshot.debian.org" and url_parts.path.endswith(
+                ".deb"
+            ):
+                # The url is assumed to be of the form
+                # http://snapshot.debian.org/archive/section/yymmddThhmmssZ/...
+                path_parts = url_parts.path.split("/")
+                # urlparse().path always starts with a / so path_parts is
+                # expected to look like ["", "archive", "section", "yymmddThhmmssZ", ...]
+                # we want to remove "archive" and "yymmddThhmmssZ" to create an url
+                # on deb.debian.org.
+                path_parts.pop(3)
+                path_parts.pop(1)
+                modified_url = urlunparse(
+                    url_parts._replace(
+                        netloc="deb.debian.org", path="/".join(path_parts)
+                    )
+                )
+                if url_exists(modified_url):
+                    with lock:
+                        url_mapping[modified_url] = url
+                    write_and_flush(proc.stdin, line.replace(url, modified_url))
+                    continue
+        write_and_flush(proc.stdin, line)
+
+    proc.stdin.close()
+    output_thread.join()
+
+
+if __name__ == "__main__":
+    main()