Added retry middleware to aiohttp musl requests

I have been notified by @guyush1 that the website is unstable, so we
retry the download 5 times.

Author: roddyrap

Dockerfile

@@ -25,12 +25,16 @@ RUN apt update && apt install -y \
     patch \
     pkg-config \
     python3.12 \
-    python3-aiohttp \
+    python3-pip \
     libpython3-dev \
     texinfo \
     wget \
     xz-utils
 
+# We require aiohttp >= 3.12 (For client middleware support), which is newer than the currently
+# available python3-aiohttp's version in Ubuntu.
+RUN python3.12 -m pip install --break-system-packages aiohttp
+
 COPY src/docker_utils/download_musl_toolchains.py .
 RUN python3.12 -u download_musl_toolchains.py
 

src/docker_utils/download_musl_toolchains.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3.12
 
-from typing import List
 from pathlib import Path
+from typing import List
 
 import tarfile
 import tempfile
@@ -23,9 +23,24 @@
 MUSL_TOOLCHAINS_DIR = Path("/musl-toolchains")
 ENTRYPOINT = Path("/entrypoint.sh")
 
+NUM_RETRIES = 5
+RETRY_WAIT = 2
+
+# Basically copied from aiohttp docs: Simple Retry Middleware
+async def retry_middleware(req: aiohttp.ClientRequest, handler: aiohttp.ClientHandlerType) -> aiohttp.ClientResponse:
+    for _ in range(NUM_RETRIES):
+        resp = await handler(req)
+        if resp.ok:
+            return resp
+
+        await asyncio.sleep(RETRY_WAIT)
+
+    return resp
+
 async def download_file(url: str, filename: str):
-    async with aiohttp.ClientSession() as session:
+    async with aiohttp.ClientSession(middlewares=(retry_middleware,)) as session:
         async with session.get(url) as response:
+            response.raise_for_status()
             with open(filename, 'wb') as f:
                 async for data in response.content.iter_chunked(CHUNK_SIZE):
                     f.write(data)