ELO scraper: discover the embed link and retry transient failures

Read the current OneDrive link from the stat-check.com/elo iframe on
each run, falling back to EMBED_URL if the page can't be read or its
link 404s. Retry 429/5xx and network errors up to three times with
backoff, after a one-off 503 from the Badger token endpoint failed a run.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

sites/40k-rankings/statcheck-elo-scraper/README.md

@@ -12,6 +12,7 @@ The Stat Check page embeds a public OneDrive Excel workbook through a `1drv.ms`
 
 The scraper reproduces the useful part of that flow:
 
+0. Read the current `1drv.ms` embed link from the Stat Check page's iframe. Stat Check replaces this link occasionally, so it is looked up on every run; `EMBED_URL` in `pure_python_elo_scrape.py` is only a fallback for when the page can't be read or its link returns 404.
 1. Request an anonymous Microsoft "Badger" token from:
    `https://api-badgerp.svc.ms/v1.0/token`
 2. Convert the public OneDrive embed URL into Microsoft Graph's `shares/u!...` id format.
@@ -24,6 +25,8 @@ The scraper reproduces the useful part of that flow:
 
 The Microsoft endpoints used here are undocumented and could change, but this currently works without browser automation.
 
+Requests that fail with HTTP 429, a 5xx status, or a network error are retried up to three times (after 5, 15 and 45 seconds).
+
 ## Usage
 
 ```bash

sites/40k-rankings/statcheck-elo-scraper/download_and_parse.py

@@ -4,8 +4,10 @@ import html
 import json
 import re
 import sys
+import time
 import zipfile
 from pathlib import Path
+from urllib.error import HTTPError, URLError
 from urllib.request import Request, urlopen
 from xml.etree.ElementTree import iterparse
 
@@ -16,6 +18,27 @@ NS = {
     "pkgrel": "http://schemas.openxmlformats.org/package/2006/relationships",
 }
 
+# Seconds to wait before each retry of a transient failure.
+RETRY_DELAYS = (5, 15, 45)
+
+
+def fetch(req: Request) -> bytes:
+    """Read a URL, retrying 429/5xx responses and network errors."""
+    for attempt, delay in enumerate((*RETRY_DELAYS, None), start=1):
+        try:
+            with urlopen(req, timeout=60) as resp:
+                return resp.read()
+        except HTTPError as e:
+            if delay is None or not (e.code == 429 or e.code >= 500):
+                raise
+            reason = f"HTTP {e.code}"
+        except (URLError, TimeoutError, ConnectionError) as e:
+            if delay is None:
+                raise
+            reason = str(e)
+        print(f"  {req.full_url.split('?')[0]}: {reason}; retry {attempt} in {delay}s", file=sys.stderr)
+        time.sleep(delay)
+
 
 def metadata_download_url(capture_path: Path) -> str:
     capture = json.loads(capture_path.read_text())
@@ -29,8 +52,7 @@ def metadata_download_url(capture_path: Path) -> str:
 
 def download(url: str, output: Path) -> None:
     req = Request(url, headers={"User-Agent": "Mozilla/5.0"})
-    with urlopen(req, timeout=60) as resp:
-        output.write_bytes(resp.read())
+    output.write_bytes(fetch(req))
 
 
 def shared_strings(zf: zipfile.ZipFile) -> list[str]:

sites/40k-rankings/statcheck-elo-scraper/pure_python_elo_scrape.py

@@ -1,14 +1,22 @@
 #!/usr/bin/env python3
 import base64
+import html
 import json
+import re
 import sys
 from pathlib import Path
+from urllib.error import HTTPError
 from urllib.parse import quote
-from urllib.request import Request, urlopen
+from urllib.request import Request
 
-from download_and_parse import download, xlsx_to_csv
+from download_and_parse import download, fetch, xlsx_to_csv
 
 
+STATCHECK_PAGE_URL = "https://www.stat-check.com/elo"
+IFRAME_SRC_RE = re.compile(r'<iframe[^>]+src="(https://1drv\.ms/x/[^"]+)"', re.I)
+
+# Fallback for when the link can't be read from the Stat Check page. Stat Check
+# replaces the share link from time to time, so this can go stale.
 EMBED_URL = (
     "https://1drv.ms/x/c/9f33f29504402fa1/"
     "IQSM-tN0M6OcTaaLY3OtMA2vAYx131Ze6y5N0aHYpoCCJ1g"
@@ -21,8 +29,16 @@ BADGER_APP_ID = "00000000-0000-0000-0000-0000481710a4"
 
 def request_json(url: str, *, method: str = "GET", data: bytes | None = None, headers: dict[str, str] | None = None) -> dict:
     req = Request(url, data=data, method=method, headers=headers or {})
-    with urlopen(req, timeout=60) as resp:
-        return json.loads(resp.read().decode("utf-8"))
+    return json.loads(fetch(req).decode("utf-8"))
+
+
+def discover_embed_url(page_url: str = STATCHECK_PAGE_URL) -> str:
+    req = Request(page_url, headers={"User-Agent": "Mozilla/5.0"})
+    page = fetch(req).decode("utf-8", errors="replace")
+    match = IFRAME_SRC_RE.search(page)
+    if not match:
+        raise RuntimeError(f"No OneDrive workbook iframe found on {page_url}")
+    return html.unescape(match.group(1))
 
 
 def badger_token() -> str:
@@ -73,10 +89,31 @@ def download_url_for_embed(embed_url: str) -> str:
     return data["@content.downloadUrl"]
 
 
+def resolve_download_url() -> str:
+    """Resolve the workbook download URL, preferring the link currently on the Stat Check page."""
+    try:
+        embed_url = discover_embed_url()
+    except Exception as e:
+        print(f"  Could not read link from {STATCHECK_PAGE_URL} ({e}); using fallback EMBED_URL", file=sys.stderr)
+        return download_url_for_embed(EMBED_URL)
+
+    print(f"  Using link from {STATCHECK_PAGE_URL}: {embed_url}")
+    if embed_url == EMBED_URL:
+        return download_url_for_embed(embed_url)
+    print("  (differs from EMBED_URL; consider updating the fallback)", file=sys.stderr)
+    try:
+        return download_url_for_embed(embed_url)
+    except HTTPError as e:
+        if e.code != 404:
+            raise
+        print("  Page link returned 404; trying fallback EMBED_URL", file=sys.stderr)
+        return download_url_for_embed(EMBED_URL)
+
+
 def main() -> None:
     xlsx_path = Path(sys.argv[1] if len(sys.argv) > 1 else "elo-pure.xlsx")
     csv_path = Path(sys.argv[2] if len(sys.argv) > 2 else "elo-pure.csv")
-    url = download_url_for_embed(EMBED_URL)
+    url = resolve_download_url()
     download(url, xlsx_path)
     xlsx_to_csv(xlsx_path, csv_path)
     print(f"downloaded={xlsx_path.stat().st_size} bytes csv={csv_path.stat().st_size} bytes")

sites/40k-rankings/statcheck-elo-scraper/refresh_elo.py

@@ -11,7 +11,7 @@ from datetime import datetime, timezone
 from pathlib import Path
 
 from download_and_parse import download, xlsx_to_csv
-from pure_python_elo_scrape import EMBED_URL, download_url_for_embed
+from pure_python_elo_scrape import resolve_download_url
 
 HERE = Path(__file__).parent
 ROOT = HERE.parent
@@ -46,7 +46,7 @@ def main() -> None:
     json_path = Path(sys.argv[3]) if len(sys.argv) > 3 else ROOT / "public" / "elo-data.json"
 
     print("Resolving OneDrive download URL…")
-    url = download_url_for_embed(EMBED_URL)
+    url = resolve_download_url()
 
     print("Downloading XLSX…")
     download(url, xlsx_path)