sync errors

uploader.py

@@ -1,6 +1,7 @@
 import hashlib
 import logging
 import re
+import time
 from pathlib import Path
 from urllib.parse import quote
 
@@ -101,20 +102,37 @@ class CalibreClient:
                 return "skipped_duplicate"
 
             mime = MIME_TYPES.get(book_path.suffix.lower(), "application/octet-stream")
-            with book_path.open("rb") as fh:
-                resp = self._session.post(
-                    f"{self._cfg.url}/upload",
-                    files={"btn-upload": (book_path.name, fh, mime)},
-                    data={"csrf_token": self._upload_csrf} if self._upload_csrf else {},
-                    timeout=120,
-                )
-            if not resp.ok:
-                log.error("Upload HTTP %s — body: %s", resp.status_code, resp.text[:300])
-            resp.raise_for_status()
-            log.info("Uploaded: %s", book_path.name)
-            db.record_book(book_path.name, file_hash, zip_source, "uploaded")
-            return "uploaded"
-        except requests.HTTPError:
+            last_err: Exception | None = None
+            for attempt in range(1, 4):
+                try:
+                    with book_path.open("rb") as fh:
+                        resp = self._session.post(
+                            f"{self._cfg.url}/upload",
+                            files={"btn-upload": (book_path.name, fh, mime)},
+                            data={"csrf_token": self._upload_csrf} if self._upload_csrf else {},
+                            timeout=120,
+                        )
+                    if not resp.ok:
+                        log.error("Upload HTTP %s (attempt %d/3) — body: %s", resp.status_code, attempt, resp.text[:300])
+                    resp.raise_for_status()
+                    log.info("Uploaded: %s", book_path.name)
+                    db.record_book(book_path.name, file_hash, zip_source, "uploaded")
+                    return "uploaded"
+                except requests.HTTPError as e:
+                    last_err = e
+                    if resp.status_code in (502, 503, 504) and attempt < 3:
+                        delay = 1 if attempt == 1 else 3
+                        log.warning("HTTP %s on attempt %d/3 — retrying in %ds ...", resp.status_code, attempt, delay)
+                        time.sleep(delay)
+                        continue
+                    if resp.status_code == 400 and attempt == 1:
+                        log.warning("HTTP 400 — CSRF token likely expired, re-authenticating ...")
+                        self._authenticated = False
+                        self._upload_csrf = None
+                        self._ensure_auth()
+                        continue
+                    break
+
             db.record_book(book_path.name, file_hash, zip_source, "error")
             return "error"
         except Exception as e: