fix: release cooldown on pre-request failures

rf4_research/community_cli.py

@@ -138,7 +138,7 @@ def mark_fetch(source: str, *, state_file: Path, now: float | None = None) -> No
 
 def check_and_reserve(
     source: str, *, state_file: Path, now: float | None = None,
-) -> None:
+) -> float:
     """A02: Atomic check-and-reserve under a single exclusive lock.
 
     Opens state file with exclusive lock, reads state, checks cooldown,
@@ -183,6 +183,36 @@ def check_and_reserve(
                 sf.flush()
                 os.fsync(sf.fileno())
             temp_file.replace(state_file)
+            return now
+        finally:
+            fcntl.flock(lf, fcntl.LOCK_UN)
+
+
+def release_reservation(source: str, *, state_file: Path, reserved_at: float) -> bool:
+    """Release only the reservation created by this attempt.
+
+    A local failure before an HTTP response must not consume the site window.
+    The timestamp comparison prevents an older process from deleting a newer
+    reservation made after its own attempt was superseded.
+    """
+    state_file.parent.mkdir(parents=True, exist_ok=True)
+    lock_file = state_file.with_suffix(".lock")
+    lock_file.touch(exist_ok=True)
+    with open(lock_file, "w") as lf:
+        fcntl.flock(lf, fcntl.LOCK_EX)
+        try:
+            state = _read_state(state_file)
+            current = state.get(source)
+            if not isinstance(current, (int, float)) or current != reserved_at:
+                return False
+            state.pop(source, None)
+            temp_file = state_file.with_suffix(".tmp")
+            with open(temp_file, "w") as sf:
+                sf.write(json.dumps(state, sort_keys=True))
+                sf.flush()
+                os.fsync(sf.fileno())
+            temp_file.replace(state_file)
+            return True
         finally:
             fcntl.flock(lf, fcntl.LOCK_UN)
 
@@ -321,9 +351,18 @@ def main(argv: list[str] | None = None) -> int:
         "--reserve-only", action="store_true",
         help="Reserve the shared site cooldown and stop before making an HTTP request",
     )
+    parser.add_argument(
+        "--release-reservation", action="store_true",
+        help="Release a reservation that failed before reaching the source",
+    )
+    parser.add_argument("--reserved-at", type=float, help="Timestamp returned by --reserve-only")
     args = parser.parse_args(argv)
     if args.html and args.reserve_only:
         parser.error("--html cannot be combined with --reserve-only")
+    if args.release_reservation and args.reserved_at is None:
+        parser.error("--release-reservation requires --reserved-at")
+    if args.release_reservation and args.html:
+        parser.error("--release-reservation cannot be combined with --html")
     if args.source in DETAIL_SOURCES and not args.url:
         parser.error(f"--url is required for {args.source}")
     default_url, parse = SOURCES.get(args.source, (None, DETAIL_SOURCES.get(args.source)))
@@ -333,12 +372,20 @@ def main(argv: list[str] | None = None) -> int:
             html = args.html.read_text(encoding="utf-8")
         else:
             site_key = fetch_site_key(url)
-            # Single atomic check-and-reserve before network I/O: failed attempts count toward the limit too.
-            check_and_reserve(site_key, state_file=args.state_file)
-            if args.reserve_only:
-                print(json.dumps({"reserved": True, "source": args.source, "site_key": site_key}, ensure_ascii=False))
+            if args.release_reservation:
+                released = release_reservation(site_key, state_file=args.state_file, reserved_at=args.reserved_at)
+                print(json.dumps({"released": released, "source": args.source, "site_key": site_key}, ensure_ascii=False))
                 return 0
-            html = fetch_html(url)
+            reserved_at = check_and_reserve(site_key, state_file=args.state_file)
+            if args.reserve_only:
+                print(json.dumps({"reserved": True, "reserved_at": reserved_at, "source": args.source, "site_key": site_key}, ensure_ascii=False))
+                return 0
+            try:
+                html = fetch_html(url)
+            except urllib.error.URLError as exc:
+                if not isinstance(exc, urllib.error.HTTPError):
+                    release_reservation(site_key, state_file=args.state_file, reserved_at=reserved_at)
+                raise
         parsed = (
             parse(html, source_url=url)
             if args.source in DETAIL_SOURCES or args.source == "rf4db-waterbodies"