better catch errors in qr code generation

Author: maede97

backend/automatic_walk_time_tables/map_downloader/create_map.py

@@ -335,23 +335,35 @@ def create_mapfish_query(
             point_layers.append(point_layer)
 
         qr_code_string = build_qr_code_image_string(self.uuid)
+        if not qr_code_string:
+            # try 3 times more
+            for _ in range(3):
+                time.sleep(0.5)
+                qr_code_string = build_qr_code_image_string(self.uuid)
+                if qr_code_string:
+                    break
+
+        attributes = {
+            "scale": "Massstab: 1:" + f"{map_scaling:,}".replace(",", "'"),
+            "map": {
+                "center": center,
+                "scale": map_scaling,
+                "dpi": 250,
+                "pdfA": True,
+                "projection": "EPSG:2056",
+                "rotation": 0,
+                "layers": point_layers + ([path_layer] + map_layers),
+            },
+        }
+
+        # Only include qr_code when we actually received a valid QR image
+        if qr_code_string:
+            attributes["qr_code"] = qr_code_string
 
         query_json = {
             "layout": "A4 landscape",
             "outputFormat": "pdf",
-            "attributes": {
-                "scale": "Massstab: 1:" + f"{map_scaling:,}".replace(",", "'"),
-                "qr_code": qr_code_string,
-                "map": {
-                    "center": center,
-                    "scale": map_scaling,
-                    "dpi": 250,
-                    "pdfA": True,
-                    "projection": "EPSG:2056",
-                    "rotation": 0,
-                    "layers": point_layers + ([path_layer] + map_layers),
-                },
-            },
+            "attributes": attributes,
         }
 
         return query_json

backend/automatic_walk_time_tables/utils/qr.py

@@ -1,20 +1,55 @@
 import requests
 import os
 import base64
+import logging
+from http.client import IncompleteRead
 
 
 def build_qr_code_image_string(uuid, raw: bool = False):
     backend_domain = os.environ["BACKEND_DOMAIN"]
     clear_url = f"{backend_domain}/gpx/{uuid}.gpx"
     b64_url = base64.b64encode(clear_url.encode("ascii")).decode("ascii")
     final_url = "https://swisstopo.app/u/" + b64_url
-    r = requests.post(
-        "https://backend.qr.cevi.tools/png",
-        json={"text": final_url},
-    )
+    try:
+        r = requests.post(
+            "https://backend.qr.cevi.tools/png",
+            json={"text": final_url},
+        )
+    except requests.exceptions.RequestException:
+        logging.exception("Failed to request QR backend for UUID=%s URL=%s", uuid, "https://backend.qr.cevi.tools/png")
+        return ""
+    except IncompleteRead:
+        logging.exception("IncompleteRead while requesting QR backend for UUID=%s", uuid)
+        return ""
+
+    def _is_image(content: bytes, content_type: str | None) -> bool:
+        if not content:
+            return False
+        if content_type and content_type.startswith("image/"):
+            return True
+        # Check common magic bytes for PNG, JPEG, GIF
+        if content.startswith(b"\x89PNG\r\n\x1a\n"):
+            return True
+        if content.startswith(b"\xff\xd8\xff"):
+            return True
+        if content[:6] in (b"GIF87a", b"GIF89a"):
+            return True
+        return False
+
     if r.status_code == 200:
         qr_code_bytes = r.content
 
+        content_type = r.headers.get("Content-Type") if hasattr(r, "headers") else None
+
+        if not _is_image(qr_code_bytes, content_type):
+            logging.debug(
+                "QR backend returned non-image content for UUID=%s content_type=%s content_len=%s",
+                uuid,
+                content_type,
+                len(qr_code_bytes) if qr_code_bytes is not None else 0,
+            )
+            return ""
+
         if raw:
             # if raw, only return the qr code image bytes
             return qr_code_bytes
@@ -30,4 +65,5 @@ def build_qr_code_image_string(uuid, raw: bool = False):
             return data_url
 
     else:
-        return ""  # TODO: does this work?
+        logging.debug("QR backend returned status %s for UUID=%s", r.status_code, uuid)
+        return ""  # no QR code