Merge pull request #227 from DHI-GRAS/flask-error-handlers

Use Flask error handlers instead of decorators (#74)

terracotta/server/colormap.py

@@ -9,7 +9,7 @@
 from flask import jsonify, request, Response
 from marshmallow import Schema, fields, validate, pre_load, ValidationError, EXCLUDE
 
-from terracotta.server.flask_api import convert_exceptions, METADATA_API
+from terracotta.server.flask_api import METADATA_API
 from terracotta.cmaps import AVAILABLE_CMAPS
 
 
@@ -52,7 +52,6 @@ def process_ranges(self, data: Mapping[str, Any], **kwargs: Any) -> Dict[str, An
 
 
 @METADATA_API.route('/colormap', methods=['GET'])
-@convert_exceptions
 def get_colormap() -> Response:
     """Get a colormap mapping pixel values to colors
     ---

terracotta/server/compute.py

@@ -10,7 +10,7 @@
                          pre_load, ValidationError, EXCLUDE)
 from flask import request, send_file, Response
 
-from terracotta.server.flask_api import convert_exceptions, TILE_API
+from terracotta.server.flask_api import TILE_API
 from terracotta.cmaps import AVAILABLE_CMAPS
 
 
@@ -75,7 +75,6 @@ def decode_json(self, data: Mapping[str, Any], **kwargs: Any) -> Dict[str, Any]:
 @TILE_API.route('/compute/<int:tile_z>/<int:tile_x>/<int:tile_y>.png', methods=['GET'])
 @TILE_API.route('/compute/<path:keys>/<int:tile_z>/<int:tile_x>/<int:tile_y>.png',
                 methods=['GET'])
-@convert_exceptions
 def get_compute(tile_z: int, tile_y: int, tile_x: int, keys: str = '') -> Response:
     """Combine datasets into a single-band PNG image through a given mathematical expression
     ---
@@ -109,7 +108,6 @@ class ComputePreviewSchema(Schema):
 
 @TILE_API.route('/compute/preview.png', methods=['GET'])
 @TILE_API.route('/compute/<path:keys>/preview.png', methods=['GET'])
-@convert_exceptions
 def get_compute_preview(keys: str = '') -> Response:
     """Combine datasets into a single-band PNG image through a given mathematical expression
     ---

terracotta/server/datasets.py

@@ -6,7 +6,7 @@
 from flask import request, jsonify, Response
 from marshmallow import Schema, fields, validate, INCLUDE
 
-from terracotta.server.flask_api import convert_exceptions, METADATA_API
+from terracotta.server.flask_api import METADATA_API
 
 
 class DatasetOptionSchema(Schema):
@@ -42,7 +42,6 @@ class Meta:
 
 
 @METADATA_API.route('/datasets', methods=['GET'])
-@convert_exceptions
 def get_datasets() -> Response:
     """Get all available key combinations
     ---

terracotta/server/flask_api.py

@@ -1,5 +1,4 @@
-from typing import Callable, Any
-import functools
+from typing import Any
 import copy
 
 from apispec import APISpec
@@ -34,40 +33,35 @@
 )
 
 
-def abort(status_code: int, message: str = '') -> Any:
+def _abort(status_code: int, message: str = '') -> Any:
     response = jsonify({'message': message})
     response.status_code = status_code
     return response
 
 
-def convert_exceptions(fun: Callable) -> Callable:
-    """Converts internal exceptions to appropriate HTTP responses"""
+def _setup_error_handlers(app: Flask) -> None:
+    @app.errorhandler(exceptions.TileOutOfBoundsError)
+    def handle_tile_out_of_bounds_error(exc: Exception) -> Any:
+        # send empty image
+        from terracotta import get_settings, image
+        settings = get_settings()
+        return send_file(image.empty_image(settings.DEFAULT_TILE_SIZE), mimetype='image/png')
 
-    @functools.wraps(fun)
-    def inner(*args: Any, **kwargs: Any) -> Any:
-        try:
-            return fun(*args, **kwargs)
+    @app.errorhandler(exceptions.DatasetNotFoundError)
+    def handle_dataset_not_found_error(exc: Exception) -> Any:
+        # wrong path -> 404
+        if current_app.debug:
+            raise exc
+        return _abort(404, str(exc))
 
-        except exceptions.TileOutOfBoundsError:
-            # send empty image
-            from terracotta import get_settings, image
-            settings = get_settings()
-            return send_file(image.empty_image(settings.DEFAULT_TILE_SIZE), mimetype='image/png')
-
-        except exceptions.DatasetNotFoundError as exc:
-            # wrong path -> 404
-            if current_app.debug:
-                raise
-            return abort(404, str(exc))
-
-        except (exceptions.InvalidArgumentsError, exceptions.InvalidKeyError,
-                marshmallow.ValidationError) as exc:
-            # wrong query arguments -> 400
-            if current_app.debug:
-                raise
-            return abort(400, str(exc))
-
-    return inner
+    @app.errorhandler(exceptions.InvalidArgumentsError)
+    @app.errorhandler(exceptions.InvalidKeyError)
+    @app.errorhandler(marshmallow.ValidationError)
+    def handle_marshmallow_validation_error(exc: Exception) -> Any:
+        # wrong query arguments -> 400
+        if current_app.debug:
+            raise exc
+        return _abort(400, str(exc))
 
 
 def create_app(debug: bool = False, profile: bool = False) -> Flask:
@@ -124,4 +118,6 @@ def create_app(debug: bool = False, profile: bool = False) -> Flask:
             ProfilerMiddleware(new_app.wsgi_app, restrictions=[30])
         )
 
+    _setup_error_handlers(new_app)
+
     return new_app

terracotta/server/keys.py

@@ -6,7 +6,7 @@
 from flask import jsonify, Response
 from marshmallow import Schema, fields
 
-from terracotta.server.flask_api import convert_exceptions, METADATA_API
+from terracotta.server.flask_api import METADATA_API
 
 
 class KeyItemSchema(Schema):
@@ -22,7 +22,6 @@ class KeySchema(Schema):
 
 
 @METADATA_API.route('/keys', methods=['GET'])
-@convert_exceptions
 def get_keys() -> Response:
     """Get all key names
     ---

terracotta/server/metadata.py

@@ -6,7 +6,7 @@
 from marshmallow import Schema, fields, validate
 from flask import jsonify, Response
 
-from terracotta.server.flask_api import convert_exceptions, METADATA_API
+from terracotta.server.flask_api import METADATA_API
 
 
 class MetadataSchema(Schema):
@@ -30,7 +30,6 @@ class Meta:
 
 
 @METADATA_API.route('/metadata/<path:keys>', methods=['GET'])
-@convert_exceptions
 def get_metadata(keys: str) -> Response:
     """Get metadata for given dataset
     ---

terracotta/server/rgb.py

@@ -9,7 +9,7 @@
 from marshmallow import Schema, fields, validate, pre_load, ValidationError, EXCLUDE
 from flask import request, send_file, Response
 
-from terracotta.server.flask_api import convert_exceptions, TILE_API
+from terracotta.server.flask_api import TILE_API
 
 
 class RGBQuerySchema(Schema):
@@ -58,7 +58,6 @@ def process_ranges(self, data: Mapping[str, Any], **kwargs: Any) -> Dict[str, An
 
 @TILE_API.route('/rgb/<int:tile_z>/<int:tile_x>/<int:tile_y>.png', methods=['GET'])
 @TILE_API.route('/rgb/<path:keys>/<int:tile_z>/<int:tile_x>/<int:tile_y>.png', methods=['GET'])
-@convert_exceptions
 def get_rgb(tile_z: int, tile_y: int, tile_x: int, keys: str = '') -> Response:
     """Return the requested RGB tile as a PNG image.
     ---
@@ -91,7 +90,6 @@ class RGBPreviewQuerySchema(Schema):
 
 @TILE_API.route('/rgb/preview.png', methods=['GET'])
 @TILE_API.route('/rgb/<path:keys>/preview.png', methods=['GET'])
-@convert_exceptions
 def get_rgb_preview(keys: str = '') -> Response:
     """Return the requested RGB dataset preview as a PNG image.
     ---

terracotta/server/singleband.py

@@ -10,7 +10,7 @@
                          pre_load, ValidationError, EXCLUDE)
 from flask import request, send_file, Response
 
-from terracotta.server.flask_api import convert_exceptions, TILE_API
+from terracotta.server.flask_api import TILE_API
 from terracotta.cmaps import AVAILABLE_CMAPS
 
 
@@ -94,7 +94,6 @@ def decode_json(self, data: Mapping[str, Any], **kwargs: Any) -> Dict[str, Any]:
 
 @TILE_API.route('/singleband/<path:keys>/<int:tile_z>/<int:tile_x>/<int:tile_y>.png',
                 methods=['GET'])
-@convert_exceptions
 def get_singleband(tile_z: int, tile_y: int, tile_x: int, keys: str) -> Response:
     """Return single-band PNG image of requested tile
     ---
@@ -126,7 +125,6 @@ class SinglebandPreviewSchema(Schema):
 
 
 @TILE_API.route('/singleband/<path:keys>/preview.png', methods=['GET'])
-@convert_exceptions
 def get_singleband_preview(keys: str) -> Response:
     """Return single-band PNG preview image of requested dataset
     ---