feat: enable ETag header for dashboard GET requests (apache#10963)

* feat: add etag for dashboard load requests

* fix review comments

superset/config.py

@@ -297,6 +297,7 @@ def _try_json_readsha(  # pylint: disable=unused-argument
     # Experimental feature introducing a client (browser) cache
     "CLIENT_CACHE": False,
     "ENABLE_EXPLORE_JSON_CSRF_PROTECTION": False,
+    "ENABLE_DASHBOARD_ETAG_HEADER": False,
     "KV_STORE": False,
     "PRESTO_EXPAND_DATA": False,
     # Exposes API endpoint to compute thumbnails

superset/utils/decorators.py

@@ -17,7 +17,7 @@
 import logging
 from datetime import datetime, timedelta
 from functools import wraps
-from typing import Any, Callable, Iterator
+from typing import Any, Callable, Iterator, Optional
 
 from contextlib2 import contextmanager
 from flask import request
@@ -46,7 +46,12 @@ def stats_timing(stats_key: str, stats_logger: BaseStatsLogger) -> Iterator[floa
         stats_logger.timing(stats_key, now_as_float() - start_ts)
 
 
-def etag_cache(max_age: int, check_perms: Callable[..., Any]) -> Callable[..., Any]:
+def etag_cache(
+    max_age: int,
+    check_perms: Callable[..., Any],
+    get_last_modified: Optional[Callable[..., Any]] = None,
+    skip: Optional[Callable[..., Any]] = None,
+) -> Callable[..., Any]:
     """
     A decorator for caching views and handling etag conditional requests.
 
@@ -69,7 +74,7 @@ def wrapper(*args: Any, **kwargs: Any) -> ETagResponseMixin:
             # for POST requests we can't set cache headers, use the response
             # cache nor use conditional requests; this will still use the
             # dataframe cache in `superset/viz.py`, though.
-            if request.method == "POST":
+            if request.method == "POST" or (skip and skip(*args, **kwargs)):
                 return f(*args, **kwargs)
 
             response = None
@@ -89,13 +94,28 @@ def wrapper(*args: Any, **kwargs: Any) -> ETagResponseMixin:
                         raise
                     logger.exception("Exception possibly due to cache backend.")
 
+            # if cache is stale?
+            if get_last_modified:
+                content_changed_time = get_last_modified(*args, **kwargs)
+                if (
+                    response
+                    and response.last_modified
+                    and response.last_modified.timestamp()
+                    < content_changed_time.timestamp()
+                ):
+                    response = None
+            else:
+                # if caller didn't provide content's last_modified time, assume
+                # its cache won't be stale.
+                content_changed_time = datetime.utcnow()
+
             # if no response was cached, compute it using the wrapped function
             if response is None:
                 response = f(*args, **kwargs)
 
                 # add headers for caching: Last Modified, Expires and ETag
                 response.cache_control.public = True
-                response.last_modified = datetime.utcnow()
+                response.last_modified = content_changed_time
                 expiration = max_age if max_age != 0 else FAR_FUTURE
                 response.expires = response.last_modified + timedelta(
                     seconds=expiration

superset/views/core.py

@@ -26,7 +26,17 @@
 import backoff
 import pandas as pd
 import simplejson as json
-from flask import abort, flash, g, Markup, redirect, render_template, request, Response
+from flask import (
+    abort,
+    flash,
+    g,
+    make_response,
+    Markup,
+    redirect,
+    render_template,
+    request,
+    Response,
+)
 from flask_appbuilder import expose
 from flask_appbuilder.models.sqla.interface import SQLAInterface
 from flask_appbuilder.security.decorators import has_access, has_access_api
@@ -114,9 +124,12 @@
     _deserialize_results_payload,
     apply_display_max_row_limit,
     bootstrap_user_data,
+    check_dashboard_perms,
     check_datasource_perms,
     check_slice_perms,
     get_cta_schema_name,
+    get_dashboard,
+    get_dashboard_changedon_dt,
     get_dashboard_extra_filters,
     get_datasource_info,
     get_form_data,
@@ -1585,49 +1598,32 @@ def publish(  # pylint: disable=no-self-use
         return json_success(json.dumps({"published": dash.published}))
 
     @has_access
+    @etag_cache(
+        0,
+        check_perms=check_dashboard_perms,
+        get_last_modified=get_dashboard_changedon_dt,
+        skip=lambda _self, dashboard_id_or_slug: not is_feature_enabled(
+            "ENABLE_DASHBOARD_ETAG_HEADER"
+        ),
+    )
     @expose("/dashboard/<dashboard_id_or_slug>/")
     def dashboard(  # pylint: disable=too-many-locals
         self, dashboard_id_or_slug: str
     ) -> FlaskResponse:
         """Server side rendering for a dashboard"""
-        session = db.session()
-        qry = session.query(Dashboard)
-        if dashboard_id_or_slug.isdigit():
-            qry = qry.filter_by(id=int(dashboard_id_or_slug))
-        else:
-            qry = qry.filter_by(slug=dashboard_id_or_slug)
+        dash = get_dashboard(dashboard_id_or_slug)
 
-        dash = qry.one_or_none()
-        if not dash:
-            abort(404)
-
-        datasources = defaultdict(list)
+        slices_by_datasources = defaultdict(list)
         for slc in dash.slices:
             datasource = slc.datasource
             if datasource:
-                datasources[datasource].append(slc)
-
-        if config["ENABLE_ACCESS_REQUEST"]:
-            for datasource in datasources:
-                if datasource and not security_manager.can_access_datasource(
-                    datasource
-                ):
-                    flash(
-                        __(
-                            security_manager.get_datasource_access_error_msg(datasource)
-                        ),
-                        "danger",
-                    )
-                    return redirect(
-                        "superset/request_access/?" f"dashboard_id={dash.id}&"
-                    )
-
+                slices_by_datasources[datasource].append(slc)
         # Filter out unneeded fields from the datasource payload
         datasources_payload = {
             datasource.uid: datasource.data_for_slices(slices)
             if is_feature_enabled("REDUCE_DASHBOARD_BOOTSTRAP_PAYLOAD")
             else datasource.data
-            for datasource, slices in datasources.items()
+            for datasource, slices in slices_by_datasources.items()
         }
 
         dash_edit_perm = check_ownership(
@@ -1661,7 +1657,7 @@ def dashboard(**_: Any) -> None:
         if is_feature_enabled("REMOVE_SLICE_LEVEL_LABEL_COLORS"):
             # dashboard metadata has dashboard-level label_colors,
             # so remove slice-level label_colors from its form_data
-            for slc in dashboard_data.get("slices"):
+            for slc in dashboard_data.get("slices") or []:
                 form_data = slc.get("form_data")
                 form_data.pop("label_colors", None)
 
@@ -1695,15 +1691,17 @@ def dashboard(**_: Any) -> None:
                 json.dumps(bootstrap_data, default=utils.pessimistic_json_iso_dttm_ser)
             )
 
-        return self.render_template(
-            "superset/dashboard.html",
-            entry="dashboard",
-            standalone_mode=standalone_mode,
-            title=dash.dashboard_title,
-            custom_css=dashboard_data.get("css"),
-            bootstrap_data=json.dumps(
-                bootstrap_data, default=utils.pessimistic_json_iso_dttm_ser
-            ),
+        return make_response(
+            self.render_template(
+                "superset/dashboard.html",
+                entry="dashboard",
+                standalone_mode=standalone_mode,
+                title=dash.dashboard_title,
+                custom_css=dashboard_data.get("css"),
+                bootstrap_data=json.dumps(
+                    bootstrap_data, default=utils.pessimistic_json_iso_dttm_ser
+                ),
+            )
         )
 
     @api

superset/views/utils.py

@@ -16,19 +16,27 @@
 # under the License.
 import logging
 from collections import defaultdict
-from datetime import date
+from datetime import date, datetime
 from typing import Any, Callable, DefaultDict, Dict, List, Optional, Set, Tuple, Union
 from urllib import parse
 
 import msgpack
 import pyarrow as pa
 import simplejson as json
-from flask import g, request
+from flask import abort, flash, g, redirect, request
 from flask_appbuilder.security.sqla import models as ab_models
 from flask_appbuilder.security.sqla.models import User
+from flask_babel import gettext as __
 
 import superset.models.core as models
-from superset import app, dataframe, db, is_feature_enabled, result_set
+from superset import (
+    app,
+    dataframe,
+    db,
+    is_feature_enabled,
+    result_set,
+    security_manager,
+)
 from superset.connectors.connector_registry import ConnectorRegistry
 from superset.errors import ErrorLevel, SupersetError, SupersetErrorType
 from superset.exceptions import SupersetException, SupersetSecurityException
@@ -298,6 +306,36 @@ def get_time_range_endpoints(
 CONTAINER_TYPES = ["COLUMN", "GRID", "TABS", "TAB", "ROW"]
 
 
+def get_dashboard(dashboard_id_or_slug: str,) -> Dashboard:
+    session = db.session()
+    qry = session.query(Dashboard)
+    if dashboard_id_or_slug.isdigit():
+        qry = qry.filter_by(id=int(dashboard_id_or_slug))
+    else:
+        qry = qry.filter_by(slug=dashboard_id_or_slug)
+    dashboard = qry.one_or_none()
+
+    if not dashboard:
+        abort(404)
+
+    return dashboard
+
+
+def get_dashboard_changedon_dt(_self: Any, dashboard_id_or_slug: str) -> datetime:
+    """
+    Get latest changed datetime for a dashboard. The change could be dashboard
+    metadata change, or any of its slice data change.
+
+    This function takes `self` since it must have the same signature as the
+    the decorated method.
+    """
+    dash = get_dashboard(dashboard_id_or_slug)
+    dash_changed_on = dash.changed_on
+    slices_changed_on = max([s.changed_on for s in dash.slices])
+    # drop microseconds in datetime to match with last_modified header
+    return max(dash_changed_on, slices_changed_on).replace(microsecond=0)
+
+
 def get_dashboard_extra_filters(
     slice_id: int, dashboard_id: int
 ) -> List[Dict[str, Any]]:
@@ -490,6 +528,26 @@ def check_slice_perms(_self: Any, slice_id: int) -> None:
         viz_obj.raise_for_access()
 
 
+def check_dashboard_perms(_self: Any, dashboard_id_or_slug: str) -> None:
+    """
+    Check if user can access a cached response from explore_json.
+
+    This function takes `self` since it must have the same signature as the
+    the decorated method.
+    """
+
+    dash = get_dashboard(dashboard_id_or_slug)
+    datasources = list(dash.datasources)
+    if app.config["ENABLE_ACCESS_REQUEST"]:
+        for datasource in datasources:
+            if datasource and not security_manager.can_access_datasource(datasource):
+                flash(
+                    __(security_manager.get_datasource_access_error_msg(datasource)),
+                    "danger",
+                )
+                redirect("superset/request_access/?" f"dashboard_id={dash.id}&")
+
+
 def _deserialize_results_payload(
     payload: Union[bytes, str], query: Query, use_msgpack: Optional[bool] = False
 ) -> Dict[str, Any]:

tests/utils_tests.py

@@ -67,6 +67,7 @@
 from superset.utils import schema
 from superset.views.utils import (
     build_extra_filters,
+    get_dashboard_changedon_dt,
     get_form_data,
     get_time_range_endpoints,
 )
@@ -1134,3 +1135,14 @@ def test_get_form_data_token(self):
         assert get_form_data_token({"token": "token_abcdefg1"}) == "token_abcdefg1"
         generated_token = get_form_data_token({})
         assert re.match(r"^token_[a-z0-9]{8}$", generated_token) is not None
+
+    def test_get_dashboard_changedon_dt(self) -> None:
+        slug = "world_health"
+        dashboard = db.session.query(Dashboard).filter_by(slug=slug).one()
+        dashboard_last_changedon = dashboard.changed_on
+        slices = dashboard.slices
+        slices_last_changedon = max([slc.changed_on for slc in slices])
+        # drop microsecond in datetime
+        assert get_dashboard_changedon_dt(self, slug) == max(
+            dashboard_last_changedon, slices_last_changedon
+        ).replace(microsecond=0)