[thumbnails] thumbnails for dashboards and charts

docs/installation.rst

@@ -647,6 +647,74 @@ section in `config.py`:
 This will cache all the charts in the top 5 most popular dashboards every hour.
 For other strategies, check the `superset/tasks/cache.py` file.
 
+Caching Thumbnails
+------------------
+
+This is an optional feature that can be turned on by activating it's feature flag on config:
+
+.. code-block:: python
+
+    FEATURE_FLAGS = {
+        "THUMBNAILS": True,
+        "THUMBNAILS_SQLA_LISTENERS": True,
+    }
+
+
+For this feature you will need a cache system and celery workers. All thumbnails are store on cache and are processed
+asynchronously by the workers.
+
+An example config where images are stored on S3 could be:
+
+.. code-block:: python
+
+    from flask import Flask
+    from s3cache.s3cache import S3Cache
+
+    ...
+
+    class CeleryConfig(object):
+        BROKER_URL = "redis://localhost:6379/0"
+        CELERY_IMPORTS = ("superset.sql_lab", "superset.tasks", "superset.tasks.thumbnails")
+        CELERY_RESULT_BACKEND = "redis://localhost:6379/0"
+        CELERYD_PREFETCH_MULTIPLIER = 10
+        CELERY_ACKS_LATE = True
+
+
+    CELERY_CONFIG = CeleryConfig
+
+    def init_thumbnail_cache(app: Flask) -> S3Cache:
+        return S3Cache("bucket_name", 'thumbs_cache/')
+
+
+    THUMBNAIL_CACHE_CONFIG = init_thumbnail_cache
+    # Async selenium thumbnail task will use the following user
+    THUMBNAIL_SELENIUM_USER = "Admin"
+
+Using the above example cache keys for dashboards will be `superset_thumb__dashboard__{ID}`
+
+You can override the base URL for selenium using:
+
+.. code-block:: python
+
+    WEBDRIVER_BASEURL = "https://superset.company.com"
+
+
+Additional selenium web drive config can be set using `WEBDRIVER_CONFIGURATION`
+
+You can implement a custom function to authenticate selenium, the default uses flask-login session cookie.
+An example of a custom function signature:
+
+.. code-block:: python
+
+    def auth_driver(driver: WebDriver, user: "User") -> WebDriver:
+        pass
+
+
+Then on config:
+
+.. code-block:: python
+
+    WEBDRIVER_AUTH_FUNC = auth_driver
 
 Deeper SQLAlchemy integration
 -----------------------------

requirements-dev.txt

@@ -33,3 +33,4 @@ redis==3.2.1
 requests==2.22.0
 statsd==3.3.0
 tox==3.11.1
+pillow==7.0.0

setup.py

@@ -118,6 +118,7 @@ def get_git_sha():
         "hana": ["hdbcli==2.4.162", "sqlalchemy_hana==0.4.0"],
         "dremio": ["sqlalchemy_dremio>=0.5.0dev0"],
         "cockroachdb": ["cockroachdb==0.3.3"],
+        "thumbnails": ["Pillow>=7.0.0, <8.0.0"],
     },
     python_requires="~=3.6",
     author="Apache Software Foundation",

superset/__init__.py

@@ -51,3 +51,4 @@
     lambda: results_backend_manager.should_use_msgpack
 )
 tables_cache = LocalProxy(lambda: cache_manager.tables_cache)
+thumbnail_cache = LocalProxy(lambda: cache_manager.thumbnail_cache)

superset/charts/api.py

@@ -20,7 +20,9 @@
 from flask_appbuilder.api import expose, protect, rison, safe
 from flask_appbuilder.models.sqla.interface import SQLAInterface
 from flask_babel import ngettext
+from werkzeug.wsgi import FileWrapper
 
+from superset import is_feature_enabled, thumbnail_cache
 from superset.charts.commands.bulk_delete import BulkDeleteChartCommand
 from superset.charts.commands.create import CreateChartCommand
 from superset.charts.commands.delete import DeleteChartCommand
@@ -39,9 +41,12 @@
     ChartPostSchema,
     ChartPutSchema,
     get_delete_ids_schema,
+    thumbnail_query_schema,
 )
 from superset.constants import RouteMethod
 from superset.models.slice import Slice
+from superset.tasks.thumbnails import cache_chart_thumbnail
+from superset.utils.selenium import ChartScreenshot
 from superset.views.base_api import BaseSupersetModelRestApi
 
 logger = logging.getLogger(__name__)
@@ -118,6 +123,11 @@ class ChartRestApi(BaseSupersetModelRestApi):
     filter_rel_fields_field = {"owners": "first_name"}
     allowed_rel_fields = {"owners"}
 
+    def __init__(self, *args, **kwargs):
+        if is_feature_enabled("THUMBNAILS"):
+            self.include_route_methods = self.include_route_methods | {"thumbnail"}
+        super().__init__(*args, **kwargs)
+
     @expose("/", methods=["POST"])
     @protect()
     @safe
@@ -340,3 +350,58 @@ def bulk_delete(self, **kwargs) -> Response:  # pylint: disable=arguments-differ
             return self.response_403()
         except ChartBulkDeleteFailedError as e:
             return self.response_422(message=str(e))
+
+    @expose("/<pk>/thumbnail/<digest>/", methods=["GET"])
+    @protect()
+    @rison(thumbnail_query_schema)
+    @safe
+    def thumbnail(self, pk, digest, **kwargs):  # pylint: disable=invalid-name
+        """Get Chart thumbnail
+        ---
+        get:
+          description: Compute or get already computed chart thumbnail from cache
+          parameters:
+          - in: path
+            schema:
+              type: integer
+            name: pk
+          - in: path
+            schema:
+              type: string
+            name: sha
+          responses:
+            200:
+              description: Chart thumbnail image
+              content:
+               image/*:
+                 schema:
+                   type: string
+                   format: binary
+            401:
+              $ref: '#/components/responses/401'
+            404:
+              $ref: '#/components/responses/404'
+            422:
+              $ref: '#/components/responses/422'
+            500:
+              $ref: '#/components/responses/500'
+        """
+        chart = self.datamodel.get(pk, self._base_filters)
+        if not chart:
+            return self.response_404()
+        if kwargs["rison"].get("force", False):
+            cache_chart_thumbnail.delay(chart.id, force=True)
+            return self.response(202, message="OK Async")
+        # fetch the chart screenshot using the current user and cache if set
+        screenshot = ChartScreenshot(pk).get_from_cache(cache=thumbnail_cache)
+        # If not screenshot then send request to compute thumb to celery
+        if not screenshot:
+            cache_chart_thumbnail.delay(chart.id, force=True)
+            return self.response(202, message="OK Async")
+        # If digests
+        if chart.digest != digest:
+            logger.info("Requested thumbnail digest differs from actual digest")
+            return self.response(304, message="Digest differs")
+        return Response(
+            FileWrapper(screenshot), mimetype="image/png", direct_passthrough=True
+        )

superset/charts/schemas.py

@@ -22,6 +22,10 @@
 from superset.utils import core as utils
 
 get_delete_ids_schema = {"type": "array", "items": {"type": "integer"}}
+thumbnail_query_schema = {
+    "type": "object",
+    "properties": {"force": {"type": "boolean"}},
+}
 
 
 def validate_json(value):

superset/cli.py

@@ -19,6 +19,7 @@
 from datetime import datetime
 from subprocess import Popen
 from sys import stdout
+from typing import Type, Union
 
 import click
 import yaml
@@ -454,6 +455,78 @@ def flower(port, address):
     Popen(cmd, shell=True).wait()
 
 
+@superset.command()
+@with_appcontext
+@click.option(
+    "--asynchronous",
+    "-a",
+    is_flag=True,
+    default=False,
+    help="Trigger commands to run remotely on a worker",
+)
+@click.option(
+    "--dashboards_only",
+    "-d",
+    is_flag=True,
+    default=False,
+    help="Only process dashboards",
+)
+@click.option(
+    "--charts_only", "-c", is_flag=True, default=False, help="Only process charts"
+)
+@click.option(
+    "--force",
+    "-f",
+    is_flag=True,
+    default=False,
+    help="Force refresh, even if previously cached",
+)
+@click.option("--model_id", "-i", multiple=True)
+def compute_thumbnails(
+    asynchronous: bool,
+    dashboards_only: bool,
+    charts_only: bool,
+    force: bool,
+    model_id: int,
+):
+    """Compute thumbnails"""
+    from superset.models.dashboard import Dashboard
+    from superset.models.slice import Slice
+    from superset.tasks.thumbnails import (
+        cache_chart_thumbnail,
+        cache_dashboard_thumbnail,
+    )
+
+    def compute_generic_thumbnail(
+        friendly_type: str,
+        model_cls: Union[Type[Dashboard], Type[Slice]],
+        model_id: int,
+        compute_func,
+    ):
+        query = db.session.query(model_cls)
+        if model_id:
+            query = query.filter(model_cls.id.in_(model_id))
+        dashboards = query.all()
+        count = len(dashboards)
+        for i, model in enumerate(dashboards):
+            if asynchronous:
+                func = compute_func.delay
+                action = "Triggering"
+            else:
+                func = compute_func
+                action = "Processing"
+            msg = f'{action} {friendly_type} "{model}" ({i+1}/{count})'
+            click.secho(msg, fg="green")
+            func(model.id, force=force)
+
+    if not charts_only:
+        compute_generic_thumbnail(
+            "dashboard", Dashboard, model_id, cache_dashboard_thumbnail
+        )
+    if not dashboards_only:
+        compute_generic_thumbnail("chart", Slice, model_id, cache_chart_thumbnail)
+
+
 @superset.command()
 @with_appcontext
 def load_test_users():

superset/config.py

@@ -282,6 +282,8 @@ def _try_json_readsha(filepath, length):  # pylint: disable=unused-argument
     "ENABLE_EXPLORE_JSON_CSRF_PROTECTION": False,
     "KV_STORE": False,
     "PRESTO_EXPAND_DATA": False,
+    # Exposes API endpoint to compute thumbnails
+    "THUMBNAILS": False,
     "REDUCE_DASHBOARD_BOOTSTRAP_PAYLOAD": False,
     "SHARE_QUERIES_VIA_KV_STORE": False,
     "TAGGING_SYSTEM": False,
@@ -307,6 +309,11 @@ def _try_json_readsha(filepath, length):  # pylint: disable=unused-argument
 #     return feature_flags_dict
 GET_FEATURE_FLAGS_FUNC: Optional[Callable[[Dict[str, bool]], Dict[str, bool]]] = None
 
+# ---------------------------------------------------
+# Thumbnail config (behind feature flag)
+# ---------------------------------------------------
+THUMBNAIL_SELENIUM_USER = "Admin"
+THUMBNAIL_CACHE_CONFIG: CacheConfig = {"CACHE_TYPE": "null"}
 
 # ---------------------------------------------------
 # Image and file configuration