api: cache previews on s3, and invalidate on dev portal updates

Author: jwise

appstore/api.py

@@ -1,16 +1,20 @@
+import io
 import urllib.parse
 
 from flask import Blueprint, request, jsonify, abort, url_for, make_response
 from flask_cors import CORS
 from sqlalchemy import and_
 
 from sqlalchemy.orm.exc import NoResultFound
+from sqlalchemy.exc import PendingRollbackError
 
 from appstore.utils import jsonify_app, asset_fallback, generate_image_url, get_access_token, plat_dimensions, HARDWARE_SUPPORT
 from .models import App, Collection, HomeBanners, Category, db, Release
 from .settings import config
 from .image import generate_preview_image
 
+from .s3 import upload_asset, download_asset
+
 parent_app = None
 api = Blueprint('api', __name__)
 CORS(api)
@@ -71,18 +75,44 @@ def apps_by_id(key):
 @api.route('/apps/id/<key>/preview')
 def app_image_by_id(key):
     app = App.query.filter_by(id=key).one_or_none()
-    screenshots = {}
-    for hw in ['aplite', 'basalt', 'chalk', 'diorite', 'emery', 'flint']:
-        if hw in app.asset_collections:
-            screenshot = app.asset_collections[hw].screenshots[0]
-            if screenshot:
-              screenshots[hw] = screenshot
-
-    icon = None
-    if app.type == 'watchapp':
-        icon = app.icon_large
-    png = generate_preview_image(title=app.title, developer=app.developer.name, icon=icon, screenshots=screenshots)
-    response = make_response(png)
+    
+    if not app.preview_image:
+        # Guess we will have to generate one.
+        screenshots = {}
+        for hw in ['aplite', 'basalt', 'chalk', 'diorite', 'emery', 'flint']:
+            if hw in app.asset_collections:
+                screenshot = app.asset_collections[hw].screenshots[0]
+                if screenshot:
+                  screenshots[hw] = screenshot
+
+        icon = None
+        if app.type == 'watchapp':
+            icon = app.icon_large
+        png = generate_preview_image(title=app.title, developer=app.developer.name, icon=icon, screenshots=screenshots)
+        
+        buf = io.BytesIO()
+        buf.write(png)
+        buf.seek(0)
+        # HACK: upload_asset puts this in a print, which is only really valid for actual Files...
+        setattr(buf, 'name', "preview.png")
+        asset = upload_asset(buf, mime_type = 'image/png', path = config['S3_PREVIEW_PATH'])
+        
+        app.preview_image = asset
+        try:
+            db.session.commit()
+        except PendingRollbackError:
+            # if someone else gets to it at the same time, no big deal
+            pass
+        
+        response = make_response(png)
+        response.headers.set('Content-Type', 'image/png')
+        return response
+    
+    # looks like there's a cached version -- grab it!
+    buf = io.BytesIO()
+    download_asset(app.preview_image, buf, path = config['S3_PREVIEW_PATH'])
+    buf.seek(0)
+    response = make_response(buf.read())
     response.headers.set('Content-Type', 'image/png')
     return response
 

appstore/developer_portal_api.py

@@ -450,6 +450,9 @@ def new_app_screenshots(app_id, platform):
     new_image_id = upload_asset(new_image, new_image.content_type)
     screenshots.append(new_image_id)
     asset_collection.screenshots = screenshots
+
+    # Invalidate the cached preview.
+    app.preview_image = None
     db.session.commit()
 
     return jsonify(success=True, id=new_image_id, platform=platform)
@@ -485,6 +488,10 @@ def delete_screenshot(app_id, platform, screenshot_id):
         ), 409
 
     asset_collection.screenshots = list(filter(lambda x: x != screenshot_id, asset_collection.screenshots))
+
+    # Invalidate the cached preview.
+    app.preview_image = None
+
     db.session.commit()
     return jsonify(success=True, message=f"Deleted screenshot {screenshot_id}", id=screenshot_id, platform=platform)
 
@@ -551,6 +558,10 @@ def new_app_banner(app_id, platform):
     new_image_id = upload_asset(new_image, new_image.content_type)
     headers.append(new_image_id)
     asset_collection.headers = headers
+
+    # Invalidate the cached preview.
+    app.preview_image = None
+
     db.session.commit()
 
     return jsonify(success=True, id=new_image_id, platform=platform)
@@ -586,6 +597,10 @@ def delete_banner(app_id, platform, banner_id):
         ), 409
 
     asset_collection.headers = list(filter(lambda x: x != banner_id, asset_collection.headers))
+
+    # Invalidate the cached preview.
+    app.preview_image = None
+
     db.session.commit()
     return jsonify(success=True, message=f"Deleted banner {banner_id}", id=banner_id, platform=platform)
 
@@ -646,6 +661,9 @@ def new_app_icon(app_id, size):
         app.icon_large = new_image_id
     elif size == "small":
         app.icon_small = new_image_id
+    
+    # Invalidate the cached preview.
+    app.preview_image = None
     db.session.commit()
 
     return jsonify(success=True, id=new_image_id, size=size)

appstore/models.py

@@ -79,6 +79,7 @@ class App(db.Model):
     timeline_token = db.Column(db.String, index=True)
     installs = db.Column(db.Integer, index=True)
     discourse_topic_id = db.Column(db.Integer)
+    preview_image = db.Column(db.String)
 
 
 category_banner_apps = Table('category_banner_apps', db.Model.metadata,

appstore/s3.py

@@ -82,9 +82,9 @@ def download_pbw(id, file):
         s3.download_fileobj(config['S3_BUCKET'], filename, file)
 
 
-def upload_asset(file, mime_type = None):
+def upload_asset(file, mime_type = None, path = config['S3_ASSET_PATH']):
     id = id_generator.generate()
-    filename = f"{config['S3_ASSET_PATH']}{id}"
+    filename = f"{path}{id}"
 
     if isinstance(file, str):
         print(f"uploading file {file} to {config['S3_ASSET_BUCKET']}:{filename}")
@@ -110,8 +110,8 @@ def upload_asset(file, mime_type = None):
 
     return id    
 
-def download_asset(id, file):
-    filename = f"{config['S3_ASSET_PATH']}{id}"
+def download_asset(id, file, path = config['S3_ASSET_PATH']):
+    filename = f"{path}{id}"
     s3 = _client_for_endpoint(s3_endpoint)
     if isinstance(file, str):
         s3.download_file(config['S3_ASSET_BUCKET'], filename, file)

appstore/settings.py

@@ -18,6 +18,7 @@
     'S3_PATH': os.environ.get('S3_PATH', 'pbw/'),
     'S3_ASSET_BUCKET': os.environ.get('S3_ASSET_BUCKET', 'rebble-appstore-assets'),
     'S3_ASSET_PATH': os.environ.get('S3_ASSET_PATH', ''),
+    'S3_PREVIEW_PATH': os.environ.get('S3_PREVIEW_PATH', 'preview_images/'),
     'S3_ARCHIVE_BUCKET': os.environ.get('S3_ARCHIVE_BUCKET', 'rebble-archive'),
     'S3_ARCHIVE_PATH':   os.environ.get('S3_ARCHIVE_PATH'  , 'appstore/'),
     'HONEYCOMB_KEY': os.environ.get('HONEYCOMB_KEY', None),

migrations/versions/0c3a1cfa6af5_app_add_preview_image_cache.py

@@ -0,0 +1,28 @@
+"""app: add preview_image cache
+
+Revision ID: 0c3a1cfa6af5
+Revises: 89e32c02be56
+Create Date: 2025-12-11 08:34:29.526881
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '0c3a1cfa6af5'
+down_revision = '89e32c02be56'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('apps', sa.Column('preview_image', sa.String(), nullable=True))
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_constraint(None, 'user_flags', type_='foreignkey')
+    # ### end Alembic commands ###