feat: cache codemeta json string for quicker page loads

introduces a simple scheme for caching properties of a codebase or
release that get invalidated every time the codebase or release are
updated

django/library/models.py

@@ -802,6 +802,15 @@ def create_git_mirror(self, repository_name, **kwargs):
             self.save()
         return self.git_mirror
 
+    @property
+    def invalidate_on_save_cache_prefix(self):
+        """prefix for cache keys that should be invalidated on save"""
+        return f"codebase:{self.id}"
+
+    def invalidate_cached_properties(self):
+        keys = cache.keys(f"{self.invalidate_on_save_cache_prefix}:*")
+        cache.delete_many(keys)
+
     @property
     def codebase_contributors_redis_key(self):
         return f"codebase:contributors:{self.identifier}"
@@ -1715,7 +1724,6 @@ def common_metadata(self):
         return CommonMetadata(self)
 
     # FIXME: is there any reason for this to be a cached property?
-    # the json string that gets used in the page could benefit from being *globally* cached though
     # it may also be wise to have a minimal codemeta dict that gets generated in case of an exception
     # when using codemeticulous
     @cached_property
@@ -1784,8 +1792,31 @@ def get_status_color(self):
         return COLOR_MAP.get(self.status)
 
     @property
-    def codemeta_json(self):
-        return self.codemeta.json()
+    def invalidate_on_save_cache_prefix(self):
+        """prefix for cache keys that should be invalidated on save"""
+        return f"{self.codebase.invalidate_on_save_cache_prefix}:release:{self.id}"
+
+    def invalidate_cached_properties(self):
+        keys = cache.keys(f"{self.invalidate_on_save_cache_prefix}:*")
+        cache.delete_many(keys)
+
+    @property
+    def codemeta_json(self) -> str:
+        """Returns the codemeta json string for this release. This property
+        is cached for 30 days to reduce page load times. The cache gets invalidated
+        every time the release or parent codebase is updated (post-save signal handler).
+
+        Use codemeta.json() instead to re-generate"""
+        key = f"{self.invalidate_on_save_cache_prefix}:codemeta_json"
+        json_str = cache.get(key)
+        if json_str is None:
+            json_str = self.codemeta.json()
+            cache.set(
+                key,
+                json_str,
+                timeout=60 * 60 * 24 * 30,
+            )
+        return json_str
 
     def create_or_update_codemeta(self, force=True):
         return self.get_fs_api().create_or_update_codemeta(force=force)

django/library/signals.py

@@ -1,7 +1,6 @@
 import logging
-import shortuuid
 
-from django.conf import settings
+from django.core.cache import cache
 from django.db.models.signals import post_save
 from django.dispatch import receiver
 
@@ -16,10 +15,13 @@
 )
 def on_codebase_release_save(sender, instance: CodebaseRelease, **kwargs):
     """
-    update the metadata in the git mirror for a codebase release if it has a git mirror
-    and the metadata changed
+    * update the metadata in the git mirror for a codebase release if it has a git mirror
+      and the metadata changed
+    * invalidate any cached properties for this release with the invalidation prefix
     """
     release = instance
+    release.invalidate_cached_properties()
+
     codebase = release.codebase
     mirror = codebase.git_mirror
     if mirror and mirror.remote_url:
@@ -29,10 +31,13 @@ def on_codebase_release_save(sender, instance: CodebaseRelease, **kwargs):
 @receiver(post_save, sender=Codebase, dispatch_uid="update_mirrored_codebase_metadata")
 def on_codebase_save(sender, instance: Codebase, **kwargs):
     """
-    update the metadata in the git mirror for a codebase if it has a git mirror
-    and the metadata changed
+    * update the metadata in the git mirror for a codebase if it has a git mirror
+      and the metadata changed
+    * invalidate any cached properties for this codebase with the invalidation prefix
     """
     codebase = instance
+    codebase.invalidate_cached_properties()
+
     mirror = codebase.git_mirror
     if mirror and mirror.remote_url:
         update_mirrored_codebase_metadata(codebase.id)