[performance] handle emoji refreshes asynchronously when fetched as part of account|status dereferences (#4486)

# Description

Updates our dereferencer emoji handling to work asynchronously when going through the route of account or status dereferencing.

closes https://codeberg.org/superseriousbusiness/gotosocial/issues/4485

## Checklist

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [ ] I/we have commented the added code, particularly in hard-to-understand areas.
- [ ] I/we have made any necessary changes to documentation.
- [ ] I/we have added tests that cover new code.
- [ ] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4486
Co-authored-by: kim <grufwub@gmail.com>
Co-committed-by: kim <grufwub@gmail.com>

internal/federation/dereferencing/emoji.go

@@ -51,6 +51,7 @@ func (d *Dereferencer) GetEmoji(
 	remoteURL string,
 	info media.AdditionalEmojiInfo,
 	refresh bool,
+	async bool,
 ) (
 	*gtsmodel.Emoji,
 	error,
@@ -66,7 +67,7 @@ func (d *Dereferencer) GetEmoji(
 
 	if emoji != nil {
 		// This was an existing emoji, pass to refresh func.
-		return d.RefreshEmoji(ctx, emoji, info, refresh)
+		return d.RefreshEmoji(ctx, emoji, info, refresh, async)
 	}
 
 	if domain == "" {
@@ -112,6 +113,7 @@ func (d *Dereferencer) GetEmoji(
 				info,
 			)
 		},
+		async,
 	)
 }
 
@@ -130,6 +132,7 @@ func (d *Dereferencer) RefreshEmoji(
 	emoji *gtsmodel.Emoji,
 	info media.AdditionalEmojiInfo,
 	force bool,
+	async bool,
 ) (
 	*gtsmodel.Emoji,
 	error,
@@ -162,7 +165,7 @@ func (d *Dereferencer) RefreshEmoji(
 		// We still want to make sure
 		// the emoji is cached. Simply
 		// check whether emoji is cached.
-		return d.RecacheEmoji(ctx, emoji)
+		return d.RecacheEmoji(ctx, emoji, async)
 	}
 
 	// Can't refresh local.
@@ -207,6 +210,7 @@ func (d *Dereferencer) RefreshEmoji(
 				info,
 			)
 		},
+		async,
 	)
 }
 
@@ -222,6 +226,7 @@ func (d *Dereferencer) RefreshEmoji(
 func (d *Dereferencer) RecacheEmoji(
 	ctx context.Context,
 	emoji *gtsmodel.Emoji,
+	async bool,
 ) (
 	*gtsmodel.Emoji,
 	error,
@@ -272,23 +277,24 @@ func (d *Dereferencer) RecacheEmoji(
 				data,
 			)
 		},
+		async,
 	)
-
 }
 
 // processingEmojiSafely provides concurrency-safe processing of
 // an emoji with given shortcode+domain. if a copy of the emoji is
 // not already being processed, the given 'process' callback will
-// be used to generate new *media.ProcessingEmoji{} instance.
+// be used to generate new *media.ProcessingEmoji{} instance. async
+// determines whether to load it immediately, or in the background.
 func (d *Dereferencer) processEmojiSafely(
 	ctx context.Context,
 	shortcodeDomain string,
 	process func() (*media.ProcessingEmoji, error),
+	async bool,
 ) (
 	emoji *gtsmodel.Emoji,
 	err error,
 ) {
-
 	// Acquire map lock.
 	d.derefEmojisMu.Lock()
 
@@ -309,17 +315,25 @@ func (d *Dereferencer) processEmojiSafely(
 
 		// Add processing emoji media to hash map.
 		d.derefEmojis[shortcodeDomain] = processing
+	}
 
+	// Unlock map.
+	unlock()
+
+	if async {
+		emoji = processing.LoadAsync(func() {
+			// Remove on finish.
+			d.derefEmojisMu.Lock()
+			delete(d.derefEmojis, shortcodeDomain)
+			d.derefEmojisMu.Unlock()
+		})
+	} else {
 		defer func() {
 			// Remove on finish.
 			d.derefEmojisMu.Lock()
 			delete(d.derefEmojis, shortcodeDomain)
 			d.derefEmojisMu.Unlock()
 		}()
-	}
-
-	// Unlock map.
-	unlock()
 
 		// Perform emoji load operation.
 		emoji, err = processing.Load(ctx)
@@ -329,6 +343,7 @@ func (d *Dereferencer) processEmojiSafely(
 			// TODO: in time we should return checkable flags by gtserror.Is___()
 			// which can determine if loading error should allow remaining placeholder.
 		}
+	}
 
 	return
 }
@@ -364,7 +379,7 @@ func (d *Dereferencer) fetchEmojis(
 				URI:                  &placeholder.URI,
 				ImageRemoteURL:       &placeholder.ImageRemoteURL,
 				ImageStaticRemoteURL: &placeholder.ImageStaticRemoteURL,
-			}, force)
+			}, force, true)
 			if err != nil {
 				log.Errorf(ctx, "error refreshing emoji: %v", err)
 
@@ -396,6 +411,7 @@ func (d *Dereferencer) fetchEmojis(
 				ImageStaticRemoteURL: &placeholder.ImageStaticRemoteURL,
 			},
 			false,
+			true,
 		)
 		if err != nil {
 			if emoji == nil {

internal/federation/dereferencing/emoji_test.go

@@ -54,6 +54,7 @@ func (suite *EmojiTestSuite) TestDereferenceEmojiBlocking() {
 			VisibleInPicker:      &emojiVisibleInPicker,
 		},
 		false,
+		false,
 	)
 	suite.NoError(err)
 	suite.NotNil(emoji)

internal/media/processingemoji.go

@@ -44,11 +44,6 @@ type ProcessingEmoji struct {
 	mgr       *Manager          // mgr instance (access to db / storage)
 }
 
-// ID returns the ID of the underlying emoji.
-func (p *ProcessingEmoji) ID() string {
-	return p.emoji.ID // immutable, safe outside mutex.
-}
-
 // LoadEmoji blocks until the static and fullsize image has been processed, and then returns the completed emoji.
 func (p *ProcessingEmoji) Load(ctx context.Context) (*gtsmodel.Emoji, error) {
 	emoji, done, err := p.load(ctx)
@@ -63,6 +58,33 @@ func (p *ProcessingEmoji) Load(ctx context.Context) (*gtsmodel.Emoji, error) {
 	return emoji, err
 }
 
+func (p *ProcessingEmoji) LoadAsync(deferred func()) *gtsmodel.Emoji {
+	p.mgr.state.Workers.Dereference.Queue.Push(func(ctx context.Context) {
+		if deferred != nil {
+			defer deferred()
+		}
+
+		if _, _, err := p.load(ctx); err != nil {
+			log.Errorf(ctx, "error loading emoji: %v", err)
+		}
+	})
+
+	// Placeholder returns a copy of internally stored processing placeholder,
+	// returning only the fields that may be known *before* completion,
+	// and as such all fields which are safe to concurrently read.
+	placeholder := new(gtsmodel.Emoji)
+	placeholder.ID = p.emoji.ID
+	placeholder.Shortcode = p.emoji.Shortcode
+	placeholder.Domain = p.emoji.Domain
+	placeholder.Cached = new(bool)
+	placeholder.ImageRemoteURL = p.emoji.ImageRemoteURL
+	placeholder.ImageStaticRemoteURL = p.emoji.ImageStaticRemoteURL
+	placeholder.Disabled = p.emoji.Disabled
+	placeholder.VisibleInPicker = p.emoji.VisibleInPicker
+	placeholder.CategoryID = p.emoji.CategoryID
+	return placeholder
+}
+
 // load is the package private form of load() that is wrapped to catch context canceled.
 func (p *ProcessingEmoji) load(ctx context.Context) (
 	emoji *gtsmodel.Emoji,

internal/processing/admin/emoji.go

@@ -293,6 +293,7 @@ func (p *Processor) emojiUpdateCopy(
 	// Ensure target emoji is locally cached.
 	target, err := p.federator.RecacheEmoji(ctx,
 		target,
+		false,
 	)
 	if err != nil {
 		err := gtserror.Newf("error recaching emoji %s: %w", target.ImageRemoteURL, err)

internal/processing/media/getfile.go

@@ -247,6 +247,7 @@ func (p *Processor) getEmojiContent(
 	emoji, err = p.federator.RecacheEmoji(
 		ctx,
 		emoji,
+		false,
 	)
 	if err != nil {
 		err := gtserror.Newf("error recaching emoji: %w", err)