[feature] Cleanup unattached local media (#680)

* add localUnattached db function

* add parseOlderThan util function

* add pruneunusedlocalattachments to media manager

* add unusedlocal pruning to schedule + admin call

* set number of days to keep as a const

* fix test

1 files changed, 24 insertions, 2 deletions

diff --git a/internal/media/manager.go b/internal/media/manager.go
index 663f74123..aacf607cc 100644
--- a/internal/media/manager.go
+++ b/internal/media/manager.go
@@ -34,6 +34,10 @@ import (
 // selectPruneLimit is the amount of media entries to select at a time from the db when pruning
 const selectPruneLimit = 20
 
+// UnusedLocalAttachmentCacheDays is the amount of days to keep local media in storage if it
+// is not attached to a status, or was never attached to a status.
+const UnusedLocalAttachmentCacheDays = 3
+
 // Manager provides an interface for managing media: parsing, storing, and retrieving media objects like photos, videos, and gifs.
 type Manager interface {
 	// ProcessMedia begins the process of decoding and storing the given data as an attachment.
@@ -75,11 +79,16 @@ type Manager interface {
 	//
 	// The returned int is the amount of media that was pruned by this function.
 	PruneAllRemote(ctx context.Context, olderThanDays int) (int, error)
-	// PruneAllMeta prunes unused meta media -- currently, this means unused avatars + headers, but can also be extended
-	// to include things like attachments that were uploaded on this server but left unused, etc.
+	// PruneAllMeta prunes unused/out of date headers and avatars cached on this instance.
 	//
 	// The returned int is the amount of media that was pruned by this function.
 	PruneAllMeta(ctx context.Context) (int, error)
+	// PruneUnusedLocalAttachments prunes unused media attachments that were uploaded by
+	// a user on this instance, but never actually attached to a status, or attached but
+	// later detached.
+	//
+	// The returned int is the amount of media that was pruned by this function.
+	PruneUnusedLocalAttachments(ctx context.Context) (int, error)
 
 	// Stop stops the underlying worker pool of the manager. It should be called
 	// when closing GoToSocial in order to cleanly finish any in-progress jobs.
@@ -210,6 +219,19 @@ func scheduleCleanupJobs(m *manager) error {
 		return fmt.Errorf("error starting media manager meta cleanup job: %s", err)
 	}
 
+	if _, err := c.AddFunc("@midnight", func() {
+		begin := time.Now()
+		pruned, err := m.PruneUnusedLocalAttachments(pruneCtx)
+		if err != nil {
+			logrus.Errorf("media manager: error pruning unused local attachments: %s", err)
+			return
+		}
+		logrus.Infof("media manager: pruned %d unused local attachments in %s", pruned, time.Since(begin))
+	}); err != nil {
+		pruneCancel()
+		return fmt.Errorf("error starting media manager unused local attachments cleanup job: %s", err)
+	}
+
 	// start remote cache cleanup cronjob if configured
 	if mediaRemoteCacheDays := config.GetMediaRemoteCacheDays(); mediaRemoteCacheDays > 0 {
 		if _, err := c.AddFunc("@midnight", func() {