feat: add garbage collection

Author: franklinkim

lock.go

@@ -610,6 +610,23 @@ func (c *Client) Renew(ctx context.Context, lockId string, ttl uint) ([]LockStat
 	return statuses, nil
 }
 
+// GC removes all lock entries in the collection that have expired
+// Specifically, this removes lock entries where exclusive.lockId is nil AND shared.count is 0
+func (c *Client) GC(ctx context.Context) error {
+	// Get all empty locks and remove
+	selector := bson.M{
+		"exclusive.lockId": nil,
+		"shared.count":     0,
+	}
+
+	_, err := c.collection.DeleteMany(ctx, selector)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // ------------------------------------------------------------------------- //
 
 // xUnlock unlocks an exclusive lock on a resource.

purge.go

@@ -49,5 +49,11 @@ func (p *purger) Purge(ctx context.Context) ([]LockStatus, error) {
 		allUnlocked = append(allUnlocked, unlocked...)
 	}
 
+	// Garbage collect unused lock records
+	err = p.client.GC(ctx)
+	if err != nil {
+		return allUnlocked, err
+	}
+
 	return allUnlocked, nil
 }