fix: handle large terminated sessions caching with pagination to prevent RAM overflow;

feat: add paginated query for terminated sessions GUIDs with limit and offset;
refactor: batch processing terminated sessions in Redis with pipeline;
chore: log batch caching progress for terminated sessions;
fix: set TTL for session termination cache keys (8 hours);
refactor: update SQL query for terminated sessions to use pagination;
fix: correct loop structure in auth service initialization

backend/internal/database/query.sql.go

@@ -508,15 +508,22 @@ func (q *Queries) GetSessionByGuid(ctx context.Context, guid string) (Session, e
 	return i, err
 }
 
-const getUnexpiredTerminatedSessionsGuids = `-- name: GetUnexpiredTerminatedSessionsGuids :many
+const getUnexpiredTerminatedSessionsGuidsPaginated = `-- name: GetUnexpiredTerminatedSessionsGuidsPaginated :many
 SELECT guid FROM sessions
 WHERE 
   terminated IS TRUE AND
   last_refresh_exp_time > CURRENT_TIMESTAMP
+LIMIT $1::integer
+OFFSET $2
 `
 
-func (q *Queries) GetUnexpiredTerminatedSessionsGuids(ctx context.Context) ([]pgtype.UUID, error) {
-	rows, err := q.db.Query(ctx, getUnexpiredTerminatedSessionsGuids)
+type GetUnexpiredTerminatedSessionsGuidsPaginatedParams struct {
+	BatchSize int32
+	Offset    int64
+}
+
+func (q *Queries) GetUnexpiredTerminatedSessionsGuidsPaginated(ctx context.Context, arg GetUnexpiredTerminatedSessionsGuidsPaginatedParams) ([]pgtype.UUID, error) {
+	rows, err := q.db.Query(ctx, getUnexpiredTerminatedSessionsGuidsPaginated, arg.BatchSize, arg.Offset)
 	if err != nil {
 		return nil, err
 	}

backend/internal/services/auth.go

@@ -57,34 +57,59 @@ type authServiceImpl struct {
 }
 
 func NewAuthService(_log *zap.Logger, _dbctx database.DbContext, _redis *redis.Client, _smtp SmtpService) AuthService {
-
 	authService := &authServiceImpl{log: _log, dbctx: _dbctx, redis: _redis, smtp: _smtp}
-
-	// Cache terminated sessions
-	// FIXME: review possible RAM overflow
-	db := database.NewDbHelper(_dbctx)
-	guids, err := db.Queries.GetUnexpiredTerminatedSessionsGuids(db.CTX)
-	if err != nil {
-		panic("Failed to load terminated sessions' GUIDs")
-	}
-
 	ctx := context.TODO()
-	// FIXME: review possible problems due to a large pipeline request
-	pipe := _redis.Pipeline()
-	for _, guid := range guids {
-		if err := pipe.Set(ctx, fmt.Sprintf("session::%s::is_terminated", guid), true, 0).Err(); err != nil {
-			panic("Failed to cache terminated session: " + err.Error())
+	db := database.NewDbHelper(_dbctx)
+
+	// Batch processing parameters
+	batchSize := 1000
+	offset := 0
+	totalCached := 0
+
+	for {
+		guids, err := db.Queries.GetUnexpiredTerminatedSessionsGuidsPaginated(
+			db.CTX,
+			database.GetUnexpiredTerminatedSessionsGuidsPaginatedParams{
+				BatchSize: int32(batchSize),
+				Offset: int64(offset),
+			},	
+		)
+		if err != nil {
+			panic("Failed to load terminated sessions' GUIDs: " + err.Error())
 		}
-	}
 
-	if _, err := pipe.Exec(ctx); err != nil {
-		panic("Failed to execute redis pipeline request for caching terminated sessions: " + err.Error())
-	}
+		// Break loop when no more records
+		if len(guids) == 0 {
+			break
+		}
 
-	_log.Info("Cached terminated sessions' GUIDs in Redis", zap.Int("amount", len(guids)))
-	return authService
+		// Process batch in Redis pipeline
+		pipe := _redis.Pipeline()
+		for _, guid := range guids {
+			key := fmt.Sprintf("session::%s::is_terminated", guid)
+			pipe.Set(ctx, key, true, time.Duration(8 * time.Hour)) // XXX: magic number
+		}
+
+		if _, err := pipe.Exec(ctx); err != nil {
+			panic("Failed to cache terminated sessions: " + err.Error())
+		}
+
+		totalCached += len(guids)
+		offset += len(guids)
+
+		_log.Info(
+			"Cached batch of terminated sessions",
+			zap.Int("batch_size", len(guids)),
+			zap.Int("total_cached", totalCached))
 }
 
+_log.Info("Finished caching terminated sessions",
+	zap.Int("total_sessions", totalCached),
+		)
+
+		return authService
+	}
+
 func (a *authServiceImpl) terminateAllSessionsForUser(ctx context.Context, username string, queries *database.Queries) error {
 
 	sessionGuids, err := queries.TerminateAllSessionsForUserByUsername(ctx, username); if err != nil {

sqlc/query.sql

@@ -253,11 +253,13 @@ WHERE
   user_id = $1 AND terminated IS FALSE AND
   last_refresh_exp_time > CURRENT_TIMESTAMP;
 
-;-- name: GetUnexpiredTerminatedSessionsGuids :many
+-- name: GetUnexpiredTerminatedSessionsGuidsPaginated :many
 SELECT guid FROM sessions
 WHERE 
   terminated IS TRUE AND
-  last_refresh_exp_time > CURRENT_TIMESTAMP;
+  last_refresh_exp_time > CURRENT_TIMESTAMP
+LIMIT @batch_size::integer
+OFFSET $2;
 
 ;-- name: TerminateAllSessionsForUserByUsername :many
 UPDATE sessions