dgraph-io/badger · error

Assert failed

Error message

Assert failed

What it means

Assert failed is the fatal message emitted by y.AssertTrue when its boolean condition is false: the process calls log.Fatalf and terminates immediately. It is an internal invariant check, not a recoverable error — firing means Badger reached a state the authors considered impossible (e.g. memtable capacity assumptions in ensureRoomForWrite, flushMemtable or bench harness invariants). The fault is a bug in Badger or memory corruption, not in caller input, so there is no error value to inspect; the program has already died by the time it is observed.

Source

Thrown at y/error.go:43

var debugMode = false

// Check logs fatal if err != nil.
func Check(err error) {
	if err != nil {
		log.Fatalf("%+v", Wrap(err, ""))
	}
}

// Check2 acts as convenience wrapper around Check, using the 2nd argument as error.
func Check2(_ interface{}, err error) {
	Check(err)
}

// AssertTrue asserts that b is true. Otherwise, it would log fatal.
func AssertTrue(b bool) {
	if !b {
		log.Fatalf("%+v", errors.New("Assert failed"))
	}
}

// AssertTruef is AssertTrue with extra info.
func AssertTruef(b bool, format string, args ...interface{}) {
	if !b {
		log.Fatalf("%+v", fmt.Errorf(format, args...))
	}
}

// Wrap wraps errors from external lib.
func Wrap(err error, msg string) error {
	if !debugMode {
		if err == nil {
			return nil
		}
		return fmt.Errorf("%s err: %+v", msg, err)
	}

View on GitHub (pinned to 2a001d466f)

Solutions

1. Capture the fatal log output — it identifies the failing invariant and file/line; report it as a Badger issue with the stack trace and reproduction steps
2. Upgrade to the latest badger/v4 patch release, since many assertion bugs are fixed over time
3. Check for resource exhaustion (disk full, mmap failures, OOM) and hardware/disk errors that commonly trigger invariant breaks
4. Restore from backup into a fresh directory if a specific dataset persistently trips the assertion

When it happens

Trigger: Thrown at y/error.go:43 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of dgraph-io/badger@2a001d466f (2026-09-05). Data as JSON: /api/errors/62916b8286bb4a90. Report an issue: GitHub.