hashicorp/nomad · error

dequeue requires at least one scheduler type

Error message

dequeue requires at least one scheduler type

What it means

Guard in Eval.Dequeue: the server-only dequeue request listed no scheduler types, so the eval broker cannot match the request to any queued evaluation; at least one scheduler name is required.

Source

Thrown at nomad/eval_endpoint.go:136

// Dequeue is used to dequeue a pending evaluation
func (e *Eval) Dequeue(args *structs.EvalDequeueRequest,
	reply *structs.EvalDequeueResponse) error {

	aclObj, err := e.srv.AuthenticateServerOnly(e.ctx, args)
	e.srv.MeasureRPCRate("eval", structs.RateMetricWrite, args)
	if err != nil || !aclObj.AllowServerOp() {
		return structs.ErrPermissionDenied
	}

	if done, err := e.srv.forward("Eval.Dequeue", args, args, reply); done {
		return err
	}
	defer metrics.MeasureSince([]string{"nomad", "eval", "dequeue"}, time.Now())

	// Ensure there is at least one scheduler
	if len(args.Schedulers) == 0 {
		return fmt.Errorf("dequeue requires at least one scheduler type")
	}

	// Check that there isn't a scheduler version mismatch
	if args.SchedulerVersion != scheduler.SchedulerVersion {
		return fmt.Errorf("dequeue disallowed: calling scheduler version is %d; leader version is %d",
			args.SchedulerVersion, scheduler.SchedulerVersion)
	}

	// Ensure there is a default timeout
	if args.Timeout <= 0 {
		args.Timeout = DefaultDequeueTimeout
	}

	// If the eval broker is paused, attempt to block and wait for a state
	// change before returning. This avoids a tight loop and mimics the
	// behaviour where there are no evals to process.
	//
	// The call can return because either the timeout is reached or the broker

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Include the scheduler type(s) the caller supports in the dequeue request
2. Use the CLI/API which always specifies scheduler types

When it happens

Trigger: Thrown at nomad/eval_endpoint.go:136 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/28743119e470277e. Report an issue: GitHub.