hashicorp/nomad · error

only a single eval can be created

Error message

only a single eval can be created

What it means

Guard in Eval.Create: the request contains a number of evaluations other than one; creating evals via this RPC is single-eval by contract with the eval token bookkeeping.

Source

Thrown at nomad/eval_endpoint.go:334

// Create is used to make a new evaluation
func (e *Eval) Create(args *structs.EvalUpdateRequest,
	reply *structs.GenericResponse) 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.Create", args, args, reply); done {
		return err
	}
	defer metrics.MeasureSince([]string{"nomad", "eval", "create"}, time.Now())

	// Ensure there is only a single update with token
	if len(args.Evals) != 1 {
		return fmt.Errorf("only a single eval can be created")
	}
	eval := args.Evals[0]

	// Verify the parent evaluation is outstanding, and that the tokens match.
	if err := e.srv.evalBroker.OutstandingReset(eval.PreviousEval, args.EvalToken); err != nil {
		return err
	}

	// Look for the eval
	snap, err := e.srv.fsm.State().Snapshot()
	if err != nil {
		return err
	}

	ws := memdb.NewWatchSet()
	out, err := snap.EvalByID(ws, eval.ID)
	if err != nil {
		return err

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Submit exactly one evaluation per Eval.Create request

When it happens

Trigger: Thrown at nomad/eval_endpoint.go:334 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/780fe8931a061db0. Report an issue: GitHub.