hashicorp/nomad · error

failed to encode driver config: %v

Error message

failed to encode driver config: %v

What it means

runDriver: after successfully parsing the task's HCL config, taskConfig.EncodeDriverConfig failed converting the parsed values into the driver's protobuf config (type mismatch between task config block and driver schema); the task fails validation and the driver never starts.

Source

Thrown at client/allocrunner/taskrunner/task_runner.go:951

			if tr.logger.IsTrace() {
				// Verbosely log every diagnostic for debugging
				tr.logger.Trace("error building environment variables", "key", k, "error", err)
			}
		}

		tr.logger.Warn("some environment variables not available for rendering", "keys", strings.Join(keys, ", "))
	}

	val, diag, diagErrs := hclutils.ParseHclInterface(tr.task.Config, tr.taskSchema, vars)
	if diag.HasErrors() {
		parseErr := multierror.Append(errors.New("failed to parse config: "), diagErrs...)
		tr.EmitEvent(structs.NewTaskEvent(structs.TaskFailedValidation).SetValidationError(parseErr))
		return parseErr
	}

	if err := taskConfig.EncodeDriverConfig(val); err != nil {
		encodeErr := fmt.Errorf("failed to encode driver config: %v", err)
		tr.EmitEvent(structs.NewTaskEvent(structs.TaskFailedValidation).SetValidationError(encodeErr))
		return encodeErr
	}

	// If there's already a task handle (eg from a Restore) there's nothing
	// to do except update state.
	if tr.getDriverHandle() != nil {
		// Ensure running state is persisted but do *not* append a new
		// task event as restoring is a client event and not relevant
		// to a task's lifecycle.
		if err := tr.updateStateImpl(structs.TaskStateRunning); err != nil {
			//TODO return error and destroy task to avoid an orphaned task?
			tr.logger.Warn("error persisting task state", "error", err)
		}
		return nil
	}

	// Start the job if there's no existing handle (or if RecoverTask failed)

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Check the driver config block in the job spec against the driver's schema
2. Verify driver plugin version matches expected config fields
3. Look for wrong-typed values (string vs number) in the task config

When it happens

Trigger: Thrown at client/allocrunner/taskrunner/task_runner.go:951 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/3d51d64393a96d16. Report an issue: GitHub.