hashicorp/nomad · error

Invalid unblock channel given

Error message

Invalid unblock channel given

What it means

TaskTemplateManagerConfig.Validate guard: UnblockCh is nil (or otherwise invalid) in the config, so the template manager would have no way to signal when templates finish rendering; construction aborts.

Source

Thrown at client/allocrunner/taskrunner/template/template.go:154

	// TaskID is a unique identifier for this task's template manager, for use
	// in downstream platform-specific template runner consumers
	TaskID string

	Logger hclog.Logger

	// RenderFunc allows custom rendering of templated data, and overrides the
	// Nomad custom RenderFunc used for sandboxing. This is currently used by
	// the secrets block to hold all templated data in memory.
	RenderFunc renderer.Renderer
}

// Validate validates the configuration.
func (c *TaskTemplateManagerConfig) Validate() error {
	if c == nil {
		return fmt.Errorf("Nil config passed")
	} else if c.UnblockCh == nil {
		return fmt.Errorf("Invalid unblock channel given")
	} else if c.Lifecycle == nil {
		return fmt.Errorf("Invalid lifecycle hooks given")
	} else if c.Events == nil {
		return fmt.Errorf("Invalid event hook given")
	} else if c.ClientConfig == nil {
		return fmt.Errorf("Invalid client config given")
	} else if c.TaskDir == "" {
		return fmt.Errorf("Invalid task directory given: %q", c.TaskDir)
	} else if c.EnvBuilder == nil {
		return fmt.Errorf("Invalid task environment given")
	} else if c.MaxTemplateEventRate == 0 {
		return fmt.Errorf("Invalid max template event rate given")
	}

	// Once is a runner config, but in Nomad it is set per template, so all
	// templates given to a runner should have the same value for Once.
	var once bool
	for i, t := range c.Templates {

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Report as a bug; the task runner must supply an unblock channel
2. Check the template hook's construction of UnblockCh before calling NewTaskTemplateManager

When it happens

Trigger: Thrown at client/allocrunner/taskrunner/template/template.go:154 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/8803d596e257cd5d. Report an issue: GitHub.