hashicorp/nomad · error

failed to build ReattachConfig from taskConfig state: %v

Error message

failed to build ReattachConfig from taskConfig state: %v

What it means

After decoding TaskState, RecoverTask converts the stored ReattachConfig into a go-plugin reattach config via pstructs.ReattachConfigToGoPlugin. If the stored reattach data is invalid (nil protocol, bad addr/pid fields), this wrapped error is returned.

Source

Thrown at drivers/qemu/driver.go:309

	// If already attached to handle there's nothing to recover.
	if _, ok := d.tasks.Get(handle.Config.ID); ok {
		d.logger.Trace("nothing to recover; task already exists",
			"task_id", handle.Config.ID,
			"task_name", handle.Config.Name,
		)
		return nil
	}

	var taskState TaskState
	if err := handle.GetDriverState(&taskState); err != nil {
		d.logger.Error("failed to decode taskConfig state from handle", "error", err, "task_id", handle.Config.ID)
		return fmt.Errorf("failed to decode taskConfig state from handle: %v", err)
	}

	plugRC, err := pstructs.ReattachConfigToGoPlugin(taskState.ReattachConfig)
	if err != nil {
		d.logger.Error("failed to build ReattachConfig from taskConfig state", "error", err, "task_id", handle.Config.ID)
		return fmt.Errorf("failed to build ReattachConfig from taskConfig state: %v", err)
	}

	execImpl, pluginClient, err := executor.ReattachToExecutor(
		plugRC,
		d.logger.With("task_name", handle.Config.Name, "alloc_id", handle.Config.AllocID),
		d.nomadConfig.Topology.Compute(),
	)
	if err != nil {
		d.logger.Error("failed to reattach to executor", "error", err, "task_id", handle.Config.ID)
		return fmt.Errorf("failed to reattach to executor: %v", err)
	}

	// Try to restore monitor socket path.
	taskDir := filepath.Join(handle.Config.AllocDir, handle.Config.Name)
	possiblePaths := []string{
		filepath.Join(taskDir, qemuMonitorSocketName),
		// Support restoring tasks that used the old socket name.
		filepath.Join(taskDir, "qemu-monitor.sock"),

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Confirm the executor process is still alive and its recorded PID/ReattachConfig are valid; if not, reschedule the allocation.
2. Upgrade/downgrade to matching Nomad versions so the ReattachConfig schema matches what was persisted.
3. Inspect the inner error in the message for which reattach field failed conversion.

err := d.RecoverTask(handle)
if err != nil && strings.Contains(err.Error(), "failed to build ReattachConfig") {
    // reattach data is invalid; give up recovery and reschedule
    return reschedule(allocID)
}

When it happens

Trigger: TaskState.ReattachConfig missing required fields (Pid, Protocol, Addr) or containing values that ReattachConfigToGoPlugin rejects during RecoverTask.

Common situations: Executor plugin died and left partial/invalid state; state persisted from an incompatible Nomad version with a different ReattachConfig shape.

Related errors

• failed to build ReattachConfig from taskConfig state: %v
• failed to reattach to executor: %v
• failed to reattach to executor: %v
• error: handle cannot be nil
• failed to decode taskConfig state from handle: %v

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/556966e2ebf192f6. Report an issue: GitHub.