hashicorp/nomad · error

failed to launch docker logger plugin: %v

Error message

failed to launch docker logger plugin: %v

What it means

This error comes from setupNewDockerLogger when `docklog.LaunchDockerLogger(d.logger)` cannot spawn the docker-logger plugin subprocess (a go-plugin launch). Any plugin.Client launch failure is wrapped here; if a pluginClient handle was partially created it is killed first, then the task start/recover aborts with this message.

Source

Thrown at drivers/docker/driver.go:222

	if err != nil {
		return nil, nil, err
	}

	dlogger, dloggerPluginClient, err := docklog.ReattachDockerLogger(reattach)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to reattach to docker logger process: %v", err)
	}

	return dlogger, dloggerPluginClient, nil
}

func (d *Driver) setupNewDockerLogger(container mclient.ContainerInspectResult, cfg *drivers.TaskConfig, startTime time.Time) (docklog.DockerLogger, *plugin.Client, error) {
	dlogger, pluginClient, err := docklog.LaunchDockerLogger(d.logger)
	if err != nil {
		if pluginClient != nil {
			pluginClient.Kill()
		}
		return nil, nil, fmt.Errorf("failed to launch docker logger plugin: %v", err)
	}

	if err := dlogger.Start(&docklog.StartOpts{
		Endpoint:    d.config.Endpoint,
		ContainerID: container.Container.ID,
		TTY:         container.Container.Config.Tty,
		Stdout:      cfg.StdoutPath,
		Stderr:      cfg.StderrPath,
		TLSCert:     d.config.TLS.Cert,
		TLSKey:      d.config.TLS.Key,
		TLSCA:       d.config.TLS.CA,
		StartTime:   startTime.Unix(),
	}); err != nil {
		pluginClient.Kill()
		return nil, nil, fmt.Errorf("failed to launch docker logger process %s: %v", container.Container.ID, err)
	}

	return dlogger, pluginClient, nil

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Confirm the docker-logger plugin binary exists in the expected plugin path and is executable (chmod +x).
2. Reinstall or repair the Nomad client installation so the plugin ships with a matching version.
3. Check client logs for the underlying launch error (exec not found vs handshake timeout) and fix permissions/SELinux/AppArmor accordingly.
4. Ensure the plugin handshake timeout is sufficient on slow or heavily loaded hosts.

Example fix

// before: plugin missing or not executable
-rw-r--r-- nomad-docker-logger
// after
chmod +x /opt/nomad/plugins/nomad-docker-logger && systemctl restart nomad

p := filepath.Join(pluginDir, "nomad-docker-logger")
if fi, err := os.Stat(p); err != nil || !isExecutable(fi) {
    return fmt.Errorf("docker logger plugin missing or not executable at %s", p)
}

func isPluginLaunchErr(err error) bool { return err != nil && strings.Contains(err.Error(), "failed to launch docker logger plugin") }

dlogger, client, err := setupNewDockerLogger(...)
if err != nil {
    if isPluginLaunchErr(err) {
        logger.Error("plugin launch failed; check binary/permissions", "err", err)
        return retry.NewBackoff().Do(func() error { return startTask(cfg) })
    }
    return err
}

When it happens

Trigger: StartTask or RecoverTask call setupNewDockerLogger and the plugin launcher fails: the docker-logger binary is missing or not executable, the plugin handshake timed out, or the launch failed at exec time.

Common situations: Nomad data_dir or plugin directory missing/inaccessible; binary removed by a partial upgrade; overly restrictive permissions or AppArmor/SELinux blocking exec of the plugin; environment (e.g. containerized client) lacking the runtime to execute the plugin.

Related errors

• failed to reattach to docker logger process: %v
• failed to launch docker logger process %s: %v
• failed to get docker client: %w
• task with ID %q already started
• failed to decode driver config: %v

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/388e7fb82b558fe3. Report an issue: GitHub.