alertmanager receivers incorrect syntax

[anarcat]

How to reproduce (e.g Puppet code you use)

In Debian:

  class { 'prometheus::alertmanager':
    package_ensure => 'present',
    service_ensure => 'running',
    install_method => 'package',
    init_style     => 'none',
    user           => 'prometheus',
    group          => 'prometheus',
    package_name   => 'prometheus-alertmanager',
    service_name   => 'prometheus-alertmanager',
    # disable clustering
    extra_options  => '--cluster.listen-address=',
}

But I suspect a simple:

include prometheus::alertmanager

would also trigger this.

What are you seeing

Mar 31 18:16:43 hetzner-nbg1-02 prometheus-alertmanager[9316]: level=info ts=2021-03-31T18:16:43.376918397Z caller=main.go:322 msg="Loading configuration file" file=/etc/alertmanager/alertmanager.yaml
Mar 31 18:16:43 hetzner-nbg1-02 prometheus-alertmanager[9316]: level=error ts=2021-03-31T18:16:43.377199383Z caller=main.go:325 msg="Loading configuration file failed" file=/etc/alertmanager/alertmanager.yaml err="missing name in receiver"
Mar 31 18:16:43 hetzner-nbg1-02 systemd[1]: prometheus-alertmanager.service: Main process exited, code=exited, status=1/FAILURE

What behaviour did you expect instead

If I add this to the class, it works:

    receivers      => [
      {
        'name'          => 'Admin',
        'email_configs' => [
          'to'          => 'root@localhost',
        ],
      }
    ],

I suspect the syntax of the YAML file is incorrect.