I think this is slightly different. The code for searching for networks is OK because the add_interfaces_to_compute_attrs method in orchestration/compute.rb copies the interfaces_attributes into the compute_attributes into the right place, this all seems to be working correctly.

It appears that if you just pass:

        "interfaces_attributes": {
            "0": {
                "compute_attributes": {
                    "network": "SDC1_111" 
                }
            }
        }

into a host creation, then Host::Base creates a second, primary interface as it doesn't think there is a primary supplied. This second interface doesn't have any compute_attributes and so you get the blank network ID error.

In my test it was generating these two NICs when I passed the interfaces_attributes above:

=> [#<Nic::Managed id: nil, mac: nil, ip: nil, type: "Nic::Managed", name: nil, host_id: nil, subnet_id: nil, domain_id: nil, attrs: {}, created_at: nil, updated_at: nil, provider: nil, username: nil, password: nil, virtual: false, link: true, identifier: nil, tag: "", at
tached_to: "", managed: true, mode: "balance-rr", attached_devices: "", bond_options: "", primary: false, provision: false, compute_attributes: {"network"=>"SDC1_111"}>,
 #<Nic::Managed id: nil, mac: nil, ip: "192.168.122.118", type: "Nic::Managed", name: "dcleal-test2.example.com", host_id: nil, subnet_id: 4, domain_id: 6, attrs: {}, created_at: nil, updated_at: nil, provider: nil, username: nil, password: nil, virtual: false, link: true
, identifier: nil, tag: "", attached_to: "", managed: true, mode: "balance-rr", attached_devices: "", bond_options: "", primary: true, provision: true, compute_attributes: {}>]

When I send this, it generates only one NIC and works better:

{
    "interfaces_attributes": {
        "0": {
            "primary": 1,
            "compute_attributes": {
                "network": "SDC1_111" 
            }
        }
    }
}

Can we specify primary with Hammer, or should we improve the logic for primary NIC creation in Host::Base to merge interface_attributes into the new primary NIC if there's only one supplied?