seqdiag {
    node_width = 80;
    edge_length = 100;

    "Client"
    "Tacker-server"
    "Tacker-conductor"
    "VnfLcmDriver"
    "OpenstackDriver"
    "Heat"
    "MgmtDriver"
    "VnfInstance(Tacker DB)"
    "RemoteCommandExecutor"
    "Ansible"
    "NfvoPlugin"

    Client -> "Tacker-server"
      [label = "1. POST /vnf_instances/{vnfInstanceId}/instantiate"];
    Client <-- "Tacker-server"
      [label = "Response 202 Accepted"];
    "Tacker-server" -> "Tacker-conductor"
      [label = "2. Trigger asynchronous task"];

   "Tacker-conductor" -> "VnfLcmDriver"
      [label = "3. Execute VnfLcmDriver"];
    "VnfLcmDriver" -> "OpenstackDriver"
      [label = "4. Execute OpenstackDriver"];
    "OpenstackDriver" -> "Heat"
      [label = "5. Create stack"];
    "OpenstackDriver" <-- "Heat"
      [label = "Return stack id"];
    "VnfLcmDriver" <-- "OpenstackDriver"
      [label = "Return instance_id"];

    "VnfLcmDriver" -> "MgmtDriver"
      [label = "6. Instantiate_end"];
    "MgmtDriver" -> "VnfInstance(Tacker DB)"
      [label = "7. Get stack id"];
    "MgmtDriver" <-- "VnfInstance(Tacker DB)"
      [label = ""];
    "MgmtDriver" -> "Heat"
      [label = "8. Get SSH IP address"];
    "MgmtDriver" <-- "Heat"
      [label = ""];
    "MgmtDriver" -> "MgmtDriver"
      [label = "9. Generate a new inventory file"];
    "MgmtDriver" -> "RemoteCommandExecutor"
      [label = "10. Call Ansible via SSH"];
    "RemoteCommandExecutor" -> "Ansible"
      [label = "11. Run playbooks"];
    "RemoteCommandExecutor" <-- "Ansible"
      [label = ""];
    "MgmtDriver" <-- "RemoteCommandExecutor"
      [label = ""];
    "MgmtDriver" -> "RemoteCommandExecutor"
      [label = "12. Get access info of Kubernetes cluster"];
    "MgmtDriver" <-- "RemoteCommandExecutor"
      [label = ""];
    "MgmtDriver" -> "NfvoPlugin"
      [label = "13. Register Kubernetes VIM to tacker"];
    "MgmtDriver" <-- "NfvoPlugin"
      [label = ""];
    "MgmtDriver" -> "VnfInstance(Tacker DB)"
      [label = "14. Update VimConnectionInfo with access info of Kubernetes cluster"];
    "MgmtDriver" <-- "VnfInstance(Tacker DB)"
      [label = ""];
    "MgmtDriver" -> "RemoteCommandExecutor"
      [label = "15. Install and configure ExternalLB"];
    "MgmtDriver" <-- "RemoteCommandExecutor"
      [label = ""];
    "VnfLcmDriver" <-- "MgmtDriver"
      [label = ""];
    "Tacker-conductor" <-- "VnfLcmDriver"
      [label = ""];

  }