Using logically structured Stack Resources

Goal

In this tutorial you will learn how to organise stack resources that depend on each other in a structured way.
One example use case is to create your network before you create and add servers to it.

Prerequisites

You should be able to use simple heat templates, like shown in the first steps tutorial.
You know the basics of using the OpenStack CLI-Tools.
Environment variables are set, like shown in the API-Access-Tutorial.

The Problem: Creating Resources fails

If Resources are not created in a defined order, they will be created randomly. This can cause stack creation to fail:

syselevenstack@kickstart:~/failingDemo$ openstack stack create -t clustersetup.yaml -e clustersetup-env.yaml noDependencies --wait
2016-10-18 13:50:48 [noDependencies]: CREATE_IN_PROGRESS  Stack CREATE started
2016-10-18 13:50:48 [syseleven_net]: CREATE_IN_PROGRESS  state changed
2016-10-18 13:50:48 [syseleven_router]: CREATE_IN_PROGRESS  state changed
2016-10-18 13:50:50 [syseleven_net]: CREATE_COMPLETE  state changed
2016-10-18 13:50:50 [syseleven_router]: CREATE_COMPLETE  state changed
2016-10-18 13:50:50 [dbserver_group]: CREATE_IN_PROGRESS  state changed
2016-10-18 13:50:51 [servicehost_group]: CREATE_IN_PROGRESS  state changed
2016-10-18 13:50:53 [lb_group]: CREATE_IN_PROGRESS  state changed
2016-10-18 13:50:55 [appserver_group]: CREATE_IN_PROGRESS  state changed
2016-10-18 13:50:58 [syseleven_subnet]: CREATE_IN_PROGRESS  state changed
2016-10-18 13:51:00 [syseleven_subnet]: CREATE_COMPLETE  state changed
2016-10-18 13:51:00 [router_subnet_connect]: CREATE_IN_PROGRESS  state changed
2016-10-18 13:51:02 [router_subnet_connect]: CREATE_COMPLETE  state changed
2016-10-18 13:51:02 [dbserver_group]: CREATE_FAILED  BadRequest: resources.dbserver_group.resources[0].resources.dbserver: Port de3404ba-3b43-4123-bf1d-1a1809ea434a requires a FixedIP in order to be used. (HTTP 400) (Request-ID: req-bcd57a8b-7290-4311-8800-46fc78fb0f8d)
2016-10-18 13:51:10 [lb_group]: CREATE_COMPLETE  state changed
2016-10-18 13:51:11 [servicehost_group]: CREATE_COMPLETE  state changed
2016-10-18 13:51:17 [appserver_group]: CREATE_COMPLETE  state changed
2016-10-18 13:51:17 [noDependencies]: CREATE_FAILED  Resource CREATE failed: BadRequest: resources.dbserver_group.resources[0].resources.dbserver: Port de3404ba-3b43-4123-bf1d-1a1809ea434a requires a FixedIP in order to be used. (HTTP 400) (Request-ID: req-bcd57a8b-7290-4311-8800-46fc78fb0f8d)

 Stack noDependencies CREATE_FAILED

syselevenstack@kickstart:~/failingDemo$

The Solution: Define the Order of Resource Creation

In a Heat template you can define dependencies using the keyword depends_on:

resources:
  syseleven_net:
    type: OS::Neutron::Net
    properties:
      name: syseleven-net

  syseleven_subnet:
    type: OS::Neutron::Subnet
    depends_on: [ syseleven_net ] # <-- Here the order while creating and deleting resourcces is defined.

You can observe this using the option --wait when using the OpenStack command line tools to create a stack:

syselevenstack@kickstart:~/heat-examples/example-setup$ openstack stack create -t clustersetup.yaml -e clustersetup-env.yaml depTest --wait
2016-10-19 11:42:17 [depTest]: CREATE_IN_PROGRESS  Stack CREATE started
2016-10-19 11:42:17 [syseleven_net]: CREATE_IN_PROGRESS  state changed
2016-10-19 11:42:18 [syseleven_net]: CREATE_COMPLETE  state changed
2016-10-19 11:42:18 [syseleven_subnet]: CREATE_IN_PROGRESS  state changed
2016-10-19 11:42:20 [syseleven_subnet]: CREATE_COMPLETE  state changed
2016-10-19 11:42:20 [syseleven_router]: CREATE_IN_PROGRESS  state changed
2016-10-19 11:42:22 [syseleven_router]: CREATE_COMPLETE  state changed
2016-10-19 11:42:22 [router_subnet_connect]: CREATE_IN_PROGRESS  state changed
2016-10-19 11:42:25 [router_subnet_connect]: CREATE_COMPLETE  state changed
2016-10-19 11:42:25 [servicehost_group]: CREATE_IN_PROGRESS  state changed
2016-10-19 11:42:26 [lb_group]: CREATE_IN_PROGRESS  state changed
2016-10-19 11:42:27 [appserver_group]: CREATE_IN_PROGRESS  state changed
2016-10-19 11:42:31 [dbserver_group]: CREATE_IN_PROGRESS  state changed
2016-10-19 11:42:43 [servicehost_group]: CREATE_COMPLETE  state changed
2016-10-19 11:42:44 [dbserver_group]: CREATE_COMPLETE  state changed
2016-10-19 11:42:45 [lb_group]: CREATE_COMPLETE  state changed
2016-10-19 11:42:50 [appserver_group]: CREATE_COMPLETE  state changed
2016-10-19 11:42:50 [depTest]: CREATE_COMPLETE  Stack CREATE completed successfully
+---------------------+-----------------------------------------------------------------+
| Field               | Value                                                           |
+---------------------+-----------------------------------------------------------------+
| id                  | cc2dd31a-feb0-4026-8693-29926c8b1191                            |
| stack_name          | depTest                                                         |
| description         | A template to deploy and configure a loadbalanced server setup. |
| creation_time       | 2016-10-19T11:42:17                                             |
| updated_time        | None                                                            |
| stack_status        | CREATE_COMPLETE                                                 |
| stack_status_reason | Stack CREATE completed successfully                             |
+---------------------+-----------------------------------------------------------------+

Examples

We provided an example setup on github which uses dependencies.