Contents
Section Six: Orchestration¶
Note
Sorry! We’re not quite happy with this chapter. It will give you an introduction to heat, but it’s a little dry at the moment. We’d like to write a template for the Fractals app instead of using the “hello world” style ones, so stay tuned!
Throughout this guide, we’ve talked about the importance of durability and scalability for your cloud-based applications. In most cases, really achieving these qualities means automating tasks such as scaling and other operational tasks.
The Orchestration module provides a template-based way to describe a cloud application, then coordinates running the needed OpenStack API calls to run cloud applications. The templates allow you to create most OpenStack resource types, such as instances, networking information, volumes, security groups and even users. It also provides more advanced functionality, such as instance high availability, instance auto-scaling, and nested stacks.
The OpenStack Orchestration API contains the following constructs:
- Stacks
- Resources
- Templates
Stacks are created from Templates, which contain Resources. Resources are an abstraction in the HOT (Heat Orchestration Template) template language, which enables you to define different cloud resources by setting the type attibute.
For example, you might use the Orchestration API to create two compute instances by creating a Stack and by passing a Template to the Orchestration API. That Template would contain two Resources with the type attribute set to OS::Nova::Server.
That’s a simplistic example, of course, but the flexibility of the Resource object enables the creation of Templates that contain all the required cloud infrastructure to run an application, such as load balancers, block storage volumes, compute instances, networking topology, and security policies.
Note
The Orchestration module isn’t deployed by default in every cloud. If these commands don’t work, it means the Orchestration API isn’t available; ask your support team for assistance.
This section introduces the HOT templating language, and takes you throughsome of the common calls you will make when working with OpenStack Orchestration.
Unlike previous sections of this guide, in which you used your SDK to programmatically interact with OpenStack, in this section you’ll be using the Orchestration API directly through Template files, so we’ll work from the command line.
Install the ‘heat’ commandline client by following this guide: http://docs.openstack.org/cli-reference/content/install_clients.html
then set up the necessary variables for your cloud in an ‘openrc’ file using this guide: http://docs.openstack.org/cli-reference/content/cli_openrc.html
Warning
libcloud does not currently support OpenStack Orchestration.
HOT Templating Language¶
The best place to learn about the template syntax for OpenStack Orchestration is the Heat Orchestration Template (HOT) Guide You should read the HOT Guide first to learn how to create basic templates, their inputs and outputs.
Working with Stacks: Basics¶
- Stack create
In the following example, we use the hello_world Hot template to demonstrate creating a Nova compute instance, with a few configuration settings passed in, such as an administrative password and the unique identifier (UUID) of an image:
$ wget https://raw.githubusercontent.com/openstack/heat-templates/master/hot/hello_world.yaml
$ heat stack-create --template-file hello_world.yaml \
--parameters admin_pass=Test123\;key_name=test\;image=5bbe4073-90c0-4ec9-833c-092459cc4539 hello_world
+--------------------------------------+-------------+--------------------+----------------------+
| id | stack_name | stack_status | creation_time |
+--------------------------------------+-------------+--------------------+----------------------+
| 0db2c026-fb9a-4849-b51d-b1df244096cd | hello_world | CREATE_IN_PROGRESS | 2015-04-01T03:20:25Z |
+--------------------------------------+-------------+--------------------+----------------------+
The resulting stack creates a Nova instance automatically, which you can see here:
$ nova list
+--------------------------------------+---------------------------------+--------+------------+-------------+------------------+
| ID | Name | Status | Task State | Power State | Networks |
+--------------------------------------+---------------------------------+--------+------------+-------------+------------------+
| 9bdf0e2f-415e-43a0-90ea-63a5faf86cf9 | hello_world-server-dwmwhzfxgoor | ACTIVE | - | Running | private=10.0.0.3 |
+--------------------------------------+---------------------------------+--------+------------+-------------+------------------+
Verify that the stack was successfully created using the following command:
$ heat stack-list
+--------------------------------------+-------------+-----------------+----------------------+
| id | stack_name | stack_status | creation_time |
+--------------------------------------+-------------+-----------------+----------------------+
| 0db2c026-fb9a-4849-b51d-b1df244096cd | hello_world | CREATE_COMPLETE | 2015-04-01T03:20:25Z |
+--------------------------------------+-------------+-----------------+----------------------+
Remove the stack:
$ heat stack-delete hello_world
+--------------------------------------+-------------+--------------------+----------------------+
| id | stack_name | stack_status | creation_time |
+--------------------------------------+-------------+--------------------+----------------------+
| 0db2c026-fb9a-4849-b51d-b1df244096cd | hello_world | DELETE_IN_PROGRESS | 2015-04-01T03:20:25Z |
+--------------------------------------+-------------+--------------------+----------------------+
Verify that the removal of the stack has deleted the nova instance:
$ nova list
+----+------+--------+------------+-------------+----------+
| ID | Name | Status | Task State | Power State | Networks |
+----+------+--------+------------+-------------+----------+
+----+------+--------+------------+-------------+----------+
While this stack is not very interesting - it just starts a single instance - it is possible to make very complicated templates that involve dozens of instances or adds and removes instances based on demand. Continue to the next section to learn more.
Working with Stacks: Advanced¶
With the use of the Orchestration API, the Fractal app can create an autoscaling group for all parts of the application, in order to dynamically provision more compute resources during periods of heavy utilization, and also terminate compute instances to scale down, as demand decreases.
There are two helpful articles available to learn about autoscaling with the Orchestration API:
- http://superuser.openstack.org/articles/simple-auto-scaling-environment-with-heat
- http://superuser.openstack.org/articles/understanding-openstack-heat-auto-scaling
An example template that creates an auto-scaling wordpress instance can be found in the heat template repository
Next Steps¶
You should now be fairly confident working with the Orchestration service. There are several calls we did not cover. To see these and more, refer to the volume documentation of your SDK, or try a different step in the tutorial, including:
- Section Seven: Networking - to learn about more complex networking
- Section Eight: Advice for Developers new to Operations - for advice for developers new to operations
- Section Nine: Going Crazy - to see all the crazy things we think ordinary folks won’t want to do ;)
Except where otherwise noted, this document is licensed under Creative Commons Attribution 3.0 License http://creativecommons.org/licenses/by/3.0/legalcode.