Decompose cluster template for Heat¶
https://blueprints.launchpad.net/sahara/+spec/heat-template-decomposition
Currently Sahara creates one large template with a lot of copy-paste resources. Heat features like template composition could help to move all composition work from Sahara to Heat. This will also allow sahara to have individual cluster parts as separate templates and insert them as resources (in comparison to current text manipulations).
Problem description¶
Currently Sahara serializes cluster resources as text to heat template. There are several issues with this approach:
Code duplication. If a node group contains 10 instances the template will contain all instance-dependent resources 10 times.
No code validation. There is no guarantee that resulting template will be syntactically correct (Sahara treats it as text). Missing comma in one resource could influence the other resource.
Not Sahara’s work. Sahara micro-manages the process of infrastructure creation. This is Heat’s job.
Proposed change¶
Use OS::Heat::ResourceGroup for resources inside node group. Each node group will contain only one resource group and specify number of instances needed. Each individual instance of resource group will contain all resources needed for a corresponding sahara instance (nova server, security group, volume, floating ip, etc.).
This change will also prepare ground for node group auto-scaling feature.
Alternatives¶
None.
Data model impact¶
None.
REST API impact¶
None.
Other end user impact¶
Resulting Sahara stack in Heat will contain nested stacks.
Deployer impact¶
None.
Developer impact¶
None.
Sahara-image-elements impact¶
None.
Sahara-dashboard / Horizon impact¶
None.
Implementation¶
Assignee(s)¶
- Primary assignee:
alazarev (Andrew Lazarev)
- Other contributors:
None
Work Items¶
Add ability to generate separate ResourceGroup for a single instance of node group
Switch template for node groups to ResourceGroup with specified count of instances
Update unit tests
Make sure that Sahara with heat engine still works for all supported configurations
Dependencies¶
None.
Testing¶
Manually. CI will also cover changes in heat.
Documentation Impact¶
None.
References¶
None.
