Add versioned Beta support to google_compute_instance_group_manager

[rileykarson]

Split of #198 - Part 1/2

Add support for multiple versions to google_compute_instance_group_manager, by adding simultaneous support for v1 and v0beta. No fields are v0beta yet, so it will not enter that state. Setting InstanceGroupManagerBaseVersion to v0beta instead of v1 will allow you to test the beta code.

This is the first versioned resource for #93

@danawillow

[rileykarson]

I just caught an issue that wasn't failing before and is now; ForceSendFields is lost when converting between versions, and target_size needs to be force sent if it has a 0 value. The rest of my local tests are still running but I expect them to pass, target_size was updated on master and had to be merged.

The last 2 commits still need to be reviewed, the rest were covered in past pull requests.

[rileykarson]

Just finished my local test run and all of them are passing now.

[catsby]

Before this or other Beta features are merged I would like to see some documentation on how users will be exposed to this and expected to use it. Specifically:

• is the idea to document specific attributes as Beta and users are implicitly opting in by specifying that attribute?
• are these features likely to change or be not as reliable as Production features?
• what is the plan for promoting these attributes to production ready, non-beta status?
• what is the plan for breaking changes to beta attributes?

[rileykarson]

Hi @catsby!

I'm not sure where this kind of documentation would live yet; if you have a good idea of where it should go, I'd love the advice. It doesn't seem to fit with the main provider page, which is about authentication, for example. For now, to go over your questions;

1 - Enrolling in Beta Features

Users of the Terraform GCP Provider will enroll in Beta features implicitly by using fields that are marked Beta in the documentation. Resources that are considered to be in Beta will use the v0beta endpoints of the Compute API, instead of the v1 endpoints.

While this has not been realised yet, some resources may begin supporting the Update operation only in the Beta API for fields that are otherwise GA. When this is the case, or if it has explicit demand, support for a provider-level “GA-only” field will be added that a user can set to cause Terraform to return an error if it would have used a non-GA Compute API (in case the customer has a strict need for GA-only features/APIs).

When the support for custom diffs has evolved in Terraform’s core/helper libraries, we will investigate populating diffs with information about what API is being used.

2 - Beta Feature Reliability

GCP does not offer SLAs for features in Beta; they are not necessarily going to be as reliable as GA resources. As highlighted in the GCP Launch Stages documentation, Beta releases tend to be feature-complete but may be more unstable than a release in GA, with some open outstanding issues still present.

In practice, this should mean that Beta releases are stable & reliable releases, especially if they have been in Beta for some amount of time.

3 - Feature Promotion

When a feature is promoted to GA from Beta, we will remove the “Beta” tag in documentation and remove the field from the list of Beta fields in code. The next time Terraform performs a refresh, it will implicitly be read as a GA resource, and operations will be performed against GA APIs again.

4 - Breaking Changes

Breaking changes are less of a concern for Beta releases from GCP than the label Beta might suggest; as shown in Launch Stages, any Beta release will be feature complete and should not surface breaking changes on the path to GA outside of extraordinary circumstances. Beta releases are the time that a GCP feature has entered the public eye.

While we don’t present an SLA or deprecation policy for Beta features, that doesn’t necessarily mean that they will go without a deprecation period. For example, Managed Instance Group Updates, an Alpha feature, has gone through a deprecation period beginning in September 2016 that is still ongoing: from rolling updates to managed instance groups to updating managed instance groups.

Major breaking changes for Beta features can be handled on a case by case basis; if a feature is removed entirely, we will need to deprecate and remove it quickly, generating a major version out of schedule if necessary. If a feature is renamed/replaced, we will prioritise adding support for the new version, deprecating the old one, and removing it when appropriate.

[danawillow]

I'm happy with this, though we should probably wait on a response from @catsby before merging.

[catsby]

My primary concern is the UX when enabling/using Beta features. I'm not immediately aware of other instances in Terraform where Beta features are used yet, but I want to keep the usage consistent. Perhaps even as far as a boolean field in the schema that will automatically present a notice to the user that they are using a Beta feature, but we can cross that bridge later I suppose.

No fields are v0beta yet, so it will not enter that state

👍

I would appreciate a ping on any future PRs that actually introduce beta attributes, if that's not too much to ask 😄

The rest LGTM

[catsby]

Can we bump this up to above the schema declaration? It's kind of tucked away here on line 147, all by itself.

Also, but not required, I'd name it something that describes it's function/intent better, so specifically calling out that we're setting the base API version that the resource is talking to. Without getting too wordy, something like igmBaseAPIVersion. Not required though.

[rileykarson]

Done.

[rileykarson]

@catsby: Will do!

Tests:

==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./google -v -run=TestAccInstanceGroupManager_ -timeout 120m
=== RUN   TestAccInstanceGroupManager_importBasic
--- PASS: TestAccInstanceGroupManager_importBasic (265.09s)
=== RUN   TestAccInstanceGroupManager_importUpdate
--- PASS: TestAccInstanceGroupManager_importUpdate (212.84s)
=== RUN   TestAccInstanceGroupManager_basic
--- PASS: TestAccInstanceGroupManager_basic (221.84s)
=== RUN   TestAccInstanceGroupManager_targetSizeZero
--- PASS: TestAccInstanceGroupManager_targetSizeZero (45.23s)
=== RUN   TestAccInstanceGroupManager_update
--- PASS: TestAccInstanceGroupManager_update (277.79s)
=== RUN   TestAccInstanceGroupManager_updateLifecycle
--- PASS: TestAccInstanceGroupManager_updateLifecycle (105.11s)
=== RUN   TestAccInstanceGroupManager_updateStrategy
--- PASS: TestAccInstanceGroupManager_updateStrategy (211.10s)
=== RUN   TestAccInstanceGroupManager_separateRegions
--- PASS: TestAccInstanceGroupManager_separateRegions (212.83s)
PASS
ok  	github.com/terraform-providers/terraform-provider-google/google	1552.027s

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