Allow forced replacement of route table associated with subnet

[YakDriver]

Fixes #73

UPDATE 7/19/19: Rather than force replacement, allow the import of route table associations allows the associations to be updated. See below.

Changes proposed in this pull request:

• r/aws_route_table_association: Add new argument force_replace allowing a route table to be associated with a subnet even if another route table is already associated. Add corresponding docs & tests.
• r/aws_route_table_association: Implement import so that associations can be updated after they are imported.

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccAWSRouteTableAssociation_'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./... -v -parallel 20 -run=TestAccAWSRouteTableAssociation_ -timeout 120m
?   	github.com/terraform-providers/terraform-provider-aws	[no test files]
=== RUN   TestAccAWSRouteTableAssociation_basic
=== PAUSE TestAccAWSRouteTableAssociation_basic
=== RUN   TestAccAWSRouteTableAssociation_replace
=== PAUSE TestAccAWSRouteTableAssociation_replace
=== CONT  TestAccAWSRouteTableAssociation_basic
=== CONT  TestAccAWSRouteTableAssociation_replace
--- PASS: TestAccAWSRouteTableAssociation_replace (63.32s)
--- PASS: TestAccAWSRouteTableAssociation_basic (63.59s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	63.696s

[YakDriver]

Here is a usage example.

Assume that subnet-04ff24b9b39f3822b was already associated with a route table. Normally, attempting to associate another route table, you would receive an error like this:

* aws_route_table_association.new_assoc: Resource.AlreadyAssociated: the specified association for route table rtb-05c7d040bf39801b0 conflicts with an existing association

However, with this PR, you can set the force_replace argument to true, and the association will replace the prior association.

resource "aws_route_table_association" "new_assoc" {
  route_table_id = "${aws_route_table.new_guy.id}"
  subnet_id      = "subnet-04ff24b9b39f3822b"
  force_replace  = true
}

$ terraform apply
aws_route_table.new_guy: Creation complete after 0s (ID: rtb-0833a30c3ba11dc03)
aws_route_table_association.new_assoc: Creating...
  force_replace:  "" => "true"
  route_table_id: "" => "rtb-0833a30c3ba11dc03"
  subnet_id:      "" => "subnet-04ff24b9b39f3822b"
aws_route_table_association.new_assoc: Creation complete after 1s (ID: rtbassoc-08cbb18f6a3d7a975)

Apply complete! Resources: 2 added, 0 changed, 0 destroyed.

[yves-vogl]

I'm hitting this issue too and would like to thank you for this patch.

[janjur]

Please, merge.

[aleksap]

Please merge! We are hitting a major blocker with this issue.
Thanks!

[ibehren1]

Please merge -- need this as well.

[pit]

Waiting for merge also!

My case is importing existing resources into terraform state. And it's not possible to import aws_route_table_association (#561) and not possible to force old route table recreation.

[lorengordon]

Anything we can do to promote this patch? Keep having to pop into the console to deal with this one, when people re-associate a route table improperly, since terraform fails to override this association. :(

[aleksap]

Any good soul out there that could merge this? ^^

[YakDriver]

@bflad As discussed, I've implemented import for route table associations and taken out the force_replace argument. I've updated the docs and acceptance tests to test imports and updates.

example

A simplified example of using this.

Environment 1:

resource "aws_subnet" "client-network" {
...
}

resource "aws_route_table" "client-routes" {
...
}

resource "aws_route_table_association" "client-routes" {
  route_table_id = aws_route_table.client-routes.id
  subnet_id      = aws_subnet.client-network.id
}

$ terraform apply

Environment 2:

resource "aws_subnet" "new_sn" {
...
}

resource "aws_route_table_association" "replace" {
  route_table_id = var.route_table_id
  subnet_id      = aws_subnet. new_sn.id
}

$ terraform import aws_route_table_association.assoc subnet-6777656e646f6c796e/rtb-656c65616e6f72
$ terraform apply

Voilà. Association updated.

acceptance tests

$ make testacc TEST=./aws TESTARGS='-run=TestAccAWSRouteTableAssociation_'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./aws -v -parallel 20 -run=TestAccAWSRouteTableAssociation_ -timeout 120m
=== RUN   TestAccAWSRouteTableAssociation_basic
=== PAUSE TestAccAWSRouteTableAssociation_basic
=== RUN   TestAccAWSRouteTableAssociation_replace
=== PAUSE TestAccAWSRouteTableAssociation_replace
=== CONT  TestAccAWSRouteTableAssociation_basic
=== CONT  TestAccAWSRouteTableAssociation_replace
--- PASS: TestAccAWSRouteTableAssociation_basic (84.47s)
--- PASS: TestAccAWSRouteTableAssociation_replace (87.10s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	87.162s

[YakDriver]

@aleksap @lorengordon @pit @ibehren1 @janjur @yves-vogl Please speak up if there are scenarios where import -> modify won't work and where you'd still need to force replace an association. My thinking is that having import capability (this PR) should cover most/all scenarios.

[bflad]

Hi @YakDriver 👋 Thanks so much for the updates and sticking through this one. Overall looking really good, just a few minor things. Please reach out with any questions or if you do not have time to implement the feedback. 👍

[YakDriver]

@bflad I made the changes you requested. Let me know if there is anything else you see.

$ make testacc TESTARGS='-run=TestAccAWSRouteTableAssociation_'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./... -v -parallel 20 -run=TestAccAWSRouteTableAssociation_ -timeout 120m
?   	github.com/terraform-providers/terraform-provider-aws	[no test files]
=== RUN   TestAccAWSRouteTableAssociation_basic
=== PAUSE TestAccAWSRouteTableAssociation_basic
=== RUN   TestAccAWSRouteTableAssociation_replace
=== PAUSE TestAccAWSRouteTableAssociation_replace
=== CONT  TestAccAWSRouteTableAssociation_basic
=== CONT  TestAccAWSRouteTableAssociation_replace
--- PASS: TestAccAWSRouteTableAssociation_basic (69.87s)
--- PASS: TestAccAWSRouteTableAssociation_replace (70.10s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	70.190s

[bflad]

Looks great, @YakDriver, thanks! 🚀

--- PASS: TestAccAWSRouteTableAssociation_replace (27.43s)
--- PASS: TestAccAWSRouteTableAssociation_basic (27.60s)

[ghost]

This has been released in version 2.22.0 of the Terraform AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template for triage. Thanks!

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!