resource/aws_main_route_table_association: Crash during creation

[ghost]

This issue was originally opened by @paschalidi as hashicorp/terraform#27142. It was migrated here as a result of the provider split. The original body of the issue is below.

---

Version

Terraform v0.13.5
+ provider registry.terraform.io/hashicorp/aws v3.19.0

https://gist.github.com/paschalidi/acdf7d52afbe0e415a5a26dca96e2478

[bflad]

Relevant snippet of log:

2020-12-04T14:18:21.552Z [DEBUG] plugin.terraform-provider-aws_v3.19.0_x5: panic: runtime error: invalid memory address or nil pointer dereference
2020-12-04T14:18:21.552Z [DEBUG] plugin.terraform-provider-aws_v3.19.0_x5: [signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x50f1174]
2020-12-04T14:18:21.552Z [DEBUG] plugin.terraform-provider-aws_v3.19.0_x5: 
2020-12-04T14:18:21.552Z [DEBUG] plugin.terraform-provider-aws_v3.19.0_x5: goroutine 133 [running]:
2020-12-04T14:18:21.552Z [DEBUG] plugin.terraform-provider-aws_v3.19.0_x5: github.com/terraform-providers/terraform-provider-aws/aws.resourceAwsMainRouteTableAssociationCreate(0xc0019c9280, 0x6259600, 0xc0016fc100, 0x0, 0xffffffffffffffff)
2020-12-04T14:18:21.552Z [DEBUG] plugin.terraform-provider-aws_v3.19.0_x5: 	/opt/teamcity-agent/work/5d79fe75d4460a2f/src/github.com/hashicorp/terraform-provider-aws/aws/resource_aws_main_route_table_association.go:55 +0x244

Given the code:

terraform-provider-aws/aws/resource_aws_main_route_table_association.go

Lines 49 to 55 in b31cce2

	mainAssociation, err := findMainRouteTableAssociation(conn, vpcId)
	if err != nil {
	return err
	}
	resp, err := conn.ReplaceRouteTableAssociation(&ec2.ReplaceRouteTableAssociationInput{
	AssociationId: mainAssociation.RouteTableAssociationId,

The mainAssociation needs a nil check to return an error before dereferencing, e.g.

	mainAssociation, err := findMainRouteTableAssociation(conn, vpcId)

	if err != nil {
		return fmt.Errorf("error finding EC2 VPC (%s) main route table association: %w", vpcId, err)
	}

	if mainAssociation == nil {
		return fmt.Errorf("error finding EC2 VPC (%s) main route table association: not found", vpcId)
	}

	resp, err := conn.ReplaceRouteTableAssociation(&ec2.ReplaceRouteTableAssociationInput{

This won't prevent whatever caused the issue to begin with, but it will at least return a proper error instead of the crash.

[bflad]

@paschalidi do you have any additional information about what may have caused this crash? e.g. what you were trying to do, an example configuration, etc.

[paschalidi]

hey well, I was trying to set up a vpc with some ec2 instances. I dont know if that helps but I run many time the apply command without planning first. I did the same with the destroy.

After a while things were out of sync and terraform was crashing.

I hope this helps a little @bdoepf. Cant say more than that unfortunately, but I hope I can help

[bflad]

Fix submitted to return an error instead of crash in this situation: #16680

[paschalidi]

Thanks for looking into this @bflad.

[bflad]

The fix to prevent the crash (and instead return an error) has been merged and will release with version 3.22.0 of the Terraform AWS Provider, likely tomorrow. Please note that this fix is not intended to prevent any potentially underlying problem that might be causing the association to be non-existent when the code is executed. If the new error is being thrown in a reproducible way after this adjustment, it is best to submit a new bug report following the issue template so we have further details for troubleshooting. 👍

[ghost]

This has been released in version 3.22.0 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!