Change min forward target group action rule to one per docs

[autotune]

Description

The following would error out because target_group in forward schema was set to a minimum of two. Per the documentation, this should work correctly with a minimum of one.

resource "aws_vpc" "main" {
  cidr_block = "10.0.0.0/16"
}

resource "aws_subnet" "main" {
  vpc_id     = aws_vpc.main.id
  cidr_block = "10.0.1.0/24"


  availability_zone = "us-east-2a"
  tags = {
    Name = "Main"
  }
}

resource "aws_subnet" "secondary" {
  vpc_id     = aws_vpc.main.id
  cidr_block = "10.0.2.0/24"

  availability_zone = "us-east-2b"
  tags = {
    Name = "Main"
  }
}

resource "aws_internet_gateway" "gw" {
  vpc_id = aws_vpc.main.id

  tags = {
    Name = "main"
  }
}

resource "aws_lb" "front_end" {
  name               = "test-lb-tf"
  internal           = false
  load_balancer_type = "application"
  subnets            = [aws_subnet.main.id, aws_subnet.secondary.id]

  enable_deletion_protection = true

  tags = {
    Environment = "production"
  }
}


resource "aws_lb_target_group" "front_end" {
  name     = "tf-example-lb-tg"
  port     = 80
  protocol = "HTTP"
  vpc_id   = aws_vpc.main.id
}


resource "aws_lb_listener" "front_end" {
  load_balancer_arn = aws_lb.front_end.arn
  port              = "80"
  protocol          = "HTTP"

  default_action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.front_end.arn
      forward {
        target_group {
          arn    = aws_lb_target_group.front_end.arn 
          weight = 80
        }
      }
   }
}

resource "aws_lb_listener_rule" "front_end" {
  listener_arn = aws_lb_listener.front_end.arn

  condition {
    path_pattern {
      values = ["/ng/"]
    }
  }

  action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.front_end.arn
      forward {
        target_group {
          arn    = aws_lb_target_group.front_end.arn 
        }
      }
   }
}

Relations

Closes #13636

Output from Acceptance Testing

% make testacc TESTS=TestAccELBV2Listener_basic PKG=elbv2
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/elbv2/... -v -count 1 -parallel 20 -run='TestAccELBV2Listener_basic'  -timeout 360m
=== RUN   TestAccELBV2Listener_basic
=== PAUSE TestAccELBV2Listener_basic
=== CONT  TestAccELBV2Listener_basic
--- PASS: TestAccELBV2Listener_basic (208.97s)
PASS
ok  	github.com/hashicorp/terraform-provider-aws/internal/service/elbv2	211.154s

[github-actions]

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[jar-b]

LGTM 🎉

% make testacc TESTS=TestAccELBV2ListenerRule_ PKG=elbv2
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./internal/service/elbv2/... -v -count 1 -parallel 20 -run='TestAccELBV2ListenerRule_'  -timeout 360m

--- PASS: TestAccELBV2ListenerRule_conditionAttributesCount (441.72s)
=== CONT  TestAccELBV2ListenerRule_changeListenerRuleARNForcesNew
--- PASS: TestAccELBV2ListenerRule_conditionQueryString (902.20s)
=== CONT  TestAccELBV2ListenerRule_oidc
--- PASS: TestAccELBV2ListenerRule_conditionPathPattern (906.63s)
=== CONT  TestAccELBV2ListenerRule_cognito
--- PASS: TestAccELBV2ListenerRule_fixedResponse (915.86s)
=== CONT  TestAccELBV2ListenerRule_conditionHTTPRequestMethod
--- PASS: TestAccELBV2ListenerRule_conditionMultiple (916.77s)
=== CONT  TestAccELBV2ListenerRule_ConditionHTTPHeader_invalid
--- PASS: TestAccELBV2ListenerRule_conditionSourceIP (918.71s)
=== CONT  TestAccELBV2ListenerRule_updateRulePriority
--- PASS: TestAccELBV2ListenerRule_conditionHostHeader (924.70s)
--- PASS: TestAccELBV2ListenerRule_conditionHTTPHeader (935.31s)
--- PASS: TestAccELBV2ListenerRule_ConditionHTTPHeader_invalid (20.89s)
--- PASS: TestAccELBV2ListenerRule_backwardsCompatibility (1074.18s)
--- PASS: TestAccELBV2ListenerRule_basic (1093.57s)
--- PASS: TestAccELBV2ListenerRule_disappears (1108.64s)
--- PASS: TestAccELBV2ListenerRule_Action_order (1128.40s)
--- PASS: TestAccELBV2ListenerRule_ActionOrder_recreates (1157.47s)
=== NAME  TestAccELBV2ListenerRule_priority
    listener_rule_test.go:540: Step 2/8 error: Check failed: Check 2/2 error: aws_lb_listener_rule.last: Attribute 'priority' expected "4", got "1"
--- PASS: TestAccELBV2ListenerRule_updateFixedResponse (1300.54s)
--- PASS: TestAccELBV2ListenerRule_conditionUpdateMultiple (1315.19s)
--- FAIL: TestAccELBV2ListenerRule_priority (1331.41s)
--- PASS: TestAccELBV2ListenerRule_redirect (1512.45s)
--- PASS: TestAccELBV2ListenerRule_conditionHTTPRequestMethod (623.31s)
--- PASS: TestAccELBV2ListenerRule_conditionUpdateMixed (1560.54s)
--- PASS: TestAccELBV2ListenerRule_changeListenerRuleARNForcesNew (1122.80s)
--- PASS: TestAccELBV2ListenerRule_oidc (722.73s)
--- PASS: TestAccELBV2ListenerRule_tags (1671.71s)
--- PASS: TestAccELBV2ListenerRule_forwardWeighted (1679.47s)
--- PASS: TestAccELBV2ListenerRule_cognito (791.57s)
--- PASS: TestAccELBV2ListenerRule_updateRulePriority (836.99s)
FAIL
FAIL    github.com/hashicorp/terraform-provider-aws/internal/service/elbv2      1759.308s
FAIL
make: *** [testacc] Error 1

Failure is unrelated to this change.

[jar-b]

CreateRule documentation confirms a single target group argument is valid.

https://docs.aws.amazon.com/elasticloadbalancing/latest/APIReference/API_Action.html

ForwardConfig
... If you specify both ForwardConfig and TargetGroupArn, you can specify only one target group using ForwardConfig and it must be the same target group specified in TargetGroupArn.

https://docs.aws.amazon.com/elasticloadbalancing/latest/APIReference/API_ForwardActionConfig.html

TargetGroups.member.N
The target groups. For Network Load Balancers, you can specify a single target group.

[jar-b]

Thanks for your contribution, @autotune! 👏

[github-actions]

This functionality has been released in v5.24.0 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. Thank you!

[github-actions]

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