Completely deprecate old NLB from the metaflow-metadata-service module #9
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This PR completely the deprecation of NLB and its migration to ALB towards DAT-106. The `moved` blocks will be removed with a later PR after a subsequent apply. Test plan --- Check that terraform plan reports destroy of old NLB but no other changes.
WalkthroughThis change removes all conditional logic and variables related to optionally setting up an Application Load Balancer (ALB) or pointing the API Gateway to an ALB in the metadata-service module. The configuration now always creates and uses the Network Load Balancer (NLB), and the variables Changes
Sequence Diagram(s)sequenceDiagram
participant User
participant Terraform
participant AWS
User->>Terraform: Apply metadata-service module
Terraform->>AWS: Create NLB (aws_lb.apigw_nlb)
Terraform->>AWS: Create associated target groups, listeners, security groups
Terraform->>AWS: Configure ECS service with dynamic load balancer blocks
Terraform->>AWS: Configure API Gateway VPC link to always use NLB
Assessment against linked issues
Assessment against linked issues: Out-of-scope changes
Possibly related PRs
Suggested reviewers
Poem
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🔇 Additional comments (1)
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🔭 Outside diff range comments (1)
modules/metadata-service/ec2.tf (1)
158-166: Indexing a single-instance resource breaks the plan – remove all[0]suffixes.All ALB / NLB / SG resources have been converted from
count = 1lists to singleton resources.
However, many references still use the old indexed address (resource_name[0]). Oncecountis gone this address no longer exists andterraform planwill fail with “Invalid index” errors.Concrete offenders:
aws_security_group.metadata_alb_security_group[0].idaws_lb.alb[0].arnaws_lb_target_group.alb_main[0].arnaws_lb_target_group.alb_db_migrate[0].arnaws_lb.apigw_nlb[0].arnaws_lb_target_group.apigw_*[0].arnFix all of them by dropping the index:
- security_groups = [aws_security_group.metadata_alb_security_group[0].id] + security_groups = [aws_security_group.metadata_alb_security_group.id] - load_balancer_arn = aws_lb.alb[0].arn + load_balancer_arn = aws_lb.alb.arn - target_group_arn = aws_lb_target_group.alb_main[0].arn + target_group_arn = aws_lb_target_group.alb_main.arn…and similarly for every other occurrence.
Failing to do so will block
terraform plan/applyand leave the module undeployable.
Please update all references and run a plan to verify.Also applies to: 210-230, 258-306
🧹 Nitpick comments (2)
modules/metadata-service/api-gateway.tf (1)
53-56: Variable names now misleading – consider renaming for clarity.
local.alb_arn/alb_dns_nameactually hold the NLB’s ARN/DNS.
While not functionally wrong, the mis-label can confuse future maintainers.-locals { - alb_arn = aws_lb.apigw_nlb.arn - alb_dns_name = aws_lb.apigw_nlb.dns_name +locals { + nlb_arn = aws_lb.apigw_nlb.arn + nlb_dns_name = aws_lb.apigw_nlb.dns_name } ... - target_arns = [local.alb_arn] + target_arns = [local.nlb_arn] ... - uri = "http://${local.alb_dns_name}/{proxy}" + uri = "http://${local.nlb_dns_name}/{proxy}"Renaming avoids cognitive friction and aligns terminology.
modules/metadata-service/ecs.tf (1)
70-73: List-index mapping works but is brittle – prefer an object map.Relying on parallel lists and numeric indices (
local.alb_ports[0] ↔ local.alb_target_groups[0]) is error-prone. Represent the relationship explicitly with a map:locals { alb_lb_map = { 8080 = aws_lb_target_group.alb_main.arn 8082 = aws_lb_target_group.alb_db_migrate.arn } } dynamic "load_balancer" { for_each = local.alb_lb_map content { target_group_arn = load_balancer.value container_name = "${var.resource_prefix}service${var.resource_suffix}" container_port = tonumber(load_balancer.key) } }This removes the dependence on positional indices and scales better if more ports are added.
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📒 Files selected for processing (4)
modules/metadata-service/api-gateway.tf(1 hunks)modules/metadata-service/ec2.tf(1 hunks)modules/metadata-service/ecs.tf(1 hunks)modules/metadata-service/variables.tf(0 hunks)
💤 Files with no reviewable changes (1)
- modules/metadata-service/variables.tf
🔇 Additional comments (1)
modules/metadata-service/ec2.tf (1)
1-55:moved {}blocks are correct but incomplete without the reference fixes.The state-migration blocks accurately map
old_resource[0]→new_resource.
Yet because downstream code still points at[0], the move will succeed while the plan phase immediately crashes on those stale references (see previous comment). After fixing the indices, keep thesemovedblocks – they’ll seamlessly migrate the state.
This PR completely the deprecation of NLB and its migration to ALB towards DAT-106.
The
movedblocks will be removed with a later PR after a subsequent apply.Test plan
Check that terraform plan reports destroy of old NLB but no other changes.