在地形中使用目标选项时，为什么有时会返回目标资源旁边的其他资源

Question

我在ELB堆栈中创建了一个cloudwatch警报，如下所示：

module "elb_sg" {
source                   = "[e-mail]:terraform-aws-modules/terraform-aws-security-group.git"
name                     = "${local.name}-elb-sg"
description              = "Allow internet inbound traffic"
vpc_id                   = "${data.terraform_remote_state.vpc.vpc_id}"
ingress_with_cidr_blocks = "${data.null_data_source.elb_sg_rules.*.inputs}"
tags                     = "${local.tags}"
# Open egress for all
egress_with_cidr_blocks = "${local.open_egress}"
}
#  ELB
module "elb" {
source                      = "[e-mail]:terraform-aws-modules/terraform-aws-elb.git"
name                        = "${local.name}"
subnets                     = ["${split(",",local.elb_subnets)}"]
internal                    = "${var.internal}"
security_groups             = "${local.elb_security_group_ids}"
cross_zone_load_balancing   = "${var.cross_zone_load_balancing}"
idle_timeout                = "${var.idle_timeout}"
connection_draining         = "${var.connection_draining}"
connection_draining_timeout = "${var.connection_draining_timeout}"
listener                    = ["${var.listener}"]
access_logs                 = ["${var.access_logs}"]
health_check                = ["${var.health_check}"]
tags                        = "${local.tags}"
}

# Cloudwatch alarms
data "aws_elb" "classic_lb" {
count = "${module.elb.this_elb_name != "" ? 1 : 0}"
name  = "${module.elb.this_elb_name}"
}
resource "aws_cloudwatch_metric_alarm" "low_healthy_host_count_alarm" {
count                = "${var.create_alarm ? 1 : 0}"
# alarm_name         = "${module.elb.this_elb_name}-HealthyHostCount"
alarm_name           = "${data.aws_elb.classic_lb.name}-HealthyHostCount"
dimensions {
# LoadBalancerName = "${module.elb.this_elb_name}"
LoadBalancerName   = "${data.aws_elb.classic_lb.name}"
}
...
}

然而，我尝试使用data source以及像${module.elb.this_elb_name}这样的直接模块访问来获取ELB名称，因为它存在于AWS上(而不是在我的本地，因为有时AWS会截断长名称(。但这两次，当只针对像terraform plan -target=aws_cloudwatch_metric_alarm.low_healthy_host_count_alarm这样的警报时，我也会针对其他资源，这是我不想要的。

Terraform will perform the following actions:
+ aws_cloudwatch_metric_alarm.low_healthy_host_count_alarm
id:                                    <computed>
actions_enabled:                       "true"
...
~ module.elb_sg.aws_security_group.this
...
~ module.elb.module.elb.aws_elb.this
access_logs.#:                         "0" => "1"
access_logs.0.bucket:                  "" => "test-logs"
access_logs.0.enabled:                 "" => "true"
access_logs.0.interval:                "" => "60"
...

Plan: 1 to add, 2 to change, 0 to destroy.

当我在cloudwatch警报中为elb-in维度和alarm_name使用硬编码名称或local.name时，问题就消失了。

有人能解释到底是什么导致了这种行为吗？谢谢

Answer 1

根据这个官方文档，当我们指定模块路径时，"目标"适用于指定模块中的所有资源以及指定模块的所有派生模块。

这就是为什么当为elb使用硬编码值时，我们不会将依赖项作为目标。

但我们使用的是模块路径，文档中也提到，"如果指定的模块路径没有资源规范，则地址适用于模块中的每个资源。">