Loop on Widget part - terraform

Question

How to iterate only the widget part of the terraform script and get all the widget in a single dashboard?
locals {
instances = csvdecode(file("${path.module}/sample.csv"))
}
// if we use count it will loop this part
resource "aws_cloudwatch_dashboard" "main" {
dashboard_name = "my-dashboard"
dashboard_body = <<EOF
{
"widgets": [
{
"type":"metric",
"x":0,
"y":0,
"width":12,
"height":6,
"properties":{
"metrics":[
for itr in local.instances.id:
[
"AWS/EC2",
"CPUUtilization",
"InstanceId",
itr // want this section to fetch the value form excel
]
],
"period":300,
"stat":"Average",
"region":"ap-south-1",
"title":"EC2 Instance CPU ",
"annotations": {
"horizontal": [
{
"label": "Untitled annotation",
"value": 2
}]}
}},]}EOF}

Answer 1

If your goal is to generate JSON, it's generally better to use jsonencode rather than template_file, because it can handle the JSON syntax details automatically and thus avoid the need to tweak annoying details of a text template to get the JSON right.
For example:
dashboard_body = jsonencode({
"widgets": [
"type": "metric",
"x": 0,
"y": 0,
"width": 12,
"height": 6,
"properties": {
"metrics": [
for inst in local.instances : [
"AWS/EC2",
"CPUUtilization",
"InstanceId",
inst.id,
]
],
"period": 300,
# etc, etc
},
],
})
By using jsonencode you can use any of Terraform's normal language features and functions to produce your data structure, and leave the jsonencode function to turn that into valid JSON syntax at the end.

Answer 2

I tried to use two template_file resources.
sample.csv for test
instance_id
i-00001
i-00002
i-00003
create a template_file resouce for loop,
data "template_file" "ec2_metric" {
count = length(local.instances)
template = jsonencode([ "AWS/EC2", "CPUUtilization", "InstanceId", element(local.instances.*.instance_id, count.index)])
}
create a template_file for whole json
data "template_file" "widgets" {
template = <<JSON
{
"widgets": [
{
"type":"metric",
"x":0,
"y":0,
"width":12,
"height":6,
"properties":{
"metrics":[
${join(", \n ", data.template_file.ec2_metric.*.rendered)}
],
"period":300,
"stat":"Average",
"region":"ap-south-1",
"title":"EC2 Instance CPU ",
"annotations": {
"horizontal": [
{
"label": "Untitled annotation",
"value": 2
}]}
}},]}
JSON
}
using template_file,
resource "aws_cloudwatch_dashboard" "main" {
dashboard_name = "my-dashboard"
dashboard_body = data.template_file.widgets.rendered
...
}
Test template_file.widgets
output "test" {
value = data.template_file.widgets.rendered
}
result
Outputs:
test = {
"widgets": [
{
"type":"metric",
"x":0,
"y":0,
"width":12,
"height":6,
"properties":{
"metrics":[
["AWS/EC2","CPUUtilization","InstanceId","i-00001"],
["AWS/EC2","CPUUtilization","InstanceId","i-00002"],
["AWS/EC2","CPUUtilization","InstanceId","i-00003"]
],
"period":300,
"stat":"Average",
"region":"ap-south-1",
"title":"EC2 Instance CPU ",
"annotations": {
"horizontal": [
{
"label": "Untitled annotation",
"value": 2
}]}
}},]}