CODEWITHSUNDEEP
terraform
iGEL
iGEL

Reputation: 17392

Terraform variables and count = 0

We use the same terraform definitions across all environments. So far that worked well, but now I face a problem I couldn't solve yet. I have a RDS and ElastiCache for a service that I don't need in the demo env that I'm setting up right now, so I set the count to 0. For the other environments, I need to expose them via an output var:

resource "aws_elasticache_cluster" "cc_redis" {
  cluster_id = "cc-${var.env}"
  engine = "redis"
  node_type = "cache.t2.small"
  security_group_ids = ["..."]
  count = "${var.env == "demo" ? 0 : 1}"
}

output "cc_redis_host" {
  value = "${aws_elasticache_cluster.cc_redis.cache_nodes.0.address}"
}

Now I'm getting this error:

output.cc_redis_host: Resource 'aws_elasticache_cluster.cc_redis' not found
for variable 'aws_elasticache_cluster.cc_redis.cache_nodes.0.address'

I don't mind (much) having a useless variable set, but I can't get it to work in the first place. A simple conditional doesn't resolve this, since terraform evaluates the false side of conditionals even though it's not used. I found this hack but couldn't get it to work either.

Upvotes: 9

Views: 16040

Answers (4)

Ashish Kumar
Ashish Kumar

Reputation: 581

You can put something like below:

output "cc_redis" {
  value = var.env == "demo" : null ? aws_elasticache_cluster.cc_redis.cache_nodes.0.address
}

Output also accept null, and if its null, it will ignore it at the time of execution.

Upvotes: 0

jok
jok

Reputation: 41

For the people that are coming from google to this thread this is the terraform newer version of handling this: tolist method with the square brackets is the new approach.

value = "${element(concat(aws_elasticache_cluster.cc_redis.cache_nodes.*. address, tolist([""])), 0)}"

Upvotes: 0

KJH
KJH

Reputation: 2430

Try this:

output "cc_redis" {
  value = "${element(concat(aws_elasticache_cluster.cc_redis.*.cache_nodes.0.address, list("")), 0)}"
}

TF doesn't seem to care that the count may be 0 if you wildcard higher up the chain.

This may output more than you want, but you can parse out what you need from it.

Upvotes: 8

victor m
victor m

Reputation: 2175

Change your output to the following:

output "cc_redis_host" {
  value = "${element(concat(aws_elasticache_cluster.cc_redis.cache_nodes.*. address, list("")), 0)}"
}

It is documented somewhere on the terraform website.

Upvotes: 0

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