Escape chars in Terraform local exec provisioner - ansible

Question

I want to chain Terraform and Ansible using the local-exec provisioner;
However since this requires input to Ansible from Terraform I am stuck with the following complex command:
provisioner "local-exec" {
command = 'sleep 60; ansible-playbook -i ../ansible/inventory/ ../ansible/playbooks/site.yml --extra-vars "rancher_server_rds_endpoint="${aws_db_instance.my-server-rds.endpoint}" rancher_server_elastic_ip="${aws_eip.my-server-eip.public_ip}""'
}
which keeps returning
illegal char
error;
any suggestion about escaping correctly?
If the ansible-playbook command was to run directly in the shell it would be:
ansible-playbook -i inventory playbooks/site.yml --extra-vars "my_server_rds_endpoint=my-server-db.d30ikkj222.us-west-1.rds.amazonaws.com rancher_server_elastic_ip=88.148.17.236"
(paths differ)

Answer 1

Terraform syntax states that:
Strings are in double-quotes.
So you need to replace single quotes with double ones, and then escape quotes inside, for example:
provisioner "local-exec" {
command = "sleep 60; ansible-playbook -i ../ansible/inventory/ ../ansible/playbooks/site.yml --extra-vars \"rancher_server_rds_endpoint='${aws_db_instance.my-server-rds.endpoint}' rancher_server_elastic_ip='${aws_eip.my-server-eip.public_ip}'\""
}

Answer 2

The only way I know, that will work for any special characters in variables, is to use environment, for example:
provisioner "local-exec" {
command = join(
" ", [
"sleep 60;",
"ansible-playbook -i ../ansible/inventory/",
"../ansible/playbooks/site.yml",
"--extra-vars",
"rancher_server_rds_endpoint=\"$RANCHER_SERVER_RDS_ENDPOINT\"",
"rancher_server_elastic_ip=\"$RANCHER_SERVER_ELASTIC_IP\""
]
)
environment = {
RANCHER_SERVER_RDS_ENDPOINT = aws_db_instance.my-server-rds.endpoint
RANCHER_SERVER_ELASTIC_IP = aws_eip.my-server-eip.public_ip
}
}