Skip to content

HowtoDefineMultiStringTXTRecords.md

Latest commit

 

History

History
58 lines (42 loc) · 2.44 KB

HowtoDefineMultiStringTXTRecords.md

File metadata and controls

58 lines (42 loc) · 2.44 KB

According to DNS-SD, detailed information about a service must be provided in 1 TXT record, as key=value pairs. Different key=value pairs must be in separate DNS strings within the same TXT record.

In Route53 via Terraform

Terraform expects a list of records. Each record is a Terraform string, and becomes a TXT record. All the DNS strings for 1 DNS Record must be crammed into 1 Terraform string.

Starting from a Terraform map var.details, this can be done like this:

resource "aws_route53_record" "txt_record" {
  zone_id = "…"
  name    = "…"
  type    = "TXT"
  ttl     = "…"

  records = ["${join("\"\"", formatlist("%s=%s", keys(var.details), values(var.details)))}"]
}

formatlist combines the list of keys of the map with the list of values of the map into key=value pairs using the pattern $s=%s. The result is a list of strings, each of which is a key=value pair.

Submitting this like this to records results in a separate TXT record per key=value pair, which is not what we want.

To transform this list of strings into 1 Terraform string, we need to join the list. To make AWS Route53 understand that the parts are separate DNS strings, each part needs to be enclosed in quotes "…". In several steps, by Terraform and AWS, quotes " are added in front and at the back of this joined string. What is missing are the quotes between the key=value pairs. We can add these by using them as a weird join pattern. However, for Terraform to leave them alone when it passes them to AWS, we need to quote them. The separator pattern thus becomes \"\".

In Route53 via the Web UI

In the Route53 Web UI, we can add several strings on several lines. Each separate line becomes a separate TXT record. It is thus important to have all our key=value pairs on the same line in the TEXTAREA.

To have the AWS Route53 Web UI create separate DNS strings for each key=value pair, we need to enclose each key=value pair in double quotes: "key=value", concatenate them (without spaces or other separators) and keep all of them on one line:

"apiVersion=v6""at=2017-09-12T16:54:00Z""implVersion=v6""path=/latest""submitted=2017-09-12T23:00:02Z""txtvers=1"

In Dyn.com via the Web UI

None of the above works in the Dyn.com Web UI. It seems like it is impossible to create a multi-string TXT record in Dyn.com.

A support question was posted.