Service UDP Check: TTL must be > 0 for TTL checks

[sycured]

Overview of the Issue

I'm trying to add the service file "service_unbound.hcl" on my lab using your snippet (https://www.consul.io/docs/discovery/checks#udp-check)

service {
  name = "unbound"
  id   = "unbound"
  port = 53

  enable_tag_override = false

  check = {
    id = "dns"
    name = "DNS UDP on port 53"
    udp = "localhost:53"
    interval = "10s"
    timeout = "2s"
  }
}

Error

Error reloading: Unexpected response code: 500 (service "unbound": check "DNS UDP on port 53": TTL must be > 0 for TTL checks)

Reproduction Steps

Steps to reproduce this issue, eg:

1. Create a cluster with n client nodes n and n server nodes
2. Create the service file in /etc/consul.d/
3. Run consul reload
4. View error

Operating system and Environment details

Consul 1.13.2 (revision 0e046bb)
Oracle Linux 9 on x86_64 and aarch64

[jkirschner-hashicorp]

Hi @sycured,

I see that this is your first post here - welcome to the Consul community!

Thank you for sharing this report. Your check definition looks normal to me. (It looks like a straight copy of an example we provide in the docs.)

The error message makes it seem like Consul thinks a "TTL" type check is configured (not just a "UDP" type check). But no ttl field is provided in the check definition, so I'm not sure why that will be. Flagging this as a possible bug to investigate.

[jkirschner-hashicorp]

Hi @sycured,

Refer to PR #14885 for more details. That should be merged soon and included in 1.14.0 and the next 1.13.x patch release.

My understanding is that the bug affects check definitions registered as a part of agent configuration files (flows 4 and 5 described in the dev docs for check registration flows). I think other registration flows (e.g., CLI and HTTP API) will work as expected if a workaround is needed in the meantime.

Thanks again!

[sycured]

Hi @jkirschner-hashicorp,
Thank you for the update and possible workarounds.