Cannot use variables/interpolation with configurations expecting integers

[james-masson]

Nomad version

Nomad v0.8.7 (21a2d93eecf018ad2209a5eab6aae6c359267933+CHANGES)

Operating system and Environment details

Gentoo Linux + Docker 18.09.2

Issue

Cannot use variables/interpolation with configurations expecting integers.

I'm configuring a docker job to populate the shm_size config which expects an integer.

If submit the interpolation with surrounding quotes "${NOMAD_META_SHM_SIZE}",

I get

* field "shm_size" with input "${NOMAD_META_SHM_SIZE}" doesn't seem to be of type integer
* group "cluster" -> task "runme" -> config: 1 error(s) occurred:

If I submit the interpolation without surrounding quotes ${NOMAD_META_SHM_SIZE}

I get a syntax error

eg.

Error getting job struct: Error parsing job file from job.nomad: error parsing: At 24:20: illegal char

In terraform, this interpolated change of type seems to be handled internally, but here it seems a hard requirement of the shm_size configuration.

Job file (if appropriate)

job "stuff" {
  type = "service"
  datacenters = ["dc1"]
  meta {
    SHM_SIZE = 2000000000
  }
  group "cluster" {
    task "runme" {
      driver = "docker"
      config {
        shm_size = "${NOMAD_META_SHM_SIZE}"
        image = "image"
      }
    }
  }
}

[cgbaker]

Thanks for reporting this, @james-masson . I'll look into this right away.

[james-masson]

Thanks! - while I remember, it also makes no sense that it requires an integer, because docker also accepts strings with units - ie.

     --shm-size=""
          Size of /dev/shm. The format is <number><unit>.
          number must be greater than 0.  Unit is optional and can be b (bytes), k (kilobytes), m(megabytes), or g (gigabytes).
          If you omit the unit, the system uses bytes. If you omit the size entirely, the system uses 64m.

[cgbaker]

So, the first issue is that anything in the meta stanza for the job will be converted into strings: https://www.nomadproject.io/docs/job-specification/meta.html#meta-parameters So even if the task config interpolation supported non-strings, this field would still be a string.

I'll bring this up with the team and we can think about how this works into existing plans around HCL/HCL2 in the job spec.

[james-masson]

A nice fix for this particular occurrence would be to accept strings for docker -> shm_size

With docker-cli and docker-compose, not sure if the string/unit conversion is done on the client or the docker-daemon - but the standard seems to be to accept a string,

[cgbaker]

Agreed.

[grahamsk]

Hi all - Any update on this one? I'm looking at interpolating cpu/memory values in nomad templates.

[wiedenmeier]

+1 on this. It would be really nice to be able to specify memory as a meta parameter to a job.

I definitely see the issue with all parameters being strings, maybe a workaround would be attempting to parse string values as integers for fields that require ints?

[cgbaker]

no update, folks. this is in our internal tracker as well. thanks for pinging on this issue, will update here when this is resolved.

[tommyalatalo]

I also stumbled upon this just now, trying to set log rotation integers as meta values and using them doesn't work because of the strings issue here.

Hoping this gets updated soon so that integers get better support.

[chancez]

Ouch, i was hoping to do something like this in one of our tasks to give the a job all the resources on a particular node:

      resources {
        cpu = "${attr.cpu.totalcompute}"
        memory = "${attr.memory.totalbytes / 1024 / 1024}"
      }

[cgbaker]

@chancez, I'm not sure how to go about that. the attr block is known after scheduling, while the resources block must be known before scheduling (because it's part of the scheduling consideration).

For the rest, HCL2 support means there's probably a number of different ways to achieve this (I'm personally still learning my way around HCL2). Here's one way:

variable "shm_size" {
  type = number
  default = "12345678"
}
job "example" {
  type = "service"
  datacenters = ["dc1"]
  meta {
    SHM_SIZE = "${var.shm_size}"
  }
  group "cluster" {
    task "runme" {
      driver = "docker"
      config {
        shm_size = var.shm_size
        image = "nginx"
      }
    }
  }
}

This makes it into the API and through to docker:

$ nomad job inspect example | jq '.Job.Meta,.Job.TaskGroups[0].Tasks[0].Config'
{
  "SHM_SIZE": "12345678"
}
{
  "image": "nginx",
  "shm_size": 12345678
}

$ docker inspect 079b | jq '.[0].HostConfig.ShmSize'
12345678

edit: updated this with a nicer version after some experimentation

[chomey]

Bumping this, any update on integer interpolation? Would love to use dynamic job resource sizing (cpu/memory)

[sadjy]

Is there any update of this topic? I'm also interested in dynamic job resource sizing.

[prabirshrestha]

Hitting the same issue when trying to set port via nomadVars.

static = {{ with nomadVar "nomad/jobs/tarefik" }}{{ .port }}{{ end }}

[automatumkilian]

This would be THE essential feature for us! We start dockers with quite different memory usage from 10 GB to 100 GB and restricting them all to 100 GB would be as inefficient as we are already today. Since this ticket is already 5 years old, is there any progress to pass over some litte INT in the meantime? This would really help us.