Scaling doesn't work when inicial number of task beyond the minimum and maximum values

[alekskar]

Describe the bug When applying policy with interval [MinCount, MaxCount ] to existent job with count value lower than MinCount scaling out is not occurs.

To reproduce Steps to reproduce the behavior ideally with policy and job examples. Nomad job example

job "test1" {
    region = "us-west-2"
        datacenters = ["us-west-2"]
    type = "service"
    group "api" {
        count = 1 < -- -- -- -- -- -- -- -- -- -- --not in interval[2, 4]
        task "test" {
            driver = "docker"
            config {
                image = "nginx:latest"
                }
            resources {
                cpu = 300# MHz
                memory = 256# MB
                }
            }
        }
    }

policy {
Enabled: true,
Cooldown: 180,
MinCount: 2,
MaxCount: 4,
ScaleOutCount: 1,
ScaleInCount: 1
}

Expected behavior Desired number of tasks becomes scalled out to 2.

Environment:

• Sherpa server information (retrieve with sherpa system info):

  NomadAddress    "http://http.nomad.service.my-dev:4646"
  PolicyEngine    "Sherpa API"
  StorageBackend  "Consul"
  InternalAutoScalingEngine   true
  StrictPolicyChecking    true

• Sherpa CLI version (retrieve with sherpa --version):

  sherpa version v0.4.1
  Date:   2020-01-17 20:02:32.946360009 +0000 UTC
  Commit: d215c85
  Branch: v0.4.1
  State:  v0.4.1

• Server Operating System/Architecture: Docker on Ubuntu 18

• Sherpa server configuration parameters:

  docker run -e "CONSUL_HTTP_ADDR=consul.service.my-dev:8500" -e "NOMAD_ADDR=http://http.nomad.service.my-dev:4646" -it -p 8000:8000 jrasell/sherpa server --cluster-name sherpa-test-akar --ui --bind-addr "" --storage-consul-enabled --autoscaler-enabled --policy-engine-api-enabled --log-level=debug

[iahim]

This seems to be correct. If you want 2 counts by default (the minimum) why don't you start nomad job with count 2? OR why don't you start sherpa with min 1 and max 4 ? I think the way it is working at the moment is correct.

[jrasell]

@alekskar and @iahim thanks for the information and what you notice is correct. I have it in my backlog to fix this and relates to this tweet I sent to try and gain opinions: https://twitter.com/jrasell/status/1205786409736515584

[alekskar]

This seems to be correct. If you want 2 counts by default (the minimum) why don't you start nomad job with count 2? OR why don't you start sherpa with min 1 and max 4 ? I think the way it is working at the moment is correct.

@iahim This is just about desired state. As a user I would like to be ensure that after applying scale policy autoscaller automatically adjust number of tasks to desired count within upper and lower bounds.