system job leaks service registration

[fredwangwang]

Nomad version

0.12.5

Operating system and Environment details

linux + Consul 1.8.3

Issue

tested:
When removing the additional service stanzas from system type jobs and redeploy, the service registration leaks (not removed from Consul).

Reproduction steps

1. Deploy the job file below
2. Remove the following

-    service {
-      name = "example-service-2"
-      port = "api"
-    }

1. Redeploy the job file
2. The service registration still in Consul, and will remain there even after the job is stopped and gc-ed.

Job file (if appropriate)

job "example-system-job" {
  region      = "global"
  datacenters = ["dc1"]
  type        = "system"

  group "example-service-api-group" {
    count = 1

    network {
      mode = "bridge"
      port api  {}
    }

    service {
      name = "example-service-2"
      port = "api"
    }

    service {
      name = "example-service"
      port = "api"
      
      # this check seems have to be here, otherwise it will not trigger this bug.
      check {
        type     = "http"
        port     = "api"
        path     = "/ready"
        interval = "5s"
        timeout  = "1s"
      }
    }

    task "example-fake" {
      driver = "docker"

      config {
        image = "nicholasjackson/fake-service:v0.12.0"
      }

      env {
        LISTEN_ADDR = "0.0.0.0:${NOMAD_PORT_api}"
      }
    }
  }
}

[drewbailey]

@fredwangwang Thank you for reporting, sorry you are running into this. I've tracked the issue down to the scheduler, when an inplace update is made (like removing or updating a service block) the allocations shared (group) ports are dropped. I've created #9735 to track and will have a fix soon.

[fredwangwang]

@drewbailey thanks for investigating!

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