[Bug]: The fleet `idle_duration` property is not respected on run apply

[peterschmidt85]

Steps to reproduce

1. Define an elastic fleet (nodes set to, e.g., 0..2) with idle_duration set to a non-default, e.g. 1h
2. Create the fleet
3. Run something on this fleet, and see instance provisioned
4. Wait for 5 min

Actual behaviour

1. See the fleet instance is terminated after 5 min of idle time

Expected behaviour

1. The instance should be only terminated after the specified idle_duration (e.g. 1h that was set)

dstack version

0.19.29

Server logs

[11:12:43] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.009657s. Status: 200
           DEBUG    dstack._internal.server.services.runner.client:437 shim version: 5648 (latest) (API v2)
           DEBUG    dstack._internal.server.services.runner.client:437 shim version: 5648 (latest) (API v2)
           DEBUG    dstack._internal.server.services.runner.client:437 shim version: 5648 (latest) (API v2)
           DEBUG    dstack._internal.server.background.tasks.process_instances:753 Instance default-fleet-3 check: reachable=True health_status=HEALTHY message=None
           DEBUG    dstack._internal.server.background.tasks.process_instances:753 Instance default-fleet-0 check: reachable=True health_status=HEALTHY message=None
           DEBUG    dstack._internal.server.background.tasks.process_instances:753 Instance default-fleet-2 check: reachable=True health_status=HEALTHY message=None
[11:12:45] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.007610s. Status: 200
[11:12:47] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.008801s. Status: 200
[11:12:49] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.010839s. Status: 200
           DEBUG    dstack._internal.server.services.runner.client:437 shim version: 5648 (latest) (API v2)
           DEBUG    dstack._internal.server.background.tasks.process_instances:753 Instance default-fleet-1 check: reachable=True health_status=HEALTHY message=None
[11:12:51] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005884s. Status: 200
[11:12:53] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005520s. Status: 200
[11:12:55] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.007050s. Status: 200
[11:12:57] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.007643s. Status: 200
           INFO     dstack._internal.server.background.tasks.process_instances:244 Instance default-fleet-3 idle duration expired: idle time 304s. Terminating
           INFO     dstack._internal.server.background.tasks.process_instances:244 Instance default-fleet-0 idle duration expired: idle time 303s. Terminating
[11:12:58] DEBUG    dstack._internal.server.services.runner.client:437 shim version: 5648 (latest) (API v2)
           DEBUG    dstack._internal.server.background.tasks.process_instances:753 Instance default-fleet-2 check: reachable=True health_status=HEALTHY message=None
[11:12:59] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005763s. Status: 200
[11:13:01] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.006631s. Status: 200
           INFO     dstack._internal.server.background.tasks.process_instances:244 Instance default-fleet-1 idle duration expired: idle time 308s. Terminating
[11:13:03] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.008135s. Status: 200
[11:13:05] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.008310s. Status: 200
[11:13:07] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005859s. Status: 200
[11:13:09] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005901s. Status: 200
[11:13:11] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.008436s. Status: 200
[11:13:12] DEBUG    dstack._internal.server.background.tasks.process_instances:931 Terminating runner instance 66.201.7.150
           INFO     dstack._internal.server.background.tasks.process_instances:244 Instance default-fleet-2 idle duration expired: idle time 313s. Terminating
           DEBUG    dstack._internal.server.background.tasks.process_instances:931 Terminating runner instance 89.169.113.5
           DEBUG    dstack._internal.server.background.tasks.process_instances:931 Terminating runner instance 89.169.103.248
[11:13:13] DEBUG    dstack._internal.server.background.tasks.process_instances:945 Instance default-fleet-1 termination in progress: Requested instance deletion. Will wait for deletion before deleting
                    the boot disk. Instance state was: RUNNING
           DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.007218s. Status: 200
           DEBUG    dstack._internal.server.background.tasks.process_instances:945 Instance default-fleet-0 termination in progress: Requested instance deletion. Will wait for deletion before deleting
                    the boot disk. Instance state was: RUNNING
           DEBUG    dstack._internal.server.background.tasks.process_instances:945 Instance default-fleet-3 termination in progress: Requested instance deletion. Will wait for deletion before deleting
                    the boot disk. Instance state was: RUNNING
[11:13:15] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.004047s. Status: 200
[11:13:17] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.006713s. Status: 200
[11:13:19] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.009223s. Status: 200
[11:13:21] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005080s. Status: 200
[11:13:23] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005599s. Status: 200
[11:13:25] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.006019s. Status: 200
[11:13:27] DEBUG    dstack._internal.server.background.tasks.process_instances:931 Terminating runner instance 195.242.10.107
           DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.006627s. Status: 200
           DEBUG    dstack._internal.server.background.tasks.process_instances:945 Instance default-fleet-2 termination in progress: Requested instance deletion. Will wait for deletion before deleting
                    the boot disk. Instance state was: RUNNING
[11:13:29] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.006346s. Status: 200
[11:13:31] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.007675s. Status: 200
[11:13:33] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005842s. Status: 200
[11:13:35] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.007353s. Status: 200
[11:13:37] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.008929s. Status: 200
[11:13:39] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.009682s. Status: 200
[11:13:41] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.007881s. Status: 200
[11:13:43] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.006099s. Status: 200
[11:13:45] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.006654s. Status: 200
[11:13:47] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.008366s. Status: 200
[11:13:49] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005361s. Status: 200
[11:13:51] DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.003927s. Status: 200
[11:13:53] DEBUG    dstack._internal.server.background.tasks.process_instances:931 Terminating runner instance 89.169.103.248
           DEBUG    dstack._internal.server.background.tasks.process_instances:931 Terminating runner instance 89.169.113.5
           DEBUG    dstack._internal.server.background.tasks.process_instances:931 Terminating runner instance 66.201.7.150
           DEBUG    dstack._internal.server.background.tasks.process_instances:945 Instance default-fleet-1 termination in progress: Waiting for instance deletion before deleting the boot disk.
                    Instance state: DELETING
           DEBUG    dstack._internal.server.app:259 Processed request POST http://127.0.0.1:3000/api/project/main/fleets/list in 0.005925s. Status: 200
           INFO     dstack._internal.server.background.tasks.process_instances:969 Instance default-fleet-0 terminated
           INFO     dstack._internal.server.background.tasks.process_instances:969 Instance default-fleet-3 terminated

Additional information

In the database, the idle_duration is set to 3600:

select * from fleets where name = "my-idle-cluster";
                   id = 1df5c786461e465aa41d0fc0522d5838
                 name = my-idle-cluster
           project_id = b37112f856a84887b0df193462f98dea
           created_at = 2025-09-16 09:31:05.210792
    last_processed_at = 2025-09-16 09:31:05.210796
              deleted = 0
           deleted_at = 
               status = ACTIVE
       status_message = 
                 spec = {"configuration":{"type":"fleet","name":"my-idle-cluster","env":{},"ssh_config":null,"nodes":{"min":0,"max":2},"placement":null,"reservation":null,"resources":{"cpu":{"min":2,"max":null},"memory":{"min":8.0,"max":null},"shm_size":null,"gpu":null,"disk":{"size":{"min":100.0,"max":null}}},"blocks":1,"backends":["nebius"],"regions":null,"availability_zones":null,"instance_types":null,"spot_policy":null,"retry":null,"max_price":null,"idle_duration":3600,"tags":null},"configuration_path":".local/fleet.dstack.yml","profile":{"backends":null,"regions":null,"availability_zones":null,"instance_types":null,"reservation":null,"spot_policy":"auto","retry":null,"max_duration":null,"stop_duration":null,"max_price":1.0,"creation_policy":null,"idle_duration":null,"utilization_policy":null,"startup_order":null,"stop_criteria":null,"schedule":null,"fleets":null,"tags":null,"name":"my-profile","default":true},"autocreated":false}
consolidation_attempt = 0
 last_consolidated_at = 

Apparently, the idle_duration property is not used. See

dstack/src/dstack/_internal/server/background/tasks/process_submitted_jobs.py

Line 867 in 27a42b7

profile = run_spec.merged_profile