Why is my GKE cluster upscaling when I create a namespace?

General Discussions
1

Cluster information:

Kubernetes version: 1.15.11-gke.12
Cloud being used: GKE

I’m observing a strange behaviour of a newly created cluster in GKE. Just after creating it, there is one node. When I create my first namespace, it autoscales up to 2 nodes, although the resources on the first node are still very low. What could be the cause of that and a way to prevent it? I’ve created my cluster with the following definition (using python API):

cluster={
"name": "mycluster",
"initial_cluster_version": "latest",
"network_policy": {
    "enabled": True,
    "provider": "PROVIDER_UNSPECIFIED"
},
"node_pools": [
    {
        "name": "default",
        "autoscaling": {
            "enabled": True,
            "max_node_count": 5,
            "min_node_count": 1
        },
        "config": {
            "image_type": "UBUNTU",
            "machine_type": "n1-standard-4",
            "oauth_scopes": [
                # Allows pulling images from GCR
                "https://www.googleapis.com/auth/devstorage.read_only",
                # Needed for monitoring
                "https://www.googleapis.com/auth/logging.write",
                "https://www.googleapis.com/auth/monitoring"
            ]
        },
        "initial_node_count": 1
    }
]
},

The events logs are the following:

[
 {
   "insertId": "7be8fc3c-b770-4013-9500-09be89e39935@a1",
   "jsonPayload": {
 "status": {
   "measureTime": "1589026811",
   "autoscaledNodesCount": 1,
   "autoscaledNodesTarget": 1
 }
   },
   "resource": {
 "type": "k8s_cluster",
 "labels": {
   "project_id": "arlas-cloud-sandbox",
   "location": "europe-west1-d",
   "cluster_name": "cluster-test"
 }
   },
   "timestamp": "2020-05-09T12:20:12.229243264Z",
   "logName": "projects/arlas-cloud-sandbox/logs/container.googleapis.com%2Fcluster-autoscaler-visibility",
   "receiveTimestamp": "2020-05-09T12:20:13.028616473Z"
 },
 {
   "insertId": "9a09bd12-a44b-4360-a3c6-1072d7f9b098@a1",
   "jsonPayload": {
 "decision": {
   "scaleUp": {
     "increasedMigs": [
       {
         "requestedNodes": 1,
         "mig": {
           "zone": "europe-west1-d",
           "name": "gke-cluster-test-default-pool-e317f053-grp",
           "nodepool": "default-pool"
         }
       }
     ],
     "triggeringPodsTotalCount": 1,
     "triggeringPods": [
       {
         "controller": {
           "name": "calico-typha-8dd55d66c",
           "kind": "ReplicaSet",
           "apiVersion": "apps/v1"
         },
         "name": "calico-typha-8dd55d66c-gvwsx"
       }
     ]
   },
   "decideTime": "1589026971",
   "eventId": "15bc10aa-a0d9-4e3f-a0f9-bf3d16bd13e5"
 }
   },
   "resource": {
 "type": "k8s_cluster",
 "labels": {
   "project_id": "arlas-cloud-sandbox",
   "location": "europe-west1-d",
   "cluster_name": "cluster-test"
 }
   },
   "timestamp": "2020-05-09T12:22:51.653877878Z",
   "logName": "projects/arlas-cloud-sandbox/logs/container.googleapis.com%2Fcluster-autoscaler-visibility",
   "receiveTimestamp": "2020-05-09T12:22:52.331187267Z"
 },
 {
   "insertId": "221df494-6573-4eec-8524-a9c28e984b93@a1",
   "jsonPayload": {
 "status": {
   "autoscaledNodesTarget": 2,
   "measureTime": "1589026968",
   "autoscaledNodesCount": 1
 }
   },
   "resource": {
 "type": "k8s_cluster",
 "labels": {
   "project_id": "arlas-cloud-sandbox",
   "location": "europe-west1-d",
   "cluster_name": "cluster-test"
 }
   },
   "timestamp": "2020-05-09T12:22:51.682941907Z",
   "logName": "projects/arlas-cloud-sandbox/logs/container.googleapis.com%2Fcluster-autoscaler-visibility",
   "receiveTimestamp": "2020-05-09T12:22:52.140573874Z"
 },
 {
   "insertId": "867c38f2-caf2-47f8-a904-baed5fa79418@a1",
   "jsonPayload": {
 "status": {
   "measureTime": "1589027087",
   "autoscaledNodesCount": 2,
   "autoscaledNodesTarget": 2
 }
   },
   "resource": {
 "type": "k8s_cluster",
 "labels": {
   "cluster_name": "cluster-test",
   "project_id": "arlas-cloud-sandbox",
   "location": "europe-west1-d"
 }
   },
   "timestamp": "2020-05-09T12:24:48.480433786Z",
   "logName": "projects/arlas-cloud-sandbox/logs/container.googleapis.com%2Fcluster-autoscaler-visibility",
   "receiveTimestamp": "2020-05-09T12:24:49.510037788Z"
 },
 {
   "insertId": "4e134516-d91b-47eb-8df7-d60d7be2fcca@a1",
   "jsonPayload": {
 "resultInfo": {
   "measureTime": "1589027087",
   "results": [
     {
       "eventId": "15bc10aa-a0d9-4e3f-a0f9-bf3d16bd13e5"
     }
   ]
 }
   },
   "resource": {
 "type": "k8s_cluster",
 "labels": {
   "project_id": "arlas-cloud-sandbox",
   "location": "europe-west1-d",
   "cluster_name": "cluster-test"
 }
   },
   "timestamp": "2020-05-09T12:24:48.514851831Z",
   "logName": "projects/arlas-cloud-sandbox/logs/container.googleapis.com%2Fcluster-autoscaler-visibility",
   "receiveTimestamp": "2020-05-09T12:24:49.545221929Z"
 },
 {
   "insertId": "5674038e-8931-4530-b6b2-9854e6731573@a1",
   "jsonPayload": {
 "status": {
   "measureTime": "1589027277",
   "autoscaledNodesCount": 2,
   "autoscaledNodesTarget": 2
 }
   },
   "resource": {
 "type": "k8s_cluster",
 "labels": {
   "cluster_name": "cluster-test",
   "project_id": "arlas-cloud-sandbox",
   "location": "europe-west1-d"
 }
   },
   "timestamp": "2020-05-09T12:27:58.294272079Z",
   "logName": "projects/arlas-cloud-sandbox/logs/container.googleapis.com%2Fcluster-autoscaler-visibility",
   "receiveTimestamp": "2020-05-09T12:27:58.638736825Z"
 },
 {
   "insertId": "6d26df4f-039d-4c18-8fc0-441891b30e4b@a1",
   "jsonPayload": {
 "status": {
   "autoscaledNodesTarget": 2,
   "measureTime": "1589027467",
   "autoscaledNodesCount": 2
 }
   },
   "resource": {
 "type": "k8s_cluster",
 "labels": {
   "project_id": "arlas-cloud-sandbox",
   "location": "europe-west1-d",
   "cluster_name": "cluster-test"
 }
   },
   "timestamp": "2020-05-09T12:31:08.443814963Z",
   "logName": "projects/arlas-cloud-sandbox/logs/container.googleapis.com%2Fcluster-autoscaler-visibility",
   "receiveTimestamp": "2020-05-09T12:31:08.951331569Z"
 }
]
2

I’ve got my answer on Stackoverflow: https://stackoverflow.com/questions/61660875/why-is-my-gke-cluster-upscaling-when-i-create-a-namespace