Adds support for 'downtime-replicas' deployment annotation (#38)

* Adds support for scale-down-to pod annotation

* Updates docs

* Clarifies readme that annotation is on the deployment

* Fixes formatting

* Renames annotation to 'downtime-replicas'

Author: Jason Gwartz

README.rst

@@ -18,7 +18,7 @@ Scale down Kubernetes deployments and/or statefulsets during non-work hours.
 
 Deployments are interchangeable by statefulset for this whole guide.
 
-It will scale the deployment's replicas to zero if all of the following conditions are met:
+It will scale down the deployment's replicas if all of the following conditions are met:
 
 * current time is not part of the "uptime" schedule or current time is part of the "downtime" schedule. The schedules are being evaluated in following order:
     * ``downscaler/downtime`` annotation on the deployment/stateful set
@@ -34,7 +34,7 @@ It will scale the deployment's replicas to zero if all of the following conditio
 * the deployment is not marked for exclusion (annotation ``downscaler/exclude: "true"``)
 * there are no active pods that force the whole cluster into uptime (annotation ``downscaler/force-uptime: "true"``)
 
-
+The deployment by default will be scaled down to zero replicas. This can be configured with a deployment annotation of ``downscaler/downtime-replicas``. (eg: ``downscaler/downtime-replicas: "1"``)
 
 Example use cases:
 

kube_downscaler/scaler.py

@@ -13,6 +13,7 @@
 EXCLUDE_ANNOTATION = 'downscaler/exclude'
 UPTIME_ANNOTATION = 'downscaler/uptime'
 DOWNTIME_ANNOTATION = 'downscaler/downtime'
+DOWNTIME_REPLICAS_ANNOTATION = 'downscaler/downtime-replicas'
 
 
 def within_grace_period(deploy, grace_period: int, now: datetime.datetime):
@@ -68,7 +69,7 @@ def autoscale_resource(resource: pykube.objects.NamespacedAPIObject,
                     logger.info('%s %s/%s within grace period (%ds), not scaling down (yet)',
                                 resource.kind, resource.namespace, resource.name, grace_period)
                 else:
-                    target_replicas = 0
+                    target_replicas = resource.annotations.get(DOWNTIME_REPLICAS_ANNOTATION, 0)
                     logger.info('Scaling down %s %s/%s from %s to %s replicas (uptime: %s, downtime: %s)',
                                 resource.kind, resource.namespace, resource.name, replicas, target_replicas,
                                 uptime, downtime)

tests/test_scaler.py

@@ -105,3 +105,40 @@ def get(url, version, **kwargs):
     patch_data = {"metadata": {"name": "deploy-2", "namespace": "ns-2", "creationTimestamp": "2019-03-01T16:38:00Z"}, "spec": {"replicas": 0}}
     assert api.patch.call_args[1]['url'] == 'deployments/deploy-2'
     assert json.loads(api.patch.call_args[1]['data']) == patch_data
+
+
+def test_scaler_down_to(monkeypatch):
+    api = MagicMock()
+    monkeypatch.setattr('kube_downscaler.scaler.helper.get_kube_api', MagicMock(return_value=api))
+    SCALE_TO = 1
+
+    def get(url, version, **kwargs):
+        if url == 'pods':
+            data = {'items': []}
+        elif url == 'deployments':
+            data = {'items': [
+                {
+                    'metadata': {
+                        'name': 'deploy-1', 'namespace': 'default', 'creationTimestamp': '2019-03-01T16:38:00Z',
+                        'annotations': {'downscaler/downtime-replicas': SCALE_TO},
+                    }, 'spec': {'replicas': 5}
+                },
+                ]}
+        elif url == 'namespaces/default':
+            data = {'metadata': {}}
+        else:
+            raise Exception(f'unexpected call: {url}, {version}, {kwargs}')
+
+        response = MagicMock()
+        response.json.return_value = data
+        return response
+
+    api.get = get
+
+    kinds = frozenset(['deployment'])
+    scale(namespace=None, default_uptime='never', default_downtime='always', kinds=kinds,
+          exclude_namespaces=[], exclude_deployments=[], exclude_statefulsets=[], dry_run=False, grace_period=300)
+
+    assert api.patch.call_count == 1
+    assert api.patch.call_args[1]['url'] == 'deployments/deploy-1'
+    assert json.loads(api.patch.call_args[1]['data'])["spec"]["replicas"] == SCALE_TO