feat(config): make Dask autoscaler configurable (reanahub#604)

Closes reanahub/reana#834

reana_workflow_controller/config.py

@@ -290,6 +290,9 @@ def _parse_interactive_sessions_environments(env_var):
 DASK_ENABLED = strtobool(os.getenv("DASK_ENABLED", "true"))
 """Whether Dask is enabled in the cluster or not"""
 
+DASK_AUTOSCALER_ENABLED = os.getenv("DASK_AUTOSCALER_ENABLED", "true").lower() == "true"
+"""Whether Dask autoscaler is enabled in the cluster or not"""
+
 REANA_DASK_CLUSTER_MAX_MEMORY_LIMIT = os.getenv(
     "REANA_DASK_CLUSTER_MAX_MEMORY_LIMIT", "16Gi"
 )

reana_workflow_controller/consumer.py

@@ -47,6 +47,7 @@
 from reana_workflow_controller.errors import REANAWorkflowControllerError
 from reana_workflow_controller.k8s import delete_dask_dashboard_ingress
 
+from reana_workflow_controller.config import DASK_AUTOSCALER_ENABLED
 from reana_workflow_controller.dask import requires_dask
 
 try:
@@ -325,13 +326,15 @@ def _delete_dask_cluster(workflow: Workflow) -> None:
         name=f"reana-run-dask-{workflow.id_}",
     )
 
-    current_k8s_custom_objects_api_client.delete_namespaced_custom_object(
-        group="kubernetes.dask.org",
-        version="v1",
-        plural="daskautoscalers",
-        namespace="default",
-        name=f"dask-autoscaler-reana-run-dask-{workflow.id_}",
-    )
+    if DASK_AUTOSCALER_ENABLED:
+        current_k8s_custom_objects_api_client.delete_namespaced_custom_object(
+            group="kubernetes.dask.org",
+            version="v1",
+            plural="daskautoscalers",
+            namespace="default",
+            name=f"dask-autoscaler-reana-run-dask-{workflow.id_}",
+        )
+
     delete_dask_dashboard_ingress(
         f"dask-dashboard-ingress-reana-run-dask-{workflow.id_}", workflow.id_
     )

reana_workflow_controller/dask.py

@@ -27,7 +27,9 @@
     get_workspace_volume,
     get_reana_shared_volume,
 )
+from reana_commons.job_utils import kubernetes_memory_to_bytes
 
+from reana_workflow_controller.config import DASK_AUTOSCALER_ENABLED
 from reana_workflow_controller.k8s import create_dask_dashboard_ingress
 
 
@@ -64,7 +66,7 @@ def __init__(
         self.user_id = user_id
 
         self.cluster_spec = workflow_spec.get("resources", {}).get("dask", [])
-        self.cluster_body, self.autoscaler_body = self._load_dask_templates()
+        self.cluster_body = self._load_dask_cluster_template()
         self.cluster_image = self.cluster_spec["image"]
         self.dask_scheduler_uri = (
             f"{self.cluster_name}-scheduler.default.svc.cluster.local:8786"
@@ -77,29 +79,43 @@ def __init__(
         )
         self.kubernetes_uid = WORKFLOW_RUNTIME_USER_UID
 
-    def _load_dask_templates(self):
-        """Load Dask templates from YAML files."""
+        if DASK_AUTOSCALER_ENABLED:
+            self.autoscaler_name = f"dask-autoscaler-{cluster_name}"
+            self.autoscaler_body = self._load_dask_autoscaler_template()
+
+    def _load_dask_cluster_template(self):
+        """Load Dask cluster template from YAML file."""
         with open(
             "reana_workflow_controller/templates/dask_cluster.yaml", "r"
-        ) as dask_cluster_yaml, open(
-            "reana_workflow_controller/templates/dask_autoscaler.yaml", "r"
-        ) as dask_autoscaler_yaml:
+        ) as dask_cluster_yaml:
             dask_cluster_body = yaml.safe_load(dask_cluster_yaml)
-            dask_autoscaler_body = yaml.safe_load(dask_autoscaler_yaml)
             dask_cluster_body["spec"]["worker"]["spec"]["initContainers"] = []
             dask_cluster_body["spec"]["worker"]["spec"]["containers"][0]["env"] = []
             dask_cluster_body["spec"]["worker"]["spec"]["containers"][0][
                 "volumeMounts"
             ] = []
             dask_cluster_body["spec"]["worker"]["spec"]["volumes"] = []
 
-            return dask_cluster_body, dask_autoscaler_body
+            return dask_cluster_body
+
+    def _load_dask_autoscaler_template(self):
+        """Load Dask autoscaler template from YAML file."""
+        with open(
+            "reana_workflow_controller/templates/dask_autoscaler.yaml", "r"
+        ) as dask_autoscaler_yaml:
+            dask_autoscaler_body = yaml.safe_load(dask_autoscaler_yaml)
+
+            return dask_autoscaler_body
 
     def create_dask_resources(self):
         """Create necessary Dask resources for the workflow."""
         self._prepare_cluster()
         self._create_dask_cluster()
-        self._create_dask_autoscaler()
+
+        if DASK_AUTOSCALER_ENABLED:
+            self._prepare_autoscaler()
+            self._create_dask_autoscaler()
+
         create_dask_dashboard_ingress(self.cluster_name, self.workflow_id)
 
     def _prepare_cluster(self):
@@ -113,16 +129,10 @@ def _prepare_cluster(self):
         # Add the name of the cluster, used in scheduler service name
         self.cluster_body["metadata"] = {"name": self.cluster_name}
 
-        # Add the name of the dask autoscaler
-        self.autoscaler_body["metadata"] = {"name": self.autoscaler_name}
-
         self.cluster_body["spec"]["scheduler"]["service"]["selector"][
             "dask.org/cluster-name"
         ] = self.cluster_name
 
-        # Connect autoscaler to the cluster
-        self.autoscaler_body["spec"]["cluster"] = self.cluster_name
-
         # Add image to worker and scheduler
         self.cluster_body["spec"]["worker"]["spec"]["containers"][0][
             "image"
@@ -141,8 +151,9 @@ def _prepare_cluster(self):
             "limits": {"memory": f"{self.single_worker_memory}", "cpu": "1"}
         }
 
-        # Set max limit on autoscaler
-        self.autoscaler_body["spec"]["maximum"] = self.num_of_workers
+        self.cluster_body["spec"]["worker"]["replicas"] = (
+            0 if DASK_AUTOSCALER_ENABLED else self.num_of_workers
+        )
 
         # Add DASK SCHEDULER URI env variable
         self.cluster_body["spec"]["worker"]["spec"]["containers"][0]["env"].append(
@@ -174,6 +185,17 @@ def _prepare_cluster(self):
         if rucio:
             self._add_rucio_init_container()
 
+    def _prepare_autoscaler(self):
+        """Prepare Dask autoscaler body."""
+        # Add the name of the dask autoscaler
+        self.autoscaler_body["metadata"] = {"name": self.autoscaler_name}
+
+        # Connect autoscaler to the cluster
+        self.autoscaler_body["spec"]["cluster"] = self.cluster_name
+
+        # Set max limit on autoscaler
+        self.autoscaler_body["spec"]["maximum"] = self.num_of_workers
+
     def _add_image_pull_secrets(self):
         """Attach the configured image pull secrets to scheduler and worker containers."""
         image_pull_secrets = []

tests/test_dask.py

@@ -415,10 +415,6 @@ def test_prepare_cluster(dask_resource_manager):
             dask_resource_manager.cluster_body["metadata"]["name"]
             == dask_resource_manager.cluster_name
         )
-        assert (
-            dask_resource_manager.autoscaler_body["metadata"]["name"]
-            == dask_resource_manager.autoscaler_name
-        )
 
         assert {
             "name": "DASK_SCHEDULER_URI",
@@ -462,11 +458,6 @@ def test_prepare_cluster(dask_resource_manager):
             "worker"
         ]["spec"]["volumes"]
 
-        assert (
-            dask_resource_manager.autoscaler_body["spec"]["cluster"]
-            == dask_resource_manager.cluster_name
-        )
-
         assert (
             dask_resource_manager.cluster_body["spec"]["scheduler"]["service"][
                 "selector"