Add node selector strategy for exclusive job placement per topology

api/jobset/v1alpha2/jobset_types.go

@@ -27,6 +27,13 @@ const (
 	JobKey                string = "jobset.sigs.k8s.io/job-key"
 	JobNameKey            string = "job-name" // TODO(#26): Migrate to the fully qualified label name.
 	ExclusiveKey          string = "alpha.jobset.sigs.k8s.io/exclusive-topology"
+	// NodeSelectorStrategyKey is an annotation that acts as a flag, the value does not matter.
+	// If set, the JobSet controller will automatically inject nodeSelectors for the JobSetNameKey label to
+	// ensure exclusive job placement per topology, instead of injecting pod affinity/anti-affinites for this.
+	// The user must add the JobSet name node label to the desired topologies separately.
+	NodeSelectorStrategyKey string = "alpha.jobset.sigs.k8s.io/node-selector"
+	NamespacedJobKey        string = "alpha.jobset.sigs.k8s.io/namespaced-job"
+	NoScheduleTaintKey      string = "alpha.jobset.sigs.k8s.io/no-schedule"
 )
 
 type JobSetConditionType string

hack/label_nodes/label_nodes.py

@@ -0,0 +1,104 @@
+#!/usr/bin/python3
+import sys
+import yaml
+import argparse
+import kubernetes.client
+import kubernetes.config
+
+NAMESPACED_JOB_KEY = "alpha.jobset.sigs.k8s.io/namespaced-job"
+NODE_POOL_KEY = "cloud.google.com/gke-nodepool"
+NO_SCHEDULE_TAINT_KEY = "alpha.jobset.sigs.k8s.io/no-schedule"
+
+def main(node_pools: str, jobset_yaml: str) -> None:
+    namespaced_jobs = generate_namespaced_jobs(jobset_yaml)
+
+    # Get target set of node pools to label from user input.
+    target_node_pools = parse_node_pools(node_pools)
+
+    # Validate we have 1 job per node pool.
+    if len(namespaced_jobs) != len(target_node_pools):
+        raise ValueError(f"number of node pools ({len(target_node_pools)}) does not match number of child jobs ({len(namespaced_jobs)})")
+
+    # Map each job to a node pool.
+    job_mapping = generate_job_mapping(namespaced_jobs, target_node_pools)
+
+    # Load the Kubernetes configuration from the default location.
+    kubernetes.config.load_kube_config()
+
+    # Create a new Kubernetes client.
+    client = kubernetes.client.CoreV1Api()
+
+    # Get a list of all the nodes in the cluster.
+    nodes = client.list_node().items
+
+    # Add the label to each node that is part of a target node pool.
+    for node in nodes:
+        node_pool = node.metadata.labels[NODE_POOL_KEY]
+        if node_pool not in target_node_pools:
+            continue
+
+        # Look up the job this node pool is assigned and add it as a label.
+        body = {
+            "metadata": {
+                "labels": {
+                    NAMESPACED_JOB_KEY: job_mapping[node_pool],
+                },
+            },
+            "spec": {
+                "taints": [
+                    {
+                        "key": NO_SCHEDULE_TAINT_KEY,
+                        "value": "true",
+                        "effect": "NoSchedule"
+                    }
+                ],
+            },
+        }
+
+        client.patch_node(node.metadata.name, body)
+        print(f"Successfully added label {NAMESPACED_JOB_KEY}={job_mapping[node_pool]} to node {node.metadata.name}")
+        print(f"Successfully added taint key={NO_SCHEDULE_TAINT_KEY}, value=true, effect=NoSchedule to node {node.metadata.name}")
+
+
+def parse_node_pools(node_pools: str) -> set:
+    '''Parse comma separated list of node pools into a set, and confirm with user before continuing.'''
+    node_pools_set = set(node_pools.split(','))
+
+    print("Adding namespaced job name labels to the following node pools:")
+    for np in node_pools_set:
+        print(np)    
+
+    input('Once confirmed, hit any key to continue, or ctrl+C to exit.')
+    return node_pools_set
+
+
+def generate_namespaced_jobs(jobset_yaml: str) -> list:
+    '''Generate list of namespaced jobs from the jobset config.'''
+    with open(jobset_yaml, 'r') as f:
+        jobset = yaml.safe_load(f.read())
+
+    jobset_name = jobset['metadata']['name']
+    namespace = jobset['metadata'].get('namespace', 'default') # default namespace if unspecified
+
+    jobs = []
+    for replicated_job in jobset['spec']['replicatedJobs']:
+        replicas = int(replicated_job.get('replicas', '1')) # replicas defaults to 1 if unspecified
+        for job_idx in range(replicas):
+            jobs.append(f"{namespace}_{jobset_name}-{replicated_job['name']}-{job_idx}")
+    return jobs
+
+
+def generate_job_mapping(namespaced_jobs: list[str], node_pools: set) -> dict:
+    '''Map each job to a node pool, and return this mapping in a dictionary.'''
+    mapping = {}
+    for np in node_pools:
+        mapping[np] = namespaced_jobs.pop()
+    return mapping
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument("jobset", help="jobset yaml config")
+    parser.add_argument("nodepools", help="comma separated list of nodepool names")
+    args = parser.parse_args()
+    main(args.nodepools, args.jobset)

hack/label_nodes/requirements.txt

@@ -0,0 +1,2 @@
+kubernetes
+pyyaml

pkg/controllers/jobset_controller.go

@@ -594,10 +594,20 @@ func constructJob(js *jobset.JobSet, rjob *jobset.ReplicatedJob, jobIdx int) (*b
 		job.Spec.Template.Spec.Subdomain = js.Spec.Network.Subdomain
 	}
 
-	// If this job should be exclusive per topology, set the pod affinities/anti-affinities accordingly.
+	// If this job should be exclusive per topology, configure the scheduling constraints accordingly.
 	if topologyDomain, ok := js.Annotations[jobset.ExclusiveKey]; ok {
-		setExclusiveAffinities(job, topologyDomain)
+		// If user has set the nodeSelectorStrategy annotation flag, add the job name label as a
+		// nodeSelector, and add a toleration for the no schedule taint.
+		// The node label and node taint must be added separately by a user/script.
+		if _, exists := js.Annotations[jobset.NodeSelectorStrategyKey]; exists {
+			addNodeSelector(job)
+			addTaintToleration(job)
+		} else {
+			// Otherwise, default to using exclusive pod affinities/anti-affinities strategy.
+			setExclusiveAffinities(job, topologyDomain)
+		}
 	}
+
 	// if Suspend is set, then we assume all jobs will be suspended also.
 	jobsetSuspended := js.Spec.Suspend != nil && *js.Spec.Suspend
 	job.Spec.Suspend = ptr.To(jobsetSuspended)
@@ -652,6 +662,23 @@ func setExclusiveAffinities(job *batchv1.Job, topologyKey string) {
 		})
 }
 
+func addNodeSelector(job *batchv1.Job) {
+	if job.Spec.Template.Spec.NodeSelector == nil {
+		job.Spec.Template.Spec.NodeSelector = make(map[string]string)
+	}
+	job.Spec.Template.Spec.NodeSelector[jobset.NamespacedJobKey] = namespacedJobName(job.Namespace, job.Name)
+}
+
+func addTaintToleration(job *batchv1.Job) {
+	job.Spec.Template.Spec.Tolerations = append(job.Spec.Template.Spec.Tolerations,
+		corev1.Toleration{
+			Key:      jobset.NoScheduleTaintKey,
+			Operator: corev1.TolerationOpExists,
+			Effect:   corev1.TaintEffectNoSchedule,
+		},
+	)
+}
+
 func shouldCreateJob(jobName string, ownedJobs *childJobs) bool {
 	// Check if this job exists already.
 	// TODO: maybe we can use a job map here so we can do O(1) lookups
@@ -703,10 +730,16 @@ func GenSubdomain(js *jobset.JobSet) string {
 }
 
 // jobHashKey returns the SHA1 hash of the namespaced job name (i.e. <namespace>/<jobName>).
-func jobHashKey(ns string, jobName string) string {
+func jobHashKey(ns, jobName string) string {
 	return sha1Hash(fmt.Sprintf("%s/%s", ns, jobName))
 }
 
+// Human readable namespaced job name. We must use '_' to separate namespace and job instead of '/'
+// since the '/' character is not allowed in label values.
+func namespacedJobName(ns, jobName string) string {
+	return fmt.Sprintf("%s_%s", ns, jobName)
+}
+
 func jobSetFinished(js *jobset.JobSet) bool {
 	for _, c := range js.Status.Conditions {
 		if (c.Type == string(jobset.JobSetCompleted) || c.Type == string(jobset.JobSetFailed)) && c.Status == metav1.ConditionTrue {

pkg/controllers/jobset_controller_test.go

@@ -600,6 +600,44 @@ func TestConstructJobsFromTemplate(t *testing.T) {
 					Subdomain(jobSetName).Obj(),
 			},
 		},
+		{
+			name: "node selector exclusive placement strategy enabled",
+			js: testutils.MakeJobSet(jobSetName, ns).
+				SetAnnotations(map[string]string{
+					jobset.ExclusiveKey:            "cloud.google.com/gke-nodepool",
+					jobset.NodeSelectorStrategyKey: "true",
+				}).
+				EnableDNSHostnames(true).
+				NetworkSubdomain(jobSetName).
+				ReplicatedJob(testutils.MakeReplicatedJob(replicatedJobName).
+					Job(testutils.MakeJobTemplate(jobName, ns).Obj()).
+					Subdomain(jobSetName).
+					Replicas(1).
+					Obj()).
+				Obj(),
+			ownedJobs: &childJobs{},
+			want: []*batchv1.Job{
+				makeJob(&makeJobArgs{
+					jobSetName:        jobSetName,
+					replicatedJobName: replicatedJobName,
+					jobName:           "test-jobset-replicated-job-0",
+					ns:                ns,
+					replicas:          1,
+					jobIdx:            0}).
+					Suspend(false).
+					Subdomain(jobSetName).
+					NodeSelector(map[string]string{
+						jobset.NamespacedJobKey: namespacedJobName(ns, "test-jobset-replicated-job-0"),
+					}).
+					Tolerations([]corev1.Toleration{
+						{
+							Key:      jobset.NoScheduleTaintKey,
+							Operator: corev1.TolerationOpExists,
+							Effect:   corev1.TaintEffectNoSchedule,
+						},
+					}).Obj(),
+			},
+		},
 	}
 
 	for _, tc := range tests {

pkg/util/testing/wrappers.go

@@ -278,6 +278,18 @@ func (j *JobWrapper) Ready(ready int32) *JobWrapper {
 	return j
 }
 
+// Tolerations set the tolerations.
+func (j *JobWrapper) Tolerations(t []corev1.Toleration) *JobWrapper {
+	j.Spec.Template.Spec.Tolerations = t
+	return j
+}
+
+// NodeSelector sets the node selector.
+func (j *JobWrapper) NodeSelector(nodeSelector map[string]string) *JobWrapper {
+	j.Spec.Template.Spec.NodeSelector = nodeSelector
+	return j
+}
+
 // Obj returns the wrapped Job.
 func (j *JobWrapper) Obj() *batchv1.Job {
 	return &j.Job