Github user mccheah commented on a diff in the pull request:
https://github.com/apache/spark/pull/21366#discussion_r195561927
--- Diff:
resource-managers/kubernetes/core/src/main/scala/org/apache/spark/scheduler/cluster/k8s/ExecutorPodsPollingSnapshotSource.scala
---
@@ -0,0 +1,65 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.spark.scheduler.cluster.k8s
+
+import java.util.concurrent.{Future, ScheduledExecutorService, TimeUnit}
+
+import io.fabric8.kubernetes.client.KubernetesClient
+import scala.collection.JavaConverters._
+
+import org.apache.spark.SparkConf
+import org.apache.spark.deploy.k8s.Config._
+import org.apache.spark.deploy.k8s.Constants._
+import org.apache.spark.util.ThreadUtils
+
+private[spark] class ExecutorPodsPollingSnapshotSource(
+ conf: SparkConf,
+ kubernetesClient: KubernetesClient,
+ snapshotsStore: ExecutorPodsSnapshotsStore,
+ pollingExecutor: ScheduledExecutorService) {
+
+ private val pollingInterval =
conf.get(KUBERNETES_EXECUTOR_API_POLLING_INTERVAL)
+
+ private var pollingFuture: Future[_] = _
+
+ def start(applicationId: String): Unit = {
+ require(pollingFuture == null, "Cannot start polling more than once.")
+ pollingFuture = pollingExecutor.scheduleWithFixedDelay(
+ new PollRunnable(applicationId), pollingInterval, pollingInterval,
TimeUnit.MILLISECONDS)
+ }
+
+ def stop(): Unit = {
+ if (pollingFuture != null) {
+ pollingFuture.cancel(true)
+ pollingFuture = null
+ }
+ ThreadUtils.shutdown(pollingExecutor)
+ }
+
+ private class PollRunnable(applicationId: String) extends Runnable {
+ override def run(): Unit = {
+ snapshotsStore.replaceSnapshot(kubernetesClient
--- End diff --
And though we don't allow for this right now, the above would allow
subscribers to be added midway through to receive the most recent snapshot
immediately. But again we don't do this right now - we setup all subscribers on
startup before starting pushing snapshots.
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