Github user mccheah commented on a diff in the pull request:
https://github.com/apache/spark/pull/21366#discussion_r195512808
--- 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 --
Not strictly why that's done here but a side-effect I suppose. Really the
snapshots store should push an initial empty snapshot to all subscribers when
it starts, and the unit tests do check for that - it's the responsibility of
the snapshots store.
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