Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/2315#discussion_r75147221
--- Diff:
flink-mesos/src/main/scala/org/apache/flink/mesos/scheduler/LaunchCoordinator.scala
---
@@ -0,0 +1,349 @@
+/*
+ * 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.flink.mesos.scheduler
+
+import akka.actor.{Actor, ActorRef, FSM, Props}
+import com.netflix.fenzo._
+import com.netflix.fenzo.functions.Action1
+import com.netflix.fenzo.plugins.VMLeaseObject
+import grizzled.slf4j.Logger
+import org.apache.flink.api.java.tuple.{Tuple2=>FlinkTuple2}
+import org.apache.flink.configuration.Configuration
+import org.apache.flink.mesos.scheduler.LaunchCoordinator._
+import org.apache.flink.mesos.scheduler.messages._
+import org.apache.mesos.Protos.TaskInfo
+import org.apache.mesos.{SchedulerDriver, Protos}
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable.{Map => MutableMap}
+import scala.concurrent.duration._
+
+/**
+ * The launch coordinator handles offer processing, including
+ * matching offers to tasks and making reservations.
+ *
+ * The coordinator uses Netflix Fenzo to optimize task placement.
During the GatheringOffers phase,
+ * offers are evaluated by Fenzo for suitability to the planned tasks.
Reservations are then placed
+ * against the best offers, leading to revised offers containing reserved
resources with which to launch task(s).
+ */
+class LaunchCoordinator(
+ manager: ActorRef,
+ config: Configuration,
+ schedulerDriver: SchedulerDriver,
+ optimizerBuilder: TaskSchedulerBuilder
+ ) extends Actor with FSM[TaskState, GatherData] {
+
+ val LOG = Logger(getClass)
+
+ /**
+ * The task placement optimizer.
+ *
+ * The optimizer contains the following state:
+ * - unused offers
+ * - existing task placement (for fitness calculation involving task
colocation)
+ */
+ private[mesos] val optimizer: TaskScheduler = {
+ optimizerBuilder
+ .withLeaseRejectAction(new Action1[VirtualMachineLease]() {
+ def call(lease: VirtualMachineLease) {
+ LOG.info(s"Declined offer ${lease.getId} from
${lease.hostname()} of ${lease.memoryMB()} MB, ${lease.cpuCores()} cpus.")
+ schedulerDriver.declineOffer(lease.getOffer.getId)
+ }
+ }).build
+ }
+
+ override def postStop(): Unit = {
+ optimizer.shutdown()
+ super.postStop()
+ }
+
+ /**
+ * Initial state
+ */
+ startWith(Suspended, GatherData(tasks = Nil, newLeases = Nil))
+
+ /**
+ * State: Suspended
+ *
+ * Wait for (re-)connection to Mesos. No offers exist in this state,
but outstanding tasks might.
+ */
+ when(Suspended) {
+ case Event(msg: Connected, data: GatherData) =>
+ if(data.tasks.nonEmpty) goto(GatheringOffers)
+ else goto(Idle)
+ }
+
+ /**
+ * State: Idle
+ *
+ * Wait for a task request to arrive, then transition into gathering
offers.
+ */
+ onTransition {
+ case _ -> Idle => assert(nextStateData.tasks.isEmpty)
+ }
+
+ when(Idle) {
+ case Event(msg: Disconnected, data: GatherData) =>
+ goto(Suspended)
+
+ case Event(offers: ResourceOffers, data: GatherData) =>
+ // decline any offers that come in
+ schedulerDriver.suppressOffers()
+ for(offer <- offers.offers().asScala) {
schedulerDriver.declineOffer(offer.getId) }
+ stay()
+
+ case Event(msg: Launch, data: GatherData) =>
+ goto(GatheringOffers) using data.copy(tasks = data.tasks ++
msg.tasks.asScala)
+ }
+
+ /**
+ * Transition logic to control the flow of offers.
+ */
+ onTransition {
+ case _ -> GatheringOffers =>
+ LOG.info(s"Now gathering offers for at least
${nextStateData.tasks.length} task(s).")
+ schedulerDriver.reviveOffers()
+
+ case GatheringOffers -> _ =>
+ // decline any outstanding offers and suppress future offers
+ LOG.info(s"No longer gathering offers; all requests fulfilled.")
+
+ assert(nextStateData.newLeases.isEmpty)
+ schedulerDriver.suppressOffers()
+ optimizer.expireAllLeases()
+ }
+
+ /**
+ * State: GatheringOffers
+ *
+ * Wait for offers to accumulate for a fixed length of time or from
specific slaves.
--- End diff --
Why do we wait for offers being accumulated? Why not starting tasks as soon
as we get offers?
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