[GitHub] rabbah commented on a change in pull request #3240: Add a loadbalancer with local state and horizontal invoker sharding.

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rabbah commented on a change in pull request #3240: Add a loadbalancer with local state and horizontal invoker sharding.
URL: https://github.com/apache/incubator-openwhisk/pull/3240#discussion_r166901098
 
 

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 File path: core/controller/src/main/scala/whisk/core/loadBalancer/ShardingContainerPoolBalancer.scala
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+/*
+ * 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 whisk.core.loadBalancer
+
+import java.nio.charset.StandardCharsets
+import java.util.concurrent.atomic.LongAdder
+import java.util.concurrent.ThreadLocalRandom
+
+import akka.actor.{Actor, ActorSystem, Props}
+import akka.cluster.ClusterEvent._
+import akka.cluster.{Cluster, Member, MemberStatus}
+import akka.event.Logging.InfoLevel
+import akka.stream.ActorMaterializer
+import org.apache.kafka.clients.producer.RecordMetadata
+import pureconfig._
+import whisk.common.{ForcableSemaphore, Logging, LoggingMarkers, TransactionId}
+import whisk.core.WhiskConfig._
+import whisk.core.connector._
+import whisk.core.entity._
+import whisk.core.{ConfigKeys, WhiskConfig}
+import whisk.spi.SpiLoader
+
+import scala.annotation.tailrec
+import scala.collection.concurrent.TrieMap
+import scala.concurrent.duration._
+import scala.concurrent.{ExecutionContext, Future, Promise}
+import scala.util.{Failure, Success}
+
+/**
+ * A loadbalancer that uses "horizontal" sharding to not collide with fellow loadbalancers.
+ *
+ * Horizontal sharding means, that each invoker's capacity is evenly divided between the loadbalancers. If an invoker
+ * has at most 16 slots available, those will be divided to 8 slots for each loadbalancer (if there are 2).
+ */
+class ShardingContainerPoolBalancer(config: WhiskConfig, controllerInstance: InstanceId)(
+  implicit val actorSystem: ActorSystem,
+  logging: Logging,
+  materializer: ActorMaterializer)
+    extends LoadBalancer {
+
+  private implicit val executionContext: ExecutionContext = actorSystem.dispatcher
+
+  /** Build a cluster of all loadbalancers */
+  val seedNodesProvider = new StaticSeedNodesProvider(config.controllerSeedNodes, actorSystem.name)
+  val cluster = Cluster(actorSystem)
+  cluster.joinSeedNodes(seedNodesProvider.getSeedNodes())
+
+  /** Used to manage an action for testing invoker health */
+  private val entityStore = WhiskEntityStore.datastore(config)
+
+  /** State related to invocations and throttling */
+  private val activations = TrieMap[ActivationId, ActivationEntry]()
+  private val activationsPerNamespace = TrieMap[UUID, LongAdder]()
+  private val totalActivations = new LongAdder()
+
+  /** State needed for scheduling. */
+  private val schedulingState = ShardingContainerPoolBalancerState()()
+
+  /**
+   * Monitors invoker supervision and the cluster to update the state sequentially
+   *
+   * All state updates should go through this actor to guarantee, that `updateState` and `updateCluster` are called
+   * mutually exclusive and not concurrently.
+   */
+  private val monitor = actorSystem.actorOf(Props(new Actor {
+    override def preStart(): Unit = {
+      cluster.subscribe(self, classOf[MemberEvent], classOf[ReachabilityEvent])
+    }
+
+    // all members of the cluster that are available
+    var availableMembers = Set.empty[Member]
+
+    override def receive: Receive = {
+      case CurrentInvokerPoolState(newState) =>
+        schedulingState.updateInvokers(newState)
+
+      // State of the cluster as it is right now
+      case CurrentClusterState(members, _, _, _, _) =>
+        availableMembers = members.filter(_.status == MemberStatus.Up)
+        schedulingState.updateCluster(availableMembers.size)
+
+      // General lifecycle events and events concerning the reachability of members. Split-brain is not a huge concern
+      // in this case as only the invoker-threshold is adjusted according to the perceived cluster-size.
+      // Taking the unreachable member out of the cluster from that point-of-view results in a better experience
+      // even under split-brain-conditions, as that (in the worst-case) results in premature overloading of invokers vs.
+      // going into overflow mode prematurely.
+      case event: ClusterDomainEvent =>
+        availableMembers = event match {
+          case MemberUp(member)          => availableMembers + member
+          case ReachableMember(member)   => availableMembers + member
+          case MemberRemoved(member, _)  => availableMembers - member
+          case UnreachableMember(member) => availableMembers - member
+          case _                         => availableMembers
+        }
+
+        schedulingState.updateCluster(availableMembers.size)
+    }
+  }))
+
+  /** Loadbalancer interface methods */
+  override def invokerHealth(): Future[IndexedSeq[InvokerHealth]] = Future.successful(schedulingState.invokers)
+  override def activeActivationsFor(namespace: UUID): Future[Int] =
+    Future.successful(activationsPerNamespace.get(namespace).map(_.intValue()).getOrElse(0))
+  override def totalActiveActivations: Future[Int] = Future.successful(totalActivations.intValue())
+
+  /** 1. Publish a message to the loadbalancer */
+  override def publish(action: ExecutableWhiskActionMetaData, msg: ActivationMessage)(
+    implicit transid: TransactionId): Future[Future[Either[ActivationId, WhiskActivation]]] = {
+
+    val invokersToUse = if (action.exec.pull) schedulingState.blackboxInvokers else schedulingState.managedInvokers
+    val chosen = if (invokersToUse.nonEmpty) {
+      val hash = ShardingContainerPoolBalancer.generateHash(msg.user.namespace, action.fullyQualifiedName(false))
+      val homeInvoker = hash % invokersToUse.size
+      val stepSize = schedulingState.stepSizes(hash % schedulingState.stepSizes.size)
+      ShardingContainerPoolBalancer.schedule(invokersToUse, schedulingState.invokerSlots, homeInvoker, stepSize)
+    } else {
+      None
+    }
+
+    chosen
+      .map { invoker =>
+        val entry = setupActivation(msg, action, invoker)
+        sendActivationToInvoker(messageProducer, msg, invoker).map { _ =>
+          entry.promise.future
+        }
+      }
+      .getOrElse(Future.failed(LoadBalancerException("No invokers available")))
+  }
+
+  /** 2. Update local state with the to be executed activation */
+  private def setupActivation(msg: ActivationMessage,
+                              action: ExecutableWhiskActionMetaData,
+                              instance: InstanceId): ActivationEntry = {
+
+    totalActivations.increment()
+    activationsPerNamespace.getOrElseUpdate(msg.user.uuid, new LongAdder()).increment()
+
+    val timeout = action.limits.timeout.duration.max(TimeLimit.STD_DURATION) + 1.minute
+    // Install a timeout handler for the catastrophic case where an active ack is not received at all
+    // (because say an invoker is down completely, or the connection to the message bus is disrupted) or when
+    // the active ack is significantly delayed (possibly dues to long queues but the subject should not be penalized);
+    // in this case, if the activation handler is still registered, remove it and update the books.
+    activations.getOrElseUpdate(
+      msg.activationId, {
+        val timeoutHandler = actorSystem.scheduler.scheduleOnce(timeout) {
+          processCompletion(Left(msg.activationId), msg.transid, forced = true, invoker = instance)
+        }
+
+        // please note: timeoutHandler.cancel must be called on all non-timeout paths, e.g. Success
+        ActivationEntry(
+          msg.activationId,
+          msg.user.uuid,
+          instance,
+          timeoutHandler,
+          Promise[Either[ActivationId, WhiskActivation]]())
+      })
+  }
+
+  private val messagingProvider = SpiLoader.get[MessagingProvider]
+  private val messageProducer = messagingProvider.getProducer(config, executionContext)
+
+  /** 3. Send the activation to the invoker */
+  private def sendActivationToInvoker(producer: MessageProducer,
+                                      msg: ActivationMessage,
+                                      invoker: InstanceId): Future[RecordMetadata] = {
+    implicit val transid: TransactionId = msg.transid
+
+    val topic = s"invoker${invoker.toInt}"
+    val start = transid.started(
+      this,
+      LoggingMarkers.CONTROLLER_KAFKA,
+      s"posting topic '$topic' with activation id '${msg.activationId}'",
 
 Review comment:
   Pick up message from @mhenkes ?s pr?

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