org.apache.twill.internal.appmaster.ApplicationMasterService.java Source code

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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 org.apache.twill.internal.appmaster;

import com.google.common.base.Charsets;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.base.Strings;
import com.google.common.base.Supplier;
import com.google.common.base.Throwables;
import com.google.common.collect.DiscreteDomains;
import com.google.common.collect.HashMultiset;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Multiset;
import com.google.common.collect.Ranges;
import com.google.common.collect.Sets;
import com.google.common.io.Files;
import com.google.common.io.InputSupplier;
import com.google.common.reflect.TypeToken;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.SettableFuture;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.security.Credentials;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.yarn.api.records.ContainerId;
import org.apache.hadoop.yarn.api.records.Resource;
import org.apache.hadoop.yarn.util.Records;
import org.apache.twill.api.Command;
import org.apache.twill.api.EventHandler;
import org.apache.twill.api.EventHandlerSpecification;
import org.apache.twill.api.LocalFile;
import org.apache.twill.api.ResourceReport;
import org.apache.twill.api.ResourceSpecification;
import org.apache.twill.api.RunId;
import org.apache.twill.api.RuntimeSpecification;
import org.apache.twill.api.TwillRunResources;
import org.apache.twill.api.TwillSpecification;
import org.apache.twill.common.Threads;
import org.apache.twill.filesystem.Location;
import org.apache.twill.internal.Configs;
import org.apache.twill.internal.Constants;
import org.apache.twill.internal.ContainerInfo;
import org.apache.twill.internal.DefaultTwillRunResources;
import org.apache.twill.internal.EnvKeys;
import org.apache.twill.internal.JvmOptions;
import org.apache.twill.internal.ProcessLauncher;
import org.apache.twill.internal.TwillContainerLauncher;
import org.apache.twill.internal.json.JvmOptionsCodec;
import org.apache.twill.internal.json.LocalFileCodec;
import org.apache.twill.internal.json.TwillSpecificationAdapter;
import org.apache.twill.internal.state.Message;
import org.apache.twill.internal.utils.Instances;
import org.apache.twill.internal.yarn.AbstractYarnTwillService;
import org.apache.twill.internal.yarn.YarnAMClient;
import org.apache.twill.internal.yarn.YarnContainerInfo;
import org.apache.twill.internal.yarn.YarnContainerStatus;
import org.apache.twill.internal.yarn.YarnUtils;
import org.apache.twill.zookeeper.ZKClient;
import org.apache.twill.zookeeper.ZKClients;
import org.apache.zookeeper.CreateMode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import javax.annotation.Nullable;

/**
 * The class that acts as {@code ApplicationMaster} for Twill applications.
 */
public final class ApplicationMasterService extends AbstractYarnTwillService implements Supplier<ResourceReport> {

    private static final Logger LOG = LoggerFactory.getLogger(ApplicationMasterService.class);
    private static final Gson GSON = new Gson();

    // Copied from org.apache.hadoop.yarn.security.AMRMTokenIdentifier.KIND_NAME since it's missing in Hadoop-2.0
    private static final Text AMRM_TOKEN_KIND_NAME = new Text("YARN_AM_RM_TOKEN");

    private final RunId runId;
    private final ZKClient zkClient;
    private final TwillSpecification twillSpec;
    private final ApplicationMasterLiveNodeData amLiveNode;
    private final RunningContainers runningContainers;
    private final ExpectedContainers expectedContainers;
    private final YarnAMClient amClient;
    private final JvmOptions jvmOpts;
    private final int reservedMemory;
    private final EventHandler eventHandler;
    private final Location applicationLocation;
    private final PlacementPolicyManager placementPolicyManager;
    private final Map<String, Map<String, String>> environments;

    private volatile boolean stopped;
    private Queue<RunnableContainerRequest> runnableContainerRequests;
    private ExecutorService instanceChangeExecutor;

    public ApplicationMasterService(RunId runId, ZKClient zkClient, File twillSpecFile, YarnAMClient amClient,
            Location applicationLocation) throws Exception {
        super(zkClient, runId, applicationLocation);

        this.runId = runId;
        this.twillSpec = TwillSpecificationAdapter.create().fromJson(twillSpecFile);
        this.zkClient = zkClient;
        this.applicationLocation = applicationLocation;
        this.amClient = amClient;
        this.credentials = createCredentials();
        this.jvmOpts = loadJvmOptions();
        this.reservedMemory = getReservedMemory();
        this.placementPolicyManager = new PlacementPolicyManager(twillSpec.getPlacementPolicies());
        this.environments = getEnvironments();

        this.amLiveNode = new ApplicationMasterLiveNodeData(Integer.parseInt(System.getenv(EnvKeys.YARN_APP_ID)),
                Long.parseLong(System.getenv(EnvKeys.YARN_APP_ID_CLUSTER_TIME)),
                amClient.getContainerId().toString());

        expectedContainers = initExpectedContainers(twillSpec);
        runningContainers = initRunningContainers(amClient.getContainerId(), amClient.getHost());
        eventHandler = createEventHandler(twillSpec);
    }

    private JvmOptions loadJvmOptions() throws IOException {
        final File jvmOptsFile = new File(Constants.Files.JVM_OPTIONS);
        if (!jvmOptsFile.exists()) {
            return new JvmOptions(null, JvmOptions.DebugOptions.NO_DEBUG);
        }
        return JvmOptionsCodec.decode(new InputSupplier<Reader>() {
            @Override
            public Reader getInput() throws IOException {
                return new FileReader(jvmOptsFile);
            }
        });
    }

    private int getReservedMemory() {
        String value = System.getenv(EnvKeys.TWILL_RESERVED_MEMORY_MB);
        if (value == null) {
            return Configs.Defaults.JAVA_RESERVED_MEMORY_MB;
        }
        try {
            return Integer.parseInt(value);
        } catch (Exception e) {
            return Configs.Defaults.JAVA_RESERVED_MEMORY_MB;
        }
    }

    @SuppressWarnings("unchecked")
    @Nullable
    private EventHandler createEventHandler(TwillSpecification twillSpec) {
        try {
            // Should be able to load by this class ClassLoader, as they packaged in the same jar.
            EventHandlerSpecification handlerSpec = twillSpec.getEventHandler();
            if (handlerSpec == null) {
                return null;
            }

            Class<?> handlerClass = getClass().getClassLoader().loadClass(handlerSpec.getClassName());
            Preconditions.checkArgument(EventHandler.class.isAssignableFrom(handlerClass),
                    "Class {} does not implements {}", handlerClass, EventHandler.class.getName());
            return Instances.newInstance((Class<? extends EventHandler>) handlerClass);
        } catch (Exception e) {
            throw Throwables.propagate(e);
        }
    }

    private RunningContainers initRunningContainers(ContainerId appMasterContainerId, String appMasterHost)
            throws Exception {
        TwillRunResources appMasterResources = new DefaultTwillRunResources(0, appMasterContainerId.toString(),
                Integer.parseInt(System.getenv(EnvKeys.YARN_CONTAINER_VIRTUAL_CORES)),
                Integer.parseInt(System.getenv(EnvKeys.YARN_CONTAINER_MEMORY_MB)), appMasterHost, null, null);
        String appId = appMasterContainerId.getApplicationAttemptId().getApplicationId().toString();
        return new RunningContainers(appId, appMasterResources, zkClient);
    }

    private ExpectedContainers initExpectedContainers(TwillSpecification twillSpec) {
        Map<String, Integer> expectedCounts = Maps.newHashMap();
        for (RuntimeSpecification runtimeSpec : twillSpec.getRunnables().values()) {
            expectedCounts.put(runtimeSpec.getName(), runtimeSpec.getResourceSpecification().getInstances());
        }
        return new ExpectedContainers(expectedCounts);
    }

    @Override
    public ResourceReport get() {
        return runningContainers.getResourceReport();
    }

    @Override
    protected void doStart() throws Exception {
        LOG.info("Start application master with spec: " + TwillSpecificationAdapter.create().toJson(twillSpec));

        // initialize the event handler, if it fails, it will fail the application.
        if (eventHandler != null) {
            eventHandler.initialize(new BasicEventHandlerContext(twillSpec.getEventHandler()));
        }

        instanceChangeExecutor = Executors
                .newSingleThreadExecutor(Threads.createDaemonThreadFactory("instanceChanger"));

        // Creates ZK path for runnable
        zkClient.create("/" + runId.getId() + "/runnables", null, CreateMode.PERSISTENT).get();
        runningContainers.addWatcher(Constants.DISCOVERY_PATH_PREFIX);
        runnableContainerRequests = initContainerRequests();
    }

    @Override
    protected void doStop() throws Exception {
        Thread.interrupted(); // This is just to clear the interrupt flag

        LOG.info("Stop application master with spec: {}", TwillSpecificationAdapter.create().toJson(twillSpec));

        if (eventHandler != null) {
            try {
                // call event handler destroy. If there is error, only log and not affected stop sequence.
                eventHandler.destroy();
            } catch (Throwable t) {
                LOG.warn("Exception when calling {}.destroy()", eventHandler.getClass().getName(), t);
            }
        }

        instanceChangeExecutor.shutdownNow();

        // For checking if all containers are stopped.
        final Set<String> ids = Sets.newHashSet(runningContainers.getContainerIds());
        YarnAMClient.AllocateHandler handler = new YarnAMClient.AllocateHandler() {
            @Override
            public void acquired(List<? extends ProcessLauncher<YarnContainerInfo>> launchers) {
                // no-op
            }

            @Override
            public void completed(List<YarnContainerStatus> completed) {
                for (YarnContainerStatus status : completed) {
                    ids.remove(status.getContainerId());
                }
            }
        };

        runningContainers.stopAll();

        // Poll for 5 seconds to wait for containers to stop.
        int count = 0;
        while (!ids.isEmpty() && count++ < 5) {
            amClient.allocate(0.0f, handler);
            TimeUnit.SECONDS.sleep(1);
        }

        cleanupDir();
    }

    @Override
    protected Object getLiveNodeData() {
        return amLiveNode;
    }

    @Override
    public ListenableFuture<String> onReceived(String messageId, Message message) {
        LOG.debug("Message received: {} {}.", messageId, message);

        SettableFuture<String> result = SettableFuture.create();
        Runnable completion = getMessageCompletion(messageId, result);

        if (handleSecureStoreUpdate(message)) {
            runningContainers.sendToAll(message, completion);
            return result;
        }

        if (handleSetInstances(message, completion)) {
            return result;
        }

        if (handleRestartRunnablesInstances(message, completion)) {
            return result;
        }

        // Replicate messages to all runnables
        if (message.getScope() == Message.Scope.ALL_RUNNABLE) {
            runningContainers.sendToAll(message, completion);
            return result;
        }

        // Replicate message to a particular runnable.
        if (message.getScope() == Message.Scope.RUNNABLE) {
            runningContainers.sendToRunnable(message.getRunnableName(), message, completion);
            return result;
        }

        LOG.info("Message ignored. {}", message);
        return Futures.immediateFuture(messageId);
    }

    @Override
    protected void triggerShutdown() {
        stopped = true;
    }

    private void cleanupDir() {
        try {
            if (applicationLocation.delete(true)) {
                LOG.info("Application directory deleted: {}", applicationLocation);
            } else {
                LOG.warn("Failed to cleanup directory {}.", applicationLocation);
            }
        } catch (Exception e) {
            LOG.warn("Exception while cleanup directory {}.", applicationLocation, e);
        }
    }

    @Override
    protected void doRun() throws Exception {
        // The main loop
        Map.Entry<AllocationSpecification, ? extends Collection<RuntimeSpecification>> currentRequest = null;
        final Queue<ProvisionRequest> provisioning = Lists.newLinkedList();

        YarnAMClient.AllocateHandler allocateHandler = new YarnAMClient.AllocateHandler() {
            @Override
            public void acquired(List<? extends ProcessLauncher<YarnContainerInfo>> launchers) {
                launchRunnable(launchers, provisioning);
            }

            @Override
            public void completed(List<YarnContainerStatus> completed) {
                handleCompleted(completed);
            }
        };

        long requestStartTime = 0;
        boolean isRequestRelaxed = false;
        long nextTimeoutCheck = System.currentTimeMillis() + Constants.PROVISION_TIMEOUT;
        while (!stopped) {
            // Call allocate. It has to be made at first in order to be able to get cluster resource availability.
            amClient.allocate(0.0f, allocateHandler);

            // Looks for containers requests.
            if (provisioning.isEmpty() && runnableContainerRequests.isEmpty() && runningContainers.isEmpty()) {
                LOG.info("All containers completed. Shutting down application master.");
                break;
            }

            // If nothing is in provisioning, and no pending request, move to next one
            while (provisioning.isEmpty() && currentRequest == null && !runnableContainerRequests.isEmpty()) {
                RunnableContainerRequest runnableContainerRequest = runnableContainerRequests.peek();
                if (!runnableContainerRequest.isReadyToBeProvisioned()) {
                    // take it out from queue and put it back at the end for second chance.
                    runnableContainerRequest = runnableContainerRequests.poll();
                    runnableContainerRequests.add(runnableContainerRequest);

                    continue;
                }
                currentRequest = runnableContainerRequest.takeRequest();
                if (currentRequest == null) {
                    // All different types of resource request from current order is done, move to next one
                    // TODO: Need to handle order type as well
                    runnableContainerRequests.poll();
                }
            }

            // Nothing in provision, makes the next batch of provision request
            if (provisioning.isEmpty() && currentRequest != null) {
                manageBlacklist(currentRequest);
                addContainerRequests(currentRequest.getKey().getResource(), currentRequest.getValue(), provisioning,
                        currentRequest.getKey().getType());
                currentRequest = null;
                requestStartTime = System.currentTimeMillis();
                isRequestRelaxed = false;
            }

            // Check for provision request timeout i.e. check if any provision request has been pending
            // for more than the designated time. On timeout, relax the request constraints.
            if (!provisioning.isEmpty() && !isRequestRelaxed && (System.currentTimeMillis()
                    - requestStartTime) > Constants.CONSTRAINED_PROVISION_REQUEST_TIMEOUT) {
                LOG.info("Relaxing provisioning constraints for request {}", provisioning.peek().getRequestId());
                // Clear the blacklist for the pending provision request(s).
                amClient.clearBlacklist();
                isRequestRelaxed = true;
            }

            nextTimeoutCheck = checkProvisionTimeout(nextTimeoutCheck);

            if (isRunning()) {
                TimeUnit.SECONDS.sleep(1);
            }
        }
    }

    /**
     * Manage Blacklist for a given request.
     */
    private void manageBlacklist(
            Map.Entry<AllocationSpecification, ? extends Collection<RuntimeSpecification>> request) {
        amClient.clearBlacklist();

        //Check the allocation strategy
        AllocationSpecification currentAllocationSpecification = request.getKey();
        if (currentAllocationSpecification.getType()
                .equals(AllocationSpecification.Type.ALLOCATE_ONE_INSTANCE_AT_A_TIME)) {

            //Check the placement policy
            TwillSpecification.PlacementPolicy placementPolicy = placementPolicyManager
                    .getPlacementPolicy(currentAllocationSpecification.getRunnableName());
            if (placementPolicy.getType().equals(TwillSpecification.PlacementPolicy.Type.DISTRIBUTED)) {

                //Update blacklist with hosts which are running DISTRIBUTED runnables
                for (String runnable : placementPolicyManager
                        .getFellowRunnables(request.getKey().getRunnableName())) {
                    Collection<ContainerInfo> containerStats = runningContainers.getContainerInfo(runnable);
                    for (ContainerInfo containerInfo : containerStats) {
                        // Yarn Resource Manager may include port in the node name depending on the setting
                        // YarnConfiguration.RM_SCHEDULER_INCLUDE_PORT_IN_NODE_NAME. It is safe to add both
                        // the names (with and without port) to the blacklist.
                        amClient.addToBlacklist(containerInfo.getHost().getHostName());
                        amClient.addToBlacklist(
                                containerInfo.getHost().getHostName() + ":" + containerInfo.getPort());
                    }
                }
            }
        }
    }

    /**
     * Handling containers that are completed.
     */
    private void handleCompleted(List<YarnContainerStatus> completedContainersStatuses) {
        Multiset<String> restartRunnables = HashMultiset.create();
        for (YarnContainerStatus status : completedContainersStatuses) {
            LOG.info("Container {} completed with {}:{}.", status.getContainerId(), status.getState(),
                    status.getDiagnostics());
            runningContainers.handleCompleted(status, restartRunnables);
        }

        for (Multiset.Entry<String> entry : restartRunnables.entrySet()) {
            LOG.info("Re-request container for {} with {} instances.", entry.getElement(), entry.getCount());
            for (int i = 0; i < entry.getCount(); i++) {
                runnableContainerRequests.add(createRunnableContainerRequest(entry.getElement()));
            }
        }

        // For all runnables that needs to re-request for containers, update the expected count timestamp
        // so that the EventHandler would triggered with the right expiration timestamp.
        expectedContainers.updateRequestTime(restartRunnables.elementSet());
    }

    /**
     * Check for containers provision timeout and invoke eventHandler if necessary.
     *
     * @return the timestamp for the next time this method needs to be called.
     */
    private long checkProvisionTimeout(long nextTimeoutCheck) {
        if (System.currentTimeMillis() < nextTimeoutCheck) {
            return nextTimeoutCheck;
        }

        // Invoke event handler for provision request timeout
        Map<String, ExpectedContainers.ExpectedCount> expiredRequests = expectedContainers.getAll();
        Map<String, Integer> runningCounts = runningContainers.countAll();
        Map<String, Integer> completedContainerCount = runningContainers.getCompletedContainerCount();

        List<EventHandler.TimeoutEvent> timeoutEvents = Lists.newArrayList();
        for (Map.Entry<String, ExpectedContainers.ExpectedCount> entry : expiredRequests.entrySet()) {
            String runnableName = entry.getKey();
            ExpectedContainers.ExpectedCount expectedCount = entry.getValue();
            int runningCount = runningCounts.containsKey(runnableName) ? runningCounts.get(runnableName) : 0;
            int completedCount = completedContainerCount.containsKey(runnableName)
                    ? completedContainerCount.get(runnableName)
                    : 0;
            if (expectedCount.getCount() > runningCount + completedCount) {
                timeoutEvents.add(new EventHandler.TimeoutEvent(runnableName, expectedCount.getCount(),
                        runningCount, expectedCount.getTimestamp()));
            }
        }

        if (!timeoutEvents.isEmpty() && eventHandler != null) {
            try {
                EventHandler.TimeoutAction action = eventHandler.launchTimeout(timeoutEvents);
                if (action.getTimeout() < 0) {
                    // Abort application
                    stop();
                } else {
                    return nextTimeoutCheck + action.getTimeout();
                }
            } catch (Throwable t) {
                LOG.warn("Exception when calling EventHandler {}. Ignore the result.", t);
            }
        }
        return nextTimeoutCheck + Constants.PROVISION_TIMEOUT;
    }

    private Credentials createCredentials() {
        Credentials credentials = new Credentials();
        if (!UserGroupInformation.isSecurityEnabled()) {
            return credentials;
        }

        try {
            credentials.addAll(UserGroupInformation.getCurrentUser().getCredentials());

            // Remove the AM->RM tokens
            Iterator<Token<?>> iter = credentials.getAllTokens().iterator();
            while (iter.hasNext()) {
                Token<?> token = iter.next();
                if (token.getKind().equals(AMRM_TOKEN_KIND_NAME)) {
                    iter.remove();
                }
            }
        } catch (IOException e) {
            LOG.warn("Failed to get current user. No credentials will be provided to containers.", e);
        }

        return credentials;
    }

    private Queue<RunnableContainerRequest> initContainerRequests() {
        // Orderly stores container requests.
        Queue<RunnableContainerRequest> requests = new ConcurrentLinkedQueue<>();
        // For each order in the twillSpec, create container request for runnables, depending on Placement policy.
        for (TwillSpecification.Order order : twillSpec.getOrders()) {
            Set<String> distributedRunnables = placementPolicyManager.getDistributedRunnables(order.getNames());
            Set<String> defaultRunnables = Sets.newHashSet();
            defaultRunnables.addAll(order.getNames());
            defaultRunnables.removeAll(distributedRunnables);
            Map<AllocationSpecification, Collection<RuntimeSpecification>> requestsMap = Maps.newHashMap();
            for (String runnableName : distributedRunnables) {
                RuntimeSpecification runtimeSpec = twillSpec.getRunnables().get(runnableName);
                Resource capability = createCapability(runtimeSpec.getResourceSpecification());
                for (int instanceId = 0; instanceId < runtimeSpec.getResourceSpecification()
                        .getInstances(); instanceId++) {
                    AllocationSpecification allocationSpecification = new AllocationSpecification(capability,
                            AllocationSpecification.Type.ALLOCATE_ONE_INSTANCE_AT_A_TIME, runnableName, instanceId);
                    addAllocationSpecification(allocationSpecification, requestsMap, runtimeSpec);
                }
            }
            for (String runnableName : defaultRunnables) {
                RuntimeSpecification runtimeSpec = twillSpec.getRunnables().get(runnableName);
                Resource capability = createCapability(runtimeSpec.getResourceSpecification());
                AllocationSpecification allocationSpecification = new AllocationSpecification(capability);
                addAllocationSpecification(allocationSpecification, requestsMap, runtimeSpec);
            }
            requests.add(new RunnableContainerRequest(order.getType(), requestsMap));
        }
        return requests;
    }

    /**
     * Helper method to create {@link org.apache.twill.internal.appmaster.RunnableContainerRequest}.
     */
    private void addAllocationSpecification(AllocationSpecification allocationSpecification,
            Map<AllocationSpecification, Collection<RuntimeSpecification>> map, RuntimeSpecification runtimeSpec) {
        if (!map.containsKey(allocationSpecification)) {
            map.put(allocationSpecification, Lists.<RuntimeSpecification>newLinkedList());
        }
        map.get(allocationSpecification).add(runtimeSpec);
    }

    /**
     * Adds container requests with the given resource capability for each runtime.
     */
    private void addContainerRequests(Resource capability, Collection<RuntimeSpecification> runtimeSpecs,
            Queue<ProvisionRequest> provisioning, AllocationSpecification.Type allocationType) {
        for (RuntimeSpecification runtimeSpec : runtimeSpecs) {
            String name = runtimeSpec.getName();
            int newContainers = expectedContainers.getExpected(name) - runningContainers.count(name);
            if (newContainers > 0) {
                if (allocationType.equals(AllocationSpecification.Type.ALLOCATE_ONE_INSTANCE_AT_A_TIME)) {
                    //Spawning 1 instance at a time
                    newContainers = 1;
                }
                TwillSpecification.PlacementPolicy placementPolicy = placementPolicyManager
                        .getPlacementPolicy(name);
                Set<String> hosts = Sets.newHashSet();
                Set<String> racks = Sets.newHashSet();
                if (placementPolicy != null) {
                    hosts = placementPolicy.getHosts();
                    racks = placementPolicy.getRacks();
                }
                // TODO: Allow user to set priority?
                LOG.info("Request {} container with capability {} for runnable {}", newContainers, capability,
                        name);
                String requestId = amClient.addContainerRequest(capability, newContainers).addHosts(hosts)
                        .addRacks(racks).setPriority(0).apply();
                provisioning.add(new ProvisionRequest(runtimeSpec, requestId, newContainers, allocationType));
            }
        }
    }

    /**
     * Launches runnables in the provisioned containers.
     */
    private void launchRunnable(List<? extends ProcessLauncher<YarnContainerInfo>> launchers,
            Queue<ProvisionRequest> provisioning) {
        for (ProcessLauncher<YarnContainerInfo> processLauncher : launchers) {
            LOG.info("Got container {}", processLauncher.getContainerInfo().getId());
            ProvisionRequest provisionRequest = provisioning.peek();
            if (provisionRequest == null) {
                continue;
            }

            String runnableName = provisionRequest.getRuntimeSpec().getName();
            LOG.info("Starting runnable {} with {}", runnableName, processLauncher);

            LOG.debug("Log level for Twill runnable {} is {}", runnableName,
                    System.getenv(EnvKeys.TWILL_APP_LOG_LEVEL));

            int containerCount = expectedContainers.getExpected(runnableName);

            // Setup container environment variables
            Map<String, String> env = new LinkedHashMap<>();
            if (environments.containsKey(runnableName)) {
                env.putAll(environments.get(runnableName));
            }
            // Override with system env
            env.put(EnvKeys.TWILL_APP_DIR, System.getenv(EnvKeys.TWILL_APP_DIR));
            env.put(EnvKeys.TWILL_FS_USER, System.getenv(EnvKeys.TWILL_FS_USER));
            env.put(EnvKeys.TWILL_APP_RUN_ID, runId.getId());
            env.put(EnvKeys.TWILL_APP_NAME, twillSpec.getName());
            env.put(EnvKeys.TWILL_APP_LOG_LEVEL, System.getenv(EnvKeys.TWILL_APP_LOG_LEVEL));
            env.put(EnvKeys.TWILL_ZK_CONNECT, System.getenv(EnvKeys.TWILL_ZK_CONNECT));
            env.put(EnvKeys.TWILL_LOG_KAFKA_ZK, getKafkaZKConnect());

            ProcessLauncher.PrepareLaunchContext launchContext = processLauncher.prepareLaunch(env,
                    getLocalizeFiles(), credentials);

            TwillContainerLauncher launcher = new TwillContainerLauncher(twillSpec.getRunnables().get(runnableName),
                    processLauncher.getContainerInfo(), launchContext,
                    ZKClients.namespace(zkClient, getZKNamespace(runnableName)), containerCount, jvmOpts,
                    reservedMemory, getSecureStoreLocation());

            runningContainers.start(runnableName, processLauncher.getContainerInfo(), launcher);

            // Need to call complete to workaround bug in YARN AMRMClient
            if (provisionRequest.containerAcquired()) {
                amClient.completeContainerRequest(provisionRequest.getRequestId());
            }

            if (expectedContainers.getExpected(runnableName) == runningContainers.count(runnableName)
                    || provisioning.peek().getType()
                            .equals(AllocationSpecification.Type.ALLOCATE_ONE_INSTANCE_AT_A_TIME)) {
                provisioning.poll();
            }
            if (expectedContainers.getExpected(runnableName) == runningContainers.count(runnableName)) {
                LOG.info("Runnable " + runnableName + " fully provisioned with " + containerCount + " instances.");
            }
        }
    }

    private List<LocalFile> getLocalizeFiles() {
        try (Reader reader = Files.newReader(new File(Constants.Files.LOCALIZE_FILES), Charsets.UTF_8)) {
            return new GsonBuilder().registerTypeAdapter(LocalFile.class, new LocalFileCodec()).create()
                    .fromJson(reader, new TypeToken<List<LocalFile>>() {
                    }.getType());
        } catch (IOException e) {
            throw Throwables.propagate(e);
        }
    }

    private Map<String, Map<String, String>> getEnvironments() {
        File envFile = new File(Constants.Files.ENVIRONMENTS);
        if (!envFile.exists()) {
            return new HashMap<>();
        }

        try (Reader reader = Files.newReader(envFile, Charsets.UTF_8)) {
            return new Gson().fromJson(reader, new TypeToken<Map<String, Map<String, String>>>() {
            }.getType());
        } catch (IOException e) {
            throw Throwables.propagate(e);
        }
    }

    private String getZKNamespace(String runnableName) {
        return String.format("/%s/runnables/%s", runId.getId(), runnableName);
    }

    String getKafkaZKConnect() {
        return String.format("%s/%s/kafka", zkClient.getConnectString(), runId.getId());
    }

    /**
     * Attempts to change the number of running instances.
     * @return {@code true} if the message does requests for changes in number of running instances of a runnable,
     *         {@code false} otherwise.
     */
    private boolean handleSetInstances(final Message message, final Runnable completion) {
        if (message.getType() != Message.Type.SYSTEM || message.getScope() != Message.Scope.RUNNABLE) {
            return false;
        }

        Command command = message.getCommand();
        Map<String, String> options = command.getOptions();
        if (!"instances".equals(command.getCommand()) || !options.containsKey("count")) {
            return false;
        }

        final String runnableName = message.getRunnableName();
        if (runnableName == null || runnableName.isEmpty() || !twillSpec.getRunnables().containsKey(runnableName)) {
            LOG.info("Unknown runnable {}", runnableName);
            return false;
        }

        final int newCount = Integer.parseInt(options.get("count"));
        final int oldCount = expectedContainers.getExpected(runnableName);

        LOG.info("Received change instances request for {}, from {} to {}.", runnableName, oldCount, newCount);

        if (newCount == oldCount) { // Nothing to do, simply complete the request.
            completion.run();
            return true;
        }

        instanceChangeExecutor.execute(createSetInstanceRunnable(message, completion, oldCount, newCount));
        return true;
    }

    /**
     * Creates a Runnable for execution of change instance request.
     */
    private Runnable createSetInstanceRunnable(final Message message, final Runnable completion, final int oldCount,
            final int newCount) {
        return new Runnable() {
            @Override
            public void run() {
                final String runnableName = message.getRunnableName();

                LOG.info("Processing change instance request for {}, from {} to {}.", runnableName, oldCount,
                        newCount);
                try {
                    // Wait until running container count is the same as old count
                    runningContainers.waitForCount(runnableName, oldCount);
                    LOG.info("Confirmed {} containers running for {}.", oldCount, runnableName);

                    expectedContainers.setExpected(runnableName, newCount);

                    try {
                        if (newCount < oldCount) {
                            // Shutdown some running containers
                            for (int i = 0; i < oldCount - newCount; i++) {
                                runningContainers.removeLast(runnableName);
                            }
                        } else {
                            // Increase the number of instances
                            runnableContainerRequests
                                    .add(createRunnableContainerRequest(runnableName, newCount - oldCount));
                        }
                    } finally {
                        runningContainers.sendToRunnable(runnableName, message, completion);
                        LOG.info("Change instances request completed. From {} to {}.", oldCount, newCount);
                    }
                } catch (InterruptedException e) {
                    // If the wait is being interrupted, discard the message.
                    completion.run();
                }
            }
        };
    }

    private RunnableContainerRequest createRunnableContainerRequest(final String runnableName) {
        return createRunnableContainerRequest(runnableName, 1);
    }

    private RunnableContainerRequest createRunnableContainerRequest(final String runnableName,
            final int numberOfInstances) {
        return createRunnableContainerRequest(runnableName, numberOfInstances, true);
    }

    private RunnableContainerRequest createRunnableContainerRequest(final String runnableName,
            final int numberOfInstances, final boolean isProvisioned) {
        // Find the current order of the given runnable in order to create a RunnableContainerRequest.
        TwillSpecification.Order order = Iterables.find(twillSpec.getOrders(),
                new Predicate<TwillSpecification.Order>() {
                    @Override
                    public boolean apply(TwillSpecification.Order input) {
                        return (input.getNames().contains(runnableName));
                    }
                });

        RuntimeSpecification runtimeSpec = twillSpec.getRunnables().get(runnableName);
        Resource capability = createCapability(runtimeSpec.getResourceSpecification());
        Map<AllocationSpecification, Collection<RuntimeSpecification>> requestsMap = Maps.newHashMap();
        if (placementPolicyManager.getPlacementPolicyType(runnableName)
                .equals(TwillSpecification.PlacementPolicy.Type.DISTRIBUTED)) {
            for (int instanceId = 0; instanceId < numberOfInstances; instanceId++) {
                AllocationSpecification allocationSpecification = new AllocationSpecification(capability,
                        AllocationSpecification.Type.ALLOCATE_ONE_INSTANCE_AT_A_TIME, runnableName, instanceId);
                addAllocationSpecification(allocationSpecification, requestsMap, runtimeSpec);
            }
        } else {
            AllocationSpecification allocationSpecification = new AllocationSpecification(capability);
            addAllocationSpecification(allocationSpecification, requestsMap, runtimeSpec);
        }
        return new RunnableContainerRequest(order.getType(), requestsMap, isProvisioned);
    }

    private Runnable getMessageCompletion(final String messageId, final SettableFuture<String> future) {
        return new Runnable() {
            @Override
            public void run() {
                future.set(messageId);
            }
        };
    }

    private Resource createCapability(ResourceSpecification resourceSpec) {
        Resource capability = Records.newRecord(Resource.class);

        if (!YarnUtils.setVirtualCores(capability, resourceSpec.getVirtualCores())) {
            LOG.debug("Virtual cores limit not supported.");
        }

        capability.setMemory(resourceSpec.getMemorySize());
        return capability;
    }

    /**
     * Attempt to restart some instances from a runnable or some runnables.
     * @return {@code true} if the message requests restarting some instances and {@code false} otherwise.
     */
    private boolean handleRestartRunnablesInstances(final Message message, final Runnable completion) {
        LOG.debug("Check if it should process a restart runnable instances.");

        if (message.getType() != Message.Type.SYSTEM) {
            return false;
        }

        Message.Scope messageScope = message.getScope();
        if (messageScope != Message.Scope.RUNNABLE && messageScope != Message.Scope.RUNNABLES) {
            return false;
        }

        Command requestCommand = message.getCommand();
        if (!Constants.RESTART_ALL_RUNNABLE_INSTANCES.equals(requestCommand.getCommand())
                && !Constants.RESTART_RUNNABLES_INSTANCES.equals(requestCommand.getCommand())) {
            return false;
        }

        LOG.debug("Processing restart runnable instances message {}.", message);

        if (!Strings.isNullOrEmpty(message.getRunnableName()) && message.getScope() == Message.Scope.RUNNABLE) {
            // ... for a runnable ...
            String runnableName = message.getRunnableName();
            LOG.debug("Start restarting all runnable {} instances.", runnableName);
            restartRunnableInstances(runnableName, null, completion);
        } else {
            // ... or maybe some runnables
            for (Map.Entry<String, String> option : requestCommand.getOptions().entrySet()) {
                String runnableName = option.getKey();
                Set<Integer> restartedInstanceIds = GSON.fromJson(option.getValue(), new TypeToken<Set<Integer>>() {
                }.getType());

                LOG.debug("Start restarting runnable {} instances {}", runnableName, restartedInstanceIds);
                restartRunnableInstances(runnableName, restartedInstanceIds, completion);
            }
        }

        return true;
    }

    /**
     * Helper method to restart instances of runnables.
     */
    private void restartRunnableInstances(String runnableName, @Nullable Set<Integer> instanceIds,
            final Runnable completion) {
        Runnable restartInstancesRunnable = createRestartInstancesRunnable(runnableName, instanceIds, completion);
        instanceChangeExecutor.execute(restartInstancesRunnable);
    }

    /**
     * Creates a Runnable for execution of restart instances request.
     */
    private Runnable createRestartInstancesRunnable(final String runnableName,
            @Nullable final Set<Integer> instanceIds, final Runnable completion) {
        return new Runnable() {
            @Override
            public void run() {
                LOG.debug("Begin restart runnable {} instances.", runnableName);

                Set<Integer> instancesToRemove = instanceIds;
                if (instancesToRemove == null) {
                    instancesToRemove = Ranges.closedOpen(0, runningContainers.count(runnableName))
                            .asSet(DiscreteDomains.integers());
                }

                LOG.info("Restarting instances {} for runnable {}", instancesToRemove, runnableName);
                RunnableContainerRequest containerRequest = createRunnableContainerRequest(runnableName,
                        instancesToRemove.size(), false);
                runnableContainerRequests.add(containerRequest);

                for (int instanceId : instancesToRemove) {
                    LOG.debug("Remove instance {} for runnable {}", instanceId, runnableName);
                    try {
                        runningContainers.removeById(runnableName, instanceId);
                    } catch (Exception ex) {
                        // could be thrown if the container already stopped.
                        LOG.info("Exception thrown when stopping instance {} probably already stopped.",
                                instanceId);
                    }
                }

                // set the container request to be ready
                containerRequest.setReadyToBeProvisioned(true);

                completion.run();
            }
        };
    }
}