order

This paper mainly studies Assignment Distribution Service of storm.

AssignmentDistributionService

storm-2.0.0/storm-server/src/main/java/org/apache/storm/nimbus/AssignmentDistributionService.java

/**
 * A service for distributing master assignments to supervisors, this service makes the assignments notification
 * asynchronous.
 *
 * <p>We support multiple working threads to distribute assignment, every thread has a queue buffer.
 *
 * <p>Master will shuffle its node request to the queues, if the target queue is full, we just discard the request,
 * let the supervisors sync instead.
 *
 * <p>Caution: this class is not thread safe.
 *
 * <pre>{@code
 * Working mode
 *                      +--------+         +-----------------+
 *                      | queue1 |   ==>   | Working thread1 |
 * +--------+ shuffle   +--------+         +-----------------+
 * | Master |   ==>
 * +--------+           +--------+         +-----------------+
 *                      | queue2 |   ==>   | Working thread2 |
 *                      +--------+         +-----------------+
 * }
 * </pre>
 */
public class AssignmentDistributionService implements Closeable {
	//......
    private ExecutorService service;

    /**
     * Assignments request queue.
     */
    private volatile Map<Integer, LinkedBlockingQueue<NodeAssignments>> assignmentsQueue;

    /**
     * Add an assignments for a node/supervisor for distribution.
     * @param node node id of supervisor.
     * @param host host name for the node.
     * @param serverPort node thrift server port.
     * @param assignments the {@link org.apache.storm.generated.SupervisorAssignments}
     */
    public void addAssignmentsForNode(String node, String host, Integer serverPort, SupervisorAssignments assignments) {
        try {
            //For some reasons, we can not get supervisor port info, eg: supervisor shutdown,
            //Just skip for this scheduling round.
            if (serverPort == null) {
                LOG.warn("Discard an assignment distribution for node {} because server port info is missing.", node);
                return;
            }

            boolean success = nextQueue().offer(NodeAssignments.getInstance(node, host, serverPort, assignments), 5L, TimeUnit.SECONDS);
            if (!success) {
                LOG.warn("Discard an assignment distribution for node {} because the target sub queue is full.", node);
            }

        } catch (InterruptedException e) {
            LOG.error("Add node assignments interrupted: {}", e.getMessage());
            throw new RuntimeException(e);
        }
    }

    private LinkedBlockingQueue<NodeAssignments> nextQueue() {
        return this.assignmentsQueue.get(nextQueueId());
    }
}

• Nimbus notifies supervisor of task assignment results by calling addAs signments ForNode of Assignment Distribution Service
• AdAssignments ForNode is mainly about putting Supervisor Assignments into assignments Queue

AssignmentDistributionService.getInstance

storm-2.0.0/storm-server/src/main/java/org/apache/storm/nimbus/AssignmentDistributionService.java

    /**
     * Factory method for initialize a instance.
     * @param conf config.
     * @return an instance of {@link AssignmentDistributionService}
     */
    public static AssignmentDistributionService getInstance(Map conf) {
        AssignmentDistributionService service = new AssignmentDistributionService();
        service.prepare(conf);
        return service;
    }

    /**
     * Function for initialization.
     *
     * @param conf config
     */
    public void prepare(Map conf) {
        this.conf = conf;
        this.random = new Random(47);

        this.threadsNum = ObjectReader.getInt(conf.get(DaemonConfig.NIMBUS_ASSIGNMENTS_SERVICE_THREADS), 10);
        this.queueSize = ObjectReader.getInt(conf.get(DaemonConfig.NIMBUS_ASSIGNMENTS_SERVICE_THREAD_QUEUE_SIZE), 100);

        this.assignmentsQueue = new HashMap<>();
        for (int i = 0; i < threadsNum; i++) {
            this.assignmentsQueue.put(i, new LinkedBlockingQueue<NodeAssignments>(queueSize));
        }
        //start the thread pool
        this.service = Executors.newFixedThreadPool(threadsNum);
        this.active = true;
        //start the threads
        for (int i = 0; i < threadsNum; i++) {
            this.service.submit(new DistributeTask(this, i));
        }
        // for local cluster
        localSupervisors = new HashMap<>();
        if (ConfigUtils.isLocalMode(conf)) {
            isLocalMode = true;
        }
    }

• The getInstance method new an AssignmentDistributionService, while calling the prepare method for initialization
• At prepare time, a LinkedBlockingQueue with the number of threadsNum is created, and the queue size is DaemonConfig.NIMBUS_ASSIGNMENTS_SERVICE_THREAD_QUEUE_SIZE.
• In addition, a thread pool is created through Executors.newFixedThreadPool(threadsNum), and the number of DistributeTasks for threadsNum is submitted. Each queue corresponds to a DistributeTask.

DistributeTask

storm-2.0.0/storm-server/src/main/java/org/apache/storm/nimbus/AssignmentDistributionService.java

    /**
     * Task to distribute assignments.
     */
    static class DistributeTask implements Runnable {
        private AssignmentDistributionService service;
        private Integer queueIndex;

        DistributeTask(AssignmentDistributionService service, Integer index) {
            this.service = service;
            this.queueIndex = index;
        }

        @Override
        public void run() {
            while (service.isActive()) {
                try {
                    NodeAssignments nodeAssignments = this.service.nextAssignments(queueIndex);
                    sendAssignmentsToNode(nodeAssignments);
                } catch (InterruptedException e) {
                    if (service.isActive()) {
                        LOG.error("Get an unexpected interrupt when distributing assignments to node, {}", e.getCause());
                    } else {
                        // service is off now just interrupt it.
                        Thread.currentThread().interrupt();
                    }
                }
            }
        }

        private void sendAssignmentsToNode(NodeAssignments assignments) {
            if (this.service.isLocalMode) {
                //local node
                Supervisor supervisor = this.service.localSupervisors.get(assignments.getNode());
                if (supervisor != null) {
                    supervisor.sendSupervisorAssignments(assignments.getAssignments());
                } else {
                    LOG.error("Can not find node {} for assignments distribution", assignments.getNode());
                    throw new RuntimeException("null for node " + assignments.getNode() + " supervisor instance.");
                }
            } else {
                // distributed mode
                try (SupervisorClient client = SupervisorClient.getConfiguredClient(service.getConf(),
                                                                                    assignments.getHost(), assignments.getServerPort())) {
                    try {
                        client.getClient().sendSupervisorAssignments(assignments.getAssignments());
                    } catch (Exception e) {
                        //just ignore the exception.
                        LOG.error("Exception when trying to send assignments to node {}: {}", assignments.getNode(), e.getMessage());
                    }
                } catch (Throwable e) {
                    //just ignore any error/exception.
                    LOG.error("Exception to create supervisor client for node {}: {}", assignments.getNode(), e.getMessage());
                }

            }
        }
    }

    /**
     * Get an assignments from the target queue with the specific index.
     * @param queueIndex index of the queue
     * @return an {@link NodeAssignments}
     * @throws InterruptedException
     */
    public NodeAssignments nextAssignments(Integer queueIndex) throws InterruptedException {
        NodeAssignments target = null;
        while (true) {
            target = getQueueById(queueIndex).poll();
            if (target != null) {
                return target;
            }
            Time.sleep(100L);
        }
    }

• When the Assignment Distribution Service prepare s, it submits DistributeTask to the thread pool
• The run method of DistributeTask keeps looping, takes NodeAssignments from the corresponding queue, and then calls sendAssignmentsToNode for remote communication.
• SendAssignments ToNode calls client. getClient (). sendSupervisor Assignments (assignments. getAssignments ())

Supervisor.launchSupervisorThriftServer

storm-2.0.0/storm-server/src/main/java/org/apache/storm/daemon/supervisor/Supervisor.java

    private void launchSupervisorThriftServer(Map<String, Object> conf) throws IOException {
        // validate port
        int port = getThriftServerPort();
        try {
            ServerSocket socket = new ServerSocket(port);
            socket.close();
        } catch (BindException e) {
            LOG.error("{} is not available. Check if another process is already listening on {}", port, port);
            throw new RuntimeException(e);
        }

        TProcessor processor = new org.apache.storm.generated.Supervisor.Processor(
            new org.apache.storm.generated.Supervisor.Iface() {
                @Override
                public void sendSupervisorAssignments(SupervisorAssignments assignments)
                    throws AuthorizationException, TException {
                    checkAuthorization("sendSupervisorAssignments");
                    LOG.info("Got an assignments from master, will start to sync with assignments: {}", assignments);
                    SynchronizeAssignments syn = new SynchronizeAssignments(getSupervisor(), assignments,
                                                                            getReadClusterState());
                    getEventManger().add(syn);
                }

                //......
            });
        this.thriftServer = new ThriftServer(conf, processor, ThriftConnectionType.SUPERVISOR);
        this.thriftServer.serve();
    }

• When Supervisor. launchSupervisor Thrift Server is launched, TProcessor is added, and Supervisor Assignments are packaged as Synchronize Assignments and added to Event Manager.

SynchronizeAssignments.run

storm-2.0.0/storm-server/src/main/java/org/apache/storm/daemon/supervisor/timer/SynchronizeAssignments.java

/**
 * A runnable which will synchronize assignments to node local and then worker processes.
 */
public class SynchronizeAssignments implements Runnable {
	//......
	@Override
    public void run() {
        // first sync assignments to local, then sync processes.
        if (null == assignments) {
            getAssignmentsFromMaster(this.supervisor.getConf(), this.supervisor.getStormClusterState(), this.supervisor.getAssignmentId());
        } else {
            assignedAssignmentsToLocal(this.supervisor.getStormClusterState(), assignments);
        }
        this.readClusterState.run();
    }

    private static void assignedAssignmentsToLocal(IStormClusterState clusterState, SupervisorAssignments assignments) {
        if (null == assignments) {
            //unknown error, just skip
            return;
        }
        Map<String, byte[]> serAssignments = new HashMap<>();
        for (Map.Entry<String, Assignment> entry : assignments.get_storm_assignment().entrySet()) {
            serAssignments.put(entry.getKey(), Utils.serialize(entry.getValue()));
        }
        clusterState.syncRemoteAssignments(serAssignments);
    }
}

• This calls assignedAssignments ToLocal, and then triggers this.readClusterState.run()
• Assigned Assignments ToLocal calls clusterState.syncRemoteAssignments(serAssignments)

StormClusterStateImpl.syncRemoteAssignments

storm-2.0.0/storm-client/src/jvm/org/apache/storm/cluster/StormClusterStateImpl.java

    @Override
    public void syncRemoteAssignments(Map<String, byte[]> remote) {
        if (null != remote) {
            this.assignmentsBackend.syncRemoteAssignments(remote);
        } else {
            Map<String, byte[]> tmp = new HashMap<>();
            List<String> stormIds = this.stateStorage.get_children(ClusterUtils.ASSIGNMENTS_SUBTREE, false);
            for (String stormId : stormIds) {
                byte[] assignment = this.stateStorage.get_data(ClusterUtils.assignmentPath(stormId), false);
                tmp.put(stormId, assignment);
            }
            this.assignmentsBackend.syncRemoteAssignments(tmp);
        }
    }

• Here, update the serAssignments information to assignments Backend (local memory)
• If remote is null, the allocation information is read from zk and updated to memory; zk address is ClusterUtils.assignmentPath(stormId)(/assignments/{topologyId})

ReadClusterState.run

storm-2.0.0/storm-server/src/main/java/org/apache/storm/daemon/supervisor/ReadClusterState.java

    @Override
    public synchronized void run() {
        try {
            List<String> stormIds = stormClusterState.assignments(null);
            Map<String, Assignment> assignmentsSnapshot = getAssignmentsSnapshot(stormClusterState);

            Map<Integer, LocalAssignment> allAssignments = readAssignments(assignmentsSnapshot);
            if (allAssignments == null) {
                //Something odd happened try again later
                return;
            }
            Map<String, List<ProfileRequest>> topoIdToProfilerActions = getProfileActions(stormClusterState, stormIds);

            HashSet<Integer> assignedPorts = new HashSet<>();
            LOG.debug("Synchronizing supervisor");
            LOG.debug("All assignment: {}", allAssignments);
            LOG.debug("Topology Ids -> Profiler Actions {}", topoIdToProfilerActions);
            for (Integer port : allAssignments.keySet()) {
                if (iSuper.confirmAssigned(port)) {
                    assignedPorts.add(port);
                }
            }
            HashSet<Integer> allPorts = new HashSet<>(assignedPorts);
            iSuper.assigned(allPorts);
            allPorts.addAll(slots.keySet());

            Map<Integer, Set<TopoProfileAction>> filtered = new HashMap<>();
            for (Entry<String, List<ProfileRequest>> entry : topoIdToProfilerActions.entrySet()) {
                String topoId = entry.getKey();
                if (entry.getValue() != null) {
                    for (ProfileRequest req : entry.getValue()) {
                        NodeInfo ni = req.get_nodeInfo();
                        if (host.equals(ni.get_node())) {
                            Long port = ni.get_port().iterator().next();
                            Set<TopoProfileAction> actions = filtered.get(port.intValue());
                            if (actions == null) {
                                actions = new HashSet<>();
                                filtered.put(port.intValue(), actions);
                            }
                            actions.add(new TopoProfileAction(topoId, req));
                        }
                    }
                }
            }

            for (Integer port : allPorts) {
                Slot slot = slots.get(port);
                if (slot == null) {
                    slot = mkSlot(port);
                    slots.put(port, slot);
                    slot.start();
                }
                slot.setNewAssignment(allAssignments.get(port));
                slot.addProfilerActions(filtered.get(port));
            }

        } catch (Exception e) {
            LOG.error("Failed to Sync Supervisor", e);
            throw new RuntimeException(e);
        }
    }

• Here we call the setNewAssignment of slot for allocation, and set the Atomic Reference < LocalAssignment > newAssignment of slot.
• Slot's run method polls for judgment of new Assignment through the stateMachineStep method and then updates nextState

Summary

• Nimbus notifies supervisor of task assignment results by calling addAs signments ForNode of Assignment Distribution Service
  • Additional Assignments ForNode mainly puts Supervisor Assignments into assignments Queue; Assignment Distribution Service defaults to create a thread pool with a specified number of threads, while creating a queue with a specified number of threads and a Distribute Task
  • DistributeTask loops continuously to pull Synchronize Assignments from the specified queue, and then calls sendAssignments ToNode notification to supervisor
• Supervisor launches Supervisor Thrift Server at startup, registers the processor responding to sendSupervisor Assignments, and packages the received Supervisor Assignments as Synchronize Assignments and adds them to Event Manager
  • EventManager executes its run method when handling SynchronizeAssignments, calls assignedAssignments ToLocal, and then triggers this.readClusterState.run()
  • AssignedAssignments ToLocal calls cluster State. syncRemoteAssignments (serAssignments) to update the allocation information to local memory; readClusterState.run() mainly updates the slot's new Assignment value, then relies on Slot's polling to sense state changes, and triggers the corresponding processing.

doc

• Understanding the Parallelism of a Storm Topology