Implementing an input component

@Version(1) (1)
@Icon(Icon.IconType.DB_INPUT) (2)
@PartitionMapper(name = "Input") (3)
public class HazelcastMapper implements Serializable {
    private final HazelcastConfiguration configuration;
    private final JsonBuilderFactory jsonFactory;
    private final Jsonb jsonb;
    private final HazelcastService service;

    private final Collection<String> members;
    private transient HazelcastInstance instance;
    private transient IExecutorService executorService;

    // framework API
    public HazelcastMapper(@Option("configuration") final HazelcastConfiguration configuration,
            final JsonBuilderFactory jsonFactory,
            final Jsonb jsonb,
            final HazelcastService service) {
        this(configuration, jsonFactory, jsonb, service, emptyList());
    }

    // internal
    protected HazelcastMapper(final HazelcastConfiguration configuration,
            final JsonBuilderFactory jsonFactory,
            final Jsonb jsonb,
            final HazelcastService service,
            final Collection<String> members) {
        this.configuration = configuration;
        this.jsonFactory = jsonFactory;
        this.jsonb = jsonb;
        this.service = service;
        this.members = members;
    }

    @PostConstruct
    public void init() throws IOException {
        // Creates an instance of Hazelcast according to the provided configuration.
        // Uses the injected HazelcastService instance to perform that.
        // This service is implemented in the project. See the implementation in <1>.
        instance = service.findInstance(configuration.newConfig());
    }

    @PreDestroy
    public void close() {
        // Shuts down the instance created in the PostConstruct and frees the executorService reference.
        instance.getLifecycleService().shutdown();
        executorService = null;
    }

    @Assessor
    public long estimateSize() {
        // Calculates the whole size of all members.
        return getSizeByMembers().values().stream()
                .mapToLong(this::getFutureValue)
                .sum();
    }

    // This method returns a map of size by member of Hazelcast cluster
    private Map<Member, Future<Long>> getSizeByMembers() {
        final IExecutorService executorService = getExecutorService();
        final SerializableTask<Long> sizeComputation = new SerializableTask<Long>() {

            @Override
            public Long call() throws Exception {

                return localInstance.getMap(configuration.getMapName()).getLocalMapStats().getHeapCost();
            }
        };
        if (members.isEmpty()) { // == if no specific memebers defined, applies to all the cluster
            return executorService.submitToAllMembers(sizeComputation);
        }
        final Set<Member> members = instance.getCluster().getMembers().stream()
                .filter(m -> this.members.contains(m.getUuid()))
                .collect(toSet());
        return executorService.submitToMembers(sizeComputation, members);
    }

    // This method creates a collection of mappers according to the requested bundleSize and the dataset size.
    @Split
    public List<HazelcastMapper> split(@PartitionSize final long bundleSize) {
        final List<HazelcastMapper> partitions = new ArrayList<>();
        final Collection<Member> members = new ArrayList<>();
        long current = 0;
        for (final Map.Entry<Member, Future<Long>> entries : getSizeByMembers().entrySet()) {
            final long memberSize = getFutureValue(entries.getValue());
            if (members.isEmpty()) {
                members.add(entries.getKey());
                current += memberSize;
            } else if (current + memberSize > bundleSize) {
                partitions.add(
                        new HazelcastMapper(configuration, jsonFactory, jsonb, service, toIdentifiers(members)));
                // Resets current iteration
                members.clear();
                current = 0;
            }
        }
        if (!members.isEmpty()) {
            partitions.add(new HazelcastMapper(configuration, jsonFactory, jsonb, service, toIdentifiers(members)));
        }

        if (partitions.isEmpty()) { // just executes this if no plan (= no distribution)
            partitions.add(this);
        }
        return partitions;
    }

    //After splitting the mapper, every mappers creates an emitter that
    // reads the records according to the provided configuration.
    @Emitter
    public HazelcastSource createSource() {
        return new HazelcastSource(configuration, jsonFactory, jsonb, service, members);
    }

    private Set<String> toIdentifiers(final Collection<Member> members) {
        return members.stream().map(Member::getUuid).collect(toSet());
    }

    private long getFutureValue(final Future<Long> future) {
        try {
            return future.get(configuration.getTimeout(), SECONDS);
        } catch (final InterruptedException e) {
            Thread.currentThread().interrupt();
            throw new IllegalStateException(e);
        } catch (final ExecutionException | TimeoutException e) {
            throw new IllegalArgumentException(e);
        }
    }

    private IExecutorService getExecutorService() {
        return executorService == null ?
                executorService = instance.getExecutorService(configuration.getExecutorService()) :
                executorService;
    }
}