聊聊flink的slot.idle.timeout配置

序

本文主要研究一下flink的slot.idle.timeout配置

JobManagerOptions

flink-release-1.7.2/flink-core/src/main/java/org/apache/flink/configuration/JobManagerOptions.java

@PublicEvolving
public class JobManagerOptions {
    //......

    /**
     * The timeout in milliseconds for a idle slot in Slot Pool.
     */
    public static final ConfigOption<Long> SLOT_IDLE_TIMEOUT =
        key("slot.idle.timeout")
            // default matches heartbeat.timeout so that sticky allocation is not lost on timeouts for local recovery
            .defaultValue(HeartbeatManagerOptions.HEARTBEAT_TIMEOUT.defaultValue())
            .withDescription("The timeout in milliseconds for a idle slot in Slot Pool.");

    //......
}

• slot.idle.timeout默认为HeartbeatManagerOptions.HEARTBEAT_TIMEOUT.defaultValue()，即50000L毫秒

SlotPool

flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/jobmaster/slotpool/SlotPool.java

public class SlotPool extends RpcEndpoint implements SlotPoolGateway, AllocatedSlotActions {

    /** The interval (in milliseconds) in which the SlotPool writes its slot distribution on debug level. */
    private static final int STATUS_LOG_INTERVAL_MS = 60_000;

    private final JobID jobId;

    private final SchedulingStrategy schedulingStrategy;

    private final ProviderAndOwner providerAndOwner;

    /** All registered TaskManagers, slots will be accepted and used only if the resource is registered. */
    private final HashSet<ResourceID> registeredTaskManagers;

    /** The book-keeping of all allocated slots. */
    private final AllocatedSlots allocatedSlots;

    /** The book-keeping of all available slots. */
    private final AvailableSlots availableSlots;

    /** All pending requests waiting for slots. */
    private final DualKeyMap<SlotRequestId, AllocationID, PendingRequest> pendingRequests;

    /** The requests that are waiting for the resource manager to be connected. */
    private final HashMap<SlotRequestId, PendingRequest> waitingForResourceManager;

    /** Timeout for external request calls (e.g. to the ResourceManager or the TaskExecutor). */
    private final Time rpcTimeout;

    /** Timeout for releasing idle slots. */
    private final Time idleSlotTimeout;

    private final Clock clock;

    /** Managers for the different slot sharing groups. */
    protected final Map<SlotSharingGroupId, SlotSharingManager> slotSharingManagers;

    /** the fencing token of the job manager. */
    private JobMasterId jobMasterId;

    /** The gateway to communicate with resource manager. */
    private ResourceManagerGateway resourceManagerGateway;

    private String jobManagerAddress;

    //......

    /**
     * Start the slot pool to accept RPC calls.
     *
     * @param jobMasterId The necessary leader id for running the job.
     * @param newJobManagerAddress for the slot requests which are sent to the resource manager
     */
    public void start(JobMasterId jobMasterId, String newJobManagerAddress) throws Exception {
        this.jobMasterId = checkNotNull(jobMasterId);
        this.jobManagerAddress = checkNotNull(newJobManagerAddress);

        // TODO - start should not throw an exception
        try {
            super.start();
        } catch (Exception e) {
            throw new RuntimeException("This should never happen", e);
        }

        scheduleRunAsync(this::checkIdleSlot, idleSlotTimeout);

        if (log.isDebugEnabled()) {
            scheduleRunAsync(this::scheduledLogStatus, STATUS_LOG_INTERVAL_MS, TimeUnit.MILLISECONDS);
        }
    }

    /**
     * Check the available slots, release the slot that is idle for a long time.
     */
    private void checkIdleSlot() {

        // The timestamp in SlotAndTimestamp is relative
        final long currentRelativeTimeMillis = clock.relativeTimeMillis();

        final List<AllocatedSlot> expiredSlots = new ArrayList<>(availableSlots.size());

        for (SlotAndTimestamp slotAndTimestamp : availableSlots.availableSlots.values()) {
            if (currentRelativeTimeMillis - slotAndTimestamp.timestamp > idleSlotTimeout.toMilliseconds()) {
                expiredSlots.add(slotAndTimestamp.slot);
            }
        }

        final FlinkException cause = new FlinkException("Releasing idle slot.");

        for (AllocatedSlot expiredSlot : expiredSlots) {
            final AllocationID allocationID = expiredSlot.getAllocationId();
            if (availableSlots.tryRemove(allocationID) != null) {

                log.info("Releasing idle slot [{}].", allocationID);
                final CompletableFuture<Acknowledge> freeSlotFuture = expiredSlot.getTaskManagerGateway().freeSlot(
                    allocationID,
                    cause,
                    rpcTimeout);

                freeSlotFuture.whenCompleteAsync(
                    (Acknowledge ignored, Throwable throwable) -> {
                        if (throwable != null) {
                            if (registeredTaskManagers.contains(expiredSlot.getTaskManagerId())) {
                                log.debug("Releasing slot [{}] of registered TaskExecutor {} failed. " +
                                    "Trying to fulfill a different slot request.", allocationID, expiredSlot.getTaskManagerId(),
                                    throwable);
                                tryFulfillSlotRequestOrMakeAvailable(expiredSlot);
                            } else {
                                log.debug("Releasing slot [{}] failed and owning TaskExecutor {} is no " +
                                    "longer registered. Discarding slot.", allocationID, expiredSlot.getTaskManagerId());
                            }
                        }
                    },
                    getMainThreadExecutor());
            }
        }

        scheduleRunAsync(this::checkIdleSlot, idleSlotTimeout);
    }

    //......
}

• SlotPool在start方法里头，调用scheduleRunAsync方法，延时idleSlotTimeout调度执行checkIdleSlot；checkIdleSlot方法会挨个检查availableSlots的SlotAndTimestamp，判断当前时间与slotAndTimestamp.timestamp的时间差是否超过idleSlotTimeout，超过的话，则放入expiredSlots，之后对expiredSlots挨个进行availableSlots.tryRemove，然后调用TaskManagerGateway.freeSlot进行释放，之后再次调用scheduleRunAsync(this::checkIdleSlot, idleSlotTimeout)进行下一次的延时调度检测

RpcEndpoint

flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/rpc/RpcEndpoint.java

public abstract class RpcEndpoint implements RpcGateway {
    //......

    /**
     * Execute the runnable in the main thread of the underlying RPC endpoint, with
     * a delay of the given number of milliseconds.
     *
     * @param runnable Runnable to be executed
     * @param delay    The delay after which the runnable will be executed
     */
    protected void scheduleRunAsync(Runnable runnable, Time delay) {
        scheduleRunAsync(runnable, delay.getSize(), delay.getUnit());
    }

    /**
     * Execute the runnable in the main thread of the underlying RPC endpoint, with
     * a delay of the given number of milliseconds.
     *
     * @param runnable Runnable to be executed
     * @param delay    The delay after which the runnable will be executed
     */
    protected void scheduleRunAsync(Runnable runnable, long delay, TimeUnit unit) {
        rpcServer.scheduleRunAsync(runnable, unit.toMillis(delay));
    }

    //......
}

• RpcEndpoint提供了scheduleRunAsync，其最后调用的是rpcServer.scheduleRunAsync

小结

• slot.idle.timeout默认为HeartbeatManagerOptions.HEARTBEAT_TIMEOUT.defaultValue()，即50000L毫秒
• SlotPool在start方法里头，调用scheduleRunAsync方法，延时idleSlotTimeout调度执行checkIdleSlot；checkIdleSlot方法会挨个检查availableSlots的SlotAndTimestamp，判断当前时间与slotAndTimestamp.timestamp的时间差是否超过idleSlotTimeout，超过的话，则放入expiredSlots，之后对expiredSlots挨个进行availableSlots.tryRemove，然后调用TaskManagerGateway.freeSlot进行释放，之后再次调用scheduleRunAsync(this::checkIdleSlot, idleSlotTimeout)进行下一次的延时调度检测
• RpcEndpoint提供了scheduleRunAsync，其最后调用的是rpcServer.scheduleRunAsync

doc

• slot-idle-timeout