/** * A slot sharing units defines which different task (from different job vertices) can be * deployed together within a slot. This is a soft permission, in contrast to the hard constraint * defined by a co-location hint. */public class SlotSharingGroup implements java.io.Serializable {    private final Set<JobVertexID> ids = new TreeSet<JobVertexID>();        /** Mapping of tasks to subslots. This field is only needed inside the JobManager, and is not RPCed. */    private transient SlotSharingGroupAssignment taskAssignment;

/** * A Co-location group is a group of JobVertices, where the <i>i-th</i> subtask of one vertex * has to be executed on the same TaskManager as the <i>i-th</i> subtask of all * other JobVertices in the same group. *  * <p>The co-location group is used for example to make sure that the i-th subtasks for iteration * head and iteration tail are scheduled to the same TaskManager.</p> */public class CoLocationGroup implements java.io.Serializable {    /** The ID that describes the slot co-location-constraint as a group */     private final AbstractID id = new AbstractID();        /** The vertices participating in the co-location group */    private final List<JobVertex> vertices = new ArrayList<JobVertex>();        /** The constraints, which hold the shared slots for the co-located operators */    private transient ArrayList<CoLocationConstraint> constraints;

/** * A CoLocationConstraint manages the location of a set of tasks * (Execution Vertices). In co-location groups, the different subtasks of * different JobVertices need to be executed on the same {@link Instance}. * This is realized by creating a special shared slot that holds these tasks. *  * <p>This class tracks the location and the shared slot for this set of tasks. */public class CoLocationConstraint {    private final CoLocationGroup group;    private volatile SharedSlot sharedSlot;    private volatile ResourceID lockedLocation;

/** * The {@code AllocatedSlot} represents a slot that the JobManager allocated from a TaskManager. * It represents a slice of allocated resources from the TaskManager. *  * <p>To allocate an {@code AllocatedSlot}, the requests a slot from the ResourceManager. The * ResourceManager picks (or starts) a TaskManager that will then allocate the slot to the * JobManager and notify the JobManager. *  * <p>Note: Prior to the resource management changes introduced in (Flink Improvement Proposal 6), * an AllocatedSlot was allocated to the JobManager as soon as the TaskManager registered at the * JobManager. All slots had a default unknown resource profile.  */public class AllocatedSlot {    /** The ID under which the slot is allocated. Uniquely identifies the slot. */    private final AllocationID slotAllocationId;    /** The ID of the job this slot is allocated for */    private final JobID jobID;    /** The location information of the TaskManager to which this slot belongs */    private final TaskManagerLocation taskManagerLocation;    /** The resource profile of the slot provides */    private final ResourceProfile resourceProfile;    /** RPC gateway to call the TaskManager that holds this slot */    private final TaskManagerGateway taskManagerGateway;    /** The number of the slot on the TaskManager to which slot belongs. Purely informational. */    private final int slotNumber;

/** * Base class for slots that the Scheduler / ExecutionGraph take from the SlotPool and use to place * tasks to execute into. A slot corresponds to an AllocatedSlot (a slice of a TaskManager‘s resources), * plus additional fields to track what is currently executed in that slot, or if the slot is still * used or disposed (ExecutionGraph gave it back to the pool). * * <p>In the simplest case, a slot holds a single task ({@link SimpleSlot}). In the more complex * case, a slot is shared ({@link SharedSlot}) and contains a set of tasks. Shared slots may contain * other shared slots which in turn can hold simple slots. That way, a shared slot may define a tree * of slots that belong to it. */public abstract class Slot {    /** The allocated slot that this slot represents. */    private final AllocatedSlot allocatedSlot;    /** The owner of this slot - the slot was taken from that owner and must be disposed to it */    private final SlotOwner owner;    /** The parent of this slot in the hierarchy, or null, if this is the parent */    @Nullable    private final SharedSlot parent;    /** The id of the group that this slot is allocated to. May be null. */    @Nullable    private final AbstractID groupID;    /** The number of the slot on which the task is deployed */    private final int slotNumber;

/** * A SimpleSlot represents a single slot on a TaskManager instance, or a slot within a shared slot. * * <p>If this slot is part of a {@link SharedSlot}, then the parent attribute will point to that shared slot. * If not, then the parent attribute is null. */public class SimpleSlot extends Slot {    /** Task being executed in the slot. Volatile to force a memory barrier and allow for correct double-checking */    private volatile Execution executedTask; //非share，只有一个task    /** The locality attached to the slot, defining whether the slot was allocated at the desired location. */    private volatile Locality locality = Locality.UNCONSTRAINED;

/** * This class represents a shared slot. A shared slot can have multiple * {@link SimpleSlot} instances within itself. This allows to * schedule multiple tasks simultaneously to the same resource. Sharing a resource with multiple * tasks is crucial for simple pipelined / streamed execution, where both the sender and the receiver * are typically active at the same time. * * <p><b>IMPORTANT:</b> This class contains no synchronization. Thus, the caller has to guarantee proper * synchronization. In the current implementation, all concurrently modifying operations are * passed through a {@link SlotSharingGroupAssignment} object which is responsible for * synchronization. */public class SharedSlot extends Slot {    /** The assignment group os shared slots that manages the availability and release of the slots */    private final SlotSharingGroupAssignment assignmentGroup;    /** The set os sub-slots allocated from this shared slot */    private final Set<Slot> subSlots;

    SimpleSlot allocateSubSlot(AbstractID groupId) {        if (isAlive()) {            SimpleSlot slot = new SimpleSlot(                    getJobID(), getOwner(), getTaskManagerLocation(), subSlots.size(),                     getTaskManagerGateway(), this, groupId);            subSlots.add(slot);            return slot;        }        else {            return null;        }    }

    public SimpleSlot(            JobID jobID, SlotOwner owner, TaskManagerLocation location, int slotNumber,            TaskManagerGateway taskManagerGateway,            @Nullable SharedSlot parent, @Nullable AbstractID groupID) {        super(parent != null ? //如果有parent，即属于某个sharedSlot                parent.getAllocatedSlot() : //使用parent sharedSlot                new AllocatedSlot(NO_ALLOCATION_ID, jobID, location, slotNumber, //创建新的AllocatedSlot                        ResourceProfile.UNKNOWN, taskManagerGateway),                owner, slotNumber, parent, groupID);    }

/** * The SlotSharingGroupAssignment manages a set of shared slots, which are shared between * tasks of a {@link org.apache.flink.runtime.jobmanager.scheduler.SlotSharingGroup}. *  * <p>The assignments shares tasks by allowing a shared slot to hold one vertex per * JobVertexID. For example, consider a program consisting of job vertices "source", "map", * "reduce", and "sink". If the slot sharing group spans all four job vertices, then * each shared slot can hold one parallel subtask of the source, the map, the reduce, and the * sink vertex. Each shared slot holds the actual subtasks in child slots, which are (at the leaf level), * the {@link SimpleSlot}s.</p> *  * <p>An exception are the co-location-constraints, that define that the i-th subtask of one * vertex needs to be scheduled strictly together with the i-th subtasks of of the vertices * that share the co-location-constraint. To manage that, a co-location-constraint gets its * own shared slot inside the shared slots of a sharing group.</p> *  * <p>Consider a job set up like this:</p> *  * <pre>{@code * +-------------- Slot Sharing Group --------------+ * |                                                | * |            +-- Co Location Group --+           | * |            |                       |           | * |  (source) ---> (head) ---> (tail) ---> (sink)  | * |            |                       |           | * |            +-----------------------+           | * +------------------------------------------------+ * }</pre> *  * <p>The slot hierarchy in the slot sharing group will look like the following</p>  *  * <pre> *     Shared(0)(root) *        | *        +-- Simple(2)(sink) *        | *        +-- Shared(1)(co-location-group) *        |      | *        |      +-- Simple(0)(tail) *        |      +-- Simple(1)(head) *        | *        +-- Simple(0)(source) * </pre> */public class SlotSharingGroupAssignment {        /** All slots currently allocated to this sharing group */    private final Set<SharedSlot> allSlots = new LinkedHashSet<SharedSlot>();    /** The slots available per vertex type (JobVertexId), keyed by TaskManager, to make them locatable */    private final Map<AbstractID, Map<ResourceID, List<SharedSlot>>> availableSlotsPerJid = new LinkedHashMap<>();

   /**     * Gets a slot suitable for the given task vertex. This method will prefer slots that are local     * (with respect to {@link ExecutionVertex#getPreferredLocationsBasedOnInputs()}), but will return non local     * slots if no local slot is available. The method returns null, when this sharing group has     * no slot is available for the given JobVertexID.      *     * @param vertex The vertex to allocate a slot for.     *     * @return A slot to execute the given ExecutionVertex in, or null, if none is available.     */    public SimpleSlot getSlotForTask(ExecutionVertex vertex) {        return getSlotForTask(vertex.getJobvertexId(), vertex.getPreferredLocationsBasedOnInputs()); //默认以input所分配的slot的location信息，作为Preferred    }    /**     *      */    SimpleSlot getSlotForTask(JobVertexID vertexID, Iterable<TaskManagerLocation> locationPreferences) {        synchronized (lock) {            Tuple2<SharedSlot, Locality> p = getSlotForTaskInternal(vertexID, locationPreferences, false); //获取SharedSlot,第三个参数意思是，不是一定要local            if (p != null) {                SharedSlot ss = p.f0;                SimpleSlot slot = ss.allocateSubSlot(vertexID); //从SharedSlot中分配SimpleSlot                slot.setLocality(p.f1);                return slot;            }            else {                return null;            }        }    }

  private Tuple2<SharedSlot, Locality> getSlotForTaskInternal(            AbstractID groupId, Iterable<TaskManagerLocation> preferredLocations, boolean localOnly)    {        // check if there is anything at all in this group assignment        if (allSlots.isEmpty()) { //如果没有slots，返回            return null;        }        // get the available slots for the group        Map<ResourceID, List<SharedSlot>> slotsForGroup = availableSlotsPerJid.get(groupId); //取出JobVertex所对应的结构slotsForGroup                if (slotsForGroup == null) { //初始化slotsForGroup            // we have a new group, so all slots are available            slotsForGroup = new LinkedHashMap<>();            availableSlotsPerJid.put(groupId, slotsForGroup);            for (SharedSlot availableSlot : allSlots) { //因为allSlots是共享的，所以都可以加到slotsForGroup作为可用slots                putIntoMultiMap(slotsForGroup, availableSlot.getTaskManagerID(), availableSlot); //将availableSlot注册到slotsForGroup，也就是放到其location所对应的list里面            }        }        else if (slotsForGroup.isEmpty()) { //如果slotsForGroup存在，但是没有可用slots            // the group exists, but nothing is available for that group            return null;        }        // check whether we can schedule the task to a preferred location        boolean didNotGetPreferred = false;        if (preferredLocations != null) { //如果有perferred location            for (TaskManagerLocation location : preferredLocations) { //对每一个具体的prefer location                // set the flag that we failed a preferred location. If one will be found,                // we return early anyways and skip the flag evaluation                didNotGetPreferred = true; //tricky逻辑，如果下面return，这里的设置也没用；如果没返回，说明没有找到prefer的，所以设为true没有问题                SharedSlot slot = removeFromMultiMap(slotsForGroup, location.getResourceID()); //如果可以在slotsForGroup找到对应prefer location上的slot，为何要remove，因为一个jobvertex不可能有两个task跑在同一个slot上                if (slot != null && slot.isAlive()) {                    return new Tuple2<>(slot, Locality.LOCAL); //返回，并且满足prefer，所以是local，local的含义是和prefer在同一个taskmanager上                }            }        }        // if we want only local assignments, exit now with a "not found" result        if (didNotGetPreferred && localOnly) { //如果没有找到prefer local，并且需要localonly，返回null            return null;        }        Locality locality = didNotGetPreferred ? Locality.NON_LOCAL : Locality.UNCONSTRAINED; //走到这里，并didNotGetPreferred = false，说明preferredLocations = null，即UNCONSTRAINED，没有约束条件        // schedule the task to any available location        SharedSlot slot;        while ((slot = pollFromMultiMap(slotsForGroup)) != null) { //在不指定taskmanager location的情况下，随意找一个slot            if (slot.isAlive()) {                return new Tuple2<>(slot, locality);            }        }                // nothing available after all, all slots were dead        return null;    }

    private SimpleSlot addSharedSlotAndAllocateSubSlot(            SharedSlot sharedSlot, Locality locality, JobVertexID groupId, CoLocationConstraint constraint) {        final ResourceID location = sharedSlot.getTaskManagerID();        synchronized (lock) {                        SimpleSlot subSlot;            AbstractID groupIdForMap;                        // add to the total bookkeeping            if (!allSlots.add(sharedSlot)) { //加到allSlots中                throw new IllegalArgumentException("Slot was already contained in the assignment group");            }                                if (constraint == null) {                // allocate us a sub slot to return                subSlot = sharedSlot.allocateSubSlot(groupId); //简单的allocate一个simpleSlot                groupIdForMap = groupId;            }            else { //如果有CoLocationConstraint                            }                        if (subSlot != null) {                // preserve the locality information                subSlot.setLocality(locality);                                // let the other groups know that this slot exists and that they                // can place a task into this slot.                boolean entryForNewJidExists = false;                                for (Map.Entry<AbstractID, Map<ResourceID, List<SharedSlot>>> entry : availableSlotsPerJid.entrySet()) {                    // there is already an entry for this groupID                    if (entry.getKey().equals(groupIdForMap)) {                        entryForNewJidExists = true;                        continue;                    }                    Map<ResourceID, List<SharedSlot>> available = entry.getValue();                    putIntoMultiMap(available, location, sharedSlot); //对于其他的jobVertex，把sharedSlot加上去                }                // make sure an empty entry exists for this group, if no other entry exists                if (!entryForNewJidExists) { //如果存在参数中的groupId，那么就把它的slot信息清空                    availableSlotsPerJid.put(groupIdForMap, new LinkedHashMap<ResourceID, List<SharedSlot>>());                }                return subSlot;            }        }        // end synchronized (lock)    }

    protected SimpleSlot getNewSlotForSharingGroup(ExecutionVertex vertex,                                                    Iterable<TaskManagerLocation> requestedLocations,                                                    SlotSharingGroupAssignment groupAssignment,                                                    CoLocationConstraint constraint,                                                    boolean localOnly)    {        // we need potentially to loop multiple times, because there may be false positives        // in the set-with-available-instances        while (true) {            Pair<Instance, Locality> instanceLocalityPair = findInstance(requestedLocations, localOnly); //根据locations信息找到local的instance                        if (instanceLocalityPair == null) { //如果没有可用的instance，返回null                // nothing is available                return null;            }            final Instance instanceToUse = instanceLocalityPair.getLeft();            final Locality locality = instanceLocalityPair.getRight();            try {                JobVertexID groupID = vertex.getJobvertexId();                                // allocate a shared slot from the instance                SharedSlot sharedSlot = instanceToUse.allocateSharedSlot(vertex.getJobId(), groupAssignment); //从instance申请一个SharedSlot                // if the instance has further available slots, re-add it to the set of available resources.                if (instanceToUse.hasResourcesAvailable()) { //如果这个instance还有多余的资源，再加入instancesWithAvailableResources，下次还能继续用来分配                    this.instancesWithAvailableResources.put(instanceToUse.getTaskManagerID(), instanceToUse);                }                if (sharedSlot != null) {                    // add the shared slot to the assignment group and allocate a sub-slot                    SimpleSlot slot = constraint == null ?                            groupAssignment.addSharedSlotAndAllocateSubSlot(sharedSlot, locality, groupID) : //把分配的SharedSlot加到SlotSharingGroup的SlotSharingGroupAssignment中                            groupAssignment.addSharedSlotAndAllocateSubSlot(sharedSlot, locality, constraint);                    if (slot != null) {                        return slot;                    }                    else {                        // could not add and allocate the sub-slot, so release shared slot                        sharedSlot.releaseSlot();                    }                }            }            catch (InstanceDiedException e) {                // the instance died it has not yet been propagated to this scheduler                // remove the instance from the set of available instances                removeInstance(instanceToUse);            }            // if we failed to get a slot, fall through the loop        }    }