Kotlin Spot 공개 인터페이스¶
인터페이스 목차 · Java Spot · Spot 공통 계약
Bound Session의 relocation route 갱신은 Session–Actor binding §8.2가 소유한다.
SpotId는 UTF-8 encoded 크기 1..255 bytes의 String이며 Location Store transaction domain 전체에서 유일한 logical ID다.
비교는 case-sensitive 비교이고 Unicode normalization과 case folding을 적용하지 않는다. 일반 Spot send/request는
SpotId만 받는다. SpotRef(spotId, objectGeneration, meshName, nodeRid)는 지정한 incarnation을 close할 때만
사용하는 immutable snapshot이다. objectGeneration은 1..Long.MAX_VALUE이고 JSON에서는 decimal string이다.
User와 Instance Spot type은 UTF-8 1..255 bytes의 stable value다.
Java enum의 numeric value는 ZLinkSpotKind.INVALID=0, ENTRY=1, USER=2, INSTANCE=3이고
Kotlin은 ordinal을 계약 값으로 사용하지 않고 value()를 사용한다. Creatable kind enum은 제공하지 않는다.
ZLinkSpotManager.create(spotType)은 User Spot ID를 생성하고,
getOrCreate(spotId, spotType)은 caller가 정한 User Spot ID를 사용한다. Manager는 Instance Spot
create/get-or-create를 제공하지 않는다. 두 operation은 inMesh, request, timeout을 보존하는 Kotlin
전용 single-use wrapper를 반환한다. Terminal await() 또는
yield()를 정확히 한 번 호출한다. 중복 option과 중복 terminal, Mesh 선택, type 충돌과 deadline 규칙은
Actor operation과 같다. Entry Spot ID는
Framework가 만들며 public create 대상이 아니다.
Instance Spot cold activation과 첫 message¶
Spot send/request는 global SpotId를 받고 ZLinkKotlinSpotSendCall 또는
ZLinkKotlinSpotRequestCall<TReply>를 반환한다. Marker overload는 instanceSpot()과
instanceSpot(stableType: String)이며, Mesh 입력은 inMesh(meshName: String)이다.
Send는 suspend fun await(): Unit, request는 suspend fun await(): TReply와
suspend fun yield(): TReply로 완료 타입을 표현한다. 정확한 선언은
Kotlin source signature에 있다.
Cold activation의 type·Mesh 선택, 생성 순서와 최초 message 보존은 Spot address messaging §4가 소유한다. 완료 경계는 Spot address messaging §5를 따른다.
Stored creation intent의 재개 범위와 steady Ready owner 실패의 구분은
Object lifecycle §3가 소유한다.
Kotlin은 Java ZLinkSpotRelocationAdapter<TSpot>를 그대로 구현한다. Opaque byte[]는 ByteArray로 보이고
capture와 restore는 Java 계약과 같은 CompletionStage를 반환한다. 별도 suspending Spot adapter,
TState, stateContractId, state class와 ZLinkMessage relocation surface는 제공하지 않는다. State 보존 factory는
preserveStateWith(SpotAdapter::class.java)를 사용하고 factory target과 adapter type은 socket bind
전에 검증한다.
State를 보존하는 whole User Spot relocation은 Spot 자체에 Spot adapter를, member Actor마다 Actor adapter를 사용한다.
State를 보존하는 Instance Spot relocation은 Spot adapter를 사용한다. Same-node operation, disableRelocation()과 recreateOnRelocation()에서는
adapter를 호출하지 않는다. Capture ByteArray에는 relocation adapter 전용 size 상한이 없다. Java runtime은
completion에서 복사하고, payload를 relocationPayloadChunkLimitBytes 이하의 chunk로 나눠 source–target
ordered mesh 연결로 직접 전송한다. Source memory가 복원 원본이며 handoff payload를 Relocation
Store에 저장하지 않는다. Adapter는 completion까지 배열을 소유한다.
Restore는 호출마다 fresh defensive copy를 받고 completion 뒤 보관하지 않는다. Empty ByteArray도 유효한
보존 state다. Factory는 target attempt마다 fresh Spot instance를 만들며 source나 이전 attempt instance를
재사용하지 않는다. 같은 attempt의 restore는 반복될 수 있다. Capture exception은 source authority와 admission을
유지하고 restore exception은 target을 sealed 상태로 유지한 채 같은 target process에서 동일한 payload로 다시
시도할 수 있다. 다른 target을 자동 선택하지 않는다. Null stage와 null capture payload는 contract 위반이다. Host relocation의 precommit adapter
exception·contract violation은 deadline이 먼저 확정되지 않았으면 Blocked/StateIncompatible, deadline이 먼저
확정되면 Blocked/DeadlineExceeded다. Stale attempt cancellation은 terminal result를 commit하지 못한다.
Callback은 at-least-once이고 stale attempt와 겹칠 수 있으므로 retry-safe해야 한다.
Spot closing reason은 Java의 ZLinkSpotCloseReason을 사용하며 값은 EXPLICIT_CLOSE=0, HOST_SHUTDOWN=1,
RELOCATION_OUT=2, IDLE_EVICTED=3이다. ZLinkSpotClosingContext.deadline은 absolute Instant다. Java lifecycle interface는
context만 받고 별도 Framework cancellation 타입을 사용하지 않는다. Suspending projection은 cleanup deadline에
bridge coroutine을 cancel하며 callback은 coroutine cancellation을 그대로 따른다. Actor별 closing callback은
제공하지 않는다.
Kotlin source signature¶
interface ZLinkSuspendingSpotPacketHandler<TSpot : ZLinkSpot<*>, TMessage> {
suspend fun handle(spot: TSpot, message: TMessage)
suspend fun handle(
spot: TSpot,
message: TMessage,
context: ZLinkMessageContext,
)
}
interface ZLinkSuspendingSpotRequestHandler<TSpot : Any, TRequest, TReply> {
suspend fun handle(spot: TSpot, request: TRequest): TReply
suspend fun handle(
spot: TSpot,
request: TRequest,
context: ZLinkMessageContext,
): TReply
}
interface ZLinkSuspendingSpotSubscriptionHandler<TSpot : Any, TEvent> {
suspend fun handle(spot: TSpot, event: TEvent)
suspend fun handle(
spot: TSpot,
event: TEvent,
context: ZLinkPublishMessageContext,
)
}
interface ZLinkSuspendingSpotTimerHandler<TSpot : Any> {
suspend fun handle(spot: TSpot, tick: ZLinkTimerTick)
}
// Relocation은 logical timer와 pending tick을 Framework payload로 복원한다.
abstract class ZLinkSuspendingSpot<TActor : ZLinkActor> : ZLinkSpot<TActor> {
abstract val context: ZLinkSpotContext
final override fun context(): ZLinkSpotContext = context
protected open suspend fun onCreateSuspending(
request: ZLinkMessage,
): ZLinkSpotCreateResponse
protected open suspend fun onInitializeSuspending()
protected open suspend fun onClosingSuspending(
context: ZLinkSpotClosingContext,
)
protected open suspend fun onRelocationReadyCompletedSuspending(
completion: ZLinkSpotRelocationReadyCompletion,
)
protected abstract suspend fun onActorJoinSuspending(
actorId: String,
request: ZLinkMessage,
): ZLinkSpotActorJoinResult
protected abstract suspend fun onJoinedActorSuspending(actor: TActor)
protected abstract suspend fun onLeaveActorSuspending(actor: TActor)
protected open suspend fun onDisconnectActorSuspending(actor: TActor)
}
abstract class ZLinkSuspendingEntrySpot<TActor : ZLinkActor> :
ZLinkEntrySpot<TActor> {
abstract val context: ZLinkEntrySpotContext
final override fun context(): ZLinkEntrySpotContext = context
protected open suspend fun onInitializeSuspending()
protected open suspend fun onClosingSuspending(
context: ZLinkSpotClosingContext,
)
protected open suspend fun onCreateActorSuspending(
actor: TActor,
createRequest: ZLinkMessage,
): ZLinkActorCreateResponse
protected abstract suspend fun onJoinedActorSuspending(actor: TActor)
protected abstract suspend fun onLeaveActorSuspending(actor: TActor)
protected open suspend fun onDisconnectActorSuspending(actor: TActor)
}
abstract class ZLinkSuspendingInstanceSpot : ZLinkInstanceSpot {
abstract val context: ZLinkInstanceSpotContext
final override fun context(): ZLinkInstanceSpotContext = context
protected open suspend fun onInitializeSuspending()
protected open suspend fun onClosingSuspending(
context: ZLinkSpotClosingContext,
)
}
inline fun <reified THandler : Any> ZLinkSpotHandlerRegistry.addHandler()
interface ZLinkKotlinSpotSendCall {
fun metadata(key: String, value: String): ZLinkKotlinSpotSendCall
fun instanceSpot(): ZLinkKotlinSpotSendCall
fun instanceSpot(stableType: String): ZLinkKotlinSpotSendCall
fun inMesh(meshName: String): ZLinkKotlinSpotSendCall
suspend fun await()
}
interface ZLinkKotlinSpotRequestCall<TReply> {
fun metadata(key: String, value: String): ZLinkKotlinSpotRequestCall<TReply>
fun instanceSpot(): ZLinkKotlinSpotRequestCall<TReply>
fun instanceSpot(stableType: String): ZLinkKotlinSpotRequestCall<TReply>
fun inMesh(meshName: String): ZLinkKotlinSpotRequestCall<TReply>
fun timeout(timeout: Duration): ZLinkKotlinSpotRequestCall<TReply>
suspend fun await(): TReply
suspend fun yield(): TReply
}
interface ZLinkKotlinSpotCreateCall {
fun inMesh(meshName: String): ZLinkKotlinSpotCreateCall
fun request(request: Any): ZLinkKotlinSpotCreateCall
fun timeout(timeout: Duration): ZLinkKotlinSpotCreateCall
suspend fun await(): ZLinkSpotCreateResult
suspend fun yield(): ZLinkSpotCreateResult
}
interface ZLinkKotlinSpotManager {
fun create(spotType: String): ZLinkKotlinSpotCreateCall
fun getOrCreate(
spotId: String,
spotType: String,
): ZLinkKotlinSpotCreateCall
}
fun ZLinkKotlinRouteClient.sendToSpot(
spotId: String,
message: Any,
): ZLinkKotlinSpotSendCall
inline fun <reified TReply> ZLinkKotlinRouteClient.requestToSpot(
spotId: String,
request: Any,
): ZLinkKotlinSpotRequestCall<TReply>
Kotlin은 Java ZLinkTimerOptions와 ZLinkTimerOverrunPolicy를 그대로 사용한다. Timer option을 생략하면
overrunPolicy는 SKIP_LATE_TICKS, maxCatchUpTicks는 1이다. maxCatchUpTicks는
CATCH_UP_BOUNDED일 때만 사용하고 1..Int.MAX_VALUE 범위인지 검증한다. 다른 policy에서는 이 값을
사용하지 않으며 이 범위로 validation하지 않는다. Kotlin 전용 timer option surface는 추가하지 않는다.
User·Instance Spot relocation에서는 Java runtime이 logical timer registration, 마지막 완료 tick sequence, 다음 예정 시각과 아직 실행하지 않은 pending tick을 relocation payload에 포함한다. Target은 logical timer registration을 복원하므로 application이 timer를 다시 등록하지 않는다. 현재 실행 중인 suspending timer handler만 source에서 완료하고 target Ready 전에는 복원한 tick을 실행하지 않는다.
generated JVM signature¶
onCreateActorSuspending의 반환형 ZLinkActorCreateResponse는 JVM bridge의
onCreateActor에서도 CompletionStage<ZLinkActorCreateResponse>로 보존된다.
생성 응답의 공통 의미는 Spot 모델 §4.2가,
상위 선언은 Java Spot interface가 소유한다.
public final class systems.zlink.framework.kotlin.ZLinkSpotHandlerRegistryExtensionsKt {
public static final <THandler> void addHandler(systems.zlink.framework.spots.ZLinkSpotHandlerRegistry);
public static final void addTypedHandler(systems.zlink.framework.spots.ZLinkSpotHandlerRegistry, java.lang.Class<?>);
}
public interface systems.zlink.framework.kotlin.ZLinkSuspendingSpotPacketHandler<TSpot extends systems.zlink.framework.spots.ZLinkSpot<?>, TMessage> {
public abstract java.lang.Object handle(TSpot, TMessage, kotlin.coroutines.Continuation<? super kotlin.Unit>);
public abstract java.lang.Object handle(TSpot, TMessage, systems.zlink.framework.messaging.ZLinkMessageContext, kotlin.coroutines.Continuation<? super kotlin.Unit>);
}
public interface systems.zlink.framework.kotlin.ZLinkSuspendingSpotRequestHandler<TSpot, TRequest, TReply> {
public abstract java.lang.Object handle(TSpot, TRequest, kotlin.coroutines.Continuation<? super TReply>);
public abstract java.lang.Object handle(TSpot, TRequest, systems.zlink.framework.messaging.ZLinkMessageContext, kotlin.coroutines.Continuation<? super TReply>);
}
public interface systems.zlink.framework.kotlin.ZLinkSuspendingSpotSubscriptionHandler<TSpot, TEvent> {
public abstract java.lang.Object handle(TSpot, TEvent, kotlin.coroutines.Continuation<? super kotlin.Unit>);
public abstract java.lang.Object handle(TSpot, TEvent, systems.zlink.framework.messaging.ZLinkPublishMessageContext, kotlin.coroutines.Continuation<? super kotlin.Unit>);
}
public interface systems.zlink.framework.kotlin.ZLinkSuspendingSpotTimerHandler<TSpot> {
public abstract java.lang.Object handle(TSpot, systems.zlink.framework.spots.ZLinkTimerTick, kotlin.coroutines.Continuation<? super kotlin.Unit>);
}
public abstract class systems.zlink.framework.kotlin.ZLinkSuspendingEntrySpot<TActor extends systems.zlink.framework.actors.ZLinkActor> implements systems.zlink.framework.spots.ZLinkEntrySpot<TActor> {
public systems.zlink.framework.kotlin.ZLinkSuspendingEntrySpot();
public abstract systems.zlink.framework.spots.ZLinkEntrySpotContext getContext();
public final systems.zlink.framework.spots.ZLinkEntrySpotContext context();
public final java.util.concurrent.CompletionStage<java.lang.Void> onInitialize();
public final java.util.concurrent.CompletionStage<java.lang.Void> onClosing(systems.zlink.framework.spots.ZLinkSpotClosingContext);
public final java.util.concurrent.CompletionStage<systems.zlink.framework.spots.ZLinkActorCreateResponse> onCreateActor(TActor, systems.zlink.framework.messaging.ZLinkMessage);
public final java.util.concurrent.CompletionStage<java.lang.Void> onJoinedActor(TActor);
public final java.util.concurrent.CompletionStage<java.lang.Void> onLeaveActor(TActor);
public final java.util.concurrent.CompletionStage<java.lang.Void> onDisconnectActor(TActor);
}
public abstract class systems.zlink.framework.kotlin.ZLinkSuspendingSpot<TActor extends systems.zlink.framework.actors.ZLinkActor> implements systems.zlink.framework.spots.ZLinkSpot<TActor> {
public systems.zlink.framework.kotlin.ZLinkSuspendingSpot();
public abstract systems.zlink.framework.spots.ZLinkSpotContext getContext();
public final systems.zlink.framework.spots.ZLinkSpotContext context();
public final java.util.concurrent.CompletionStage<systems.zlink.framework.spots.ZLinkSpotCreateResponse> onCreate(systems.zlink.framework.messaging.ZLinkMessage);
public final java.util.concurrent.CompletionStage<java.lang.Void> onInitialize();
public final java.util.concurrent.CompletionStage<java.lang.Void> onClosing(systems.zlink.framework.spots.ZLinkSpotClosingContext);
public final java.util.concurrent.CompletionStage<java.lang.Void> onRelocationReadyCompleted(systems.zlink.framework.spots.ZLinkSpotRelocationReadyCompletion);
public final java.util.concurrent.CompletionStage<systems.zlink.framework.spots.ZLinkSpotActorJoinResult> onActorJoin(java.lang.String, systems.zlink.framework.messaging.ZLinkMessage);
public final java.util.concurrent.CompletionStage<java.lang.Void> onJoinedActor(TActor);
public final java.util.concurrent.CompletionStage<java.lang.Void> onLeaveActor(TActor);
public final java.util.concurrent.CompletionStage<java.lang.Void> onDisconnectActor(TActor);
}
public abstract class systems.zlink.framework.kotlin.ZLinkSuspendingInstanceSpot implements systems.zlink.framework.spots.ZLinkInstanceSpot {
public systems.zlink.framework.kotlin.ZLinkSuspendingInstanceSpot();
public abstract systems.zlink.framework.spots.ZLinkInstanceSpotContext getContext();
public final systems.zlink.framework.spots.ZLinkInstanceSpotContext context();
public final java.util.concurrent.CompletionStage<java.lang.Void> onInitialize();
public final java.util.concurrent.CompletionStage<java.lang.Void> onClosing(systems.zlink.framework.spots.ZLinkSpotClosingContext);
}
public final class systems.zlink.framework.kotlin.ZLinkFrameworkExtensionsKt {
public static final systems.zlink.framework.kotlin.ZLinkKotlinSpotSendCall sendToSpot(systems.zlink.framework.kotlin.ZLinkKotlinRouteClient, java.lang.String, java.lang.Object);
public static final <TReply> systems.zlink.framework.kotlin.ZLinkKotlinSpotRequestCall<TReply> requestToSpot(systems.zlink.framework.kotlin.ZLinkKotlinRouteClient, java.lang.String, java.lang.Object);
}
public interface systems.zlink.framework.kotlin.ZLinkKotlinSpotSendCall {
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotSendCall metadata(java.lang.String, java.lang.String);
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotSendCall instanceSpot();
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotSendCall instanceSpot(java.lang.String);
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotSendCall inMesh(java.lang.String);
public abstract java.lang.Object await(kotlin.coroutines.Continuation<? super kotlin.Unit>);
}
public interface systems.zlink.framework.kotlin.ZLinkKotlinSpotRequestCall<TReply> {
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotRequestCall<TReply> metadata(java.lang.String, java.lang.String);
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotRequestCall<TReply> instanceSpot();
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotRequestCall<TReply> instanceSpot(java.lang.String);
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotRequestCall<TReply> inMesh(java.lang.String);
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotRequestCall<TReply> timeout-LRDsOJo(long);
public abstract java.lang.Object await(kotlin.coroutines.Continuation<? super TReply>);
public abstract java.lang.Object yield(kotlin.coroutines.Continuation<? super TReply>);
}
public interface systems.zlink.framework.kotlin.ZLinkKotlinSpotCreateCall {
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotCreateCall inMesh(java.lang.String);
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotCreateCall request(java.lang.Object);
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotCreateCall timeout-LRDsOJo(long);
public abstract java.lang.Object await(kotlin.coroutines.Continuation<? super systems.zlink.framework.spots.ZLinkSpotCreateResult>);
public abstract java.lang.Object yield(kotlin.coroutines.Continuation<? super systems.zlink.framework.spots.ZLinkSpotCreateResult>);
}
public interface systems.zlink.framework.kotlin.ZLinkKotlinSpotManager {
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotCreateCall create(java.lang.String);
public abstract systems.zlink.framework.kotlin.ZLinkKotlinSpotCreateCall getOrCreate(java.lang.String, java.lang.String);
}
Kotlin suspending handler는 Java runtime과 같은 activation ownership을 사용한다. Spot handler는 Spot activation, Actor handler는 Actor activation마다 한 번 만들며 서로 다른 Actor가 handler instance나 scoped dependency를 공유하지 않는다. Same-node Join은 Actor handler를 유지하고 cross-node Join과 relocation은 target activation에서 다시 만든다. Coroutine continuation은 handler instance 수명을 늘리거나 relocation payload에 포함하지 않는다.
Kotlin은 address DTO, process-local handle, resolver와 unbounded directory를 제공하지 않는다. Kotlin-facing
route client와 manager는 fluent option과 single-use state를 보존하는 전용 wrapper를 반환하며 Java call,
CompletionStage와 Class<T>를 application에 노출하지 않는다.
close(SpotRef)는 Missing이면 false, generation 불일치는 InvalidOperation, seal된 이관 구간은
Unavailable로 처리하며 User Spot만 대상으로 한다. Instance Spot의 self-close는 Java
ZLinkInstanceSpotContext.close()를 그대로 사용한다.
Maintenance target은 Actor adapter와 queue·timer를 복원하고 Location authority·membership을
commit한 뒤 Actor message 처리를 시작한다. Bound Session의 relocation route 갱신은 Session–Actor binding §8.2가 소유한다.
Infrastructure relocation은
onJoinedActorSuspending, onLeaveActorSuspending 또는 별도 relocation callback을
호출하지 않는다. User Spot application join만
onActorJoinSuspending과 onJoinedActorSuspending을 사용한다. 새 Actor의 첫 생성은
onCreateActorSuspending의 승인과 선택적 reply만 사용하며 join/joined callback을 호출하지 않는다.
User Spot에서 Entry Spot으로 돌아갈 때는 target의 onJoinedActorSuspending과 source의
onLeaveActorSuspending을 호출한다. SpotWide User Spot aggregate와 PerActor
User Spot의 Actor relocation에서는 member의 Entry/User Spot
membership callback을 모두 호출하지 않는다.
User Spot factory mode의 기본값은 SPOT_WIDE다. 이 mode에서 suspending Spot·Actor·timer·lifecycle callback은
일반 suspension 동안 User Spot gate를 유지한다. Member Actor는 Actor FIFO claim도 함께 유지한다.
Request·worker·Actor·Spot create wrapper의 yield()만 gate를 반환하고 terminal completion 뒤 같은 gate를
다시 얻어 coroutine continuation을 실행한다. PER_ACTOR에서는 Actor별 lane, Spot direct·lifecycle lane과 timer별 lane이
독립적이며 suspension은 해당 lane permit만 유지한다. 서로 다른 Actor와 서로 다른 timer는 동시에 실행할 수
있다. SPOT_WIDE의 Close·relocation·snapshot은 새 admission을 seal하고 모든 coroutine continuation을
포함한 active lane이 안전한 turn 경계에 도달한 all-lane barrier 뒤에만 진행한다. Barrier 실패는 같은
generation의 seal 전체를 abort하고 application admission을 정확히 복원한다.
PER_ACTOR User Spot은 recreateOnRelocation()만 허용한다. Spot adapter,
Spot field와 Spot-level application timer는 relocation 대상이 아니다. 유지해야 하는 공유 state와
schedule은 application의 Redis·database·service 같은 외부 저장소에 둔다. Framework는 target에 같은
public Spot ID와 ObjectGeneration의 stateless shell을 준비하고 Spot authority를 먼저 바꾼다. 각 Actor는
자기 current turn을 끝낸 순서대로 queue·accepted journal·Actor timer와 함께 독립적으로 이전한다.
Target shell은 authority 전에는 public lookup에 노출하지 않는다. Stale source route는 operation identity,
generation, deadline, correlation과 reply route를 보존해 relay한다. Actor queue seal부터 one-way
cutover submit의 성공 또는 실패 terminal까지 source-local 1초는 운영 목표이며 초과해도 relocation을
취소하거나 rollback하지 않는다.
Factory configure callback에서 relocationCoordinationMode(...)를 생략하면
FRAMEWORK_MANAGED다. APPLICATION_SIGNALED은 SPOT_WIDE에서만 허용한다.
이 mode의 Spot turn에서는 context.relocationReady().defer()로 현재 turn 뒤의
경계를 등록한다. Framework는 source의 CONTINUED 또는 target의 RELOCATED
completion을 onRelocationReadyCompletedSuspending(...)에 전달하며 기본 구현은
no-op이다. Callback 완료 전에는 보류한 message와 timer를 실행하지 않는다.
기본 mode, PER_ACTOR, Entry·Instance Spot, Spot turn 밖과 같은 turn의 중복
defer()는 queue mutation 전에 INVALID_OPERATION이다. Recovery에서 callback이
다시 실행될 수 있으므로 override는 retry-safe해야 한다.
Yield는 Channel·Spot·Actor request, I/O·CPU worker와 Actor·Spot create/get-or-create에만 제공한다.
Entry Spot·Entry Actor·PER_ACTOR·Node·
Channel·owner context 밖에서는 coroutine suspension, operation submission, queue mutation과 gate 반환 전에
InvalidOperation으로 완료한다.