foundationdb/flow/genericactors.actor.cpp

676 lines
22 KiB
C++

/*
* genericactors.actor.cpp
*
* This source file is part of the FoundationDB open source project
*
* Copyright 2013-2026 Apple Inc. and the FoundationDB project authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "flow/flow.h"
#include "flow/UnitTest.h"
#include "genericcoros.h"
#include "flow/actorcompiler.h" // This must be the last #include.
Future<bool> allTrue(std::vector<Future<bool>> all) {
for (int i = 0; i != all.size(); ++i) {
bool r = co_await all[i];
if (!r)
co_return false;
}
co_return true;
}
ACTOR Future<Void> anyTrue(std::vector<Reference<AsyncVar<bool>>> input, Reference<AsyncVar<bool>> output) {
loop {
bool oneTrue = false;
std::vector<Future<Void>> changes;
for (auto it : input) {
if (it->get())
oneTrue = true;
changes.push_back(it->onChange());
}
output->set(oneTrue);
wait(waitForAny(changes));
}
}
Future<Void> cancelOnly([[maybe_unused]] std::vector<Future<Void>> futures) {
// We don't do anything with futures except hold them, we never return, but if we are cancelled we (naturally) drop
// the futures
co_await Future<Void>(Never());
}
ACTOR Future<Void> timeoutWarningCollector(FutureStream<Void> input, double logDelay, const char* context, UID id) {
state uint64_t counter = 0;
state Future<Void> end = delay(logDelay);
loop choose {
when(waitNext(input)) {
counter++;
}
when(wait(end)) {
if (counter)
TraceEvent(SevWarn, context, id).detail("LateProcessCount", counter).detail("LoggingDelay", logDelay);
end = delay(logDelay);
counter = 0;
}
}
}
Future<Void> waitForMost(std::vector<Future<ErrorOr<Void>>> futures,
int faultTolerance,
Error e,
double waitMultiplierForSlowFutures) {
std::vector<Future<bool>> successFutures;
double startTime = now();
successFutures.reserve(futures.size());
for (const auto& future : futures) {
successFutures.push_back(fmap([](auto const& result) { return result.present(); }, future));
}
bool success = co_await quorumEqualsTrue(successFutures, successFutures.size() - faultTolerance);
if (!success) {
throw e;
}
co_await (delay((now() - startTime) * waitMultiplierForSlowFutures) || waitForAll(successFutures));
}
ACTOR Future<bool> quorumEqualsTrue(std::vector<Future<bool>> futures, int required) {
state std::vector<Future<Void>> true_futures;
state std::vector<Future<Void>> false_futures;
true_futures.reserve(futures.size());
false_futures.reserve(futures.size());
for (int i = 0; i < futures.size(); i++) {
true_futures.push_back(onEqual(futures[i], true));
false_futures.push_back(onEqual(futures[i], false));
}
choose {
when(wait(quorum(true_futures, required))) {
return true;
}
when(wait(quorum(false_futures, futures.size() - required + 1))) {
return false;
}
}
}
ACTOR Future<bool> shortCircuitAny(std::vector<Future<bool>> f) {
std::vector<Future<Void>> sc;
sc.reserve(f.size());
for (Future<bool> fut : f) {
sc.push_back(returnIfTrue(fut));
}
choose {
when(wait(waitForAll(f))) {
// Handle a possible race condition? If the _last_ term to
// be evaluated triggers the waitForAll before bubbling
// out of the returnIfTrue quorum
for (const auto& fut : f) {
if (fut.get()) {
return true;
}
}
return false;
}
when(wait(waitForAny(sc))) {
return true;
}
}
}
Future<Void> orYield(Future<Void> f) {
if (f.isReady()) {
if (f.isError())
return tagError<Void>(yield(), f.getError());
else
return yield();
} else
return f;
}
ACTOR Future<Void> returnIfTrue(Future<bool> f) {
bool b = wait(f);
if (b) {
return Void();
}
wait(Never());
throw internal_error();
}
Future<Void> lowPriorityDelay(double waitTime) {
int totalLoops = std::max<int>(waitTime / FLOW_KNOBS->LOW_PRIORITY_MAX_DELAY, FLOW_KNOBS->LOW_PRIORITY_DELAY_COUNT);
for (int loopCount = 0; loopCount < totalLoops; ++loopCount) {
co_await delay(waitTime / totalLoops, TaskPriority::Low);
}
}
ACTOR Future<Void> delayAfterCleared(Reference<AsyncVar<bool>> condition, double time, TaskPriority taskID) {
state Future<Void> timer = condition->get() ? Never() : delay(time, taskID);
state bool previousState = condition->get();
loop choose {
when(wait(timer)) {
return Void();
}
when(wait(condition->onChange())) {
bool currentState = condition->get();
if (currentState != previousState) {
timer = currentState ? Never() : delay(time, taskID);
previousState = currentState;
}
}
}
}
// Same as delayAfterCleared, but use lowPriorityDelay.
ACTOR Future<Void> lowPriorityDelayAfterCleared(Reference<AsyncVar<bool>> condition, double time) {
state Future<Void> timer = condition->get() ? Never() : lowPriorityDelay(time);
state bool previousState = condition->get();
loop choose {
when(wait(timer)) {
return Void();
}
when(wait(condition->onChange())) {
bool currentState = condition->get();
if (currentState != previousState) {
timer = currentState ? Never() : lowPriorityDelay(time);
previousState = currentState;
}
}
}
}
struct SetAsyncVarTrue {
Reference<AsyncVar<bool>> value;
void operator()() const { value->set(true); }
};
namespace {
struct DummyState {
int changed{ 0 };
int unchanged{ 0 };
bool operator==(DummyState const& rhs) const { return changed == rhs.changed && unchanged == rhs.unchanged; }
bool operator!=(DummyState const& rhs) const { return !(*this == rhs); }
};
ACTOR Future<Void> testPublisher(Reference<AsyncVar<DummyState>> input) {
state int i = 0;
for (; i < 100; ++i) {
wait(delay(deterministicRandom()->random01()));
auto var = input->get();
++var.changed;
input->set(var);
}
return Void();
}
ACTOR Future<Void> testSubscriber(Reference<IAsyncListener<int>> output, Optional<int> expected) {
loop {
wait(output->onChange());
ASSERT(expected.present());
if (output->get() == expected.get()) {
return Void();
}
}
}
static Future<ErrorOr<Void>> goodTestFuture(double duration) {
return tag(delay(duration), ErrorOr<Void>(Void()));
}
static Future<ErrorOr<Void>> badTestFuture(double duration, Error e) {
return tag(delay(duration), ErrorOr<Void>(e));
}
ACTOR Future<int> getErrorCode(Future<int> future) {
try {
int value = wait(future);
(void)value;
return 0;
} catch (Error& e) {
return e.code();
}
}
ACTOR Future<int> getVoidErrorCode(Future<Void> future) {
try {
wait(future);
return 0;
} catch (Error& e) {
return e.code();
}
}
} // namespace
TEST_CASE("/flow/genericactors/AsyncListener") {
auto input = makeReference<AsyncVar<DummyState>>();
state Future<Void> subscriber1 =
testSubscriber(IAsyncListener<int>::create(input, [](auto const& var) { return var.changed; }), 100);
state Future<Void> subscriber2 =
testSubscriber(IAsyncListener<int>::create(input, [](auto const& var) { return var.unchanged; }), {});
wait(subscriber1 && testPublisher(input));
ASSERT(!subscriber2.isReady());
return Void();
}
TEST_CASE("/flow/genericactors/DelayedAsyncVarPreservesReentrantInputChange") {
state Reference<AsyncVar<bool>> input = makeReference<AsyncVar<bool>>(true);
state Reference<AsyncVar<bool>> output = makeReference<AsyncVar<bool>>(true);
state Future<Void> feedback = generic_coro::trigger(SetAsyncVarTrue{ input }, output->onChange());
state Future<Void> publisher = delayedAsyncVar(input, output, 0);
wait(delay(0));
input->set(false);
wait(feedback);
wait(delay(0.01));
ASSERT(input->get());
ASSERT(output->get());
publisher.cancel();
return Void();
}
TEST_CASE("/flow/genericactors/WaitForMost") {
state std::vector<Future<ErrorOr<Void>>> futures;
{
futures = { goodTestFuture(1), goodTestFuture(2), goodTestFuture(3) };
wait(waitForMost(futures, 1, operation_failed(), 0.0)); // Don't wait for slowest future
ASSERT(!futures[2].isReady());
}
{
futures = { goodTestFuture(1), goodTestFuture(2), goodTestFuture(3) };
wait(waitForMost(futures, 0, operation_failed(), 0.0)); // Wait for all futures
ASSERT(futures[2].isReady());
}
{
futures = { goodTestFuture(1), goodTestFuture(2), goodTestFuture(3) };
wait(waitForMost(futures, 1, operation_failed(), 1.0)); // Wait for slowest future
ASSERT(futures[2].isReady());
}
{
futures = { goodTestFuture(1), goodTestFuture(2), badTestFuture(1, success()) };
wait(waitForMost(futures, 1, operation_failed(), 1.0)); // Error ignored
}
{
futures = { goodTestFuture(1), goodTestFuture(2), badTestFuture(1, success()) };
try {
wait(waitForMost(futures, 0, operation_failed(), 1.0));
ASSERT(false);
} catch (Error& e) {
ASSERT_EQ(e.code(), error_code_operation_failed);
}
}
return Void();
}
Future<int64_t> notifiedWaitForForwardTest(NotifiedInt* version, bool* fired) {
co_await version->whenAtLeast(10);
*fired = true;
co_return 10;
}
Future<Void> notifiedWaitForTimeoutVoidTest(NotifiedInt* version, bool* fired) {
co_await version->whenAtLeast(10);
*fired = true;
}
Future<Void> cancelForwardWhenReady(Future<int64_t> signal, Future<int64_t>* forwarded) {
co_await signal;
forwarded->cancel();
}
Future<Void> cancelForwardOnError(Future<int64_t> signal, Future<int64_t>* forwarded) {
try {
co_await signal;
ASSERT(false);
} catch (Error& e) {
ASSERT_EQ(e.code(), error_code_operation_failed);
forwarded->cancel();
}
}
TEST_CASE("/flow/genericactors/NotifiedCancellation") {
state NotifiedInt version(0);
state bool forwardedWaitFired = false;
state Promise<int64_t> forwardedReply;
state Future<int64_t> cancelledForward =
forward(notifiedWaitForForwardTest(&version, &forwardedWaitFired), forwardedReply);
cancelledForward.cancel();
ASSERT(cancelledForward.isError() && cancelledForward.getError().code() == error_code_actor_cancelled);
version.set(10);
ASSERT(!forwardedWaitFired);
version = NotifiedInt(0);
state bool chosenWaitFired = false;
state Promise<int64_t> otherChoice;
state Future<int64_t> cancelledChoice =
chooseActor(notifiedWaitForForwardTest(&version, &chosenWaitFired), otherChoice.getFuture());
cancelledChoice.cancel();
ASSERT(cancelledChoice.isError() && cancelledChoice.getError().code() == error_code_actor_cancelled);
version.set(10);
ASSERT(!chosenWaitFired);
version = NotifiedInt(0);
state bool brokenWaitFired = false;
state Future<int64_t> cancelledBroken =
brokenPromiseToNever(notifiedWaitForForwardTest(&version, &brokenWaitFired));
cancelledBroken.cancel();
ASSERT(cancelledBroken.isError() && cancelledBroken.getError().code() == error_code_actor_cancelled);
version.set(10);
ASSERT(!brokenWaitFired);
version = NotifiedInt(0);
state bool timedWaitFired = false;
state Future<Optional<int64_t>> cancelledTimeout =
timeout(notifiedWaitForForwardTest(&version, &timedWaitFired), 60.0);
cancelledTimeout.cancel();
ASSERT(cancelledTimeout.isError() && cancelledTimeout.getError().code() == error_code_actor_cancelled);
version.set(10);
ASSERT(!timedWaitFired);
version = NotifiedInt(0);
state bool expiredWaitFired = false;
state Future<Optional<int64_t>> expiredTimeout =
timeout(notifiedWaitForForwardTest(&version, &expiredWaitFired), 0.0);
Optional<int64_t> timeoutResult = wait(expiredTimeout);
ASSERT(!timeoutResult.present());
version.set(10);
ASSERT(!expiredWaitFired);
version = NotifiedInt(0);
state bool timedValueWaitFired = false;
state Future<int64_t> cancelledTimeoutValue =
timeout(notifiedWaitForForwardTest(&version, &timedValueWaitFired), 60.0, int64_t(-1));
cancelledTimeoutValue.cancel();
ASSERT(cancelledTimeoutValue.isError() && cancelledTimeoutValue.getError().code() == error_code_actor_cancelled);
version.set(10);
ASSERT(!timedValueWaitFired);
version = NotifiedInt(0);
state bool expiredValueWaitFired = false;
state Future<int64_t> expiredTimeoutValue =
timeout(notifiedWaitForForwardTest(&version, &expiredValueWaitFired), 0.0, int64_t(-1));
int64_t timeoutValue = wait(expiredTimeoutValue);
ASSERT_EQ(timeoutValue, -1);
version.set(10);
ASSERT(!expiredValueWaitFired);
version = NotifiedInt(0);
state bool timedVoidWaitFired = false;
state Future<Void> cancelledTimeoutVoid =
timeout(notifiedWaitForTimeoutVoidTest(&version, &timedVoidWaitFired), 60.0, Void());
cancelledTimeoutVoid.cancel();
ASSERT(cancelledTimeoutVoid.isError() && cancelledTimeoutVoid.getError().code() == error_code_actor_cancelled);
version.set(10);
ASSERT(!timedVoidWaitFired);
version = NotifiedInt(0);
state bool expiredVoidWaitFired = false;
state Future<Void> expiredTimeoutVoid =
timeout(notifiedWaitForTimeoutVoidTest(&version, &expiredVoidWaitFired), 0.0, Void());
wait(expiredTimeoutVoid);
version.set(10);
ASSERT(!expiredVoidWaitFired);
version = NotifiedInt(0);
state bool timedErrorWaitFired = false;
state Future<int64_t> cancelledTimeoutError =
timeoutError(notifiedWaitForForwardTest(&version, &timedErrorWaitFired), 60.0);
cancelledTimeoutError.cancel();
ASSERT(cancelledTimeoutError.isError() && cancelledTimeoutError.getError().code() == error_code_actor_cancelled);
version.set(10);
ASSERT(!timedErrorWaitFired);
version = NotifiedInt(0);
state bool expiredErrorWaitFired = false;
state Future<int64_t> expiredTimeoutError =
timeoutError(notifiedWaitForForwardTest(&version, &expiredErrorWaitFired), 0.0);
try {
int64_t unused = wait(expiredTimeoutError);
(void)unused;
ASSERT(false);
} catch (Error& e) {
ASSERT_EQ(e.code(), error_code_timed_out);
}
version.set(10);
ASSERT(!expiredErrorWaitFired);
version = NotifiedInt(0);
state bool errorWaitFired = false;
state Future<int64_t> cancelledWaitOrError =
waitOrError(notifiedWaitForForwardTest(&version, &errorWaitFired), Future<Void>(Never()));
cancelledWaitOrError.cancel();
ASSERT(cancelledWaitOrError.isError() && cancelledWaitOrError.getError().code() == error_code_actor_cancelled);
version.set(10);
ASSERT(!errorWaitFired);
state Promise<int64_t> forwardedInput;
state Promise<int64_t> reentrantReply;
state Future<int64_t> reentrantForward = forward(forwardedInput.getFuture(), reentrantReply);
state Future<Void> reentrantCancel = cancelForwardWhenReady(reentrantReply.getFuture(), &reentrantForward);
forwardedInput.send(10);
wait(reentrantCancel);
int64_t forwardedValue = wait(reentrantForward);
ASSERT_EQ(forwardedValue, 10);
state Promise<int64_t> erroredInput;
state Promise<int64_t> erroredReply;
state Future<int64_t> erroredForward = forward(erroredInput.getFuture(), erroredReply);
state Future<Void> errorCancel = cancelForwardOnError(erroredReply.getFuture(), &erroredForward);
erroredInput.sendError(operation_failed());
wait(errorCancel);
ASSERT(erroredForward.isError() && erroredForward.getError().code() == error_code_operation_failed);
return Void();
}
TEST_CASE("/flow/genericactors/WaitForFirstReleasesCapturedState") {
state Promise<int64_t> pendingSuccess;
state Future<int64_t> completed =
waitForFirst(std::vector<Future<int64_t>>{ Future<int64_t>(10), pendingSuccess.getFuture() });
ASSERT(completed.isReady() && !completed.isError() && completed.get() == 10);
ASSERT_EQ(pendingSuccess.getFutureReferenceCount(), 0);
state Promise<int64_t> pendingError;
state Future<int64_t> failed =
waitForFirst(std::vector<Future<int64_t>>{ Future<int64_t>(operation_failed()), pendingError.getFuture() });
ASSERT(failed.isError() && failed.getError().code() == error_code_operation_failed);
ASSERT_EQ(pendingError.getFutureReferenceCount(), 0);
state Promise<int64_t> pendingCancellation;
state Future<int64_t> cancelled = waitForFirst(std::vector<Future<int64_t>>{ pendingCancellation.getFuture() });
cancelled.cancel();
ASSERT(cancelled.isError() && cancelled.getError().code() == error_code_actor_cancelled);
ASSERT_EQ(pendingCancellation.getFutureReferenceCount(), 0);
return Void();
}
TEST_CASE("/flow/genericactors/ReadyRaceReleasesCapturedState") {
state NotifiedInt version(0);
state bool pendingFirstChoiceFired = false;
state Future<int64_t> readySecondChoice =
chooseActor(notifiedWaitForForwardTest(&version, &pendingFirstChoiceFired), Future<int64_t>(10));
ASSERT(readySecondChoice.isReady() && !readySecondChoice.isError() && readySecondChoice.get() == 10);
version.set(10);
ASSERT(!pendingFirstChoiceFired);
version = NotifiedInt(0);
state bool pendingSecondChoiceFired = false;
state Future<int64_t> readyFirstChoice =
chooseActor(Future<int64_t>(10), notifiedWaitForForwardTest(&version, &pendingSecondChoiceFired));
ASSERT(readyFirstChoice.isReady() && !readyFirstChoice.isError() && readyFirstChoice.get() == 10);
version.set(10);
ASSERT(!pendingSecondChoiceFired);
version = NotifiedInt(0);
state bool failedWaitFired = false;
state Future<int64_t> failedWait =
waitOrError(notifiedWaitForForwardTest(&version, &failedWaitFired), Future<Void>(operation_failed()));
ASSERT(failedWait.isError() && failedWait.getError().code() == error_code_operation_failed);
version.set(10);
ASSERT(!failedWaitFired);
state Promise<Void> unusedErrorSignal;
state Future<int64_t> readyValue = waitOrError(Future<int64_t>(10), unusedErrorSignal.getFuture());
ASSERT(readyValue.isReady() && !readyValue.isError() && readyValue.get() == 10);
ASSERT_EQ(unusedErrorSignal.getFutureReferenceCount(), 0);
state PromiseStream<int64_t> pendingStream;
state Future<int64_t> failedStreamWait = waitOrError(pendingStream.getFuture(), Future<Void>(operation_failed()));
ASSERT(failedStreamWait.isError() && failedStreamWait.getError().code() == error_code_operation_failed);
ASSERT_EQ(pendingStream.getFutureReferenceCount(), 0);
return Void();
}
TEST_CASE("/flow/genericactors/HoldWhileReleasesCapturedState") {
state FlowLock lock(1);
wait(lock.take());
state Promise<int64_t> completedInput;
state Future<int64_t> completed =
holdWhile(std::make_shared<FlowLock::Releaser>(lock, 1), completedInput.getFuture());
ASSERT_EQ(lock.available(), 0);
completedInput.send(10);
ASSERT(completed.isReady() && !completed.isError() && completed.get() == 10);
ASSERT_EQ(lock.available(), 1);
wait(lock.take());
state Promise<int64_t> erroredInput;
state Future<int64_t> errored = holdWhile(std::make_shared<FlowLock::Releaser>(lock, 1), erroredInput.getFuture());
ASSERT_EQ(lock.available(), 0);
erroredInput.sendError(operation_failed());
ASSERT(errored.isError() && errored.getError().code() == error_code_operation_failed);
ASSERT_EQ(lock.available(), 1);
wait(lock.take());
state Promise<int64_t> cancelledInput;
state Future<int64_t> cancelled =
holdWhile(std::make_shared<FlowLock::Releaser>(lock, 1), cancelledInput.getFuture());
ASSERT_EQ(lock.available(), 0);
cancelled.cancel();
ASSERT(cancelled.isError() && cancelled.getError().code() == error_code_actor_cancelled);
ASSERT_EQ(lock.available(), 1);
return Void();
}
TEST_CASE("/flow/genericcoros/ThrowErrorOr") {
int value = wait(generic_coro::throwErrorOr<int>(Future<ErrorOr<int>>(ErrorOr<int>(7))));
ASSERT_EQ(value, 7);
int errorCode =
wait(getErrorCode(generic_coro::throwErrorOr<int>(Future<ErrorOr<int>>(ErrorOr<int>(operation_failed())))));
ASSERT_EQ(errorCode, error_code_operation_failed);
return Void();
}
TEST_CASE("/flow/genericcoros/TraceAfter") {
int value = wait(generic_coro::traceAfter<int>(Future<int>(7), "GenericCorosTraceAfter"));
ASSERT_EQ(value, 7);
int errorCode = wait(
getErrorCode(generic_coro::traceAfter<int>(Future<int>(operation_failed()), "GenericCorosTraceAfterError")));
ASSERT_EQ(errorCode, error_code_operation_failed);
return Void();
}
TEST_CASE("/flow/genericcoros/TransformErrors") {
int value = wait(generic_coro::transformErrors<int>(Future<int>(7), operation_failed()));
ASSERT_EQ(value, 7);
int errorCode =
wait(getErrorCode(generic_coro::transformErrors<int>(Future<int>(transaction_too_old()), operation_failed())));
ASSERT_EQ(errorCode, error_code_operation_failed);
return Void();
}
TEST_CASE("/flow/genericcoros/TransformError") {
int value = wait(generic_coro::transformError<int>(Future<int>(7), transaction_too_old(), operation_failed()));
ASSERT_EQ(value, 7);
int transformedErrorCode = wait(getErrorCode(generic_coro::transformError<int>(
Future<int>(transaction_too_old()), transaction_too_old(), operation_failed())));
ASSERT_EQ(transformedErrorCode, error_code_operation_failed);
int preservedErrorCode = wait(getErrorCode(
generic_coro::transformError<int>(Future<int>(process_behind()), transaction_too_old(), operation_failed())));
ASSERT_EQ(preservedErrorCode, error_code_process_behind);
return Void();
}
TEST_CASE("/flow/genericcoros/WaitForAllReady") {
state std::vector<Future<int>> results;
results = { Future<int>(1), Future<int>(operation_failed()), Future<int>(3) };
wait(generic_coro::waitForAllReady<int>(results));
return Void();
}
TEST_CASE("/flow/genericcoros/Timeout") {
int readyValue = wait(generic_coro::timeout<int>(Future<int>(7), 0.0, -1));
ASSERT_EQ(readyValue, 7);
int timedOutValue = wait(generic_coro::timeout<int>(Future<int>(Never()), 0.0, -1));
ASSERT_EQ(timedOutValue, -1);
Optional<int> readyOptional = wait(generic_coro::timeout<int>(Future<int>(7), 0.0));
ASSERT(readyOptional.present());
ASSERT_EQ(readyOptional.get(), 7);
Optional<int> timedOutOptional = wait(generic_coro::timeout<int>(Future<int>(Never()), 0.0));
ASSERT(!timedOutOptional.present());
int errorCode = wait(getErrorCode(generic_coro::timeoutError<int>(Future<int>(Never()), 0.0)));
ASSERT_EQ(errorCode, error_code_timed_out);
return Void();
}
TEST_CASE("/flow/genericcoros/Delayed") {
int value = wait(generic_coro::delayed<int>(Future<int>(7)));
ASSERT_EQ(value, 7);
int errorCode = wait(getErrorCode(generic_coro::delayed<int>(Future<int>(operation_failed()))));
ASSERT_EQ(errorCode, error_code_operation_failed);
return Void();
}
TEST_CASE("/flow/genericcoros/Trigger") {
state Reference<AsyncVar<bool>> called = makeReference<AsyncVar<bool>>(false);
state Promise<Void> signal;
state Future<Void> triggered = generic_coro::trigger(SetAsyncVarTrue{ called }, signal.getFuture());
ASSERT(!called->get());
ASSERT(!triggered.isReady());
signal.send(Void());
wait(triggered);
ASSERT(called->get());
called->set(false);
int errorCode =
wait(getVoidErrorCode(generic_coro::trigger(SetAsyncVarTrue{ called }, Future<Void>(operation_failed()))));
ASSERT_EQ(errorCode, error_code_operation_failed);
ASSERT(!called->get());
return Void();
}