Skip to content

F
folly
Commit fc6f0a5f authored by Hans Fugal's avatar Hans Fugal Committed by Alecs King
Browse files
Options

(futures) Make executors sticky 

Summary:
Instead of returning a deactivated future, have `via` just set the executor. Propagate the executor from `then`. This fixes the `via().get()` problem, and has semantics similar to before for `via().then().then()`.

However, the semantics are now slightly different - each `then` goes back through the executor. This adds some overhead and tweaks the semantics (e.g. if the executor is a threadpool it might execute subsequent `then`s in another thread). However, with `futures::chain` recently introduced, and any other convenience methods that you can dream up and make a case for, we can reasonably get the old once-through-the-executor behavior when performance or other concerns demand it. e.g. `via().then(futures::chain(a, b, c))`.

Test Plan: unit tests

Reviewed By: hannesr@fb.com

Subscribers: zeus-diffs@, mmandal, steveo, rituraj, trunkagent, exa, folly-diffs@, yfeldblum, jsedgwick, davejwatson

FB internal diff: D1839691

Tasks: 6048744

Signature: t1:1839691:1424397180:ca0b0ea7b3867769ab8abd254a510059df67011e
parent 5e32096c
Show whitespace changes
Inline Side-by-side
Showing with 47 additions and 122 deletions
folly/futures/Future-inl.h
View file @ fc6f0a5f
......@@ -115,6 +115,9 @@ Future<T>::thenImplementation(F func, detail::argResult<isTry, F, Args...>) {
// grab the Future now before we lose our handle on the Promise
auto f = p->getFuture();
if (getExecutor()) {
f.setExecutor(getExecutor());
}
/* This is a bit tricky.
......@@ -179,6 +182,9 @@ Future<T>::thenImplementation(F func, detail::argResult<isTry, F, Args...>) {
// grab the Future now before we lose our handle on the Promise
auto f = p->getFuture();
if (getExecutor()) {
f.setExecutor(getExecutor());
}
setCallback_(
[p, funcm](Try<T>&& t) mutable {
......@@ -318,8 +324,7 @@ template <typename Executor>
inline Future<T> Future<T>::via(Executor* executor) && {
throwIfInvalid();
this->deactivate();
core_->setExecutor(executor);
setExecutor(executor);
return std::move(*this);
}
......
folly/futures/Future.h
View file @ fc6f0a5f
......@@ -448,7 +448,7 @@ class Future {
/// Overload of waitVia() for rvalue Futures
Future<T>&& waitVia(DrivableExecutor* e) &&;
private:
protected:
typedef detail::Core<T>* corePtr;
// shared core state object
......@@ -462,6 +462,7 @@ class Future {
void throwIfInvalid() const;
friend class Promise<T>;
template <class> friend class Future;
// Variant: returns a value
// e.g. f.then([](Try<T> t){ return t.value(); });
......@@ -474,6 +475,9 @@ class Future {
template <typename F, typename R, bool isTry, typename... Args>
typename std::enable_if<R::ReturnsFuture::value, typename R::Return>::type
thenImplementation(F func, detail::argResult<isTry, F, Args...>);
Executor* getExecutor() { return core_->getExecutor(); }
void setExecutor(Executor* x) { core_->setExecutor(x); }
};
/**
......
folly/futures/detail/Core.h
View file @ fc6f0a5f
......@@ -178,7 +178,7 @@ class Core {
/// Called by a destructing Future (in the Future thread, by definition)
void detachFuture() {
activate();
activateNoDeprecatedWarning();
detachOne();
}
......@@ -193,14 +193,13 @@ class Core {
}
/// May call from any thread
void deactivate() {
void deactivate() DEPRECATED {
active_ = false;
}
/// May call from any thread
void activate() {
active_ = true;
maybeCallback();
void activate() DEPRECATED {
activateNoDeprecatedWarning();
}
/// May call from any thread
......@@ -211,6 +210,10 @@ class Core {
executor_ = x;
}
Executor* getExecutor() {
return executor_;
}
/// Call only from Future thread
void raise(exception_wrapper e) {
std::lock_guard<decltype(interruptLock_)> guard(interruptLock_);
......@@ -234,7 +237,12 @@ class Core {
}
}
private:
protected:
void activateNoDeprecatedWarning() {
active_ = true;
maybeCallback();
}
void maybeCallback() {
FSM_START(fsm_)
case State::Armed:
......
folly/futures/test/FutureTest.cpp
View file @ fc6f0a5f
......@@ -1135,7 +1135,7 @@ TEST(Future, waitVia) {
{
// try rvalue as well
ManualExecutor x;
auto f = via(&x).activate().then().waitVia(&x);
auto f = via(&x).then().waitVia(&x);
EXPECT_TRUE(f.isReady());
}
......@@ -1146,53 +1146,6 @@ TEST(Future, waitVia) {
}
}
TEST(Future, callbackAfterActivate) {
Promise<void> p;
auto f = p.getFuture();
f.deactivate();
size_t count = 0;
f.then([&](Try<void>&&) { count++; });
p.setValue();
EXPECT_EQ(0, count);
f.activate();
EXPECT_EQ(1, count);
}
TEST(Future, activateOnDestruct) {
auto f = std::make_shared<Future<void>>(makeFuture());
f->deactivate();
size_t count = 0;
f->then([&](Try<void>&&) { count++; });
EXPECT_EQ(0, count);
f.reset();
EXPECT_EQ(1, count);
}
TEST(Future, viaActsCold) {
ManualExecutor x;
size_t count = 0;
auto fv = via(&x);
fv.then([&](Try<void>&&) { count++; });
EXPECT_EQ(0, count);
fv.activate();
EXPECT_EQ(1, x.run());
EXPECT_EQ(1, count);
}
TEST(Future, viaIsCold) {
ManualExecutor x;
EXPECT_FALSE(via(&x).isActive());
}
TEST(Future, viaRaces) {
ManualExecutor x;
Promise<void> p;
......@@ -1216,35 +1169,6 @@ TEST(Future, viaRaces) {
t2.join();
}
// TODO(#4920689)
TEST(Future, viaRaces_2stage) {
ManualExecutor x;
Promise<void> p;
auto tid = std::this_thread::get_id();
bool done = false;
std::thread t1([&] {
auto f2 = p.getFuture().via(&x);
f2.then([&](Try<void>&&) { EXPECT_EQ(tid, std::this_thread::get_id()); })
.then([&](Try<void>&&) { EXPECT_EQ(tid, std::this_thread::get_id()); })
.then([&](Try<void>&&) { done = true; });
// the bug was in the promise being fulfilled before f2 is reactivated. we
// could sleep, but yielding should cause this to fail with reasonable
// probability
std::this_thread::yield();
f2.activate();
});
std::thread t2([&] {
p.setValue();
});
while (!done) x.run();
t1.join();
t2.join();
}
TEST(Future, getFuture_after_setValue) {
Promise<int> p;
p.setValue(42);
......
folly/futures/test/ViaTest.cpp
View file @ fc6f0a5f
......@@ -92,8 +92,7 @@ TEST(Via, then_future) {
auto future = makeFuture(1)
.then([](Try<int>&& t) {
return makeFuture(t.value() == 1);
})
;
});
EXPECT_TRUE(future.value());
}
......@@ -120,27 +119,6 @@ TEST(Via, then_function) {
EXPECT_EQ(f.value(), "start;static;class-static;class");
}
TEST_F(ViaFixture, deactivateChain) {
bool flag = false;
auto f = makeFuture().deactivate();
EXPECT_FALSE(f.isActive());
auto f2 = f.then([&](Try<void>){ flag = true; });
EXPECT_FALSE(flag);
}
TEST_F(ViaFixture, deactivateActivateChain) {
bool flag = false;
// you can do this all day long with temporaries.
auto f1 = makeFuture().deactivate().activate().deactivate();
// Chaining on activate/deactivate requires an rvalue, so you have to move
// one of these two ways (if you're not using a temporary).
auto f2 = std::move(f1).activate();
f2.deactivate();
auto f3 = std::move(f2.activate());
f3.then([&](Try<void>){ flag = true; });
EXPECT_TRUE(flag);
}
TEST_F(ViaFixture, thread_hops) {
auto westThreadId = std::this_thread::get_id();
auto f = via(eastExecutor.get()).then([=](Try<void>&& t) {
......@@ -156,22 +134,28 @@ TEST_F(ViaFixture, thread_hops) {
TEST_F(ViaFixture, chain_vias) {
auto westThreadId = std::this_thread::get_id();
auto f = via(eastExecutor.get()).then([=](Try<void>&& t) {
auto f = via(eastExecutor.get()).then([=]() {
EXPECT_NE(std::this_thread::get_id(), westThreadId);
return makeFuture<int>(1);
}).then([=](Try<int>&& t) {
int val = t.value();
return makeFuture(std::move(val)).via(westExecutor.get())
.then([=](Try<int>&& t) mutable {
return 1;
}).then([=](int val) {
return makeFuture(val).via(westExecutor.get())
.then([=](int val) mutable {
EXPECT_EQ(std::this_thread::get_id(), westThreadId);
return t.value();
return val + 1;
});
}).then([=](Try<int>&& t) {
}).then([=](int val) {
// even though ultimately the future that triggers this one executed in
// the west thread, this then() inherited the executor from its
// predecessor, ie the eastExecutor.
EXPECT_NE(std::this_thread::get_id(), westThreadId);
return val + 1;
}).via(westExecutor.get()).then([=](int val) {
// go back to west, so we can wait on it
EXPECT_EQ(std::this_thread::get_id(), westThreadId);
return t.value();
return val + 1;
});
EXPECT_EQ(f.getVia(waiter.get()), 1);
EXPECT_EQ(f.getVia(waiter.get()), 4);
}
TEST_F(ViaFixture, bareViaAssignment) {
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment