Default VirtualEventBase

Summary:
Make each EventBase have a defuault VirtualEventBase which is attached to it and is joined on destruction. Default VirtualEventBase is lazily created on first request.
This makes it trivial to use code switched to VirtualEventBase both with VirtualEventBase and EventBase.

Reviewed By: yfeldblum

Differential Revision: D4644639

fbshipit-source-id: cf28a3632463a1c61404c225ce1186f5a4a062a3

diff --git a/folly/fibers/test/FibersTest.cpp b/folly/fibers/test/FibersTest.cpp
index af3fe75a45d583fa71e3262c5276122bdca89bac..b3d32303c91441a475e2256ea4b152a7f49e995b 100644 (file)
--- a/folly/fibers/test/FibersTest.cpp
+++ b/folly/fibers/test/FibersTest.cpp
@@ -2042,34 +2042,36 @@ TEST(FiberManager, ABD_UserProvidedBatchDispatchThrowsTest) {
 }
 
 TEST(FiberManager, VirtualEventBase) {
-  folly::ScopedEventBaseThread thread;
-
-  auto evb1 =
-      folly::make_unique<folly::VirtualEventBase>(*thread.getEventBase());
-  auto evb2 =
-      folly::make_unique<folly::VirtualEventBase>(*thread.getEventBase());
-
   bool done1{false};
   bool done2{false};
+  {
+    folly::ScopedEventBaseThread thread;
 
-  getFiberManager(*evb1).addTaskRemote([&] {
-    Baton baton;
-    baton.timed_wait(std::chrono::milliseconds{100});
+    auto evb1 =
+        folly::make_unique<folly::VirtualEventBase>(*thread.getEventBase());
+    auto& evb2 = thread.getEventBase()->getVirtualEventBase();
 
-    done1 = true;
-  });
+    getFiberManager(*evb1).addTaskRemote([&] {
+      Baton baton;
+      baton.timed_wait(std::chrono::milliseconds{100});
 
-  getFiberManager(*evb2).addTaskRemote([&] {
-    Baton baton;
-    baton.timed_wait(std::chrono::milliseconds{200});
+      done1 = true;
+    });
 
-    done2 = true;
-  });
+    getFiberManager(evb2).addTaskRemote([&] {
+      Baton baton;
+      baton.timed_wait(std::chrono::milliseconds{200});
 
-  evb1.reset();
-  EXPECT_TRUE(done1);
+      done2 = true;
+    });
+
+    EXPECT_FALSE(done1);
+    EXPECT_FALSE(done2);
 
-  evb2.reset();
+    evb1.reset();
+    EXPECT_TRUE(done1);
+    EXPECT_FALSE(done2);
+  }
   EXPECT_TRUE(done2);
 }
 

diff --git a/folly/io/async/EventBase.cpp b/folly/io/async/EventBase.cpp
index 962418f9854439d734007ca37cfbcc4534a5181e..7e043f4c9c05eae4edbe06a1ee58cf1ad32e689b 100644 (file)
--- a/folly/io/async/EventBase.cpp
+++ b/folly/io/async/EventBase.cpp
@@ -19,6 +19,7 @@
 #endif
 
 #include <folly/io/async/EventBase.h>
+#include <folly/io/async/VirtualEventBase.h>
 
 #include <folly/ThreadName.h>
 #include <folly/io/async/NotificationQueue.h>
@@ -154,6 +155,11 @@ EventBase::EventBase(event_base* evb, bool enableTimeMeasurement)
 }
 
 EventBase::~EventBase() {
+  std::future<void> virtualEventBaseDestroyFuture;
+  if (virtualEventBase_) {
+    virtualEventBaseDestroyFuture = virtualEventBase_->destroy();
+  }
+
   // Keep looping until all keep-alive handles are released. Each keep-alive
   // handle signals that some external code will still schedule some work on
   // this EventBase (so it's not safe to destroy it).
@@ -162,6 +168,10 @@ EventBase::~EventBase() {
     loopOnce();
   }
 
+  if (virtualEventBaseDestroyFuture.valid()) {
+    virtualEventBaseDestroyFuture.get();
+  }
+
   // Call all destruction callbacks, before we start cleaning up our state.
   while (!onDestructionCallbacks_.empty()) {
     LoopCallback* callback = &onDestructionCallbacks_.front();
@@ -736,4 +746,12 @@ const std::string& EventBase::getName() {
 const char* EventBase::getLibeventVersion() { return event_get_version(); }
 const char* EventBase::getLibeventMethod() { return event_get_method(); }
 
+VirtualEventBase& EventBase::getVirtualEventBase() {
+  folly::call_once(virtualEventBaseInitFlag_, [&] {
+    virtualEventBase_ = std::make_unique<VirtualEventBase>(*this);
+  });
+
+  return *virtualEventBase_;
+}
+
 } // folly

diff --git a/folly/io/async/EventBase.h b/folly/io/async/EventBase.h
index c318d609ef6c3ada5e04865cf7724ece4a168df7..8527e559aa039dd5007c31e0a0f98b9b35bf4ef0 100644 (file)
--- a/folly/io/async/EventBase.h
+++ b/folly/io/async/EventBase.h
@@ -34,6 +34,7 @@
 #include <boost/intrusive/list.hpp>
 #include <boost/utility.hpp>
 
+#include <folly/CallOnce.h>
 #include <folly/Executor.h>
 #include <folly/Function.h>
 #include <folly/Portability.h>
@@ -629,6 +630,15 @@ class EventBase : private boost::noncopyable,
     return isInEventBaseThread();
   }
 
+  // Returns a VirtualEventBase attached to this EventBase. Can be used to
+  // pass to APIs which expect VirtualEventBase. This VirtualEventBase will be
+  // destroyed together with the EventBase.
+  //
+  // Any number of VirtualEventBases instances may be independently constructed,
+  // which are backed by this EventBase. This method should be only used if you
+  // don't need to manage the life time of the VirtualEventBase used.
+  folly::VirtualEventBase& getVirtualEventBase();
+
  protected:
   void keepAliveRelease() override {
     DCHECK(isInEventBaseThread());
@@ -736,6 +746,9 @@ class EventBase : private boost::noncopyable,
   std::mutex localStorageMutex_;
   std::unordered_map<uint64_t, std::shared_ptr<void>> localStorage_;
   std::unordered_set<detail::EventBaseLocalBaseBase*> localStorageToDtor_;
+
+  folly::once_flag virtualEventBaseInitFlag_;
+  std::unique_ptr<VirtualEventBase> virtualEventBase_;
 };
 
 template <typename T>

diff --git a/folly/io/async/VirtualEventBase.cpp b/folly/io/async/VirtualEventBase.cpp
index c1dbe2e7ce86bc65996da90b4c82d5886c3d49e6..688faf5e82f4a7265767b074672696e42b082c82 100644 (file)
--- a/folly/io/async/VirtualEventBase.cpp
+++ b/folly/io/async/VirtualEventBase.cpp
@@ -22,13 +22,16 @@ VirtualEventBase::VirtualEventBase(EventBase& evb) : evb_(evb) {
   loopKeepAlive_ = getKeepAliveToken();
 }
 
-VirtualEventBase::~VirtualEventBase() {
-  CHECK(!evb_.inRunningEventBaseThread());
+std::future<void> VirtualEventBase::destroy() {
+  CHECK(evb_.runInEventBaseThread([this] { loopKeepAlive_.reset(); }));
 
-  CHECK(evb_.runInEventBaseThread([&] { loopKeepAlive_.reset(); }));
-  loopKeepAliveBaton_.wait();
+  return std::move(destroyFuture_);
+}
 
-  CHECK(evb_.runInEventBaseThreadAndWait([&] {
+void VirtualEventBase::destroyImpl() {
+  // Make sure we release EventBase KeepAlive token even if exception occurs
+  auto evbLoopKeepAlive = std::move(evbLoopKeepAlive_);
+  try {
     clearCobTimeouts();
 
     onDestructionCallbacks_.withWLock([&](LoopCallbackList& callbacks) {
@@ -39,8 +42,18 @@ VirtualEventBase::~VirtualEventBase() {
       }
     });
 
-    evbLoopKeepAlive_.reset();
-  }));
+    destroyPromise_.set_value();
+  } catch (...) {
+    destroyPromise_.set_exception(std::current_exception());
+  }
+}
+
+VirtualEventBase::~VirtualEventBase() {
+  if (!destroyFuture_.valid()) {
+    return;
+  }
+  CHECK(!evb_.inRunningEventBaseThread());
+  destroy().get();
 }
 
 void VirtualEventBase::runOnDestruction(EventBase::LoopCallback* callback) {

diff --git a/folly/io/async/VirtualEventBase.h b/folly/io/async/VirtualEventBase.h
index f356d50bdb99d5305d0c79231bd563fe62e98d9a..c67d2cb29edb1b6cf8452423b78e6cee5ee7a023 100644 (file)
--- a/folly/io/async/VirtualEventBase.h
+++ b/folly/io/async/VirtualEventBase.h
@@ -16,6 +16,8 @@
 
 #pragma once
 
+#include <future>
+
 #include <folly/Baton.h>
 #include <folly/Executor.h>
 #include <folly/io/async/EventBase.h>
@@ -147,18 +149,24 @@ class VirtualEventBase : public folly::Executor, public folly::TimeoutManager {
     }
     DCHECK(loopKeepAliveCount_ > 0);
     if (--loopKeepAliveCount_ == 0) {
-      loopKeepAliveBaton_.post();
+      destroyImpl();
     }
   }
 
  private:
+  friend class EventBase;
+
+  std::future<void> destroy();
+  void destroyImpl();
+
   using LoopCallbackList = EventBase::LoopCallback::List;
 
   EventBase& evb_;
 
   ssize_t loopKeepAliveCount_{0};
   std::atomic<ssize_t> loopKeepAliveCountAtomic_{0};
-  folly::Baton<> loopKeepAliveBaton_;
+  std::promise<void> destroyPromise_;
+  std::future<void> destroyFuture_{destroyPromise_.get_future()};
   KeepAlive loopKeepAlive_;
 
   KeepAlive evbLoopKeepAlive_;