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/**
* Copyright (C) 2020-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <exception>
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
#include "mongo/stdx/thread.h"
#include "mongo/unittest/unittest.h"
#include "mongo/util/scopeguard.h"
namespace mongo::unittest {
/**
* Worker threads cannot use ASSERT exceptions, because they'll normally crash the
* process. We provide a way for a worker to transfer ASSERT failures to the
* main thread to be rethrown from there.
*
* The main thread has to be structured such that it's waiting
* on this monitor while all other work happens in workers.
*/
class ThreadAssertionMonitor {
public:
// Monitor will `wait()` on destruction, blocking until a `notifyDone()` call has occurred.
~ThreadAssertionMonitor() noexcept(false) {
wait();
}
/** Spawn and return a `stdx::thread` that invokes `f` as if by `exec(f)`. */
template <typename F>
stdx::thread spawn(F&& f) {
return stdx::thread{[this, f = std::move(f)]() mutable { exec(std::move(f)); }};
}
/** Spawn a thread that will invoke monitor.notifyDone()` when it finishes. */
template <typename F>
stdx::thread spawnController(F&& f) {
return spawn([this, f = std::move(f)]() mutable {
auto notifyDoneGuard = makeGuard([this] { notifyDone(); });
exec(std::move(f));
});
}
/** Invokes `f` inside a try/catch that routes any ASSERT failures to the monitor. */
template <typename F>
void exec(F&& f) {
try {
std::invoke(std::forward<F>(f));
} catch (const unittest::TestAssertionFailureException&) {
// Transport ASSERT failures to the monitor.
bool notify = false;
{
stdx::unique_lock lk(_mu); // NOLINT
if (!_ex) {
_ex = std::current_exception();
notify = true;
}
}
if (notify)
_cv.notify_one();
}
}
void notifyDone() {
{
stdx::unique_lock lk(_mu);
_done = true;
}
_cv.notify_one();
}
// Blocks until `notifyDone` is called.
// Throws if an ASSERT exception was reported by any exec invocation.
void wait() {
stdx::unique_lock lk(_mu);
do {
_cv.wait(lk, [&] { return _done || _ex; });
if (_ex)
std::rethrow_exception(std::exchange(_ex, nullptr));
} while (!_done);
}
private:
stdx::mutex _mu; // NOLINT
stdx::condition_variable _cv;
std::exception_ptr _ex;
bool _done = false;
};
/**
* Covers probably most cases of multithreaded tests.
* The body of a test can be passed in as an `f` that
* accepts a `unittest::ThreadAssertionMonitor&`.
* `f(monitor)` will to become the body of a "controller" thread.
*
* Any `stdx::thread(...)` constructors in the test must then be
* converted to `monitor.spawn(...)` calls. Then the ASSERT
* calls in the test will be managed by the monitor and propagate
* to be rethrown from the main thread, cleanly failing the unit test.
*
* The controller thread is joined inside this function,
* but user code is still responsible for joining the spawned
* worker threads as usual.
*/
template <typename F>
void threadAssertionMonitoredTest(F&& f) {
ThreadAssertionMonitor monitor;
monitor.spawnController([&, f] { std::invoke(f, monitor); }).join();
}
} // namespace mongo::unittest
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