SERVER-39146 Refactor Baton

Refactor the baton into regular and networking batons while also
cleaning up the basic baton implementation.

1 files changed, 154 insertions, 0 deletions

diff --git a/src/mongo/db/default_baton.cpp b/src/mongo/db/default_baton.cpp
new file mode 100644
index 00000000000..9855957135a
--- /dev/null
+++ b/src/mongo/db/default_baton.cpp
@@ -0,0 +1,154 @@
+
+/**
+ *    Copyright (C) 2019-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.
+ */
+
+#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kDefault
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/db/default_baton.h"
+
+#include "mongo/db/operation_context.h"
+#include "mongo/util/scopeguard.h"
+
+namespace mongo {
+
+DefaultBaton::DefaultBaton(OperationContext* opCtx) : _opCtx(opCtx) {}
+
+DefaultBaton::~DefaultBaton() {
+    invariant(!_opCtx);
+    invariant(_scheduled.empty());
+}
+
+void DefaultBaton::markKillOnClientDisconnect() noexcept {
+    if (_opCtx->getClient() && _opCtx->getClient()->session()) {
+        _hasIngressSocket = true;
+    }
+}
+
+void DefaultBaton::detachImpl() noexcept {
+    decltype(_scheduled) scheduled;
+
+    {
+        stdx::lock_guard<stdx::mutex> lk(_mutex);
+
+        {
+            stdx::lock_guard<Client> lk(*_opCtx->getClient());
+            invariant(_opCtx->getBaton().get() == this);
+            _opCtx->setBaton(nullptr);
+        }
+
+        _opCtx = nullptr;
+        _hasIngressSocket = false;
+
+        using std::swap;
+        swap(_scheduled, scheduled);
+    }
+
+    for (auto& job : scheduled) {
+        job(nullptr);
+    }
+}
+
+void DefaultBaton::schedule(unique_function<void(OperationContext*)> func) noexcept {
+    stdx::unique_lock<stdx::mutex> lk(_mutex);
+
+    if (!_opCtx) {
+        lk.unlock();
+        func(nullptr);
+
+        return;
+    }
+
+    _scheduled.push_back(std::move(func));
+
+    if (_sleeping && !_notified) {
+        _notified = true;
+        _cv.notify_one();
+    }
+}
+
+void DefaultBaton::notify() noexcept {
+    stdx::lock_guard<stdx::mutex> lk(_mutex);
+    _notified = true;
+    _cv.notify_one();
+}
+
+Waitable::TimeoutState DefaultBaton::run_until(ClockSource* clkSource,
+                                               Date_t oldDeadline) noexcept {
+    stdx::unique_lock<stdx::mutex> lk(_mutex);
+
+    // We'll fulfill promises and run jobs on the way out, ensuring we don't hold any locks
+    const auto guard = makeGuard([&] {
+        // While we have scheduled work, keep running jobs
+        while (_scheduled.size()) {
+            auto toRun = std::exchange(_scheduled, {});
+
+            lk.unlock();
+            for (auto& job : toRun) {
+                job(_opCtx);
+            }
+            lk.lock();
+        }
+    });
+
+    // If anything was scheduled, run it now.
+    if (_scheduled.size()) {
+        return Waitable::TimeoutState::NoTimeout;
+    }
+
+    auto newDeadline = oldDeadline;
+
+    // If we have an ingress socket, sleep no more than 1 second (so we poll for closure in the
+    // outside opCtx waitForConditionOrInterruptUntil implementation)
+    if (_hasIngressSocket) {
+        newDeadline = std::min(oldDeadline, clkSource->now() + Seconds(1));
+    }
+
+    // we mark sleeping, so that we receive notifications
+    _sleeping = true;
+
+    // while we're not notified
+    auto notified =
+        clkSource->waitForConditionUntil(_cv, lk, newDeadline, [&] { return _notified; });
+
+    _sleeping = false;
+    _notified = false;
+
+    // If we've been notified, or we haven't timed out yet, return as if by spurious wakeup.
+    // Otherwise call it a timeout.
+    return (notified || (clkSource->now() < oldDeadline)) ? Waitable::TimeoutState::NoTimeout
+                                                          : Waitable::TimeoutState::Timeout;
+}
+
+void DefaultBaton::run(ClockSource* clkSource) noexcept {
+    run_until(clkSource, Date_t::max());
+}
+
+}  // namespace mongo