SERVER-33197 Implement joining behavior for movePrimary on shards

1 files changed, 124 insertions, 0 deletions

diff --git a/src/mongo/db/s/active_move_primaries_registry.cpp b/src/mongo/db/s/active_move_primaries_registry.cpp
new file mode 100644
index 00000000000..eaf2a01a74e
--- /dev/null
+++ b/src/mongo/db/s/active_move_primaries_registry.cpp
@@ -0,0 +1,124 @@
+/**
+ *    Copyright (C) 2018 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    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
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    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 GNU Affero General 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.
+ */
+
+#include "mongo/db/s/active_move_primaries_registry.h"
+
+#include "mongo/util/assert_util.h"
+
+namespace mongo {
+
+ActiveMovePrimariesRegistry::ActiveMovePrimariesRegistry() = default;
+
+ActiveMovePrimariesRegistry::~ActiveMovePrimariesRegistry() {
+    invariant(!_activeMovePrimaryState);
+}
+
+StatusWith<ScopedMovePrimary> ActiveMovePrimariesRegistry::registerMovePrimary(
+    const ShardMovePrimary& requestArgs) {
+    stdx::lock_guard<stdx::mutex> lk(_mutex);
+    if (_activeMovePrimaryState) {
+        if (_activeMovePrimaryState->requestArgs == requestArgs) {
+            return {ScopedMovePrimary(nullptr, false, _activeMovePrimaryState->notification)};
+        }
+
+        return _activeMovePrimaryState->constructErrorStatus();
+    }
+
+    _activeMovePrimaryState.emplace(requestArgs);
+
+    return {ScopedMovePrimary(this, true, _activeMovePrimaryState->notification)};
+}
+
+boost::optional<NamespaceString> ActiveMovePrimariesRegistry::getActiveMovePrimaryNss() {
+    stdx::lock_guard<stdx::mutex> lk(_mutex);
+    if (_activeMovePrimaryState) {
+        return _activeMovePrimaryState->requestArgs.get_movePrimary();
+    }
+
+    return boost::none;
+}
+
+void ActiveMovePrimariesRegistry::_clearMovePrimary() {
+    stdx::lock_guard<stdx::mutex> lk(_mutex);
+    invariant(_activeMovePrimaryState);
+    _activeMovePrimaryState.reset();
+}
+
+Status ActiveMovePrimariesRegistry::ActiveMovePrimaryState::constructErrorStatus() const {
+    return {ErrorCodes::ConflictingOperationInProgress,
+            str::stream()
+                << "Unable to start new movePrimary operation because this shard is currently "
+                   "moving its primary for namespace "
+                << requestArgs.get_movePrimary().ns()
+                << " to "
+                << requestArgs.getTo()};
+}
+
+ScopedMovePrimary::ScopedMovePrimary(ActiveMovePrimariesRegistry* registry,
+                                     bool shouldExecute,
+                                     std::shared_ptr<Notification<Status>> completionNotification)
+    : _registry(registry),
+      _shouldExecute(shouldExecute),
+      _completionNotification(std::move(completionNotification)) {}
+
+ScopedMovePrimary::~ScopedMovePrimary() {
+    if (_registry) {
+        // If this is a movePrimary that didn't join an existing movePrimary, the caller must
+        // signal on completion.
+        invariant(_shouldExecute);
+        invariant(*_completionNotification);
+        _registry->_clearMovePrimary();
+    }
+}
+
+ScopedMovePrimary::ScopedMovePrimary(ScopedMovePrimary&& other) {
+    *this = std::move(other);
+}
+
+ScopedMovePrimary& ScopedMovePrimary::operator=(ScopedMovePrimary&& other) {
+    if (&other != this) {
+        _registry = other._registry;
+        other._registry = nullptr;
+        _shouldExecute = other._shouldExecute;
+        _completionNotification = std::move(other._completionNotification);
+    }
+
+    return *this;
+}
+
+void ScopedMovePrimary::signalComplete(Status status) {
+    invariant(_shouldExecute);
+    _completionNotification->set(status);
+}
+
+Status ScopedMovePrimary::waitForCompletion(OperationContext* opCtx) {
+    invariant(!_shouldExecute);
+    return _completionNotification->get(opCtx);
+}
+
+}  // namespace mongo