From 7aa2cf8d9f28e7d45674c1917079e4be40268de1 Mon Sep 17 00:00:00 2001
From: Ben Caimano <ben.caimano@10gen.com>
Date: Wed, 23 Sep 2020 04:03:43 +0000
Subject: SERVER-51278 Introduced ClientStrand

---
 src/mongo/db/client_strand.cpp | 95 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 src/mongo/db/client_strand.cpp

(limited to 'src/mongo/db/client_strand.cpp')

diff --git a/src/mongo/db/client_strand.cpp b/src/mongo/db/client_strand.cpp
new file mode 100644
index 00000000000..1455485ebf9
--- /dev/null
+++ b/src/mongo/db/client_strand.cpp
@@ -0,0 +1,95 @@
+/**
+ *    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.
+ */
+
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kDefault
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/db/client_strand.h"
+
+#include "mongo/logv2/log.h"
+#include "mongo/util/concurrency/thread_name.h"
+
+namespace mongo {
+namespace {
+struct ClientStrandData {
+    ClientStrand* strand = nullptr;
+};
+
+auto getClientStrandData = Client::declareDecoration<ClientStrandData>();
+}  // namespace
+
+boost::intrusive_ptr<ClientStrand> ClientStrand::make(ServiceContext::UniqueClient client) {
+    auto strand = make_intrusive<ClientStrand>(std::move(client));
+    getClientStrandData(strand->getClientPointer()).strand = strand.get();
+    return strand;
+}
+
+boost::intrusive_ptr<ClientStrand> ClientStrand::get(Client* client) {
+    return getClientStrandData(client).strand;
+}
+
+void ClientStrand::_setCurrent() noexcept {
+    invariant(_isBound.load());
+    invariant(_client);
+
+    LOGV2_DEBUG(
+        5127801, kDiagnosticLogLevel, "Setting the Client", "client"_attr = _client->desc());
+
+    // Set the Client for this thread so calls to Client::getCurrent() works as expected.
+    Client::setCurrent(std::move(_client));
+
+    // Set up the thread name.
+    auto oldThreadName = getThreadName();
+    StringData threadName = _clientPtr->desc();
+    if (oldThreadName != threadName) {
+        _oldThreadName = oldThreadName.toString();
+        setThreadName(threadName);
+        LOGV2_DEBUG(5127802, kDiagnosticLogLevel, "Set thread name", "name"_attr = threadName);
+    }
+}
+
+void ClientStrand::_releaseCurrent() noexcept {
+    invariant(_isBound.load());
+    invariant(!_client);
+
+    // Reclaim the client.
+    _client = Client::releaseCurrent();
+    invariant(_client.get() == _clientPtr, kUnableToRecoverClient);
+
+    if (!_oldThreadName.empty()) {
+        // Reset the old thread name.
+        setThreadName(_oldThreadName);
+    }
+
+    LOGV2_DEBUG(
+        5127803, kDiagnosticLogLevel, "Released the Client", "client"_attr = _client->desc());
+}
+
+}  // namespace mongo
-- 
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