1 files changed, 111 insertions, 0 deletions
diff --git a/src/mongo/db/internal_transactions_reap_service.h b/src/mongo/db/internal_transactions_reap_service.h
new file mode 100644
index 00000000000..75fd5aba30b
--- /dev/null
+++ b/src/mongo/db/internal_transactions_reap_service.h
@@ -0,0 +1,111 @@
+/**
+ *    Copyright (C) 2022-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 "mongo/db/operation_context.h"
+#include "mongo/db/repl/replica_set_aware_service.h"
+#include "mongo/util/concurrency/thread_pool.h"
+
+namespace mongo {
+
+/**
+ * Service responsible for removing completed internal transactions persisted metadata when they can
+ * no longer be used. Only enabled on replica set primary nodes.
+ */
+class InternalTransactionsReapService
+    : public ReplicaSetAwareService<InternalTransactionsReapService> {
+public:
+    InternalTransactionsReapService();
+
+    static InternalTransactionsReapService* get(ServiceContext* serviceContext);
+    static InternalTransactionsReapService* get(OperationContext* opCtx);
+
+    /**
+     * Adds the eagerly reaped sessions to the reap service to be buffered and later reaped. Does
+     * not verify they have actually expired, so callers must guarantee they are safe to remove.
+     */
+    static void onEagerlyReapedSessions(ServiceContext* service,
+                                        std::vector<LogicalSessionId> lsidsToRemove);
+
+    /**
+     * Buffers the sessions to be reaped when the max batch size has been reached, upon which a task
+     * is scheduled to reap the transactions.
+     */
+    void addEagerlyReapedSessions(ServiceContext* service,
+                                  std::vector<LogicalSessionId> lsidsToRemove);
+
+    /**
+     * Used in tests to wait for a kicked off drain to complete.
+     */
+    void waitForCurrentDrain_forTest();
+
+    /**
+     * Used in tests to detect when the drain task is running.
+     */
+    bool hasCurrentDrain_forTest();
+
+private:
+    /**
+     * Will remove all currently buffered sessions ids from config.transactions and
+     * config.image_collection.
+     */
+    void _reapInternalTransactions(ServiceContext* service);
+
+    void onStartup(OperationContext* opCtx) override final;
+    void onShutdown() override final;
+
+    void onStepUpComplete(OperationContext* opCtx, long long term) override final {
+        stdx::lock_guard lg(_mutex);
+        _enabled = true;
+    }
+
+    void onStepDown() override final {
+        stdx::lock_guard lg(_mutex);
+        _enabled = false;
+        _lsidsToEagerlyReap.clear();
+    }
+
+    void onInitialDataAvailable(OperationContext* opCtx,
+                                bool isMajorityDataAvailable) override final {}
+    void onStepUpBegin(OperationContext* opCtx, long long term) override final {}
+    void onBecomeArbiter() override final {}
+
+    std::shared_ptr<ThreadPool> _threadPool;
+
+    // Protects the state below.
+    mutable Mutex _mutex = MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(1),
+                                            "InternalTransactionsReapService::_mutex");
+
+    bool _enabled{false};
+    boost::optional<ExecutorFuture<void>> _drainedSessionsFuture;
+    std::vector<LogicalSessionId> _lsidsToEagerlyReap;
+};
+
+}  // namespace mongo