5 files changed, 36 insertions, 3 deletions

diff --git a/src/mongo/s/SConscript b/src/mongo/s/SConscript
index 3566cbbf4b3..d0940c4fd8e 100644
--- a/src/mongo/s/SConscript
+++ b/src/mongo/s/SConscript
@@ -74,6 +74,7 @@ env.Library(
     ],
     LIBDEPS_PRIVATE=[
         '$BUILD_DIR/mongo/db/session_catalog',
+        '$BUILD_DIR/mongo/db/sessions_collection',
     ],
 )
 
diff --git a/src/mongo/s/session_catalog_router.cpp b/src/mongo/s/session_catalog_router.cpp
index 3139b97637a..aa4f770bec7 100644
--- a/src/mongo/s/session_catalog_router.cpp
+++ b/src/mongo/s/session_catalog_router.cpp
@@ -33,12 +33,38 @@
 
 #include "mongo/s/session_catalog_router.h"
 
+#include "mongo/db/sessions_collection.h"
+
 namespace mongo {
 
 int RouterSessionCatalog::reapSessionsOlderThan(OperationContext* opCtx,
                                                 SessionsCollection& sessionsCollection,
                                                 Date_t possiblyExpired) {
-    return 0;
+    const auto catalog = SessionCatalog::get(opCtx);
+
+    // Capture the possbily expired in-memory session ids
+    LogicalSessionIdSet lsids;
+    catalog->scanSessions(
+        SessionKiller::Matcher(KillAllSessionsByPatternSet{makeKillAllSessionsByPattern(opCtx)}),
+        [&](const ObservableSession& session) {
+            if (session.getLastCheckout() < possiblyExpired) {
+                lsids.insert(session.getSessionId());
+            }
+        });
+
+    // From the passed-in sessions, find the ones which are actually expired/removed
+    auto expiredSessionIds = uassertStatusOK(sessionsCollection.findRemovedSessions(opCtx, lsids));
+
+    // Remove the session ids from the in-memory catalog
+    int numReaped = 0;
+    for (const auto& lsid : expiredSessionIds) {
+        catalog->scanSession(lsid, [&](ObservableSession& session) {
+            session.markForReap();
+            ++numReaped;
+        });
+    }
+
+    return numReaped;
 }
 
 RouterOperationContextSession::RouterOperationContextSession(OperationContext* opCtx)
diff --git a/src/mongo/s/session_catalog_router.h b/src/mongo/s/session_catalog_router.h
index da503404391..057f9632593 100644
--- a/src/mongo/s/session_catalog_router.h
+++ b/src/mongo/s/session_catalog_router.h
@@ -40,6 +40,8 @@ public:
     /**
      * Locates session entries from the in-memory catalog  which have not been referenced before
      * 'possiblyExpired' and deletes them.
+     *
+     * Returns the number of sessions, which were reaped from the in-memory catalog.
      */
     static int reapSessionsOlderThan(OperationContext* opCtx,
                                      SessionsCollection& sessionsCollection,
diff --git a/src/mongo/s/transaction_router.cpp b/src/mongo/s/transaction_router.cpp
index 3fe1193f1fb..4c62186fc6a 100644
--- a/src/mongo/s/transaction_router.cpp
+++ b/src/mongo/s/transaction_router.cpp
@@ -43,8 +43,6 @@
 #include "mongo/db/logical_session_id.h"
 #include "mongo/db/logical_session_id.h"
 #include "mongo/db/repl/read_concern_args.h"
-#include "mongo/db/server_options.h"
-#include "mongo/db/session_catalog.h"
 #include "mongo/executor/task_executor_pool.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/s/async_requests_sender.h"
@@ -383,6 +381,10 @@ TransactionRouter* TransactionRouter::get(OperationContext* opCtx) {
     return nullptr;
 }
 
+TransactionRouter* get(const ObservableSession& osession) {
+    return &getTransactionRouter(osession.get());
+}
+
 TransactionRouter::TransactionRouter() = default;
 
 TransactionRouter::~TransactionRouter() = default;
diff --git a/src/mongo/s/transaction_router.h b/src/mongo/s/transaction_router.h
index 4d38a52562d..ea69181a842 100644
--- a/src/mongo/s/transaction_router.h
+++ b/src/mongo/s/transaction_router.h
@@ -35,6 +35,7 @@
 #include "mongo/db/logical_session_id.h"
 #include "mongo/db/operation_context.h"
 #include "mongo/db/repl/read_concern_args.h"
+#include "mongo/db/session_catalog.h"
 #include "mongo/s/async_requests_sender.h"
 #include "mongo/s/client/shard.h"
 #include "mongo/s/shard_id.h"
@@ -174,6 +175,7 @@ public:
      * attached.
      */
     static TransactionRouter* get(OperationContext* opCtx);
+    static TransactionRouter* get(const ObservableSession& osession);
 
     /**
      * Starts a fresh transaction in this session or continue an existing one. Also cleans up the