SERVER-54064: Periodically clear out the logical session cache on arbiters.

(cherry picked from commit 8b64da4e43b7318a7ab8a7580708195b6de91200)

3 files changed, 67 insertions, 14 deletions

diff --git a/jstests/noPassthrough/server54064.js b/jstests/noPassthrough/server54064.js
new file mode 100644
index 00000000000..e4bbad6e7fd
--- /dev/null
+++ b/jstests/noPassthrough/server54064.js
@@ -0,0 +1,57 @@
+/**
+ * Assert that arbiters periodically clear out their logical session cache. Inability to do so
+ * prohibits new clients from connecting.
+ *
+ * @tags: [requires_replication]
+ */
+(function() {
+const name = "server54064";
+const replSet = new ReplSetTest({
+    name: name,
+    nodes: 2,
+    // `disableLogicalSessionCacheRefresh` is true by default, but is disabled for testing purposes
+    // in servers spawned from the shell.
+    nodeOptions: {
+        setParameter: {
+            // Each refresh on an arbiter will empty the cache.
+            logicalSessionRefreshMillis: 10000,
+            // The number of connections/sessions before the cache is full, prohibiting new clients
+            // from connecting.
+            maxSessions: 3,
+            disableLogicalSessionCacheRefresh: false
+        }
+    }
+});
+const nodes = replSet.nodeList();
+
+replSet.startSet();
+replSet.initiate({
+    _id: name,
+    members: [{_id: 0, host: nodes[0]}, {_id: 1, host: nodes[1], arbiterOnly: true}],
+});
+
+let arbConn = replSet.getArbiter();
+assert.soon(() => {
+    // Connect to mongo in a tight loop to exhaust the number of available logical sessions in the
+    // cache.
+    const result = new Mongo(arbConn.host).adminCommand({hello: 1});
+    if (result['ok'] === 0) {
+        assert.commandFailedWithCode(result, ErrorCodes.TooManyLogicalSessions);
+        return true;
+    }
+    return false;
+});
+
+assert.soon(() => {
+    // Once we observe that the number of sessions is maxed out, loop again to confirm that the
+    // cache eventually does get cleared.
+    const result = new Mongo(arbConn.host).adminCommand({hello: 1});
+    if (result['ok'] === 0) {
+        assert.commandFailedWithCode(result, ErrorCodes.TooManyLogicalSessions);
+        return false;
+    }
+    return true;
+});
+
+replSet.stopSet();
+})();
diff --git a/src/mongo/db/logical_session_cache_impl.cpp b/src/mongo/db/logical_session_cache_impl.cpp
index 857e33b1568..349da7906f9 100644
--- a/src/mongo/db/logical_session_cache_impl.cpp
+++ b/src/mongo/db/logical_session_cache_impl.cpp
@@ -182,19 +182,11 @@ Status LogicalSessionCacheImpl::_reap(Client* client) {
         try {
             _sessionsColl->checkSessionsCollectionExists(opCtx);
         } catch (const DBException& ex) {
-            if (ex.code() != ErrorCodes::NamespaceNotFound ||
-                ex.code() != ErrorCodes::NamespaceNotSharded) {
-                LOGV2(
-                    20712,
-                    "Sessions collection is not set up: {error}; waiting until next sessions reap "
-                    "interval",
-                    "Sessions collection is not set up; waiting until next sessions reap interval",
-                    "error"_attr = redact(ex));
-            } else {
-                LOGV2(20713,
-                      "Sessions collection is not set up because the namespace is either not found"
-                      "or not sharded; waiting until next sessions reap interval");
-            }
+            LOGV2(20712,
+                  "Sessions collection is not set up: {error}; waiting until next sessions reap "
+                  "interval",
+                  "Sessions collection is not set up; waiting until next sessions reap interval",
+                  "error"_attr = redact(ex));
             return Status::OK();
         }
         numReaped = _reapSessionsOlderThanFn(opCtx,
@@ -235,6 +227,8 @@ void LogicalSessionCacheImpl::_refresh(Client* client) {
 
     const auto replCoord = repl::ReplicationCoordinator::get(opCtx);
     if (replCoord && replCoord->isReplEnabled() && replCoord->getMemberState().arbiter()) {
+        stdx::lock_guard<Latch> lk(_mutex);
+        _activeSessions.clear();
         return;
     }
 
diff --git a/src/mongo/shell/servers.js b/src/mongo/shell/servers.js
index b5ee35bab4d..a60fcf8fe2a 100644
--- a/src/mongo/shell/servers.js
+++ b/src/mongo/shell/servers.js
@@ -1137,7 +1137,9 @@ function appendSetParameterArgs(argArray) {
             }
 
             // Disable background cache refreshing to avoid races in tests
-            argArray.push(...['--setParameter', "disableLogicalSessionCacheRefresh=true"]);
+            if (!argArrayContainsSetParameterValue('disableLogicalSessionCacheRefresh=')) {
+                argArray.push(...['--setParameter', "disableLogicalSessionCacheRefresh=true"]);
+            }
         }
 
         // Since options may not be backward compatible, mongos options are not