fix: Keep FullBelowCache entries until the first validated ledger

.github/scripts/levelization/results/ordering.txt

@@ -71,6 +71,7 @@ test.app > xrpld.app
 test.app > xrpld.core
 test.app > xrpld.overlay
 test.app > xrpld.rpc
+test.app > xrpld.shamap
 test.app > xrpl.json
 test.app > xrpl.ledger
 test.app > xrpl.nodestore

src/test/app/NodeFamily_test.cpp

@@ -0,0 +1,54 @@
+#include <test/jtx/Env.h>
+
+#include <xrpld/app/ledger/LedgerMaster.h>
+#include <xrpld/app/main/Application.h>
+#include <xrpld/app/main/Tuning.h>
+#include <xrpld/shamap/NodeFamily.h>
+
+#include <xrpl/basics/base_uint.h>
+#include <xrpl/basics/chrono.h>
+#include <xrpl/beast/unit_test/suite.h>
+
+#include <chrono>
+
+namespace xrpl::test {
+
+class NodeFamily_test : public beast::unit_test::Suite
+{
+    void
+    testFullBelowKeptUntilValidated()
+    {
+        testcase("FullBelowCache kept until the first validated ledger");
+        using namespace std::chrono_literals;
+
+        jtx::Env env{*this};
+        TestStopwatch clock;
+        NodeFamily family(env.app(), env.app().getCollectorManager(), clock);
+        auto const fullBelow = family.getFullBelowCache();
+
+        fullBelow->insert(UInt256{1});
+        clock.advance(kFullBelowExpiration + 1s);
+        family.sweep(false);
+        BEAST_EXPECT(fullBelow->size() == 1);
+        family.sweep(true);
+        BEAST_EXPECT(fullBelow->size() == 0);
+
+        // A standalone Env has a validated ledger, so sweep() expires the entry.
+        BEAST_EXPECT(env.app().getLedgerMaster().haveValidated());
+        fullBelow->insert(UInt256{2});
+        clock.advance(kFullBelowExpiration + 1s);
+        family.sweep();
+        BEAST_EXPECT(fullBelow->size() == 0);
+    }
+
+public:
+    void
+    run() override
+    {
+        testFullBelowKeptUntilValidated();
+    }
+};
+
+BEAST_DEFINE_TESTSUITE(NodeFamily, app, xrpl);
+
+}  // namespace xrpl::test

src/xrpld/shamap/NodeFamily.cpp

@@ -21,14 +21,14 @@
 
 namespace xrpl {
 
-NodeFamily::NodeFamily(Application& app, CollectorManager& cm)
+NodeFamily::NodeFamily(Application& app, CollectorManager& cm, Stopwatch& clock)
     : app_(app)
     , db_(app.getNodeStore())
     , j_(app.getJournal("NodeFamily"))
     , fbCache_(
           std::make_shared<FullBelowCache>(
               "Node family full below cache",
-              stopwatch(),
+              clock,
               app.getJournal("NodeFamilyFulLBelowCache"),
               cm.collector(),
               kFullBelowTargetSize,
@@ -38,7 +38,7 @@ NodeFamily::NodeFamily(Application& app, CollectorManager& cm)
               "Node family tree node cache",
               app.config().getValueFor(SizedItem::TreeCacheSize),
               std::chrono::seconds(app.config().getValueFor(SizedItem::TreeCacheAge)),
-              stopwatch(),
+              clock,
               j_))
 {
 }
@@ -46,7 +46,17 @@ NodeFamily::NodeFamily(Application& app, CollectorManager& cm)
 void
 NodeFamily::sweep()
 {
-    fbCache_->sweep();
+    sweep(app_.getLedgerMaster().haveValidated());
+}
+
+void
+NodeFamily::sweep(bool haveValidated)
+{
+    // Keep FullBelowCache entries until a ledger is validated: a first sync grows the cache past
+    // kFullBelowTargetSize, and TaggedCache::sweep then expires entries far younger than
+    // kFullBelowExpiration.
+    if (haveValidated)
+        fbCache_->sweep();
     tnCache_->sweep();
 }
 

src/xrpld/shamap/NodeFamily.h

@@ -3,6 +3,7 @@
 #include <xrpld/app/main/CollectorManager.h>
 
 #include <xrpl/basics/base_uint.h>
+#include <xrpl/basics/chrono.h>
 #include <xrpl/beast/utility/Journal.h>
 #include <xrpl/nodestore/Database.h>
 #include <xrpl/protocol/Protocol.h>
@@ -31,7 +32,12 @@ public:
     NodeFamily&
     operator=(NodeFamily&&) = delete;
 
-    NodeFamily(Application& app, CollectorManager& cm);
+    /**
+     * @param app The application whose node store and ledger master the family uses.
+     * @param cm The collector for cache statistics.
+     * @param clock The clock the FullBelowCache and TreeNodeCache age their entries by.
+     */
+    NodeFamily(Application& app, CollectorManager& cm, Stopwatch& clock = stopwatch());
 
     node_store::Database&
     db() override
@@ -66,6 +72,16 @@ public:
     void
     sweep() override;
 
+    /**
+     * Sweep the TreeNodeCache, and the FullBelowCache only when haveValidated is true, so a
+     * first sync keeps the FullBelowCache entries it has built.
+     *
+     * @param haveValidated Whether the node has a validated ledger
+     *        (LedgerMaster::haveValidated()).
+     */
+    void
+    sweep(bool haveValidated);
+
     void
     reset() override;