From 41479ed1d23ea752d0ce14c2cf5627f43bceb722 Mon Sep 17 00:00:00 2001
From: Andrew Toth <andrewstoth@gmail.com>
Date: Sun, 4 May 2025 13:34:29 -0400
Subject: [PATCH] test: add test for periodic flush inside ActivateBestChain

---
 src/test/chainstate_write_tests.cpp | 61 ++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 2 deletions(-)

diff --git a/src/test/chainstate_write_tests.cpp b/src/test/chainstate_write_tests.cpp
index ccca2f9be10..e1b82ebc121 100644
--- a/src/test/chainstate_write_tests.cpp
+++ b/src/test/chainstate_write_tests.cpp
@@ -8,6 +8,10 @@
 
 #include <boost/test/unit_test.hpp>
 
+// Taken from validation.cpp
+static constexpr auto DATABASE_WRITE_INTERVAL_MIN{50min};
+static constexpr auto DATABASE_WRITE_INTERVAL_MAX{70min};
+
 BOOST_AUTO_TEST_SUITE(chainstate_write_tests)
 
 BOOST_FIXTURE_TEST_CASE(chainstate_write_interval, TestingSetup)
@@ -31,15 +35,68 @@ BOOST_FIXTURE_TEST_CASE(chainstate_write_interval, TestingSetup)
     BOOST_CHECK(!sub->m_did_flush);
 
     // The periodic flush interval is between 50 and 70 minutes (inclusive)
-    SetMockTime(GetTime<std::chrono::minutes>() + 49min);
+    SetMockTime(GetTime<std::chrono::minutes>() + DATABASE_WRITE_INTERVAL_MIN - 1min);
     chainstate.FlushStateToDisk(state_dummy, FlushStateMode::PERIODIC);
     m_node.validation_signals->SyncWithValidationInterfaceQueue();
     BOOST_CHECK(!sub->m_did_flush);
 
-    SetMockTime(GetTime<std::chrono::minutes>() + 70min);
+    SetMockTime(GetTime<std::chrono::minutes>() + DATABASE_WRITE_INTERVAL_MAX);
     chainstate.FlushStateToDisk(state_dummy, FlushStateMode::PERIODIC);
     m_node.validation_signals->SyncWithValidationInterfaceQueue();
     BOOST_CHECK(sub->m_did_flush);
 }
 
+// Test that we do PERIODIC flushes inside ActivateBestChain.
+// This is necessary for reindex-chainstate to be able to periodically flush
+// before reaching chain tip.
+BOOST_FIXTURE_TEST_CASE(write_during_multiblock_activation, TestChain100Setup)
+{
+    struct TestSubscriber final : CValidationInterface
+    {
+        const CBlockIndex* m_tip{nullptr};
+        const CBlockIndex* m_flushed_at_block{nullptr};
+        void ChainStateFlushed(ChainstateRole, const CBlockLocator&) override
+        {
+            m_flushed_at_block = m_tip;
+        }
+        void UpdatedBlockTip(const CBlockIndex* block_index, const CBlockIndex*, bool) override {
+            m_tip = block_index;
+        }
+    };
+
+    auto& chainstate{Assert(m_node.chainman)->ActiveChainstate()};
+    BlockValidationState state_dummy{};
+
+    // Pop two blocks from the tip
+    const CBlockIndex* tip{chainstate.m_chain.Tip()};
+    CBlockIndex* second_from_tip{tip->pprev};
+
+    {
+        LOCK2(m_node.chainman->GetMutex(), chainstate.MempoolMutex());
+        chainstate.DisconnectTip(state_dummy, nullptr);
+        chainstate.DisconnectTip(state_dummy, nullptr);
+    }
+
+    BOOST_CHECK_EQUAL(second_from_tip->pprev, chainstate.m_chain.Tip());
+
+    // Set m_next_write to current time
+    chainstate.FlushStateToDisk(state_dummy, FlushStateMode::ALWAYS);
+    m_node.validation_signals->SyncWithValidationInterfaceQueue();
+    // The periodic flush interval is between 50 and 70 minutes (inclusive)
+    // The next call to a PERIODIC write will flush
+    SetMockTime(GetMockTime() + DATABASE_WRITE_INTERVAL_MAX);
+
+    const auto sub{std::make_shared<TestSubscriber>()};
+    m_node.validation_signals->RegisterSharedValidationInterface(sub);
+
+    // ActivateBestChain back to tip
+    chainstate.ActivateBestChain(state_dummy, nullptr);
+    BOOST_CHECK_EQUAL(tip, chainstate.m_chain.Tip());
+    // Check that we flushed inside ActivateBestChain while we were at the
+    // second block from tip, since FlushStateToDisk is called with PERIODIC
+    // inside the outer loop.
+    m_node.validation_signals->SyncWithValidationInterfaceQueue();
+    BOOST_CHECK_EQUAL(sub->m_flushed_at_block, second_from_tip);
+}
+
 BOOST_AUTO_TEST_SUITE_END()