test: add test for coins view flush behavior using Sync()

Thanks to Marco Falke for help with move semantics.

Author: jamesob

src/test/coins_tests.cpp

@@ -606,9 +606,9 @@ static size_t InsertCoinsMapEntry(CCoinsMap& map, CAmount value, char flags)
     return inserted.first->second.coin.DynamicMemoryUsage();
 }
 
-void GetCoinsMapEntry(const CCoinsMap& map, CAmount& value, char& flags)
+void GetCoinsMapEntry(const CCoinsMap& map, CAmount& value, char& flags, const COutPoint& outp = OUTPOINT)
 {
-    auto it = map.find(OUTPOINT);
+    auto it = map.find(outp);
     if (it == map.end()) {
         value = ABSENT;
         flags = NO_ENTRY;
@@ -894,4 +894,205 @@ BOOST_AUTO_TEST_CASE(ccoins_write)
                     CheckWriteCoins(parent_value, child_value, parent_value, parent_flags, child_flags, parent_flags);
 }
 
+
+Coin MakeCoin()
+{
+    Coin coin;
+    coin.out.nValue = InsecureRand32();
+    coin.nHeight = InsecureRandRange(4096);
+    coin.fCoinBase = 0;
+    return coin;
+}
+
+
+//! For CCoinsViewCache instances backed by either another cache instance or
+//! leveldb, test cache behavior and flag state (DIRTY/FRESH) by
+//!
+//! 1. Adding a random coin to the child-most cache,
+//! 2. Flushing all caches (without erasing),
+//! 3. Ensure the entry still exists in the cache and has been written to parent,
+//! 4. (if `do_erasing_flush`) Flushing the caches again (with erasing),
+//! 5. (if `do_erasing_flush`) Ensure the entry has been written to the parent and is no longer in the cache,
+//! 6. Spend the coin, ensure it no longer exists in the parent.
+//!
+void TestFlushBehavior(
+    CCoinsViewCacheTest* view,
+    CCoinsViewDB& base,
+    std::vector<CCoinsViewCacheTest*>& all_caches,
+    bool do_erasing_flush)
+{
+    CAmount value;
+    char flags;
+    size_t cache_usage;
+
+    auto flush_all = [&all_caches](bool erase) {
+        // Flush in reverse order to ensure that flushes happen from children up.
+        for (auto i = all_caches.rbegin(); i != all_caches.rend(); ++i) {
+            auto cache = *i;
+            // hashBlock must be filled before flushing to disk; value is
+            // unimportant here. This is normally done during connect/disconnect block.
+            cache->SetBestBlock(InsecureRand256());
+            erase ? cache->Flush() : cache->Sync();
+        }
+    };
+
+    uint256 txid = InsecureRand256();
+    COutPoint outp = COutPoint(txid, 0);
+    Coin coin = MakeCoin();
+    // Ensure the coins views haven't seen this coin before.
+    BOOST_CHECK(!base.HaveCoin(outp));
+    BOOST_CHECK(!view->HaveCoin(outp));
+
+    // --- 1. Adding a random coin to the child cache
+    //
+    view->AddCoin(outp, Coin(coin), false);
+
+    cache_usage = view->DynamicMemoryUsage();
+    // `base` shouldn't have coin (no flush yet) but `view` should have cached it.
+    BOOST_CHECK(!base.HaveCoin(outp));
+    BOOST_CHECK(view->HaveCoin(outp));
+
+    GetCoinsMapEntry(view->map(), value, flags, outp);
+    BOOST_CHECK_EQUAL(value, coin.out.nValue);
+    BOOST_CHECK_EQUAL(flags, DIRTY|FRESH);
+
+    // --- 2. Flushing all caches (without erasing)
+    //
+    flush_all(/*erase=*/ false);
+
+    // CoinsMap usage should be unchanged since we didn't erase anything.
+    BOOST_CHECK_EQUAL(cache_usage, view->DynamicMemoryUsage());
+
+    // --- 3. Ensuring the entry still exists in the cache and has been written to parent
+    //
+    GetCoinsMapEntry(view->map(), value, flags, outp);
+    BOOST_CHECK_EQUAL(value, coin.out.nValue);
+    BOOST_CHECK_EQUAL(flags, 0);  // Flags should have been wiped.
+
+    // Both views should now have the coin.
+    BOOST_CHECK(base.HaveCoin(outp));
+    BOOST_CHECK(view->HaveCoin(outp));
+
+    if (do_erasing_flush) {
+        // --- 4. Flushing the caches again (with erasing)
+        //
+        flush_all(/*erase=*/ true);
+
+        // Memory usage should have gone down.
+        BOOST_CHECK(view->DynamicMemoryUsage() < cache_usage);
+
+        // --- 5. Ensuring the entry is no longer in the cache
+        //
+        GetCoinsMapEntry(view->map(), value, flags, outp);
+        BOOST_CHECK_EQUAL(value, ABSENT);
+        BOOST_CHECK_EQUAL(flags, NO_ENTRY);
+
+        view->AccessCoin(outp);
+        GetCoinsMapEntry(view->map(), value, flags, outp);
+        BOOST_CHECK_EQUAL(value, coin.out.nValue);
+        BOOST_CHECK_EQUAL(flags, 0);
+    }
+
+    // Can't overwrite an entry without specifying that an overwrite is
+    // expected.
+    BOOST_CHECK_THROW(
+        view->AddCoin(outp, Coin(coin), /*possible_overwrite=*/ false),
+        std::logic_error);
+
+    // --- 6. Spend the coin.
+    //
+    BOOST_CHECK(view->SpendCoin(outp));
+
+    // The coin should be in the cache, but spent and marked dirty.
+    GetCoinsMapEntry(view->map(), value, flags, outp);
+    BOOST_CHECK_EQUAL(value, SPENT);
+    BOOST_CHECK_EQUAL(flags, DIRTY);
+    BOOST_CHECK(!view->HaveCoin(outp)); // Coin should be considered spent in `view`.
+    BOOST_CHECK(base.HaveCoin(outp));  // But coin should still be unspent in `base`.
+
+    flush_all(/*erase=*/ false);
+
+    // Coin should be considered spent in both views.
+    BOOST_CHECK(!view->HaveCoin(outp));
+    BOOST_CHECK(!base.HaveCoin(outp));
+
+    // Spent coin should not be spendable.
+    BOOST_CHECK(!view->SpendCoin(outp));
+
+    // --- Bonus check: ensure that a coin added to the base view via one cache
+    //     can be spent by another cache which has never seen it.
+    //
+    txid = InsecureRand256();
+    outp = COutPoint(txid, 0);
+    coin = MakeCoin();
+    BOOST_CHECK(!base.HaveCoin(outp));
+    BOOST_CHECK(!all_caches[0]->HaveCoin(outp));
+    BOOST_CHECK(!all_caches[1]->HaveCoin(outp));
+
+    all_caches[0]->AddCoin(outp, std::move(coin), false);
+    all_caches[0]->Sync();
+    BOOST_CHECK(base.HaveCoin(outp));
+    BOOST_CHECK(all_caches[0]->HaveCoin(outp));
+    BOOST_CHECK(!all_caches[1]->HaveCoinInCache(outp));
+
+    BOOST_CHECK(all_caches[1]->SpendCoin(outp));
+    flush_all(/*erase=*/ false);
+    BOOST_CHECK(!base.HaveCoin(outp));
+    BOOST_CHECK(!all_caches[0]->HaveCoin(outp));
+    BOOST_CHECK(!all_caches[1]->HaveCoin(outp));
+
+    flush_all(/*erase=*/ true); // Erase all cache content.
+
+    // --- Bonus check 2: ensure that a FRESH, spent coin is deleted by Sync()
+    //
+    txid = InsecureRand256();
+    outp = COutPoint(txid, 0);
+    coin = MakeCoin();
+    CAmount coin_val = coin.out.nValue;
+    BOOST_CHECK(!base.HaveCoin(outp));
+    BOOST_CHECK(!all_caches[0]->HaveCoin(outp));
+    BOOST_CHECK(!all_caches[1]->HaveCoin(outp));
+
+    // Add and spend from same cache without flushing.
+    all_caches[0]->AddCoin(outp, std::move(coin), false);
+
+    // Coin should be FRESH in the cache.
+    GetCoinsMapEntry(all_caches[0]->map(), value, flags, outp);
+    BOOST_CHECK_EQUAL(value, coin_val);
+    BOOST_CHECK_EQUAL(flags, DIRTY|FRESH);
+
+    // Base shouldn't have seen coin.
+    BOOST_CHECK(!base.HaveCoin(outp));
+
+    BOOST_CHECK(all_caches[0]->SpendCoin(outp));
+    all_caches[0]->Sync();
+
+    // Ensure there is no sign of the coin after spend/flush.
+    GetCoinsMapEntry(all_caches[0]->map(), value, flags, outp);
+    BOOST_CHECK_EQUAL(value, ABSENT);
+    BOOST_CHECK_EQUAL(flags, NO_ENTRY);
+    BOOST_CHECK(!all_caches[0]->HaveCoinInCache(outp));
+    BOOST_CHECK(!base.HaveCoin(outp));
+}
+
+BOOST_AUTO_TEST_CASE(ccoins_flush_behavior)
+{
+    // Create two in-memory caches atop a leveldb view.
+    CCoinsViewDB base{"test", /*nCacheSize=*/ 1 << 23, /*fMemory=*/ true, /*fWipe=*/ false};
+    std::vector<CCoinsViewCacheTest*> caches;
+    caches.push_back(new CCoinsViewCacheTest(&base));
+    caches.push_back(new CCoinsViewCacheTest(caches.back()));
+
+    for (CCoinsViewCacheTest* view : caches) {
+        TestFlushBehavior(view, base, caches, /*do_erasing_flush=*/ false);
+        TestFlushBehavior(view, base, caches, /*do_erasing_flush=*/ true);
+    }
+
+    // Clean up the caches.
+    while (caches.size() > 0) {
+        delete caches.back();
+        caches.pop_back();
+    }
+}
+
 BOOST_AUTO_TEST_SUITE_END()