Enable parallel BucketsDB loads

src/bucket/BucketManager.h

@@ -207,9 +207,11 @@ class BucketManager : NonMovableOrCopyable
     virtual void maybeSetIndex(std::shared_ptr<Bucket> b,
                                std::unique_ptr<BucketIndex const>&& index) = 0;
 
-    virtual std::unique_ptr<SearchableBucketListSnapshot const>
+    virtual std::unique_ptr<SearchableBucketListSnapshot>
     getSearchableBucketListSnapshot() const = 0;
 
+    virtual std::recursive_mutex& getBucketSnapshotMutex() const = 0;
+
     // Scans BucketList for non-live entries to evict starting at the entry
     // pointed to by EvictionIterator. Scans until `maxEntriesToEvict` entries
     // have been evicted or maxEvictionScanSize bytes have been scanned.

src/bucket/BucketManagerImpl.cpp

@@ -907,7 +907,7 @@ BucketManagerImpl::scanForEvictionLegacySQL(AbstractLedgerTxn& ltx,
     }
 }
 
-std::unique_ptr<SearchableBucketListSnapshot const>
+std::unique_ptr<SearchableBucketListSnapshot>
 BucketManagerImpl::getSearchableBucketListSnapshot() const
 {
     releaseAssertOrThrow(mApp.getConfig().isUsingBucketListDB() && mBucketList);
@@ -919,6 +919,12 @@ BucketManagerImpl::getSearchableBucketListSnapshot() const
         new SearchableBucketListSnapshot(mApp, *mBucketList));
 }
 
+std::recursive_mutex&
+BucketManagerImpl::getBucketSnapshotMutex() const
+{
+    return mBucketSnapshotMutex;
+}
+
 medida::Meter&
 BucketManagerImpl::getBloomMissMeter() const
 {

src/bucket/BucketManagerImpl.h

@@ -143,8 +143,9 @@ class BucketManagerImpl : public BucketManager
     void scanForEvictionLegacySQL(AbstractLedgerTxn& ltx,
                                   uint32_t ledgerSeq) override;
 
-    std::unique_ptr<SearchableBucketListSnapshot const>
+    std::unique_ptr<SearchableBucketListSnapshot>
     getSearchableBucketListSnapshot() const override;
+    std::recursive_mutex& getBucketSnapshotMutex() const override;
 
     medida::Meter& getBloomMissMeter() const override;
     medida::Meter& getBloomLookupMeter() const override;

src/bucket/SearchableBucketListSnapshot.cpp

@@ -61,6 +61,26 @@ SearchableBucketListSnapshot::isWithinAllowedLedgerDrift(
     return mLCL >= minimumLCL;
 }
 
+void
+SearchableBucketListSnapshot::maybeUpdateSnapshot()
+{
+    auto currLCL = mApp.getLedgerManager().getLastClosedLedgerNum();
+    if (currLCL != mLCL)
+    {
+        mLCL = currLCL;
+        mLevels.clear();
+
+        std::lock_guard<std::recursive_mutex> lock(
+            mApp.getBucketManager().getBucketSnapshotMutex());
+        auto& bl = mApp.getBucketManager().getBucketList();
+        for (uint32_t i = 0; i < BucketList::kNumLevels; ++i)
+        {
+            auto const& level = bl.getLevel(i);
+            mLevels.emplace_back(SearchableBucketLevelSnapshot(level));
+        }
+    }
+}
+
 void
 SearchableBucketListSnapshot::loopAllBuckets(
     std::function<bool(SearchableBucketSnapshot const&)> f) const
@@ -85,13 +105,11 @@ SearchableBucketListSnapshot::loopAllBuckets(
 }
 
 std::shared_ptr<LedgerEntry>
-SearchableBucketListSnapshot::getLedgerEntry(LedgerKey const& k) const
+SearchableBucketListSnapshot::getLedgerEntry(LedgerKey const& k)
 {
     ZoneScoped;
     auto timer = getPointLoadTimer(k.type()).TimeScope();
-
-    // Snapshots not currently supported, all access must be up to date
-    releaseAssert(isWithinAllowedLedgerDrift(0));
+    maybeUpdateSnapshot();
 
     std::shared_ptr<LedgerEntry> result{};
 
@@ -117,13 +135,11 @@ SearchableBucketListSnapshot::getLedgerEntry(LedgerKey const& k) const
 
 std::vector<LedgerEntry>
 SearchableBucketListSnapshot::loadKeys(
-    std::set<LedgerKey, LedgerEntryIdCmp> const& inKeys) const
+    std::set<LedgerKey, LedgerEntryIdCmp> const& inKeys)
 {
     ZoneScoped;
     auto timer = recordBulkLoadMetrics("prefetch", inKeys.size()).TimeScope();
-
-    // Snapshots not currently supported, all access must be up to date
-    releaseAssert(isWithinAllowedLedgerDrift(0));
+    maybeUpdateSnapshot();
 
     std::vector<LedgerEntry> entries;
 
@@ -140,13 +156,11 @@ SearchableBucketListSnapshot::loadKeys(
 
 std::vector<LedgerEntry>
 SearchableBucketListSnapshot::loadPoolShareTrustLinesByAccountAndAsset(
-    AccountID const& accountID, Asset const& asset) const
+    AccountID const& accountID, Asset const& asset)
 {
     ZoneScoped;
     auto timer = recordBulkLoadMetrics("poolshareTrustlines", 0).TimeScope();
-
-    // Snapshots not currently supported, all access must be up to date
-    releaseAssert(isWithinAllowedLedgerDrift(0));
+    maybeUpdateSnapshot();
 
     UnorderedMap<LedgerKey, LedgerEntry> liquidityPoolToTrustline;
     UnorderedSet<LedgerKey> deadTrustlines;
@@ -189,13 +203,11 @@ SearchableBucketListSnapshot::loadPoolShareTrustLinesByAccountAndAsset(
 
 std::vector<InflationWinner>
 SearchableBucketListSnapshot::loadInflationWinners(size_t maxWinners,
-                                                   int64_t minBalance) const
+                                                   int64_t minBalance)
 {
     ZoneScoped;
     auto timer = recordBulkLoadMetrics("inflationWinners", 0).TimeScope();
-
-    // Snapshots not currently supported, all access must be up to date
-    releaseAssert(isWithinAllowedLedgerDrift(0));
+    maybeUpdateSnapshot();
 
     UnorderedMap<AccountID, int64_t> voteCount;
     UnorderedSet<AccountID> seen;

src/bucket/SearchableBucketListSnapshot.h

@@ -21,7 +21,7 @@ struct SearchableBucketLevelSnapshot
 
 // A lightweight wrapper around the BucketList for thread safe BucketListDB
 // lookups
-class SearchableBucketListSnapshot : public NonMovable
+class SearchableBucketListSnapshot : public NonMovableOrCopyable
 {
     Application& mApp;
     std::vector<SearchableBucketLevelSnapshot> mLevels;
@@ -53,22 +53,25 @@ class SearchableBucketListSnapshot : public NonMovable
     // allowedLedgerDrift, lcl]
     bool isWithinAllowedLedgerDrift(uint32_t allowedLedgerDrift) const;
 
+    // Checks if snapshot is behind the current LCL and updates as necessary
+    void maybeUpdateSnapshot();
+
     SearchableBucketListSnapshot(Application& app, BucketList const& bl);
 
   public:
     std::vector<LedgerEntry>
-    loadKeys(std::set<LedgerKey, LedgerEntryIdCmp> const& inKeys) const;
+    loadKeys(std::set<LedgerKey, LedgerEntryIdCmp> const& inKeys);
 
     std::vector<LedgerEntry>
     loadPoolShareTrustLinesByAccountAndAsset(AccountID const& accountID,
-                                             Asset const& asset) const;
+                                             Asset const& asset);
 
     std::vector<InflationWinner> loadInflationWinners(size_t maxWinners,
-                                                      int64_t minBalance) const;
+                                                      int64_t minBalance);
 
-    std::shared_ptr<LedgerEntry> getLedgerEntry(LedgerKey const& k) const;
+    std::shared_ptr<LedgerEntry> getLedgerEntry(LedgerKey const& k);
 
-    friend std::unique_ptr<SearchableBucketListSnapshot const>
+    friend std::unique_ptr<SearchableBucketListSnapshot>
     BucketManagerImpl::getSearchableBucketListSnapshot() const;
 };
 }

src/bucket/test/BucketListTests.cpp

@@ -15,6 +15,7 @@
 #include "bucket/BucketList.h"
 #include "bucket/BucketManager.h"
 #include "bucket/BucketOutputIterator.h"
+#include "bucket/SearchableBucketListSnapshot.h"
 #include "bucket/test/BucketTestUtils.h"
 #include "ledger/test/LedgerTestUtils.h"
 #include "lib/catch.hpp"
@@ -1113,6 +1114,47 @@ TEST_CASE_VERSIONS("eviction scan", "[bucketlist]")
     });
 }
 
+TEST_CASE_VERSIONS("Searchable BucketListDB snapshots", "[bucketlist]")
+{
+    VirtualClock clock;
+    Config cfg(getTestConfig(0, Config::TESTDB_IN_MEMORY_SQLITE));
+    cfg.EXPERIMENTAL_BUCKETLIST_DB = true;
+
+    auto app = createTestApplication<BucketTestApplication>(clock, cfg);
+    for_versions_from(20, *app, [&] {
+        LedgerManagerForBucketTests& lm = app->getLedgerManager();
+        auto& bm = app->getBucketManager();
+
+        auto entry =
+            LedgerTestUtils::generateValidLedgerEntryOfType(CLAIMABLE_BALANCE);
+        entry.data.claimableBalance().amount = 0;
+
+        auto searchableBL = bm.getSearchableBucketListSnapshot();
+
+        // Update entry every 5 ledgers so we can see bucket merge events
+        for (auto ledgerSeq = 1; ledgerSeq < 101; ++ledgerSeq)
+        {
+            if ((ledgerSeq - 1) % 5 == 0)
+            {
+                ++entry.data.claimableBalance().amount;
+                entry.lastModifiedLedgerSeq = ledgerSeq;
+                lm.setNextLedgerEntryBatchForBucketTesting({}, {entry}, {});
+            }
+            else
+            {
+                lm.setNextLedgerEntryBatchForBucketTesting({}, {}, {});
+            }
+
+            closeLedger(*app);
+
+            // Snapshot should automatically update with latest version
+            auto loadedEntry =
+                searchableBL->getLedgerEntry(LedgerEntryKey(entry));
+            REQUIRE((loadedEntry && *loadedEntry == entry));
+        }
+    });
+}
+
 static std::string
 formatX32(uint32_t v)
 {

src/ledger/LedgerTxn.cpp

@@ -3371,7 +3371,7 @@ LedgerTxnRoot::Impl::areEntriesMissingInCacheForOffer(OfferEntry const& oe)
     return false;
 }
 
-SearchableBucketListSnapshot const&
+SearchableBucketListSnapshot&
 LedgerTxnRoot::Impl::getSearchableBucketListSnapshot() const
 {
     releaseAssert(mApp.getConfig().isUsingBucketListDB());

src/ledger/LedgerTxnImpl.h

@@ -740,7 +740,7 @@ class LedgerTxnRoot::Impl
     mutable BestOffers mBestOffers;
     mutable uint64_t mPrefetchHits{0};
     mutable uint64_t mPrefetchMisses{0};
-    mutable std::unique_ptr<SearchableBucketListSnapshot const>
+    mutable std::unique_ptr<SearchableBucketListSnapshot>
         mSearchableBucketListSnapshot{};
 
     size_t mBulkLoadBatchSize;
@@ -874,7 +874,7 @@ class LedgerTxnRoot::Impl
 
     bool areEntriesMissingInCacheForOffer(OfferEntry const& oe);
 
-    SearchableBucketListSnapshot const& getSearchableBucketListSnapshot() const;
+    SearchableBucketListSnapshot& getSearchableBucketListSnapshot() const;
 
   public:
     // Constructor has the strong exception safety guarantee