Fixed prefetch metric and intialized all point load metrics on startup (#4568)

# Description

Resolves #4566

# Checklist
- [x] Reviewed the
[contributing](https://github.com/stellar/stellar-core/blob/master/CONTRIBUTING.md#submitting-changes)
document
- [x] Rebased on top of master (no merge commits)
- [x] Ran `clang-format` v8.0.0 (via `make format` or the Visual Studio
extension)
- [x] Compiles
- [x] Ran all tests
- [ ] If change impacts performance, include supporting evidence per the
[performance
document](https://github.com/stellar/stellar-core/blob/master/performance-eval/performance-eval.md)

Author: marta-lokhova

src/bucket/BucketSnapshotManager.cpp

@@ -13,7 +13,9 @@
 
 #include "medida/meter.h"
 #include "medida/metrics_registry.h"
+#include "xdr/Stellar-ledger-entries.h"
 #include <shared_mutex>
+#include <xdrpp/types.h>
 
 namespace stellar
 {
@@ -38,6 +40,16 @@ BucketSnapshotManager::BucketSnapshotManager(
     releaseAssert(threadIsMain());
     releaseAssert(mCurrLiveSnapshot);
     releaseAssert(mCurrHotArchiveSnapshot);
+
+    // Initialize point load timers for each LedgerEntry type
+    for (auto t : xdr::xdr_traits<LedgerEntryType>::enum_values())
+    {
+        auto const& label = xdr::xdr_traits<LedgerEntryType>::enum_name(
+            static_cast<LedgerEntryType>(t));
+        auto& metric =
+            mApp.getMetrics().NewTimer({"bucketlistDB", "point", label});
+        mPointTimers.emplace(static_cast<LedgerEntryType>(t), metric);
+    }
 }
 
 std::shared_ptr<SearchableLiveBucketListSnapshot>
@@ -215,14 +227,7 @@ BucketSnapshotManager::endPointLoadTimer(LedgerEntryType t,
     if (!bloomMiss)
     {
         auto iter = mPointTimers.find(t);
-        if (iter == mPointTimers.end())
-        {
-            auto const& label = xdr::xdr_traits<LedgerEntryType>::enum_name(t);
-            auto& metric =
-                mApp.getMetrics().NewTimer({"bucketlistDB", "point", label});
-            iter = mPointTimers.emplace(t, metric).first;
-        }
-
+        releaseAssert(iter != mPointTimers.end());
         iter->second.Update(duration);
     }
 }

src/bucket/SearchableBucketList.cpp

@@ -5,6 +5,7 @@
 #include "bucket/SearchableBucketList.h"
 #include "bucket/BucketInputIterator.h"
 #include "bucket/BucketListSnapshotBase.h"
+#include "util/GlobalChecks.h"
 
 #include <medida/timer.h>
 
@@ -244,6 +245,16 @@ SearchableLiveBucketListSnapshot::loadKeysWithLimits(
     std::set<LedgerKey, LedgerEntryIdCmp> const& inKeys,
     LedgerKeyMeter* lkMeter)
 {
+    if (threadIsMain())
+    {
+        auto timer =
+            mSnapshotManager.recordBulkLoadMetrics("prefetch", inKeys.size())
+                .TimeScope();
+        auto op = loadKeysInternal(inKeys, lkMeter, std::nullopt);
+        releaseAssertOrThrow(op);
+        return std::move(*op);
+    }
+
     auto op = loadKeysInternal(inKeys, lkMeter, std::nullopt);
     releaseAssertOrThrow(op);
     return std::move(*op);