From 4eb1ed650b42a39d16bdd599ed2f137b80399a84 Mon Sep 17 00:00:00 2001
From: garyschulte <garyschulte@gmail.com>
Date: Tue, 19 Sep 2023 16:11:34 -0700
Subject: [PATCH] rwlock usage in getNearest and more javadoc errata

Signed-off-by: garyschulte <garyschulte@gmail.com>
---
 .../segmented/RocksDBSnapshotTransaction.java |  3 ++
 .../SegmentedInMemoryKeyValueStorage.java     | 30 +++++++++++--------
 2 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/plugins/rocksdb/src/main/java/org/hyperledger/besu/plugin/services/storage/rocksdb/segmented/RocksDBSnapshotTransaction.java b/plugins/rocksdb/src/main/java/org/hyperledger/besu/plugin/services/storage/rocksdb/segmented/RocksDBSnapshotTransaction.java
index 6ca6c394e83..ad3438d381b 100644
--- a/plugins/rocksdb/src/main/java/org/hyperledger/besu/plugin/services/storage/rocksdb/segmented/RocksDBSnapshotTransaction.java
+++ b/plugins/rocksdb/src/main/java/org/hyperledger/besu/plugin/services/storage/rocksdb/segmented/RocksDBSnapshotTransaction.java
@@ -142,6 +142,9 @@ public void remove(final SegmentIdentifier segmentId, final byte[] key) {
    *
    * <p>be sure to close this iterator, like in a try-with-resources block, otherwise a native
    * memory leak might occur.
+   *
+   * @param segmentId id for the segment to iterate over.
+   * @return RocksIterator
    */
   public RocksIterator getIterator(final SegmentIdentifier segmentId) {
     return snapTx.getIterator(readOptions, columnFamilyMapper.apply(segmentId));
diff --git a/services/kvstore/src/main/java/org/hyperledger/besu/services/kvstore/SegmentedInMemoryKeyValueStorage.java b/services/kvstore/src/main/java/org/hyperledger/besu/services/kvstore/SegmentedInMemoryKeyValueStorage.java
index 053057b405e..e040d4233d4 100644
--- a/services/kvstore/src/main/java/org/hyperledger/besu/services/kvstore/SegmentedInMemoryKeyValueStorage.java
+++ b/services/kvstore/src/main/java/org/hyperledger/besu/services/kvstore/SegmentedInMemoryKeyValueStorage.java
@@ -116,18 +116,24 @@ public Optional<byte[]> get(final SegmentIdentifier segmentIdentifier, final byt
   public Optional<NearestKeyValue> getNearestTo(
       final SegmentIdentifier segmentIdentifier, final Bytes key) throws StorageException {
 
-    // TODO: revisit this for sort performance
-    Comparator<Map.Entry<Bytes, Optional<byte[]>>> comparing =
-        Comparator.comparing(
-                (Map.Entry<Bytes, Optional<byte[]>> a) -> a.getKey().commonPrefixLength(key))
-            .thenComparing((a, b) -> a.getKey().compareTo(b.getKey()));
-    return this.hashValueStore
-        .computeIfAbsent(segmentIdentifier, s -> new HashMap<>())
-        .entrySet()
-        .stream()
-        .sorted(comparing.reversed())
-        .findFirst()
-        .map(z -> new NearestKeyValue(z.getKey(), z.getValue()));
+    final Lock lock = rwLock.readLock();
+    lock.lock();
+    try {
+      // TODO: revisit this for sort performance
+      Comparator<Map.Entry<Bytes, Optional<byte[]>>> comparing =
+          Comparator.comparing(
+                  (Map.Entry<Bytes, Optional<byte[]>> a) -> a.getKey().commonPrefixLength(key))
+              .thenComparing((a, b) -> a.getKey().compareTo(b.getKey()));
+      return this.hashValueStore
+          .computeIfAbsent(segmentIdentifier, s -> new HashMap<>())
+          .entrySet()
+          .stream()
+          .sorted(comparing.reversed())
+          .findFirst()
+          .map(z -> new NearestKeyValue(z.getKey(), z.getValue()));
+    } finally {
+      lock.unlock();
+    }
   }
 
   @Override