From a01b588a129d2896500f49ed12a5ba7479abd0b7 Mon Sep 17 00:00:00 2001
From: "Ratan (Rai) Sur" <ratan.r.sur@gmail.com>
Date: Thu, 29 Oct 2020 16:34:18 -0400
Subject: [PATCH] Thread Safe Evicting Queue Access (#1498)

Signed-off-by: Ratan Rai Sur <ratan.r.sur@gmail.com>
---
 .../eth/transactions/PendingTransactions.java |  7 +--
 .../eth/transactions/TransactionPool.java     | 44 ++++++-------------
 2 files changed, 17 insertions(+), 34 deletions(-)

diff --git a/ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/PendingTransactions.java b/ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/PendingTransactions.java
index a5bdd84ec8..46031dc0bc 100644
--- a/ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/PendingTransactions.java
+++ b/ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/PendingTransactions.java
@@ -38,7 +38,6 @@ import java.time.Clock;
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -375,8 +374,10 @@ public class PendingTransactions {
     }
   }
 
-  Collection<Hash> getNewPooledHashes() {
-    return newPooledHashes;
+  List<Hash> getNewPooledHashes() {
+    synchronized (newPooledHashes) {
+      return List.copyOf(newPooledHashes);
+    }
   }
 
   /**
diff --git a/ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/TransactionPool.java b/ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/TransactionPool.java
index c13afe5762..9e5d26c5f4 100644
--- a/ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/TransactionPool.java
+++ b/ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/TransactionPool.java
@@ -47,10 +47,7 @@ import org.hyperledger.besu.plugin.services.metrics.Counter;
 import org.hyperledger.besu.plugin.services.metrics.LabelledMetric;
 
 import java.util.Collection;
-import java.util.ConcurrentModificationException;
 import java.util.HashSet;
-import java.util.Iterator;
-import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 
@@ -124,34 +121,19 @@ public class TransactionPool implements BlockAddedObserver {
   }
 
   void handleConnect(final EthPeer peer) {
-    final List<Transaction> localTransactions = getLocalTransactions();
-    for (final Transaction transaction : localTransactions) {
-      peerTransactionTracker.addToPeerSendQueue(peer, transaction);
-    }
-    maybePeerPendingTransactionTracker.ifPresent(
-        peerPendingTransactionTracker -> {
-          if (peerPendingTransactionTracker.isPeerSupported(peer, EthProtocol.ETH65)) {
-            Iterator<Hash> hashIterator = getNewPooledHashes().iterator();
-            while (hashIterator.hasNext()) {
-              try {
-                peerPendingTransactionTracker.addToPeerSendQueue(peer, hashIterator.next());
-              } catch (ConcurrentModificationException __) {
-                // The hash got evicted somehow.
-                // For example, it was pushed out by new pooled transaction hashes or we got the
-                // full transaction and evicted it manually.
-                // Either way, we don't care and can continue.
-              }
-            }
-          }
-        });
-  }
-
-  private List<Transaction> getLocalTransactions() {
-    return pendingTransactions.getLocalTransactions();
-  }
-
-  public Collection<Hash> getNewPooledHashes() {
-    return pendingTransactions.getNewPooledHashes();
+    pendingTransactions
+        .getLocalTransactions()
+        .forEach(transaction -> peerTransactionTracker.addToPeerSendQueue(peer, transaction));
+
+    maybePeerPendingTransactionTracker
+        .filter(
+            peerPendingTransactionTracker ->
+                peerPendingTransactionTracker.isPeerSupported(peer, EthProtocol.ETH65))
+        .ifPresent(
+            peerPendingTransactionTracker ->
+                pendingTransactions
+                    .getNewPooledHashes()
+                    .forEach(hash -> peerPendingTransactionTracker.addToPeerSendQueue(peer, hash)));
   }
 
   public boolean addTransactionHash(final Hash transactionHash) {