Load active peers from previous session saved into file.

rskj-core/src/main/java/co/rsk/RskContext.java

@@ -1588,6 +1588,13 @@ protected PeerExplorer getPeerExplorer() {
                     initialBootNodes.add(address.getHostName() + ":" + address.getPort());
                 }
             }
+
+            if (rskSystemProperties.usePeersFromLastSession()) {
+                List<String> peerLastSession = rskSystemProperties.peerLastSession();
+                logger.debug("Loading peers from previous session: {}",peerLastSession);
+                initialBootNodes.addAll(peerLastSession);
+            }
+
             peerExplorer = new PeerExplorer(
                     initialBootNodes,
                     localNode,

rskj-core/src/main/java/co/rsk/config/RskSystemProperties.java

@@ -58,6 +58,7 @@ public class RskSystemProperties extends SystemProperties {
     private static final int CHUNK_SIZE = 192;
 
     public static final String PROPERTY_SYNC_TOP_BEST = "sync.topBest";
+    public static final String USE_PEERS_FROM_LAST_SESSION = "peer.usePeersFromLastSession";
 
     //TODO: REMOVE THIS WHEN THE LocalBLockTests starts working with REMASC
     private boolean remascEnabled = true;
@@ -235,6 +236,10 @@ public boolean skipRemasc() {
         return getBoolean("rpc.skipRemasc", false);
     }
 
+    public boolean usePeersFromLastSession() {
+        return getBoolean(USE_PEERS_FROM_LAST_SESSION, false);
+    }
+
     public long peerDiscoveryMessageTimeOut() {
         return getLong("peer.discovery.msg.timeout", PD_DEFAULT_TIMEOUT_MESSAGE);
     }

rskj-core/src/main/java/org/ethereum/config/SystemProperties.java

@@ -44,6 +44,9 @@
 import java.net.URL;
 import java.net.UnknownHostException;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.*;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Collectors;
@@ -106,6 +109,7 @@ public abstract class SystemProperties {
     public static final String PROPERTY_PERSIST_BLOOMS_CACHE_SNAPSHOT = "cache.blooms.persist-snapshot";
 
     /* Testing */
+    public static final String LAST_CONNECTED_PEERS_FILE = "lastPeers.txt";
     private static final Boolean DEFAULT_VMTEST_LOAD_LOCAL = false;
 
     protected final Config configFromFiles;
@@ -251,6 +255,18 @@ public List<Node> peerActive() {
         return list.stream().map(this::parsePeer).collect(Collectors.toList());
     }
 
+    public List<String> peerLastSession() {
+        Path lastConnectedPeersFile = getLastConnectedPeersFilePath();
+        try {
+            if (Files.exists(lastConnectedPeersFile)) {
+                return Files.readAllLines(lastConnectedPeersFile);
+            }
+        } catch (IOException e) {
+            logger.error("Failed to read last connected peers file path {}. Error: {}", lastConnectedPeersFile.toAbsolutePath(), e.getMessage());
+        }
+        return Collections.emptyList();
+    }
+
     private Node parsePeer(ConfigObject configObject) {
         if (configObject.get("url") != null) {
             String url = configObject.toConfig().getString("url");
@@ -312,6 +328,10 @@ public String databaseDir() {
         return databaseDir == null ? configFromFiles.getString(PROPERTY_BASE_PATH) : databaseDir;
     }
 
+    public Path getLastConnectedPeersFilePath() {
+        return Paths.get(databaseDir(), LAST_CONNECTED_PEERS_FILE);
+    }
+
     public void setDataBaseDir(String dataBaseDir) {
         this.databaseDir = dataBaseDir;
     }

rskj-core/src/main/java/org/ethereum/net/server/ChannelManagerImpl.java

@@ -20,8 +20,8 @@
 package org.ethereum.net.server;
 
 import co.rsk.config.RskSystemProperties;
-import co.rsk.net.Peer;
 import co.rsk.net.NodeID;
+import co.rsk.net.Peer;
 import co.rsk.net.Status;
 import co.rsk.net.messages.*;
 import co.rsk.scoring.InetAddressUtils;
@@ -33,11 +33,14 @@
 import org.ethereum.core.Transaction;
 import org.ethereum.net.message.ReasonCode;
 import org.ethereum.sync.SyncPool;
+import org.ethereum.util.SimpleFileWriter;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nonnull;
+import java.io.IOException;
 import java.net.InetAddress;
+import java.nio.file.Path;
 import java.time.Duration;
 import java.time.Instant;
 import java.util.*;
@@ -74,6 +77,8 @@ public class ChannelManagerImpl implements ChannelManager {
     private final int maxActivePeers;
     private final int maxConnectionsAllowed;
     private final int networkCIDR;
+    private final Path peerListFileDir;
+    private final SimpleFileWriter fileDataSaver;
 
     private long timeLastLoggedPeers = System.currentTimeMillis();
 
@@ -87,6 +92,8 @@ public ChannelManagerImpl(RskSystemProperties config, SyncPool syncPool) {
         this.newPeers = new CopyOnWriteArrayList<>();
         this.maxConnectionsAllowed = config.maxConnectionsAllowed();
         this.networkCIDR = config.networkCIDR();
+        this.peerListFileDir = config.getLastConnectedPeersFilePath();
+        fileDataSaver = SimpleFileWriter.getInstance();
     }
 
     @Override
@@ -96,9 +103,28 @@ public void start() {
 
     @Override
     public void stop() {
+        saveActivePeersToFile();
         mainWorker.shutdown();
     }
 
+    private void saveActivePeersToFile() {
+        if (!activePeers.isEmpty()) {
+            logger.debug("Shutting down ChannelManagerImpl. Showing list of active peers");
+
+            StringBuilder sb = new StringBuilder();
+            for (Channel peerChannel : activePeers.values()) {
+                sb.append(peerChannel.getAddress().getCanonicalHostName()).append(":").append(peerChannel.getInetSocketAddress().getPort()).append("\n");
+            }
+            logger.debug("Active peer to save: -> {}", sb);
+            try {
+                fileDataSaver.saveDataIntoFile(sb.toString(), peerListFileDir);
+            } catch (IOException e) {
+                logger.error("Error saving active peers to file: {}", e.getMessage());
+            }
+        }
+    }
+
+
     private void handleNewPeersAndDisconnections() {
         this.tryProcessNewPeers();
         this.cleanDisconnections();
@@ -175,6 +201,7 @@ private boolean isRecent(Instant disconnectionTimeout, Instant currentTime) {
     }
 
     private void addToActives(Channel peer) {
+
         if (peer.isUsingNewProtocol() || peer.hasEthStatusSucceeded()) {
             syncPool.add(peer);
             synchronized (activePeersLock) {

rskj-core/src/main/java/org/ethereum/util/SimpleFileWriter.java

@@ -0,0 +1,52 @@
+/*
+ * This file is part of RskJ
+ * Copyright (C) 2023 RSK Labs Ltd.
+ * (derived from ethereumJ library, Copyright (c) 2016 <ether.camp>)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.ethereum.util;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;
+
+public class SimpleFileWriter {
+    private static final String TMP = ".tmp";
+    private static SimpleFileWriter instance;
+
+    private SimpleFileWriter() {
+    }
+
+    public static SimpleFileWriter getInstance() {
+        if (instance == null) {
+            instance = new SimpleFileWriter();
+        }
+        return instance;
+    }
+
+    public void saveDataIntoFile(String data, Path filePath) throws IOException {
+        File tempFile = File.createTempFile(filePath.toString(), TMP);
+        try (FileWriter writer = new FileWriter(tempFile, false)) {
+            writer.write(data);
+        }
+
+        Files.move(tempFile.toPath(), filePath, REPLACE_EXISTING);
+    }
+}
+

rskj-core/src/main/resources/expected.conf

@@ -101,6 +101,9 @@ blockchain = {
 }
 
 peer = {
+
+    usePeersFromLastSession = <boolean>
+
     active = [
         {
             url = <url>

rskj-core/src/main/resources/reference.conf

@@ -92,6 +92,9 @@ peer {
     # Use to connect to specific nodes
     active = [ ]
 
+    # If true, the node will try to connect to the peers from the last session
+    usePeersFromLastSession = false
+
     # list of trusted peers the incoming connections is always accepted from. Even if the max amount of connections is reached
     # This is used to create a filter of Trusted peers
     trusted = [