feat: Add support for reading static peers from file

acceptance-tests/src/testFixtures/java/tech/pegasys/teku/test/acceptance/dsl/TekuNodeConfigBuilder.java

@@ -547,6 +547,13 @@ public TekuNodeConfigBuilder withPeers(final TekuBeaconNode... nodes) {
     return this;
   }
 
+  public TekuNodeConfigBuilder withPeersFile(final String peersFilePath) {
+    mustBe(NodeType.BEACON_NODE);
+    LOG.debug("p2p-static-peers-file={}", peersFilePath);
+    configMap.put("p2p-static-peers-file", peersFilePath);
+    return this;
+  }
+
   public TekuNodeConfigBuilder withExternalSignerUrl(final String externalSignerUrl) {
     LOG.debug("validators-external-signer-url={}", externalSignerUrl);
     configMap.put("validators-external-signer-url", externalSignerUrl);

teku/src/main/java/tech/pegasys/teku/cli/options/P2POptions.java

@@ -20,16 +20,21 @@
 import static tech.pegasys.teku.networking.p2p.discovery.DiscoveryConfig.DEFAULT_P2P_PEERS_UPPER_BOUND_ALL_SUBNETS;
 import static tech.pegasys.teku.validator.api.ValidatorConfig.DEFAULT_EXECUTOR_MAX_QUEUE_SIZE_ALL_SUBNETS;
 
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
 import java.util.OptionalInt;
+import java.util.stream.Collectors;
 import picocli.CommandLine.Help.Visibility;
 import picocli.CommandLine.Mixin;
 import picocli.CommandLine.Option;
 import tech.pegasys.teku.beacon.sync.SyncConfig;
 import tech.pegasys.teku.cli.converter.OptionalIntConverter;
 import tech.pegasys.teku.config.TekuConfiguration;
+import tech.pegasys.teku.infrastructure.exceptions.InvalidConfigurationException;
 import tech.pegasys.teku.networking.eth2.P2PConfig;
 import tech.pegasys.teku.networking.p2p.discovery.DiscoveryConfig;
 import tech.pegasys.teku.networking.p2p.gossip.config.GossipConfig;
@@ -218,6 +223,14 @@ The network interface(s) on which the node listens for P2P communication.
       arity = "0..*")
   private List<String> p2pStaticPeers = new ArrayList<>();
 
+  @Option(
+      names = {"--p2p-static-peers-file"},
+      paramLabel = "<FILENAME>",
+      description =
+          "Specifies a file containing a list of 'static' peers (one per line) with which to establish and maintain connections",
+      arity = "1")
+  private String p2pStaticPeersFile;
+
   @Option(
       names = {"--p2p-direct-peers"},
       paramLabel = "<PEER_ADDRESSES>",
@@ -447,12 +460,35 @@ private OptionalInt getP2pLowerBound() {
   }
 
   private OptionalInt getP2pUpperBound() {
-    if (p2pUpperBound.isPresent() && p2pLowerBound.isPresent()) {
-      return p2pLowerBound.getAsInt() > p2pUpperBound.getAsInt() ? p2pLowerBound : p2pUpperBound;
-    }
     return p2pUpperBound;
   }
 
+  private List<String> getStaticPeersList() {
+    List<String> staticPeers = new ArrayList<>(p2pStaticPeers);
+
+    if (p2pStaticPeersFile != null) {
+      try {
+        Path filePath = Path.of(p2pStaticPeersFile);
+        if (Files.exists(filePath)) {
+          List<String> peersFromFile =
+              Files.readAllLines(filePath).stream()
+                  .map(String::trim)
+                  .filter(line -> !line.isEmpty() && !line.startsWith("#"))
+                  .collect(Collectors.toList());
+          staticPeers.addAll(peersFromFile);
+        } else {
+          throw new InvalidConfigurationException(
+              String.format("Static peers file not found: %s", p2pStaticPeersFile));
+        }
+      } catch (IOException e) {
+        throw new InvalidConfigurationException(
+            String.format("Failed to read static peers from file: %s", p2pStaticPeersFile), e);
+      }
+    }
+
+    return staticPeers;
+  }
+
   public void configure(final TekuConfiguration.Builder builder) {
     // From a discovery configuration perspective, direct peers are static peers
     p2pStaticPeers.addAll(p2pDirectPeers);
@@ -507,7 +543,7 @@ public void configure(final TekuConfiguration.Builder builder) {
                 d.advertisedUdpPortIpv6(OptionalInt.of(p2pAdvertisedPortIpv6));
               }
               d.isDiscoveryEnabled(p2pDiscoveryEnabled)
-                  .staticPeers(p2pStaticPeers)
+                  .staticPeers(getStaticPeersList())
                   .siteLocalAddressesEnabled(siteLocalAddressesEnabled);
             })
         .network(

teku/src/test/java/tech/pegasys/teku/cli/options/P2POptionsTest.java

@@ -15,6 +15,7 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.assertj.core.api.Assertions.fail;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static tech.pegasys.teku.infrastructure.async.AsyncRunnerFactory.DEFAULT_MAX_QUEUE_SIZE_ALL_SUBNETS;
 import static tech.pegasys.teku.networking.eth2.P2PConfig.DEFAULT_GOSSIP_BLOBS_AFTER_BLOCK_ENABLED;
@@ -27,8 +28,13 @@
 import static tech.pegasys.teku.validator.api.ValidatorConfig.DEFAULT_EXECUTOR_MAX_QUEUE_SIZE_ALL_SUBNETS;
 
 import com.google.common.base.Supplier;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.List;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
 import tech.pegasys.teku.beacon.sync.SyncConfig;
 import tech.pegasys.teku.cli.AbstractBeaconNodeCommandTest;
 import tech.pegasys.teku.config.TekuConfiguration;
@@ -472,4 +478,59 @@ public void defaultPortsAreSetCorrectly() {
     assertThat(networkConfig.getAdvertisedPort()).isEqualTo(DEFAULT_P2P_PORT);
     assertThat(networkConfig.getAdvertisedPortIpv6()).isEqualTo(DEFAULT_P2P_PORT_IPV6);
   }
+
+  @Test
+  public void staticPeersFile_shouldReadPeersFromFile(@TempDir final Path tempDir)
+      throws Exception {
+    // Create a test file with peers
+    Path peersFile = tempDir.resolve("static-peers.txt");
+    Files.writeString(peersFile, "peer1\npeer2\n#comment\n\npeer3");
+
+    TekuConfiguration tekuConfiguration =
+        getTekuConfigurationFromArguments(
+            "--p2p-static-peers-file", peersFile.toAbsolutePath().toString());
+
+    assertThat(tekuConfiguration.discovery().getStaticPeers())
+        .containsExactlyInAnyOrder("peer1", "peer2", "peer3");
+  }
+
+  @Test
+  public void staticPeersFile_shouldCombineWithCommandLinePeers(@TempDir final Path tempDir)
+      throws Exception {
+    // Create a test file with peers
+    Path peersFile = tempDir.resolve("static-peers.txt");
+    Files.writeString(peersFile, "peer1\npeer2");
+
+    TekuConfiguration tekuConfiguration =
+        getTekuConfigurationFromArguments(
+            "--p2p-static-peers-file",
+            peersFile.toAbsolutePath().toString(),
+            "--p2p-static-peers",
+            "peer3,peer4");
+
+    assertThat(tekuConfiguration.discovery().getStaticPeers())
+        .containsExactlyInAnyOrder("peer1", "peer2", "peer3", "peer4");
+  }
+
+  @Test
+  public void staticPeersFile_shouldThrowIfFileDoesNotExist() {
+    // Create a dummy instance of P2POptions
+    P2POptions p2pOptions = new P2POptions();
+
+    // Use reflection to access a private field and set its value
+    try {
+      Field field = P2POptions.class.getDeclaredField("p2pStaticPeersFile");
+      field.setAccessible(true);
+      field.set(p2pOptions, "/non/existent/file.txt");
+
+      // Use reflection to call a private method getStaticPeersList
+      Method method = P2POptions.class.getDeclaredMethod("getStaticPeersList");
+      method.setAccessible(true);
+
+      assertThatThrownBy(() -> method.invoke(p2pOptions))
+          .hasCauseInstanceOf(InvalidConfigurationException.class);
+    } catch (Exception e) {
+      fail("Test setup failed: " + e.getMessage(), e);
+    }
+  }
 }