datanode preflight dns check (#20492)

* datanode preflight dns check

* code cleanup

* better error message

* fix dns preflight check

* changelog

* Update data-node/src/main/java/org/graylog/datanode/bootstrap/preflight/DatanodeDnsPreflightCheck.java

Co-authored-by: Matthias Oesterheld <[email protected]>

---------

Co-authored-by: Matthias Oesterheld <[email protected]>

changelog/unreleased/issue-20503.toml

@@ -0,0 +1,5 @@
+type="c"
+message="Datanode preflight check that verifies if hostname is bound to an IP"
+
+issues=["20503"]
+pulls=["20492"]

data-node/src/main/java/org/graylog/datanode/bindings/PreflightChecksBindings.java

@@ -19,6 +19,7 @@
 import com.google.inject.AbstractModule;
 import com.google.inject.multibindings.MapBinder;
 import org.graylog.datanode.bootstrap.preflight.DatanodeDirectoriesLockfileCheck;
+import org.graylog.datanode.bootstrap.preflight.DatanodeDnsPreflightCheck;
 import org.graylog.datanode.bootstrap.preflight.DatanodeKeystoreCheck;
 import org.graylog.datanode.bootstrap.preflight.OpenSearchPreconditionsCheck;
 import org.graylog.datanode.bootstrap.preflight.OpensearchBinPreflightCheck;
@@ -41,6 +42,7 @@ protected void configure() {
         bind(CertificateExchange.class).to(CertificateExchangeImpl.class);
 
         addPreflightCheck(OpensearchConfigSync.class);
+        addPreflightCheck(DatanodeDnsPreflightCheck.class);
         addPreflightCheck(OpensearchBinPreflightCheck.class);
         addPreflightCheck(DatanodeDirectoriesLockfileCheck.class);
         addPreflightCheck(OpenSearchPreconditionsCheck.class);

data-node/src/main/java/org/graylog/datanode/bootstrap/preflight/DatanodeDnsPreflightCheck.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2020 Graylog, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the Server Side Public License, version 1,
+ * as published by MongoDB, Inc.
+ *
+ * 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
+ * Server Side Public License for more details.
+ *
+ * You should have received a copy of the Server Side Public License
+ * along with this program. If not, see
+ * <http://www.mongodb.com/licensing/server-side-public-license>.
+ */
+package org.graylog.datanode.bootstrap.preflight;
+
+import jakarta.inject.Inject;
+import org.graylog.datanode.Configuration;
+import org.graylog2.bootstrap.preflight.PreflightCheck;
+import org.graylog2.bootstrap.preflight.PreflightCheckException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.List;
+import java.util.stream.Stream;
+
+public class DatanodeDnsPreflightCheck implements PreflightCheck {
+
+    private static final Logger LOG = LoggerFactory.getLogger(DatanodeDnsPreflightCheck.class);
+
+    private final String configuredHostname;
+
+    @Inject
+    public DatanodeDnsPreflightCheck(Configuration datanodeConfiguration) {
+        configuredHostname = datanodeConfiguration.getHostname();
+    }
+
+    @Override
+    public void runCheck() throws PreflightCheckException {
+        try {
+            final InetAddress[] addresses = InetAddress.getAllByName(configuredHostname);
+            final List<String> ips = Stream.of(addresses).map(InetAddress::getHostAddress).toList();
+            LOG.debug("Datanode host {} is available on {} addresses", configuredHostname, ips);
+        } catch (UnknownHostException e) {
+            throw new PreflightCheckException("Configured hostname " + configuredHostname + " is not bound to any address! Please configure your DNS so the hostname points to this machine");
+        }
+    }
+}