adding a deprecation info check for search.remote properties (#76954)

The search.remote.* properties have been removed in 8.0 and replaced with cluster.remote.* properties.
This adds a check for these properties in the deprecation info API.
Relates #42404 and #42381

Author: masseyke

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationChecks.java

@@ -95,6 +95,7 @@ private DeprecationChecks() {
                     NodeDeprecationChecks::checkSharedDataPathSetting,
                     NodeDeprecationChecks::checkSingleDataNodeWatermarkSetting,
                     NodeDeprecationChecks::checkImplicitlyDisabledSecurityOnBasicAndTrial,
+                    NodeDeprecationChecks::checkSearchRemoteSettings,
                     NodeDeprecationChecks::checkMonitoringExporterPassword,
                     NodeDeprecationChecks::checkAcceptDefaultPasswordSetting,
                     NodeDeprecationChecks::checkAcceptRolesCacheMaxSizeSetting,

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecks.java

@@ -31,6 +31,7 @@
 import org.elasticsearch.script.ScriptService;
 import org.elasticsearch.threadpool.FixedExecutorBuilder;
 import org.elasticsearch.transport.RemoteClusterService;
+import org.elasticsearch.transport.SniffConnectionStrategy;
 import org.elasticsearch.xpack.core.XPackSettings;
 import org.elasticsearch.xpack.core.security.SecurityField;
 import org.elasticsearch.xpack.core.security.authc.RealmConfig;
@@ -593,6 +594,50 @@ static DeprecationIssue checkMonitoringExporterPassword(
         return new DeprecationIssue(DeprecationIssue.Level.CRITICAL, message, url, details, false, null);
     }
 
+    static DeprecationIssue checkSearchRemoteSettings(
+        final Settings settings,
+        final PluginsAndModules pluginsAndModules,
+        ClusterState cs,
+        XPackLicenseState licenseState
+    ) {
+        List<Setting<?>> remoteClusterSettings = new ArrayList<>();
+        remoteClusterSettings.addAll(SniffConnectionStrategy.SEARCH_REMOTE_CLUSTERS_SEEDS.getAllConcreteSettings(settings)
+            .sorted(Comparator.comparing(Setting::getKey)).collect(Collectors.toList()));
+        remoteClusterSettings.addAll(SniffConnectionStrategy.SEARCH_REMOTE_CLUSTERS_PROXY.getAllConcreteSettings(settings)
+            .sorted(Comparator.comparing(Setting::getKey)).collect(Collectors.toList()));
+        remoteClusterSettings.addAll(RemoteClusterService.SEARCH_REMOTE_CLUSTER_SKIP_UNAVAILABLE.getAllConcreteSettings(settings)
+            .sorted(Comparator.comparing(Setting::getKey)).collect(Collectors.toList()));
+        if (SniffConnectionStrategy.SEARCH_REMOTE_CONNECTIONS_PER_CLUSTER.exists(settings)) {
+            remoteClusterSettings.add(SniffConnectionStrategy.SEARCH_REMOTE_CONNECTIONS_PER_CLUSTER);
+        }
+        if (RemoteClusterService.SEARCH_REMOTE_INITIAL_CONNECTION_TIMEOUT_SETTING.exists(settings)) {
+            remoteClusterSettings.add(RemoteClusterService.SEARCH_REMOTE_INITIAL_CONNECTION_TIMEOUT_SETTING);
+        }
+        if (RemoteClusterService.SEARCH_REMOTE_NODE_ATTRIBUTE.exists(settings)) {
+            remoteClusterSettings.add(RemoteClusterService.SEARCH_REMOTE_NODE_ATTRIBUTE);
+        }
+        if (RemoteClusterService.SEARCH_ENABLE_REMOTE_CLUSTERS.exists(settings)) {
+            remoteClusterSettings.add(RemoteClusterService.SEARCH_ENABLE_REMOTE_CLUSTERS);
+        }
+        if (remoteClusterSettings.isEmpty()) {
+            return null;
+        }
+        final String remoteClusterSeedSettings = remoteClusterSettings.stream().map(Setting::getKey).collect(Collectors.joining(","));
+        final String message = String.format(
+            Locale.ROOT,
+            "search.remote settings [%s] are deprecated and will be removed in the next major version",
+            remoteClusterSeedSettings
+        );
+        final String details = String.format(
+            Locale.ROOT,
+            "replace search.remote settings [%s] with their secure 'cluster.remote' replacements",
+            remoteClusterSeedSettings
+        );
+        final String url =
+            "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-8.0.html#breaking_80_settings_changes";
+        return new DeprecationIssue(DeprecationIssue.Level.CRITICAL, message, url, details, false, null);
+    }
+
     static DeprecationIssue checkClusterRoutingAllocationIncludeRelocationsSetting(final Settings settings,
                                                                                    final PluginsAndModules pluginsAndModules,
                                                                                    final ClusterState clusterState,

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecksTests.java

@@ -798,6 +798,64 @@ public void testMonitoringExporterPassword() {
         assertThat(issue, nullValue());
     }
 
+    public void testCheckSearchRemoteSettings() {
+        // test for presence of deprecated exporter passwords
+        final int numClusters = randomIntBetween(1, 3);
+        final String[] clusterNames = new String[numClusters];
+        final Settings.Builder settingsBuilder = Settings.builder();
+        for (int k = 0; k < numClusters; k++) {
+            clusterNames[k] = randomAlphaOfLength(5);
+            settingsBuilder.put("search.remote." + clusterNames[k] + ".seeds", randomAlphaOfLength(5));
+            settingsBuilder.put("search.remote." + clusterNames[k] + ".proxy", randomAlphaOfLength(5));
+            settingsBuilder.put("search.remote." + clusterNames[k] + ".skip_unavailable", randomBoolean());
+        }
+        settingsBuilder.put("search.remote.connections_per_cluster", randomIntBetween(0, 100));
+        settingsBuilder.put("search.remote.initial_connect_timeout", randomIntBetween(30, 60));
+        settingsBuilder.put("search.remote.connect", randomBoolean());
+        final Settings settings = settingsBuilder.build();
+        final XPackLicenseState licenseState = new XPackLicenseState(Settings.EMPTY, () -> 0);
+        DeprecationIssue issue = NodeDeprecationChecks.checkSearchRemoteSettings(settings, null, null , licenseState);
+
+        final String expectedUrl =
+            "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-8.0.html#breaking_80_settings_changes";
+        String joinedNames = Arrays
+            .stream(clusterNames)
+            .map(s -> "search.remote." + s + ".seeds")
+            .sorted()
+            .collect(Collectors.joining(","));
+        joinedNames += ",";
+        joinedNames += Arrays
+            .stream(clusterNames)
+            .map(s -> "search.remote." + s + ".proxy")
+            .sorted()
+            .collect(Collectors.joining(","));
+        joinedNames += ",";
+        joinedNames += Arrays
+            .stream(clusterNames)
+            .map(s -> "search.remote." + s + ".skip_unavailable")
+            .sorted()
+            .collect(Collectors.joining(","));
+        joinedNames += ",search.remote.connections_per_cluster,search.remote.initial_connect_timeout,search.remote.connect";
+
+        assertThat(issue, equalTo(new DeprecationIssue(
+            DeprecationIssue.Level.CRITICAL,
+            String.format(
+                Locale.ROOT,
+                "search.remote settings [%s] are deprecated and will be removed in the next major version",
+                joinedNames
+            ),
+            expectedUrl,
+            String.format(
+                Locale.ROOT,
+                "replace search.remote settings [%s] with their secure 'cluster.remote' replacements",
+                joinedNames
+            ), false, null)));
+
+        // test for absence of deprecated exporter passwords
+        issue = NodeDeprecationChecks.checkMonitoringExporterPassword(Settings.builder().build(), null, null, licenseState);
+        assertThat(issue, nullValue());
+    }
+
     public void testClusterRoutingAllocationIncludeRelocationsSetting() {
         boolean settingValue = randomBoolean();
         String settingKey = CLUSTER_ROUTING_ALLOCATION_INCLUDE_RELOCATIONS_SETTING.getKey();