Add discovery types to cluster stats (#36442)

Adds information about the used discovery types to the cluster stats, similar as we have for the network types.

docs/reference/cluster/stats.asciidoc

@@ -202,20 +202,25 @@ Will return, for example:
         },
         ...
       ],
-      ...
+      "network_types": {
+        ...
+      },
+      "discovery_types": {
+        ...
+      }
    }
 }
 --------------------------------------------------
 // TESTRESPONSE[s/"plugins": \[[^\]]*\]/"plugins": $body.$_path/]
-// TESTRESPONSE[s/\.\.\./"network_types": "replace_me"/]
+// TESTRESPONSE[s/"network_types": \{[^\}]*\}/"network_types": $body.$_path/]
+// TESTRESPONSE[s/"discovery_types": \{[^\}]*\}/"discovery_types": $body.$_path/]
 // TESTRESPONSE[s/: (\-)?[0-9]+/: $body.$_path/]
 // TESTRESPONSE[s/: "[^"]*"/: $body.$_path/]
 // These replacements do a few things:
 // 1. Ignore the contents of the `plugins` object because we don't know all of
 //    the plugins that will be in it. And because we figure folks don't need to
 //    see an exhaustive list anyway.
-// 2. The last ... contains more things that we don't think are important to
-//    include in the output.
+// 2. Similarly, ignore the contents of `network_types` and `discovery_types`.
 // 3. All of the numbers and strings on the right hand side of *every* field in
 //    the response are ignored. So we're really only asserting things about the
 //    the shape of this response, not the values in it.

rest-api-spec/src/main/resources/rest-api-spec/test/cluster.stats/10_basic.yml

@@ -66,3 +66,14 @@
   - is_true: nodes.fs
   - is_true: nodes.plugins
   - is_true: nodes.network_types
+
+---
+"get cluster stats returns discovery types":
+  - skip:
+      version: " - 6.99.99"
+      reason:  "discovery types are added for v7.0.0"
+
+  - do:
+      cluster.stats: {}
+
+  - is_true: nodes.discovery_types

server/src/main/java/org/elasticsearch/action/admin/cluster/stats/ClusterStatsNodes.java

@@ -34,6 +34,7 @@ import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.ToXContentFragment;
 import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.discovery.DiscoveryModule;
 import org.elasticsearch.monitor.fs.FsInfo;
 import org.elasticsearch.monitor.jvm.JvmInfo;
 import org.elasticsearch.plugins.PluginInfo;
@@ -59,6 +60,7 @@ public class ClusterStatsNodes implements ToXContentFragment {
     private final FsInfo.Path fs;
     private final Set<PluginInfo> plugins;
     private final NetworkTypes networkTypes;
+    private final DiscoveryTypes discoveryTypes;
 
     ClusterStatsNodes(List<ClusterStatsNodeResponse> nodeResponses) {
         this.versions = new HashSet<>();
@@ -90,6 +92,7 @@ public class ClusterStatsNodes implements ToXContentFragment {
         this.process = new ProcessStats(nodeStats);
         this.jvm = new JvmStats(nodeInfos, nodeStats);
         this.networkTypes = new NetworkTypes(nodeInfos);
+        this.discoveryTypes = new DiscoveryTypes(nodeInfos);
     }
 
     public Counts getCounts() {
@@ -167,6 +170,8 @@ public class ClusterStatsNodes implements ToXContentFragment {
         builder.startObject(Fields.NETWORK_TYPES);
         networkTypes.toXContent(builder, params);
         builder.endObject();
+
+        discoveryTypes.toXContent(builder, params);
         return builder;
     }
 
@@ -612,4 +617,29 @@ public class ClusterStatsNodes implements ToXContentFragment {
 
     }
 
+    static class DiscoveryTypes implements ToXContentFragment {
+
+        private final Map<String, AtomicInteger> discoveryTypes;
+
+        DiscoveryTypes(final List<NodeInfo> nodeInfos) {
+            final Map<String, AtomicInteger> discoveryTypes = new HashMap<>();
+            for (final NodeInfo nodeInfo : nodeInfos) {
+                final Settings settings = nodeInfo.getSettings();
+                final String discoveryType = DiscoveryModule.DISCOVERY_TYPE_SETTING.get(settings);
+                discoveryTypes.computeIfAbsent(discoveryType, k -> new AtomicInteger()).incrementAndGet();
+            }
+            this.discoveryTypes = Collections.unmodifiableMap(discoveryTypes);
+        }
+
+        @Override
+        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+            builder.startObject("discovery_types");
+            for (final Map.Entry<String, AtomicInteger> entry : discoveryTypes.entrySet()) {
+                builder.field(entry.getKey(), entry.getValue().get());
+            }
+            builder.endObject();
+            return builder;
+        }
+    }
+
 }

x-pack/plugin/monitoring/src/test/java/org/elasticsearch/xpack/monitoring/collector/cluster/ClusterStatsMonitoringDocTests.java

@@ -33,6 +33,7 @@ import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.common.xcontent.XContentType;
+import org.elasticsearch.discovery.DiscoveryModule;
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.license.License;
 import org.elasticsearch.monitor.fs.FsInfo;
@@ -242,6 +243,7 @@ public class ClusterStatsMonitoringDocTests extends BaseMonitoringDocTestCase<Cl
         when(mockNodeInfo.getSettings()).thenReturn(Settings.builder()
                                                             .put(NetworkModule.TRANSPORT_TYPE_KEY, "_transport")
                                                             .put(NetworkModule.HTTP_TYPE_KEY, "_http")
+                                                            .put(DiscoveryModule.DISCOVERY_TYPE_SETTING.getKey(), "_disco")
                                                             .build());
 
         final PluginsAndModules mockPluginsAndModules = mock(PluginsAndModules.class);
@@ -512,6 +514,9 @@ public class ClusterStatsMonitoringDocTests extends BaseMonitoringDocTestCase<Cl
                         + "\"http_types\":{"
                           + "\"_http\":1"
                         + "}"
+                      + "},"
+                      + "\"discovery_types\":{"
+                        + "\"_disco\":1"
                       + "}"
                     + "}"
                   + "},"