Add comments and variable refactoring

Signed-off-by: Pranshu Shukla <[email protected]>

server/src/internalClusterTest/java/org/opensearch/nodestats/NodeStatsIT.java

@@ -381,7 +381,7 @@ public void testNodeIndicesStatsWithAggregationOnNodes() {
         testLevels.forEach(testLevel -> {
             NodesStatsResponse response;
             CommonStatsFlags commonStatsFlags = new CommonStatsFlags();
-            commonStatsFlags.aggregateNodeResponsesOnLevel(true);
+            commonStatsFlags.setAggregateNodeIndicesStatsResponsesOnLevel(true);
             if (!testLevel.equals(MockFields.NULL)) {
                 ArrayList<String> level_arg = new ArrayList<>();
                 level_arg.add(testLevel.getRestName());

server/src/main/java/org/opensearch/action/admin/indices/stats/CommonStatsFlags.java

@@ -67,7 +67,7 @@ public class CommonStatsFlags implements Writeable, Cloneable {
     // Used for metric CACHE_STATS, to determine which caches to report stats for
     private EnumSet<CacheType> includeCaches = EnumSet.noneOf(CacheType.class);
     private String[] levels = new String[0];
-    private boolean aggregateNodeResponsesOnLevel = false;
+    private boolean aggregateNodeIndicesStatsResponsesOnLevel = false;
 
     /**
      * @param flags flags to set. If no flags are supplied, default flags will be set.
@@ -102,7 +102,7 @@ public CommonStatsFlags(StreamInput in) throws IOException {
             levels = in.readStringArray();
         }
         if (in.getVersion().onOrAfter(Version.V_3_0_0)) {
-            aggregateNodeResponsesOnLevel = in.readBoolean();
+            aggregateNodeIndicesStatsResponsesOnLevel = in.readBoolean();
         }
     }
 
@@ -129,7 +129,7 @@ public void writeTo(StreamOutput out) throws IOException {
             out.writeStringArrayNullable(levels);
         }
         if (out.getVersion().onOrAfter(Version.V_3_0_0)) {
-            out.writeBoolean(aggregateNodeResponsesOnLevel);
+            out.writeBoolean(aggregateNodeIndicesStatsResponsesOnLevel);
         }
     }
 
@@ -269,12 +269,12 @@ public boolean includeSegmentFileSizes() {
         return this.includeSegmentFileSizes;
     }
 
-    public void aggregateNodeResponsesOnLevel(boolean aggregateNodeResponsesOnLevel) {
-        this.aggregateNodeResponsesOnLevel = aggregateNodeResponsesOnLevel;
+    public void setAggregateNodeIndicesStatsResponsesOnLevel(boolean aggregateNodeIndicesStatsResponsesOnLevel) {
+        this.aggregateNodeIndicesStatsResponsesOnLevel = aggregateNodeIndicesStatsResponsesOnLevel;
     }
 
-    public boolean aggregateNodeResponsesOnLevel() {
-        return this.aggregateNodeResponsesOnLevel;
+    public boolean getAggregateNodeIndicesStatsResponsesOnLevel() {
+        return this.aggregateNodeIndicesStatsResponsesOnLevel;
     }
 
     public boolean isSet(Flag flag) {

server/src/main/java/org/opensearch/indices/IndicesService.java

@@ -692,7 +692,7 @@ public NodeIndicesStats stats(CommonStatsFlags flags) {
                     break;
             }
         }
-        if (flags.aggregateNodeResponsesOnLevel()) {
+        if (flags.getAggregateNodeIndicesStatsResponsesOnLevel()) {
             return new NodeIndicesStats(commonStats, statsByShard(this, flags), searchRequestStats, flags.getLevels());
         }
         return new NodeIndicesStats(commonStats, statsByShard(this, flags), searchRequestStats);

server/src/main/java/org/opensearch/indices/NodeIndicesStats.java

@@ -97,6 +97,10 @@ public NodeIndicesStats(StreamInput in) throws IOException {
         }
     }
 
+    /**
+     * Without passing the information of the levels to the constructor, we return the Node-level aggregated stats as
+     * {@link CommonStats} along with a hash-map containing Index to List of Shard Stats.
+     */
     public NodeIndicesStats(CommonStats oldStats, Map<Index, List<IndexShardStats>> statsByShard, SearchRequestStats searchRequestStats) {
         // this.stats = stats;
         this.statsByShard = statsByShard;
@@ -115,6 +119,12 @@ public NodeIndicesStats(CommonStats oldStats, Map<Index, List<IndexShardStats>>
         }
     }
 
+    /**
+     * Passing the level information to the nodes allows us to aggregate the stats based on the level passed. This
+     * allows us to aggregate based on NodeLevel (default - if no level is passed) or Index level if `indices` level is
+     * passed and finally return the statsByShards map if `shards` level is passed. This allows us to reduce ser/de of
+     * stats and return only the information that is required while returning to the client.
+     */
     public NodeIndicesStats(
         CommonStats oldStats,
         Map<Index, List<IndexShardStats>> statsByShard,
@@ -148,7 +158,13 @@ public NodeIndicesStats(
         }
     }
 
-    public static Fields getFirstAcceptedLevel(String[] levels) {
+    /**
+     * By default, the levels passed from the transport action will be a list of strings, since NodeIndicesStats can
+     * only aggregate on one level, we pick the first accepted level else we ignore if no known level is passed.
+     * @param levels - levels sent in the request.
+     * @return Corresponding identified enum {@link Fields}
+     */
+    private static Fields getFirstAcceptedLevel(String[] levels) {
         if (levels != null) {
             Optional<Fields> level = Arrays.stream(levels)
                 .flatMap(passedLevel -> Arrays.stream(Fields.values()).filter(field -> field.getRestName().equals(passedLevel)))

server/src/main/java/org/opensearch/rest/action/admin/cluster/RestNodesStatsAction.java

@@ -232,7 +232,7 @@ public RestChannelConsumer prepareRequest(final RestRequest request, final NodeC
         // If no levels are passed in this results in an empty array.
         String[] levels = Strings.splitStringByCommaToArray(request.param("level"));
         nodesStatsRequest.indices().setLevels(levels);
-        nodesStatsRequest.indices().aggregateNodeResponsesOnLevel(true);
+        nodesStatsRequest.indices().setAggregateNodeIndicesStatsResponsesOnLevel(true);
 
         return channel -> client.admin().cluster().nodesStats(nodesStatsRequest, new NodesResponseRestListener<>(channel));
     }

server/src/main/java/org/opensearch/rest/action/cat/RestNodesAction.java

@@ -146,7 +146,7 @@ public void processResponse(final NodesInfoResponse nodesInfoResponse) {
                                 NodesStatsRequest.Metric.PROCESS.metricName(),
                                 NodesStatsRequest.Metric.SCRIPT.metricName()
                             );
-                        nodesStatsRequest.indices().aggregateNodeResponsesOnLevel(true);
+                        nodesStatsRequest.indices().setAggregateNodeIndicesStatsResponsesOnLevel(true);
                         client.admin().cluster().nodesStats(nodesStatsRequest, new RestResponseListener<NodesStatsResponse>(channel) {
                             @Override
                             public RestResponse buildResponse(NodesStatsResponse nodesStatsResponse) throws Exception {

server/src/test/java/org/opensearch/action/admin/cluster/node/stats/NodeStatsTests.java

@@ -1180,7 +1180,7 @@ public void testNodeIndicesStatsSerialization() throws IOException {
         commonStatsFlags.set(CommonStatsFlags.Flag.Docs, true);
         commonStatsFlags.set(CommonStatsFlags.Flag.Store, true);
         commonStatsFlags.set(CommonStatsFlags.Flag.Indexing, true);
-        commonStatsFlags.aggregateNodeResponsesOnLevel(true);
+        commonStatsFlags.setAggregateNodeIndicesStatsResponsesOnLevel(true);
 
         levelParams.forEach(levelParam -> {
             ArrayList<String> level_arg = new ArrayList<>();
@@ -1236,7 +1236,7 @@ public void testNodeIndicesStatsToXContent() {
         commonStatsFlags.set(CommonStatsFlags.Flag.Docs, true);
         commonStatsFlags.set(CommonStatsFlags.Flag.Store, true);
         commonStatsFlags.set(CommonStatsFlags.Flag.Indexing, true);
-        commonStatsFlags.aggregateNodeResponsesOnLevel(true);
+        commonStatsFlags.setAggregateNodeIndicesStatsResponsesOnLevel(true);
 
         levelParams.forEach(levelParam -> {
             ArrayList<String> level_arg = new ArrayList<>();
@@ -1325,7 +1325,7 @@ public MockNodeIndicesStats generateMockNodeIndicesStats(CommonStats commonStats
 
         ClusterSettings clusterSettings = new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS);
 
-        if (commonStatsFlags.aggregateNodeResponsesOnLevel()) {
+        if (commonStatsFlags.getAggregateNodeIndicesStatsResponsesOnLevel()) {
             return new MockNodeIndicesStats(
                 new CommonStats(commonStatsFlags),
                 statsByShard,