Remove always-true param from IndicesService#stats (#45231)

Parameter `includePrevious` is always true, so this commit inlines it.

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

@@ -327,48 +327,36 @@ public class IndicesService extends AbstractLifecycleComponent
         return closeLatch.await(timeout, timeUnit);
     }
 
-    /**
-     * Returns the node stats indices stats. The {@code includePrevious} flag controls
-     * if old shards stats will be aggregated as well (only for relevant stats, such as
-     * refresh and indexing, not for docs/store).
-     */
-    public NodeIndicesStats stats(boolean includePrevious) {
-        return stats(includePrevious, new CommonStatsFlags().all());
-    }
-
-    public NodeIndicesStats stats(boolean includePrevious, CommonStatsFlags flags) {
-        CommonStats oldStats = new CommonStats(flags);
-
-        if (includePrevious) {
-            Flag[] setFlags = flags.getFlags();
-            for (Flag flag : setFlags) {
-                switch (flag) {
-                    case Get:
-                        oldStats.get.add(oldShardsStats.getStats);
-                        break;
-                    case Indexing:
-                        oldStats.indexing.add(oldShardsStats.indexingStats);
-                        break;
-                    case Search:
-                        oldStats.search.add(oldShardsStats.searchStats);
-                        break;
-                    case Merge:
-                        oldStats.merge.add(oldShardsStats.mergeStats);
-                        break;
-                    case Refresh:
-                        oldStats.refresh.add(oldShardsStats.refreshStats);
-                        break;
-                    case Recovery:
-                        oldStats.recoveryStats.add(oldShardsStats.recoveryStats);
-                        break;
-                    case Flush:
-                        oldStats.flush.add(oldShardsStats.flushStats);
-                        break;
-                }
+    public NodeIndicesStats stats(CommonStatsFlags flags) {
+        CommonStats commonStats = new CommonStats(flags);
+        // the cumulative statistics also account for shards that are no longer on this node, which is tracked by oldShardsStats
+        for (Flag flag : flags.getFlags()) {
+            switch (flag) {
+                case Get:
+                    commonStats.get.add(oldShardsStats.getStats);
+                    break;
+                case Indexing:
+                    commonStats.indexing.add(oldShardsStats.indexingStats);
+                    break;
+                case Search:
+                    commonStats.search.add(oldShardsStats.searchStats);
+                    break;
+                case Merge:
+                    commonStats.merge.add(oldShardsStats.mergeStats);
+                    break;
+                case Refresh:
+                    commonStats.refresh.add(oldShardsStats.refreshStats);
+                    break;
+                case Recovery:
+                    commonStats.recoveryStats.add(oldShardsStats.recoveryStats);
+                    break;
+                case Flush:
+                    commonStats.flush.add(oldShardsStats.flushStats);
+                    break;
             }
         }
 
-        return new NodeIndicesStats(oldStats, statsByShard(this, flags));
+        return new NodeIndicesStats(commonStats, statsByShard(this, flags));
     }
 
     Map<Index, List<IndexShardStats>> statsByShard(final IndicesService indicesService, final CommonStatsFlags flags) {

server/src/main/java/org/elasticsearch/node/NodeService.java

@@ -107,7 +107,7 @@ public class NodeService implements Closeable {
         // for indices stats we want to include previous allocated shards stats as well (it will
         // only be applied to the sensible ones to use, like refresh/merge/flush/indexing stats)
         return new NodeStats(transportService.getLocalNode(), System.currentTimeMillis(),
-                indices.anySet() ? indicesService.stats(true, indices) : null,
+                indices.anySet() ? indicesService.stats(indices) : null,
                 os ? monitorService.osService().stats() : null,
                 process ? monitorService.processService().stats() : null,
                 jvm ? monitorService.jvmService().stats() : null,