Create a fluent builder to help implement ChunkedToXContent

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

@@ -15,7 +15,6 @@
 import org.elasticsearch.cluster.node.DiscoveryNodeRole;
 import org.elasticsearch.cluster.routing.allocation.DiskThresholdSettings;
 import org.elasticsearch.cluster.routing.allocation.NodeAllocationStats;
-import org.elasticsearch.common.collect.Iterators;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.xcontent.ChunkedToXContent;
@@ -43,8 +42,6 @@
 import java.util.Map;
 import java.util.Objects;
 
-import static org.elasticsearch.common.xcontent.ChunkedToXContentHelper.singleChunk;
-
 /**
  * Node statistics (dynamic, changes depending on when created).
  */
@@ -345,58 +342,46 @@ public void writeTo(StreamOutput out) throws IOException {
 
     @Override
     public Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params outerParams) {
-
-        return Iterators.concat(
-
-            singleChunk((builder, params) -> {
-                builder.field("name", getNode().getName());
-                builder.field("transport_address", getNode().getAddress().toString());
-                builder.field("host", getNode().getHostName());
-                builder.field("ip", getNode().getAddress());
-
-                builder.startArray("roles");
-                for (DiscoveryNodeRole role : getNode().getRoles()) {
-                    builder.value(role.roleName());
-                }
-                builder.endArray();
-
-                if (getNode().getAttributes().isEmpty() == false) {
-                    builder.startObject("attributes");
-                    for (Map.Entry<String, String> attrEntry : getNode().getAttributes().entrySet()) {
-                        builder.field(attrEntry.getKey(), attrEntry.getValue());
-                    }
-                    builder.endObject();
+        return ChunkedToXContent.builder(outerParams).append((builder, params) -> {
+            builder.field("name", getNode().getName());
+            builder.field("transport_address", getNode().getAddress().toString());
+            builder.field("host", getNode().getHostName());
+            builder.field("ip", getNode().getAddress());
+
+            builder.startArray("roles");
+            for (DiscoveryNodeRole role : getNode().getRoles()) {
+                builder.value(role.roleName());
+            }
+            builder.endArray();
+
+            if (getNode().getAttributes().isEmpty() == false) {
+                builder.startObject("attributes");
+                for (Map.Entry<String, String> attrEntry : getNode().getAttributes().entrySet()) {
+                    builder.field(attrEntry.getKey(), attrEntry.getValue());
                 }
-
-                return builder;
-            }),
-
-            ifPresent(getIndices()).toXContentChunked(outerParams),
-
-            singleChunk(
-                (builder, p) -> builder.value(ifPresent(getOs()), p).value(ifPresent(getProcess()), p).value(ifPresent(getJvm()), p)
-            ),
-
-            ifPresent(getThreadPool()).toXContentChunked(outerParams),
-            singleChunk(ifPresent(getFs())),
-            ifPresent(getTransport()).toXContentChunked(outerParams),
-            ifPresent(getHttp()).toXContentChunked(outerParams),
-            singleChunk(ifPresent(getBreaker())),
-            ifPresent(getScriptStats()).toXContentChunked(outerParams),
-            singleChunk(ifPresent(getDiscoveryStats())),
-            ifPresent(getIngestStats()).toXContentChunked(outerParams),
-            singleChunk(ifPresent(getAdaptiveSelectionStats())),
-            ifPresent(getScriptCacheStats()).toXContentChunked(outerParams),
-            singleChunk(
+                builder.endObject();
+            }
+            return builder;
+        })
+
+            .appendIfPresent(getIndices())
+            .append((builder, p) -> builder.value(ifPresent(getOs()), p).value(ifPresent(getProcess()), p).value(ifPresent(getJvm()), p))
+
+            .appendIfPresent(getThreadPool())
+            .appendIfPresent(getFs())
+            .appendIfPresent(getTransport())
+            .appendIfPresent(getHttp())
+            .appendIfPresent(getBreaker())
+            .appendIfPresent(getScriptStats())
+            .appendIfPresent(getDiscoveryStats())
+            .appendIfPresent(getIngestStats())
+            .appendIfPresent(getAdaptiveSelectionStats())
+            .appendIfPresent(getScriptCacheStats())
+            .append(
                 (builder, p) -> builder.value(ifPresent(getIndexingPressureStats()), p)
                     .value(ifPresent(getRepositoriesStats()), p)
                     .value(ifPresent(getNodeAllocationStats()), p)
-            )
-        );
-    }
-
-    private static ChunkedToXContent ifPresent(@Nullable ChunkedToXContent chunkedToXContent) {
-        return Objects.requireNonNullElse(chunkedToXContent, ChunkedToXContent.EMPTY);
+            );
     }
 
     private static ToXContent ifPresent(@Nullable ToXContent toXContent) {

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

@@ -14,10 +14,9 @@
 import org.elasticsearch.action.support.nodes.BaseNodesXContentResponse;
 import org.elasticsearch.cluster.ClusterName;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.collect.Iterators;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
-import org.elasticsearch.common.xcontent.ChunkedToXContentHelper;
+import org.elasticsearch.common.xcontent.ChunkedToXContent;
 import org.elasticsearch.xcontent.ToXContent;
 
 import java.io.IOException;
@@ -42,15 +41,12 @@ protected void writeNodesTo(StreamOutput out, List<NodeStats> nodes) throws IOEx
 
     @Override
     protected Iterator<? extends ToXContent> xContentChunks(ToXContent.Params outerParams) {
-        return Iterators.concat(
-            ChunkedToXContentHelper.startObject("nodes"),
-            Iterators.flatMap(getNodes().iterator(), nodeStats -> Iterators.concat(Iterators.single((builder, params) -> {
-                builder.startObject(nodeStats.getNode().getId());
-                builder.field("timestamp", nodeStats.getTimestamp());
-                return builder;
-            }), nodeStats.toXContentChunked(outerParams), ChunkedToXContentHelper.endObject())),
-            ChunkedToXContentHelper.endObject()
-        );
+        return ChunkedToXContent.builder(outerParams)
+            .object(
+                "nodes",
+                getNodes().iterator(),
+                (b, ns) -> b.object(ns.getNode().getId(), ob -> ob.field("timestamp", ns.getTimestamp()).append(ns))
+            );
     }
 
     @Override

server/src/main/java/org/elasticsearch/action/support/nodes/BaseNodesXContentResponse.java

@@ -11,8 +11,7 @@
 
 import org.elasticsearch.action.FailedNodeException;
 import org.elasticsearch.cluster.ClusterName;
-import org.elasticsearch.common.collect.Iterators;
-import org.elasticsearch.common.xcontent.ChunkedToXContentHelper;
+import org.elasticsearch.common.xcontent.ChunkedToXContent;
 import org.elasticsearch.common.xcontent.ChunkedToXContentObject;
 import org.elasticsearch.rest.action.RestActions;
 import org.elasticsearch.xcontent.ToXContent;
@@ -30,11 +29,12 @@ protected BaseNodesXContentResponse(ClusterName clusterName, List<TNodeResponse>
 
     @Override
     public final Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params params) {
-        return Iterators.concat(Iterators.single((b, p) -> {
-            b.startObject();
-            RestActions.buildNodesHeader(b, p, this);
-            return b.field("cluster_name", getClusterName().value());
-        }), xContentChunks(params), ChunkedToXContentHelper.endObject());
+        return ChunkedToXContent.builder(params)
+            .object(
+                ob -> ob.append((b, p) -> RestActions.buildNodesHeader(b, p, this))
+                    .field("cluster_name", getClusterName().value())
+                    .append(xContentChunks(params))
+            );
     }
 
     protected abstract Iterator<? extends ToXContent> xContentChunks(ToXContent.Params outerParams);

server/src/main/java/org/elasticsearch/cluster/ClusterFeatures.java

@@ -9,9 +9,9 @@
 
 package org.elasticsearch.cluster;
 
-import org.elasticsearch.common.collect.Iterators;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.xcontent.ChunkedToXContent;
 import org.elasticsearch.common.xcontent.ChunkedToXContentObject;
 import org.elasticsearch.core.SuppressForbidden;
 import org.elasticsearch.features.NodeFeature;
@@ -244,15 +244,12 @@ public ClusterFeatures apply(ClusterFeatures part) {
 
     @Override
     public Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params params) {
-        return Iterators.concat(
-            Iterators.single((builder, p) -> builder.startArray()),
-            nodeFeatures.entrySet().stream().sorted(Map.Entry.comparingByKey()).<ToXContent>map(e -> (builder, p) -> {
+        return ChunkedToXContent.builder(params)
+            .array(nodeFeatures.entrySet().stream().sorted(Map.Entry.comparingByKey()).iterator(), e -> (builder, p) -> {
                 String[] features = e.getValue().toArray(String[]::new);
                 Arrays.sort(features);
                 return builder.startObject().field("node_id", e.getKey()).array("features", features).endObject();
-            }).iterator(),
-            Iterators.single((builder, p) -> builder.endArray())
-        );
+            });
     }
 
     @Override

server/src/main/java/org/elasticsearch/cluster/ClusterInfo.java

@@ -15,7 +15,6 @@
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.routing.UnassignedInfo;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.collect.Iterators;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -36,9 +35,6 @@
 
 import static org.elasticsearch.cluster.routing.ShardRouting.newUnassigned;
 import static org.elasticsearch.cluster.routing.UnassignedInfo.Reason.REINITIALIZED;
-import static org.elasticsearch.common.xcontent.ChunkedToXContentHelper.endArray;
-import static org.elasticsearch.common.xcontent.ChunkedToXContentHelper.singleChunk;
-import static org.elasticsearch.common.xcontent.ChunkedToXContentHelper.startObject;
 
 /**
  * ClusterInfo is an object representing a map of nodes to {@link DiskUsage}
@@ -142,7 +138,7 @@ private static ShardRouting createFakeShardRoutingFromNodeAndShard(NodeAndShard
 
     @Override
     public Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params params) {
-        return Iterators.concat(startObject("nodes"), Iterators.map(leastAvailableSpaceUsage.entrySet().iterator(), c -> (builder, p) -> {
+        return ChunkedToXContent.builder(params).object("nodes", leastAvailableSpaceUsage.entrySet().iterator(), c -> (builder, p) -> {
             builder.startObject(c.getKey());
             { // node
                 builder.field("node_name", c.getValue().nodeName());
@@ -160,52 +156,32 @@ public Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params params
                 }
                 builder.endObject(); // end "most_available"
             }
-            builder.endObject(); // end $nodename
-            return builder;
-        }),
-            singleChunk(
-                (builder, p) -> builder.endObject() // end "nodes"
-                    .startObject("shard_sizes")
-            ),
-
-            Iterators.map(
+            return builder.endObject(); // end $nodename
+        })
+            .object(
+                "shard_sizes",
                 shardSizes.entrySet().iterator(),
                 c -> (builder, p) -> builder.humanReadableField(c.getKey() + "_bytes", c.getKey(), ByteSizeValue.ofBytes(c.getValue()))
-            ),
-            singleChunk(
-                (builder, p) -> builder.endObject() // end "shard_sizes"
-                    .startObject("shard_data_set_sizes")
-            ),
-            Iterators.map(
+            )
+            .object(
+                "shard_data_set_sizes",
                 shardDataSetSizes.entrySet().iterator(),
                 c -> (builder, p) -> builder.humanReadableField(
                     c.getKey() + "_bytes",
                     c.getKey().toString(),
                     ByteSizeValue.ofBytes(c.getValue())
                 )
-            ),
-            singleChunk(
-                (builder, p) -> builder.endObject() // end "shard_data_set_sizes"
-                    .startObject("shard_paths")
-            ),
-            Iterators.map(dataPath.entrySet().iterator(), c -> (builder, p) -> builder.field(c.getKey().toString(), c.getValue())),
-            singleChunk(
-                (builder, p) -> builder.endObject() // end "shard_paths"
-                    .startArray("reserved_sizes")
-            ),
-            Iterators.map(reservedSpace.entrySet().iterator(), c -> (builder, p) -> {
+            )
+            .object("shard_paths", dataPath.entrySet().iterator(), (xb, c) -> xb.field(c.getKey().toString(), c.getValue()))
+            .array("reserved_sizes", reservedSpace.entrySet().iterator(), c -> (builder, p) -> {
                 builder.startObject();
                 {
                     builder.field("node_id", c.getKey().nodeId);
                     builder.field("path", c.getKey().path);
-                    c.getValue().toXContent(builder, params);
+                    c.getValue().toXContent(builder, p);
                 }
                 return builder.endObject(); // NodeAndPath
-            }),
-
-            endArray() // end "reserved_sizes"
-
-        );
+            });
     }
 
     /**
@@ -314,7 +290,7 @@ public String toString() {
 
     // exposed for tests, computed here rather than exposing all the collections separately
     int getChunkCount() {
-        return leastAvailableSpaceUsage.size() + shardSizes.size() + shardDataSetSizes.size() + dataPath.size() + reservedSpace.size() + 6;
+        return leastAvailableSpaceUsage.size() + shardSizes.size() + shardDataSetSizes.size() + dataPath.size() + reservedSpace.size() + 10;
     }
 
     public record NodeAndShard(String nodeId, ShardId shardId) implements Writeable {

server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamMetadata.java

@@ -17,10 +17,9 @@
 import org.elasticsearch.cluster.NamedDiff;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.collect.ImmutableOpenMap;
-import org.elasticsearch.common.collect.Iterators;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
-import org.elasticsearch.common.xcontent.ChunkedToXContentHelper;
+import org.elasticsearch.common.xcontent.ChunkedToXContent;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.xcontent.ConstructingObjectParser;
 import org.elasticsearch.xcontent.ParseField;
@@ -232,13 +231,10 @@ public static DataStreamMetadata fromXContent(XContentParser parser) throws IOEx
     }
 
     @Override
-    public Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params ignored) {
-        return Iterators.concat(
-            ChunkedToXContentHelper.xContentValuesMap(DATA_STREAM.getPreferredName(), dataStreams),
-            ChunkedToXContentHelper.startObject(DATA_STREAM_ALIASES.getPreferredName()),
-            dataStreamAliases.values().iterator(),
-            ChunkedToXContentHelper.endObject()
-        );
+    public Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params params) {
+        return ChunkedToXContent.builder(params)
+            .object(DATA_STREAM.getPreferredName(), b -> b.appendXContentFields(dataStreams))
+            .xContentObject(DATA_STREAM_ALIASES.getPreferredName(), dataStreamAliases.values().iterator());
     }
 
     @Override