[ML] Prevent stack overflow while copying ML jobs and datafeeds (#36370)

ML jobs and datafeeds wrap collections into their unmodifiable
equivalents in their constructor. However, the copying builder
does not make a copy of some of those collections resulting
in wrapping those again and again. This can eventually result
to stack overflow.

This commit addressed this issue by copying the collections in
question in the copying builder constructor.

Closes #36360

client/rest-high-level/src/main/java/org/elasticsearch/client/ml/datafeed/DatafeedConfig.java

@@ -286,11 +286,11 @@ public Builder(DatafeedConfig config) {
             this.jobId = config.jobId;
             this.queryDelay = config.queryDelay;
             this.frequency = config.frequency;
-            this.indices = config.indices;
-            this.types = config.types;
+            this.indices = config.indices == null ? null : new ArrayList<>(config.indices);
+            this.types = config.types == null ? null : new ArrayList<>(config.types);
             this.query = config.query;
             this.aggregations = config.aggregations;
-            this.scriptFields = config.scriptFields;
+            this.scriptFields = config.scriptFields == null ? null : new ArrayList<>(config.scriptFields);
             this.scrollSize = config.scrollSize;
             this.chunkingConfig = config.chunkingConfig;
         }

client/rest-high-level/src/main/java/org/elasticsearch/client/ml/job/config/Job.java

@@ -28,8 +28,10 @@
 import org.elasticsearch.common.xcontent.XContentBuilder;
 
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Date;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -449,7 +451,7 @@ public Builder(String id) {
         public Builder(Job job) {
             this.id = job.getId();
             this.jobType = job.getJobType();
-            this.groups = job.getGroups();
+            this.groups = new ArrayList<>(job.getGroups());
             this.description = job.getDescription();
             this.analysisConfig = job.getAnalysisConfig();
             this.analysisLimits = job.getAnalysisLimits();
@@ -463,7 +465,7 @@ public Builder(Job job) {
             this.backgroundPersistInterval = job.getBackgroundPersistInterval();
             this.modelSnapshotRetentionDays = job.getModelSnapshotRetentionDays();
             this.resultsRetentionDays = job.getResultsRetentionDays();
-            this.customSettings = job.getCustomSettings();
+            this.customSettings = job.getCustomSettings() == null ? null : new HashMap<>(job.getCustomSettings());
             this.modelSnapshotId = job.getModelSnapshotId();
             this.resultsIndexName = job.getResultsIndexNameNoPrefix();
             this.deleting = job.getDeleting();

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/datafeed/DatafeedConfig.java

@@ -38,6 +38,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -461,14 +462,14 @@ public Builder(DatafeedConfig config) {
             this.jobId = config.jobId;
             this.queryDelay = config.queryDelay;
             this.frequency = config.frequency;
-            this.indices = config.indices;
-            this.types = config.types;
+            this.indices = new ArrayList<>(config.indices);
+            this.types = new ArrayList<>(config.types);
             this.query = config.query;
             this.aggregations = config.aggregations;
-            this.scriptFields = config.scriptFields;
+            this.scriptFields = config.scriptFields == null ? null : new ArrayList<>(config.scriptFields);
             this.scrollSize = config.scrollSize;
             this.chunkingConfig = config.chunkingConfig;
-            this.headers = config.headers;
+            this.headers = new HashMap<>(config.headers);
         }
 
         public void setId(String datafeedId) {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/config/Job.java

@@ -32,6 +32,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -664,7 +665,7 @@ public Builder(Job job) {
             this.id = job.getId();
             this.jobType = job.getJobType();
             this.jobVersion = job.getJobVersion();
-            this.groups = job.getGroups();
+            this.groups = new ArrayList<>(job.getGroups());
             this.description = job.getDescription();
             this.analysisConfig = job.getAnalysisConfig();
             this.analysisLimits = job.getAnalysisLimits();
@@ -678,7 +679,7 @@ public Builder(Job job) {
             this.backgroundPersistInterval = job.getBackgroundPersistInterval();
             this.modelSnapshotRetentionDays = job.getModelSnapshotRetentionDays();
             this.resultsRetentionDays = job.getResultsRetentionDays();
-            this.customSettings = job.getCustomSettings();
+            this.customSettings = job.getCustomSettings() == null ? null : new HashMap<>(job.getCustomSettings());
             this.modelSnapshotId = job.getModelSnapshotId();
             this.resultsIndexName = job.getResultsIndexNameNoPrefix();
             this.deleting = job.isDeleting();

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/datafeed/DatafeedConfigTests.java

@@ -6,7 +6,6 @@
 package org.elasticsearch.xpack.core.ml.datafeed;
 
 import com.carrotsearch.randomizedtesting.generators.CodepointSetGenerator;
-
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -490,6 +489,13 @@ public void testDefaultFrequency_GivenAggregationsWithHistogramInterval_1_Hour()
         assertEquals(TimeValue.timeValueHours(1), datafeed.defaultFrequency(TimeValue.timeValueHours(12)));
     }
 
+    public void testCopyingDatafeedDoesNotCauseStackOverflow() {
+        DatafeedConfig datafeed = createTestInstance();
+        for (int i = 0; i < 100000; i++) {
+            datafeed = new DatafeedConfig.Builder(datafeed).build();
+        }
+    }
+
     public static String randomValidDatafeedId() {
         CodepointSetGenerator generator =  new CodepointSetGenerator("abcdefghijklmnopqrstuvwxyz".toCharArray());
         return generator.ofCodePointsLength(random(), 10, 10);

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/job/config/JobTests.java

@@ -580,6 +580,13 @@ public void testEarliestValidTimestamp_GivenDataCountsAndLatency() {
         assertThat(builder.build().earliestValidTimestamp(dataCounts), equalTo(123455789L));
     }
 
+    public void testCopyingJobDoesNotCauseStackOverflow() {
+        Job job = createRandomizedJob();
+        for (int i = 0; i < 100000; i++) {
+            job = new Job.Builder(job).build();
+        }
+    }
+
     public static Job.Builder buildJobBuilder(String id, Date date) {
         Job.Builder builder = new Job.Builder(id);
         builder.setCreateTime(date);