Deprecate setting processors to more than available

server/src/main/java/org/elasticsearch/common/util/concurrent/EsExecutors.java

@@ -19,8 +19,10 @@
 
 package org.elasticsearch.common.util.concurrent;
 
+import org.apache.logging.log4j.LogManager;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.common.SuppressForbidden;
+import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Setting.Property;
 import org.elasticsearch.common.settings.Settings;
@@ -46,12 +48,27 @@
 
 public class EsExecutors {
 
+    private static final DeprecationLogger deprecationLogger = new DeprecationLogger(LogManager.getLogger(EsExecutors.class));
+
     /**
-     * Settings key to manually set the number of available processors.
-     * This is used to adjust thread pools sizes etc. per node.
+     * Setting to manually set the number of available processors. This setting is used to adjust thread pool sizes per node.
      */
-    public static final Setting<Integer> PROCESSORS_SETTING =
-        Setting.intSetting("processors", Runtime.getRuntime().availableProcessors(), 1, Property.NodeScope);
+    public static final Setting<Integer> PROCESSORS_SETTING = new Setting<>(
+        "processors",
+        s -> Integer.toString(Runtime.getRuntime().availableProcessors()),
+        s -> {
+            final int value = Setting.parseInt(s, 1, "processors");
+            final int availableProcessors = Runtime.getRuntime().availableProcessors();
+            if (value > availableProcessors) {
+                deprecationLogger.deprecatedAndMaybeLog(
+                    "processors",
+                    "setting processors to value [{}] which is more than available processors [{}] is deprecated",
+                    value,
+                    availableProcessors);
+            }
+            return value;
+        },
+        Property.NodeScope);
 
     /**
      * Returns the number of available processors. Defaults to

test/framework/src/main/java/org/elasticsearch/test/InternalTestCluster.java

@@ -148,6 +148,7 @@
 import static org.elasticsearch.test.ESTestCase.assertBusy;
 import static org.elasticsearch.test.ESTestCase.awaitBusy;
 import static org.elasticsearch.test.ESTestCase.randomFrom;
+import static org.elasticsearch.test.ESTestCase.randomIntBetween;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThan;
 import static org.hamcrest.Matchers.greaterThanOrEqualTo;
@@ -450,7 +451,7 @@ private static Settings getRandomNodeSettings(long seed) {
             builder.put(SearchService.DEFAULT_KEEPALIVE_SETTING.getKey(), timeValueSeconds(100 + random.nextInt(5 * 60)).getStringRep());
         }
 
-        builder.put(EsExecutors.PROCESSORS_SETTING.getKey(), 1 + random.nextInt(3));
+        builder.put(EsExecutors.PROCESSORS_SETTING.getKey(), 1 + random.nextInt(Math.min(4, Runtime.getRuntime().availableProcessors())));
         if (random.nextBoolean()) {
             if (random.nextBoolean()) {
                 builder.put("indices.fielddata.cache.size", 1 + random.nextInt(1000), ByteSizeUnit.MB);

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/Watcher.java

@@ -515,11 +515,13 @@ public List<ExecutorBuilder<?>> getExecutorBuilders(final Settings settings) {
      * @param settings The current settings
      * @return A number between 5 and the number of processors
      */
-    static int getWatcherThreadPoolSize(Settings settings) {
-        boolean isDataNode = Node.NODE_DATA_SETTING.get(settings);
+    static int getWatcherThreadPoolSize(final Settings settings) {
+        return getWatcherThreadPoolSize(Node.NODE_DATA_SETTING.get(settings), EsExecutors.numberOfProcessors(settings));
+    }
+
+    static int getWatcherThreadPoolSize(final boolean isDataNode, final int numberOfProcessors) {
         if (isDataNode) {
-            int numberOfProcessors = EsExecutors.numberOfProcessors(settings);
-            long size = Math.max(Math.min(5 * numberOfProcessors, 50), numberOfProcessors);
+            final long size = Math.max(Math.min(5 * numberOfProcessors, 50), numberOfProcessors);
             return Math.toIntExact(size);
         } else {
             return 1;

x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/WatcherPluginTests.java

@@ -86,23 +86,19 @@ public void testWatcherDisabledTests() throws Exception {
 
     public void testThreadPoolSize() {
         // old calculation was 5 * number of processors
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 1).build()), is(5));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 2).build()), is(10));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 4).build()), is(20));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 8).build()), is(40));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 9).build()), is(45));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 10).build()), is(50));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 16).build()), is(50));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 24).build()), is(50));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 50).build()), is(50));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 51).build()), is(51));
-        assertThat(Watcher.getWatcherThreadPoolSize(Settings.builder().put("processors", 96).build()), is(96));
-
-        Settings noDataNodeSettings = Settings.builder()
-                .put("processors", scaledRandomIntBetween(1, 100))
-                .put("node.data", false)
-                .build();
-        assertThat(Watcher.getWatcherThreadPoolSize(noDataNodeSettings), is(1));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 1), is(5));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 2), is(10));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 4), is(20));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 8), is(40));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 9), is(45));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 10), is(50));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 16), is(50));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 24), is(50));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 50), is(50));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 51), is(51));
+        assertThat(Watcher.getWatcherThreadPoolSize(true, 96), is(96));
+
+        assertThat(Watcher.getWatcherThreadPoolSize(false, scaledRandomIntBetween(1, 100)), is(1));
     }
 
     public void testReload() {