add logger.warn if thread pool size is clipped; fix test failure

core/src/main/java/org/elasticsearch/threadpool/ThreadPool.java

@@ -533,18 +533,19 @@ public class ThreadPool extends AbstractComponent {
         throw new IllegalArgumentException("No type found [" + type + "], for [" + name + "]");
     }
 
-    private int applyHardSizeLimit(String name, int requestedSize) {
+    private int applyHardSizeLimit(String name, int size) {
         int availableProcessors = EsExecutors.boundedNumberOfProcessors(settings);
-        if (name.equals(Names.BULK) || name.equals(Names.INDEX)) {
+        if ((name.equals(Names.BULK) || name.equals(Names.INDEX)) && size > availableProcessors) {
             // We use a hard max size for the indexing pools, because if too many threads enter Lucene's IndexWriter, it means
             // too many segments written, too frequently, too much merging, etc:
-
             // TODO: I would love to be loud here (throw an exception if you ask for a too-big size), but I think this is dangerous
             // because on upgrade this setting could be in cluster state and hard for the user to correct?
-            return Math.min(requestedSize, availableProcessors);
+            logger.warn("requested thread pool size [{}] for [{}] is too large; setting to maximum [{}] instead",
-        } else {
+                        size, name, availableProcessors);
-            return requestedSize;
+            size = availableProcessors;
         }
+
+        return size;
     }
 
     private void updateSettings(Settings settings) {

core/src/test/java/org/elasticsearch/threadpool/UpdateThreadPoolSettingsTests.java

@@ -211,6 +211,14 @@ public class UpdateThreadPoolSettingsTests extends ESTestCase {
         }
     }
 
+    private static int getExpectedThreadPoolSize(Settings settings, String name, int size) {
+        if (name.equals(ThreadPool.Names.BULK) || name.equals(ThreadPool.Names.INDEX)) {
+            return Math.min(size, EsExecutors.boundedNumberOfProcessors(settings));
+        } else {
+            return size;
+        }
+    }
+
     public void testFixedExecutorType() throws InterruptedException {
         String threadPoolName = randomThreadPool(ThreadPool.ThreadPoolType.FIXED);
         ThreadPool threadPool = null;
@@ -225,12 +233,14 @@ public class UpdateThreadPoolSettingsTests extends ESTestCase {
             Settings settings = clusterSettings.applySettings(settingsBuilder()
                     .put("threadpool." + threadPoolName + ".size", "15")
                     .build());
+
+            int expectedSize = getExpectedThreadPoolSize(nodeSettings, threadPoolName, 15);
             assertEquals(info(threadPool, threadPoolName).getThreadPoolType(), ThreadPool.ThreadPoolType.FIXED);
             assertThat(threadPool.executor(threadPoolName), instanceOf(EsThreadPoolExecutor.class));
-            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getCorePoolSize(), equalTo(15));
+            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getCorePoolSize(), equalTo(expectedSize));
-            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getMaximumPoolSize(), equalTo(15));
+            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getMaximumPoolSize(), equalTo(expectedSize));
-            assertThat(info(threadPool, threadPoolName).getMin(), equalTo(15));
+            assertThat(info(threadPool, threadPoolName).getMin(), equalTo(expectedSize));
-            assertThat(info(threadPool, threadPoolName).getMax(), equalTo(15));
+            assertThat(info(threadPool, threadPoolName).getMax(), equalTo(expectedSize));
             // keep alive does not apply to fixed thread pools
             assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getKeepAliveTime(TimeUnit.MINUTES), equalTo(0L));
 
@@ -240,20 +250,23 @@ public class UpdateThreadPoolSettingsTests extends ESTestCase {
             // Make sure keep alive value is not used
             assertThat(info(threadPool, threadPoolName).getKeepAlive(), nullValue());
             // Make sure keep pool size value were reused
-            assertThat(info(threadPool, threadPoolName).getMin(), equalTo(15));
+            assertThat(info(threadPool, threadPoolName).getMin(), equalTo(expectedSize));
-            assertThat(info(threadPool, threadPoolName).getMax(), equalTo(15));
+            assertThat(info(threadPool, threadPoolName).getMax(), equalTo(expectedSize));
             assertThat(threadPool.executor(threadPoolName), instanceOf(EsThreadPoolExecutor.class));
-            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getCorePoolSize(), equalTo(15));
+            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getCorePoolSize(), equalTo(expectedSize));
-            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getMaximumPoolSize(), equalTo(15));
+            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getMaximumPoolSize(), equalTo(expectedSize));
 
             // Change size
             Executor oldExecutor = threadPool.executor(threadPoolName);
             settings = clusterSettings.applySettings(settingsBuilder().put(settings).put("threadpool." + threadPoolName + ".size", "10").build());
+
+            expectedSize = getExpectedThreadPoolSize(nodeSettings, threadPoolName, 10);
+
             // Make sure size values changed
-            assertThat(info(threadPool, threadPoolName).getMax(), equalTo(10));
+            assertThat(info(threadPool, threadPoolName).getMax(), equalTo(expectedSize));
-            assertThat(info(threadPool, threadPoolName).getMin(), equalTo(10));
+            assertThat(info(threadPool, threadPoolName).getMin(), equalTo(expectedSize));
-            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getMaximumPoolSize(), equalTo(10));
+            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getMaximumPoolSize(), equalTo(expectedSize));
-            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getCorePoolSize(), equalTo(10));
+            assertThat(((EsThreadPoolExecutor) threadPool.executor(threadPoolName)).getCorePoolSize(), equalTo(expectedSize));
             // Make sure executor didn't change
             assertEquals(info(threadPool, threadPoolName).getThreadPoolType(), ThreadPool.ThreadPoolType.FIXED);
             assertThat(threadPool.executor(threadPoolName), sameInstance(oldExecutor));