HADOOP-14617. Add ReflectionUtils.logThreadInfo that accept slf4j logger API.

Contributed by Wenxin He.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/ReflectionUtils.java

@@ -46,6 +46,7 @@ import org.apache.hadoop.io.Writable;
 import org.apache.hadoop.io.serializer.Deserializer;
 import org.apache.hadoop.io.serializer.SerializationFactory;
 import org.apache.hadoop.io.serializer.Serializer;
+import org.slf4j.Logger;
 
 /**
  * General reflection utils
@@ -228,6 +229,35 @@ public class ReflectionUtils {
     }
   }
 
+  /**
+   * Log the current thread stacks at INFO level.
+   * @param log the logger that logs the stack trace
+   * @param title a descriptive title for the call stacks
+   * @param minInterval the minimum time from the last
+   */
+  public static void logThreadInfo(Logger log,
+                                   String title,
+                                   long minInterval) {
+    boolean dumpStack = false;
+    if (log.isInfoEnabled()) {
+      synchronized (ReflectionUtils.class) {
+        long now = Time.now();
+        if (now - previousLogTime >= minInterval * 1000) {
+          previousLogTime = now;
+          dumpStack = true;
+        }
+      }
+      if (dumpStack) {
+        try {
+          ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+          printThreadInfo(new PrintStream(buffer, false, "UTF-8"), title);
+          log.info(buffer.toString(Charset.defaultCharset().name()));
+        } catch (UnsupportedEncodingException ignored) {
+        }
+      }
+    }
+  }
+
   /**
    * Return the correctly-typed {@link Class} of the given object.
    *  

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestReflectionUtils.java

@@ -25,9 +25,14 @@ import java.net.URLClassLoader;
 import java.util.HashMap;
 import java.util.List;
 
+import static org.hamcrest.CoreMatchers.containsString;
 import static org.junit.Assert.*;
+
+import org.apache.hadoop.test.GenericTestUtils.LogCapturer;
 import org.junit.Before;
 import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class TestReflectionUtils {
 
@@ -150,7 +155,19 @@ public class TestReflectionUtils {
     assertTrue("Missing parent method", containsParentMethod);
     assertTrue("Missing child method", containsChildMethod);
   }
-  
+
+  @Test
+  public void testLogThreadInfo() throws Exception {
+    Logger logger = LoggerFactory.getLogger(TestReflectionUtils.class);
+    LogCapturer logCapturer = LogCapturer.captureLogs(logger);
+
+    final String title = "title";
+    ReflectionUtils.logThreadInfo(logger, title, 0L);
+
+    assertThat(logCapturer.getOutput(),
+        containsString("Process Thread Dump: " + title));
+  }
+
   // Used for testGetDeclaredFieldsIncludingInherited
   private class Parent {
     private int parentField;