HDFS-9187. Fix null pointer error in Globber when FS was not constructed via FileSystem#createFileSystem (cmccabe)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileSystem.java

@@ -129,12 +129,6 @@ public abstract class FileSystem extends Configured implements Closeable {
   
   boolean resolveSymlinks;
 
-  private Tracer tracer;
-
-  protected final Tracer getTracer() {
-    return tracer;
-  }
-
   /**
    * This method adds a file system for testing so that we can find it later. It
    * is only for testing.
@@ -2712,7 +2706,6 @@ public abstract class FileSystem extends Configured implements Closeable {
     try {
       Class<?> clazz = getFileSystemClass(uri.getScheme(), conf);
       FileSystem fs = (FileSystem)ReflectionUtils.newInstance(clazz, conf);
-      fs.tracer = tracer;
       fs.initialize(uri, conf);
       return fs;
     } finally {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/Globber.java

@@ -47,7 +47,7 @@ class Globber {
     this.fc = null;
     this.pathPattern = pathPattern;
     this.filter = filter;
-    this.tracer = fs.getTracer();
+    this.tracer = FsTracer.get(fs.getConf());
   }
 
   public Globber(FileContext fc, Path pathPattern, PathFilter filter) {

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/tracing/TestTraceUtils.java

@@ -18,8 +18,13 @@
 package org.apache.hadoop.tracing;
 
 import static org.junit.Assert.assertEquals;
+
+import java.net.URI;
 import java.util.LinkedList;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.LocalFileSystem;
+import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.tracing.SpanReceiverInfo.ConfigurationPair;
 import org.apache.htrace.core.HTraceConfiguration;
 import org.junit.Test;
@@ -50,4 +55,17 @@ public class TestTraceUtils {
     HTraceConfiguration wrapped = TraceUtils.wrapHadoopConf(TEST_PREFIX, conf, extraConfig);
     assertEquals(newValue, wrapped.get(key));
   }
+
+  /**
+   * Test tracing the globber.  This is a regression test for HDFS-9187.
+   */
+  @Test
+  public void testTracingGlobber() throws Exception {
+    // Bypass the normal FileSystem object creation path by just creating an
+    // instance of a subclass.
+    FileSystem fs = new LocalFileSystem();
+    fs.initialize(new URI("file:///"), new Configuration());
+    fs.globStatus(new Path("/"));
+    fs.close();
+  }
 }