YARN-10976. Fix resource leak due to Files.walk (#3552)

Signed-off-by: Akira Ajisaka <aajisaka@apache.org>

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/resourceplugin/com/nec/VEDeviceDiscoverer.java

@@ -27,6 +27,7 @@ import java.nio.file.Paths;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import org.apache.commons.lang3.mutable.MutableInt;
 import org.apache.hadoop.util.Shell;
@@ -58,11 +59,11 @@ class VEDeviceDiscoverer {
 
   public Set<Device> getDevicesFromPath(String path) throws IOException {
     MutableInt counter = new MutableInt(0);
-
-    return Files.walk(Paths.get(path), 1)
-      .filter(p -> p.toFile().getName().startsWith("veslot"))
-      .map(p -> toDevice(p, counter))
-      .collect(Collectors.toSet());
+    try (Stream<Path> stream = Files.walk(Paths.get(path), 1)) {
+      return stream.filter(p -> p.toFile().getName().startsWith("veslot"))
+            .map(p -> toDevice(p, counter))
+            .collect(Collectors.toSet());
+    }
   }
 
   private Device toDevice(Path p, MutableInt counter) {
@@ -140,4 +141,4 @@ class VEDeviceDiscoverer {
       Function<String[], CommandExecutor> provider) {
     this.commandExecutorProvider = provider;
   }
-}
+}