[SPARK-3797] Minor addendum to Yarn shuffle service

I did not realize there was a `network.util.JavaUtils` when I wrote this code. This PR moves the `ByteBuffer` string conversion to the appropriate place. I tested the changes on a stable yarn cluster.

Author: Andrew Or <andrew@databricks.com>

Closes #3144 from andrewor14/yarn-shuffle-util and squashes the following commits:

b6c08bf [Andrew Or] Remove unused import
94e205c [Andrew Or] Use netty Unpooled
85202a5 [Andrew Or] Use guava Charsets
057135b [Andrew Or] Reword comment
adf186d [Andrew Or] Move byte buffer String conversion logic to JavaUtils

2 files changed, 22 insertions, 22 deletions

diff --git a/network/common/src/main/java/org/apache/spark/network/util/JavaUtils.java b/network/common/src/main/java/org/apache/spark/network/util/JavaUtils.java
index 40b71b0c87..2856d1c8c9 100644
--- a/network/common/src/main/java/org/apache/spark/network/util/JavaUtils.java
+++ b/network/common/src/main/java/org/apache/spark/network/util/JavaUtils.java
@@ -17,6 +17,8 @@
 
 package org.apache.spark.network.util;
 
+import java.nio.ByteBuffer;
+
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.Closeable;
@@ -25,6 +27,8 @@ import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 
 import com.google.common.io.Closeables;
+import com.google.common.base.Charsets;
+import io.netty.buffer.Unpooled;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -73,4 +77,20 @@ public class JavaUtils {
     int hash = obj.hashCode();
     return hash != Integer.MIN_VALUE ? Math.abs(hash) : 0;
   }
+
+  /**
+   * Convert the given string to a byte buffer. The resulting buffer can be
+   * converted back to the same string through {@link #bytesToString(ByteBuffer)}.
+   */
+  public static ByteBuffer stringToBytes(String s) {
+    return Unpooled.wrappedBuffer(s.getBytes(Charsets.UTF_8)).nioBuffer();
+  }
+
+  /**
+   * Convert the given byte buffer to a string. The resulting string can be
+   * converted back to the same byte buffer through {@link #stringToBytes(String)}.
+   */
+  public static String bytesToString(ByteBuffer b) {
+    return Unpooled.wrappedBuffer(b).toString(Charsets.UTF_8);
+  }
 }
diff --git a/network/shuffle/src/main/java/org/apache/spark/network/sasl/ShuffleSecretManager.java b/network/shuffle/src/main/java/org/apache/spark/network/sasl/ShuffleSecretManager.java
index e66c4af0f1..351c7930a9 100644
--- a/network/shuffle/src/main/java/org/apache/spark/network/sasl/ShuffleSecretManager.java
+++ b/network/shuffle/src/main/java/org/apache/spark/network/sasl/ShuffleSecretManager.java
@@ -19,13 +19,13 @@ package org.apache.spark.network.sasl;
 
 import java.lang.Override;
 import java.nio.ByteBuffer;
-import java.nio.charset.Charset;
 import java.util.concurrent.ConcurrentHashMap;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import org.apache.spark.network.sasl.SecretKeyHolder;
+import org.apache.spark.network.util.JavaUtils;
 
 /**
  * A class that manages shuffle secret used by the external shuffle service.
@@ -34,30 +34,10 @@ public class ShuffleSecretManager implements SecretKeyHolder {
   private final Logger logger = LoggerFactory.getLogger(ShuffleSecretManager.class);
   private final ConcurrentHashMap<String, String> shuffleSecretMap;
 
-  private static final Charset UTF8_CHARSET = Charset.forName("UTF-8");
-
   // Spark user used for authenticating SASL connections
   // Note that this must match the value in org.apache.spark.SecurityManager
   private static final String SPARK_SASL_USER = "sparkSaslUser";
 
-  /**
-   * Convert the given string to a byte buffer. The resulting buffer can be converted back to
-   * the same string through {@link #bytesToString(ByteBuffer)}. This is used if the external
-   * shuffle service represents shuffle secrets as bytes buffers instead of strings.
-   */
-  public static ByteBuffer stringToBytes(String s) {
-    return ByteBuffer.wrap(s.getBytes(UTF8_CHARSET));
-  }
-
-  /**
-   * Convert the given byte buffer to a string. The resulting string can be converted back to
-   * the same byte buffer through {@link #stringToBytes(String)}. This is used if the external
-   * shuffle service represents shuffle secrets as bytes buffers instead of strings.
-   */
-  public static String bytesToString(ByteBuffer b) {
-    return new String(b.array(), UTF8_CHARSET);
-  }
-
   public ShuffleSecretManager() {
     shuffleSecretMap = new ConcurrentHashMap<String, String>();
   }
@@ -80,7 +60,7 @@ public class ShuffleSecretManager implements SecretKeyHolder {
    * Register an application with its secret specified as a byte buffer.
    */
   public void registerApp(String appId, ByteBuffer shuffleSecret) {
-    registerApp(appId, bytesToString(shuffleSecret));
+    registerApp(appId, JavaUtils.bytesToString(shuffleSecret));
   }
 
   /**