address comments

Author: PradhanPrerak

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/Constants.java

@@ -775,6 +775,12 @@ private Constants() {
       "fs.s3a." + Constants.AWS_SERVICE_IDENTIFIER_STS.toLowerCase()
           + ".signing-algorithm";
 
+  /** Prefix for S3A client-specific properties. */
+  public static final String FS_S3A_CLIENT_PREFIX = "fs.s3a.client.";
+
+  /** Custom headers postfix */
+  public static final String CUSTOM_HEADER_POSTFIX = ".custom.headers";
+
   /**
    * List of custom headers to be set on the service client.
    * Multiple parameters can be used to specify custom headers.
@@ -785,12 +791,12 @@ private Constants() {
    * CustomHeaders {@literal ->} 'Header1=Value1:Value2,Header2=Value1'
    */
   public static final String CUSTOM_HEADERS_STS =
-      "fs.s3a.client." + Constants.AWS_SERVICE_IDENTIFIER_STS.toLowerCase()
-          + ".custom.headers";
+      FS_S3A_CLIENT_PREFIX + Constants.AWS_SERVICE_IDENTIFIER_STS.toLowerCase()
+          + CUSTOM_HEADER_POSTFIX;
 
   public static final String CUSTOM_HEADERS_S3 =
-          "fs.s3a.client." + Constants.AWS_SERVICE_IDENTIFIER_S3.toLowerCase()
-                  + ".custom.headers";
+      FS_S3A_CLIENT_PREFIX + Constants.AWS_SERVICE_IDENTIFIER_S3.toLowerCase()
+          + CUSTOM_HEADER_POSTFIX;
 
   public static final String S3N_FOLDER_SUFFIX = "_$folder$";
   public static final String FS_S3A_BLOCK_SIZE = "fs.s3a.block.size";

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/impl/AWSClientConfig.java

@@ -440,6 +440,7 @@ private static void initRequestHeaders(Configuration conf,
         List<String> headerValues = Arrays.asList(valueString.split(":"));
         clientConfig.putHeader(header, headerValues);
       });
+      LOG.debug("headers for {} client = {}", awsServiceIdentifier, clientConfig.headers());
     }
   }
 

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/impl/TestAwsClientConfig.java

@@ -22,7 +22,6 @@
 import java.time.Duration;
 import java.util.Arrays;
 
-import org.apache.hadoop.util.Lists;
 import org.assertj.core.api.Assertions;
 import org.junit.After;
 import org.junit.Test;
@@ -31,6 +30,7 @@
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.test.AbstractHadoopTestBase;
+import org.apache.hadoop.util.Lists;
 
 import static org.apache.hadoop.fs.s3a.Constants.AWS_SERVICE_IDENTIFIER_S3;
 import static org.apache.hadoop.fs.s3a.Constants.AWS_SERVICE_IDENTIFIER_STS;