Add string interning to user and group names

### What changes are proposed in this pull request?

Use `intern()` on frequent strings like user/group names. This should
change the string memory allocation from the heap into the internal
string pool by an extent so we allocate fewer objects (and subsequently
friendly to GC).

### Why are the changes needed?

In a heap analysis I see many duplicate Strings. For example when I run
a cluster on AWS with `ec2-user` as both user and group, I see many
duplicate "ec2-user" strings from a heap analysis:


![image](https://user-images.githubusercontent.com/14806853/147194157-ac1d7d6e-69b6-469f-a9e1-708ee1f72566.png)
My heap size is 15G and 1.7G are allocated to user/group name strings. I
have around 25 million files. Note that the 50K String objects are the
live objects. There should have been many more and GC-ed from the heap.


![image](https://user-images.githubusercontent.com/14806853/147194363-8d206578-b192-4acc-bdf0-41bea12f9701.png)

![image](https://user-images.githubusercontent.com/14806853/147194392-b4ae9ce4-5115-4ec3-bdce-69578fb1a0fa.png)
If I'm reading correctly, each string retains 56 bytes in heap.

Using `intern()` should avoid many new String allocations.
https://blog.codecentric.de/en/2012/03/save-memory-by-using-string-intern-in-java/

### Does this PR introduce any user facing changes?

The string intern table brings in a trade off in CPU time because
there's now an explicit seek overhead. Using `intern()` is not a
no-brainer.


https://blog.codecentric.de/en/2012/03/save-memory-by-using-string-intern-in-java/
This suggests that the default string intern table size has changed to
60013 in Java 8+ so we should be able to put our user/group names in the
intern table without too much seek time overhead, **without extra JVM
options**.

However there are contradicting complaints on performance like
https://stackoverflow.com/a/10628759/4933827 This is from 2017 so maybe
later version java has improved significantly.

This means we need to benchmark the performance with a little care than
just reasoning if interning makes sense or not.

pr-link: Alluxio#14743
change-id: cid-3cef909efbd39c6924c8a6abe5c920f81d248d64

core/common/src/main/java/alluxio/grpc/GrpcUtils.java

@@ -106,8 +106,8 @@ public static AccessControlList fromProto(PAcl pAcl) {
       acl = new AccessControlList();
     }
 
-    acl.setOwningUser(pAcl.getOwner());
-    acl.setOwningGroup(pAcl.getOwningGroup());
+    acl.setOwningUser(pAcl.getOwner().intern());
+    acl.setOwningGroup(pAcl.getOwningGroup().intern());
     acl.setMode((short) pAcl.getMode());
 
     if (pAcl.getEntriesCount() > 0) {

core/common/src/main/java/alluxio/security/authorization/AccessControlList.java

@@ -423,8 +423,8 @@ public static AccessControlList fromStringEntries(String owner, String owningGro
       // when the stringEntries size is 0, it can only be a DefaultAccessControlList
       acl = new DefaultAccessControlList();
     }
-    acl.setOwningUser(owner);
-    acl.setOwningGroup(owningGroup);
+    acl.setOwningUser(owner.intern());
+    acl.setOwningGroup(owningGroup.intern());
 
     for (String stringEntry : stringEntries) {
       AclEntry aclEntry = AclEntry.fromCliString(stringEntry);
@@ -506,8 +506,8 @@ public AccessControlListDeserializer() {
     public AccessControlList deserialize(JsonParser jsonParser,
         DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
       JsonNode node = jsonParser.getCodec().readTree(jsonParser);
-      String owner = node.get(OWNER_FIELD).asText();
-      String owningGroup = node.get(OWNING_GROUP_FIELD).asText();
+      String owner = node.get(OWNER_FIELD).asText().intern();
+      String owningGroup = node.get(OWNING_GROUP_FIELD).asText().intern();
       List<String> stringEntries = new ArrayList<>();
       Iterator<JsonNode> nodeIterator = node.get(STRING_ENTRY_FIELD).elements();
       while (nodeIterator.hasNext()) {

core/common/src/main/java/alluxio/util/proto/ProtoUtils.java

@@ -273,8 +273,8 @@ public static AccessControlList fromProto(Acl.AccessControlList acl) {
     } else {
       ret = new AccessControlList();
     }
-    ret.setOwningUser(acl.getOwningUser());
-    ret.setOwningGroup(acl.getOwningGroup());
+    ret.setOwningUser(acl.getOwningUser().intern());
+    ret.setOwningGroup(acl.getOwningGroup().intern());
 
     if (acl.getIsEmpty()) {
       return ret;

core/server/master/src/main/java/alluxio/master/file/meta/InodeTree.java

@@ -867,8 +867,8 @@ public List<Inode> createPath(RpcContext rpcContext, LockedInodePath inodePath,
         if (context.isMetadataLoad()) {
           // if we are creating the file as a result of loading metadata, the newDir is already
           // persisted, and we got the permissions info from the ufs.
-          newDir.setOwner(context.getOwner())
-              .setGroup(context.getGroup())
+          newDir.setOwner(context.getOwner().intern())
+              .setGroup(context.getGroup().intern())
               .setMode(context.getMode().toShort());
 
           Long operationTimeMs = context.getOperationTimeMs();
@@ -931,8 +931,8 @@ private static void inheritOwnerAndGroupIfEmpty(MutableInode<?> newInode,
     if (ServerConfiguration.getBoolean(PropertyKey.MASTER_METASTORE_INODE_INHERIT_OWNER_AND_GROUP)
         && newInode.getOwner().isEmpty() && newInode.getGroup().isEmpty()) {
       // Inherit owner / group if empty
-      newInode.setOwner(ancestorInode.getOwner());
-      newInode.setGroup(ancestorInode.getGroup());
+      newInode.setOwner(ancestorInode.getOwner().intern());
+      newInode.setGroup(ancestorInode.getGroup().intern());
     }
   }
 
@@ -1233,8 +1233,8 @@ public void syncPersistNewDirectory(MutableInodeDirectory dir)
     dir.setPersistenceState(PersistenceState.TO_BE_PERSISTED);
     syncPersistDirectory(dir).ifPresent(status -> {
       // If the directory already exists in the UFS, update our metadata to match the UFS.
-      dir.setOwner(status.getOwner())
-          .setGroup(status.getGroup())
+      dir.setOwner(status.getOwner().intern())
+          .setGroup(status.getGroup().intern())
           .setMode(status.getMode())
           .setXAttr(status.getXAttr());
 

core/server/master/src/main/java/alluxio/master/file/meta/MutableInode.java

@@ -564,7 +564,7 @@ public void updateFromEntry(UpdateInodeEntry entry) {
       setCreationTimeMs(entry.getCreationTimeMs());
     }
     if (entry.hasGroup() && !entry.getGroup().isEmpty()) {
-      setGroup(entry.getGroup());
+      setGroup(entry.getGroup().intern());
     }
     if (entry.hasLastModificationTimeMs()) {
       setLastModificationTimeMs(entry.getLastModificationTimeMs(),
@@ -584,7 +584,7 @@ public void updateFromEntry(UpdateInodeEntry entry) {
       setName(entry.getName());
     }
     if (entry.hasOwner() && !entry.getOwner().isEmpty()) {
-      setOwner(entry.getOwner());
+      setOwner(entry.getOwner().intern());
     }
     if (entry.hasParentId()) {
       setParentId(entry.getParentId());

core/server/master/src/main/java/alluxio/master/file/meta/MutableInodeDirectory.java

@@ -198,8 +198,8 @@ public static MutableInodeDirectory fromJournalEntry(InodeDirectoryEntry entry)
     } else {
       // Backward compatibility.
       AccessControlList acl = new AccessControlList();
-      acl.setOwningUser(entry.getOwner());
-      acl.setOwningGroup(entry.getGroup());
+      acl.setOwningUser(entry.getOwner().intern());
+      acl.setOwningGroup(entry.getGroup().intern());
       short mode = entry.hasMode() ? (short) entry.getMode() : Constants.DEFAULT_FILE_SYSTEM_MODE;
       acl.setMode(mode);
       ret.mAcl = acl;
@@ -233,8 +233,8 @@ public static MutableInodeDirectory create(long id, long parentId, String name,
         .setName(name)
         .setTtl(context.getTtl())
         .setTtlAction(context.getTtlAction())
-        .setOwner(context.getOwner())
-        .setGroup(context.getGroup())
+        .setOwner(context.getOwner().intern())
+        .setGroup(context.getGroup().intern())
         .setMode(context.getMode().toShort())
         .setAcl(context.getAcl())
         // SetAcl call is also setting default AclEntries

core/server/master/src/main/java/alluxio/master/file/meta/MutableInodeFile.java

@@ -406,8 +406,8 @@ public static MutableInodeFile fromJournalEntry(InodeFileEntry entry) {
     } else {
       // Backward compatibility.
       AccessControlList acl = new AccessControlList();
-      acl.setOwningUser(entry.getOwner());
-      acl.setOwningGroup(entry.getGroup());
+      acl.setOwningUser(entry.getOwner().intern());
+      acl.setOwningGroup(entry.getGroup().intern());
       short mode = entry.hasMode() ? (short) entry.getMode() : Constants.DEFAULT_FILE_SYSTEM_MODE;
       acl.setMode(mode);
       ret.mAcl = acl;
@@ -449,8 +449,8 @@ public static MutableInodeFile create(long blockContainerId, long parentId, Stri
         .setParentId(parentId)
         .setLastModificationTimeMs(context.getOperationTimeMs(), true)
         .setLastAccessTimeMs(context.getOperationTimeMs(), true)
-        .setOwner(context.getOwner())
-        .setGroup(context.getGroup())
+        .setOwner(context.getOwner().intern())
+        .setGroup(context.getGroup().intern())
         .setMode(context.getMode().toShort())
         .setAcl(context.getAcl())
         .setPersistenceState(context.isPersisted() ? PersistenceState.PERSISTED

underfs/hdfs/src/main/java/alluxio/underfs/hdfs/acl/SupportedHdfsAclProvider.java

@@ -55,8 +55,8 @@ public Pair<AccessControlList, DefaultAccessControlList> getAcl(FileSystem hdfs,
     AccessControlList acl = new AccessControlList();
     DefaultAccessControlList defaultAcl = new DefaultAccessControlList();
 
-    acl.setOwningUser(hdfsAcl.getOwner());
-    acl.setOwningGroup(hdfsAcl.getGroup());
+    acl.setOwningUser(hdfsAcl.getOwner().intern());
+    acl.setOwningGroup(hdfsAcl.getGroup().intern());
     defaultAcl.setOwningUser(hdfsAcl.getOwner());
     defaultAcl.setOwningGroup(hdfsAcl.getGroup());
     for (AclEntry entry : hdfsAcl.getEntries()) {