IMPALA-14502: Not tracking metrics in IncompleteTable

Tables that are in unloaded state are represented as IncompleteTable.
Table level metrics of them won't be used at all but occupy around 7KB
of memory for each table. This is a significant amount comparing to the
table name strings.

This patch skips initializing these metrics for IncompleteTable to save
memory usage. This reduces the initial memory requirement to launch
catalogd.

To avoid other codes unintentionally add new metrics to IncompleteTable,
overrides all Table methods that use metrics_ to return simple results,
e.g. IncompleteTable.getMedianTableLoadingTime() always returns 0.

IncompleteTable.getMetrics() shouldn't be used. Added a Precondition
check for this.

Tests:
 - Verified in a heap dump file after loading 1.3M IncompleteTables that
   the heap usage reduces to 2GB and only few instances of
   com.codahale.metrics.Timer are created. Previously catalogd OOM in a
   heap size of 18GB when running global IM, and the number of
   com.codahale.metrics.Timer instances is similar to the number of
   IncompleteTables.
 - Passed CORE tests.

Change-Id: If0fcfeab99bbfbefe618d0abf7f2482a0cc5ef9f
Reviewed-on: http://gerrit.cloudera.org:8080/23547
Reviewed-by: Riza Suminto <riza.suminto@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Reviewed-by: Michael Smith <michael.smith@cloudera.com>

fe/src/main/java/org/apache/impala/catalog/IncompleteTable.java

@@ -26,6 +26,7 @@ import org.apache.hadoop.hive.metastore.IMetaStoreClient;
 
 import org.apache.impala.common.ImpalaException;
 import org.apache.impala.common.JniUtil;
+import org.apache.impala.common.Metrics;
 import org.apache.impala.thrift.TCatalogObjectType;
 import org.apache.impala.thrift.TErrorCode;
 import org.apache.impala.thrift.TGetPartialCatalogObjectRequest;
@@ -217,4 +218,49 @@ public class IncompleteTable extends Table implements FeIncompleteTable {
     Throwables.propagateIfPossible(cause_, TableLoadingException.class);
     throw new TableLoadingException(cause_.getMessage());
   }
+
+  /**
+   * Don't initialize any metrics to save memory space.
+   */
+  @Override
+  public void initMetrics() {}
+
+  @Override
+  public Metrics getMetrics() {
+    Preconditions.checkState(false, "getMetrics() on IncompleteTable shouldn't be used");
+    return null;
+  }
+
+  @Override
+  public long getMedianTableLoadingTime() { return 0; }
+
+  @Override
+  public long getMaxTableLoadingTime() { return 0; }
+
+  @Override
+  public long get75TableLoadingTime() { return 0; }
+
+  @Override
+  public long get95TableLoadingTime() { return 0; }
+
+  @Override
+  public long get99TableLoadingTime() { return 0; }
+
+  @Override
+  public long getTableLoadingCounts() { return 0; }
+
+  @Override
+  public void updateHMSLoadTableSchemaTime(long hmsLoadTimeNS) {}
+
+  @Override
+  public boolean removeFromVersionsForInflightEvents(
+      boolean isInsertEvent, long versionNumber) {
+    return false;
+  }
+
+  @Override
+  public boolean addToVersionsForInflightEvents(
+      boolean isInsertEvent, long versionNumber) {
+    return false;
+  }
 }

fe/src/main/java/org/apache/impala/catalog/events/MetastoreEvents.java

@@ -1608,7 +1608,7 @@ public class MetastoreEvents {
     protected void process() throws MetastoreNotificationException, CatalogException {
       Timer.Context context = null;
       org.apache.impala.catalog.Table tbl = catalog_.getTableNoThrow(dbName_, tblName_);
-      if (tbl != null) {
+      if (tbl != null && !(tbl instanceof IncompleteTable)) {
         context = tbl.getMetrics().getTimer(TBL_EVENTS_PROCESS_DURATION).time();
       }
       try {

fe/src/main/java/org/apache/impala/catalog/events/RenameTableBarrierEvent.java

@@ -23,6 +23,7 @@ import com.google.common.base.Preconditions;
 
 import org.apache.impala.catalog.CatalogException;
 import org.apache.impala.catalog.Db;
+import org.apache.impala.catalog.IncompleteTable;
 import org.apache.impala.catalog.Table;
 import org.apache.impala.catalog.events.MetastoreEvents.DerivedMetastoreEventContext;
 import org.apache.impala.catalog.events.MetastoreEvents.DerivedMetastoreTableEvent;
@@ -198,7 +199,7 @@ public class RenameTableBarrierEvent extends DerivedMetastoreTableEvent {
     Db db = catalog_.getDb(getDbName());
     Table table = null;
     if (db != null) table = db.getTable(getTableName());
-    if (table != null) {
+    if (table != null && !(table instanceof IncompleteTable)) {
       context = table.getMetrics().getTimer(TBL_EVENTS_PROCESS_DURATION).time();
     }
     String fqTableName = getFullyQualifiedTblName();