Skip ColumnFamilyStore#topPartitions initialization when client or tool mode

This commit skips the initialization of `topPartitions` in `org.apache.cassandra.db.ColumnFamilyStore`
when running in client or tool mode. The `TopPartitionTracker` class will attempt to query the system
keyspace, which when running in client or tool mode will not be part of the KeyspaceMetadata. This
causes a warning to be printed out with a stacktrace that can be misleading. The warning is similar to
this:

```
WARN org.apache.cassandra.db.SystemKeyspace: Could not load stored top SIZES partitions for ...
org.apache.cassandra.db.KeyspaceNotDefinedException: keyspace system does not exist
        at org.apache.cassandra.schema.Schema.validateTable(Schema.java:xxx) ~[?:?]
        at org.apache.cassandra.cql3.statements.SelectStatement$RawStatement.prepare(SelectStatement.java:xxx) ~[?:?]
        at org.apache.cassandra.cql3.statements.SelectStatement$RawStatement.prepare(SelectStatement.java:xxx) ~[?:?]
        at org.apache.cassandra.cql3.statements.SelectStatement$RawStatement.prepare(SelectStatement.java:xxx) ~[?:?]
        at org.apache.cassandra.cql3.QueryProcessor.parseAndPrepare(QueryProcessor.java:xxx) ~[?:?]
        ...
```

In this commit, we check whether we run in client or tool mode, and skip initialization
of `topPartitions` in those cases.

Patch by Francisco Guerrero; Reviewed by Dinesh Joshi, Yifan Cai for CASSANDRA-18697

CHANGES.txt

@@ -1,4 +1,5 @@
 4.1.4
+ * Skip ColumnFamilyStore#topPartitions initialization when client or tool mode (CASSANDRA-18697)
 Merged from 4.0:
  * Fix BulkLoader ignoring cipher suites options (CASSANDRA-18582)
  * Migrate Python optparse to argparse (CASSANDRA-17914)

src/java/org/apache/cassandra/db/ColumnFamilyStore.java

@@ -549,7 +549,7 @@ public class ColumnFamilyStore implements ColumnFamilyStoreMBean, Memtable.Owner
         repairManager = new CassandraTableRepairManager(this);
         sstableImporter = new SSTableImporter(this);
 
-        if (SchemaConstants.isSystemKeyspace(keyspace.getName()))
+        if (DatabaseDescriptor.isClientOrToolInitialized() || SchemaConstants.isSystemKeyspace(keyspace.getName()))
             topPartitions = null;
         else
             topPartitions = new TopPartitionTracker(metadata());

test/unit/org/apache/cassandra/db/ColumnFamilyStoreClientModeTest.java

@@ -0,0 +1,95 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.cassandra.db;
+
+import java.io.IOException;
+import java.util.UUID;
+
+import org.apache.commons.lang3.ArrayUtils;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import org.apache.cassandra.config.DatabaseDescriptor;
+import org.apache.cassandra.cql3.statements.schema.CreateTableStatement;
+import org.apache.cassandra.dht.Murmur3Partitioner;
+import org.apache.cassandra.locator.SimpleSnitch;
+import org.apache.cassandra.schema.KeyspaceMetadata;
+import org.apache.cassandra.schema.KeyspaceParams;
+import org.apache.cassandra.schema.Schema;
+import org.apache.cassandra.schema.SchemaTransformations;
+import org.apache.cassandra.schema.TableId;
+import org.apache.cassandra.schema.TableMetadata;
+import org.apache.cassandra.schema.TableMetadataRef;
+import org.apache.cassandra.schema.Types;
+import org.apache.cassandra.service.ClientState;
+
+import static org.apache.cassandra.cql3.CQLTester.KEYSPACE;
+import static org.apache.cassandra.cql3.QueryProcessor.parseStatement;
+import static org.junit.Assert.assertNull;
+
+/**
+ * Unit tests for {@link ColumnFamilyStore} when the library is running as tool
+ * or client mode.
+ */
+public class ColumnFamilyStoreClientModeTest
+{
+    public static final String TABLE = "test1";
+
+    @ClassRule
+    public static TemporaryFolder tempFolder = new TemporaryFolder();
+
+    @BeforeClass
+    public static void setUpClass()
+    {
+        DatabaseDescriptor.clientInitialization();
+        DatabaseDescriptor.setEndpointSnitch(new SimpleSnitch());
+        DatabaseDescriptor.getRawConfig().memtable_flush_writers = 1;
+        DatabaseDescriptor.getRawConfig().local_system_data_file_directory = tempFolder.toString();
+        DatabaseDescriptor.getRawConfig().partitioner = "Murmur3Partitioner";
+        DatabaseDescriptor.applyPartitioner();
+    }
+
+    @Test
+    public void testTopPartitionsAreNotInitialized() throws IOException
+    {
+        CreateTableStatement.Raw schemaStatement = parseStatement("CREATE TABLE " + KEYSPACE + '.' + TABLE + " (a int, b text, PRIMARY KEY (a))", CreateTableStatement.Raw.class, "CREATE TABLE");
+
+        Schema.instance.transform(SchemaTransformations.addKeyspace(KeyspaceMetadata.create(KEYSPACE, KeyspaceParams.simple(1)), true));
+
+        Types types = Types.rawBuilder(KEYSPACE).build();
+        Schema.instance.transform(SchemaTransformations.addTypes(types, true));
+
+        ClientState state = ClientState.forInternalCalls(KEYSPACE);
+        CreateTableStatement statement = schemaStatement.prepare(state);
+        statement.validate(state);
+
+        TableMetadata tableMetadata = statement.builder(types)
+                                               .id(TableId.fromUUID(UUID.nameUUIDFromBytes(ArrayUtils.addAll(schemaStatement.keyspace().getBytes(), schemaStatement.table().getBytes()))))
+                                               .partitioner(Murmur3Partitioner.instance)
+                                               .build();
+        Keyspace.setInitialized();
+        Directories directories = new Directories(tableMetadata, new Directories.DataDirectory[]{ new Directories.DataDirectory(new org.apache.cassandra.io.util.File(tempFolder.newFolder("datadir"))) });
+        Keyspace ks = Keyspace.openWithoutSSTables(KEYSPACE);
+        ColumnFamilyStore cfs = ColumnFamilyStore.createColumnFamilyStore(ks, TABLE, TableMetadataRef.forOfflineTools(tableMetadata), directories, false, false, true);
+
+        assertNull(cfs.topPartitions);
+    }
+}