narendly commented on a change in pull request #788: Implement request
forwarding for ZkRoutingDataWriter
URL: https://github.com/apache/helix/pull/788#discussion_r384859506
##########
File path:
helix-rest/src/main/java/org/apache/helix/rest/metadatastore/ZkMetadataStoreDirectory.java
##########
@@ -42,49 +42,69 @@
/**
+ * NOTE: This is a singleton class. DO NOT EXTEND!
* ZK-based MetadataStoreDirectory that listens on the routing data in routing
ZKs with a update
* callback.
*/
public class ZkMetadataStoreDirectory implements MetadataStoreDirectory,
RoutingDataListener {
private static final Logger LOG =
LoggerFactory.getLogger(ZkMetadataStoreDirectory.class);
- // TODO: enable the line below when implementation is complete
// The following maps' keys represent the namespace
- private final Map<String, MetadataStoreRoutingDataReader>
_routingDataReaderMap;
- private final Map<String, MetadataStoreRoutingDataWriter>
_routingDataWriterMap;
- private final Map<String, MetadataStoreRoutingData> _routingDataMap;
- private final Map<String, String> _routingZkAddressMap;
+ // NOTE: made protected for testing reasons. DO NOT MODIFY!
+ protected final Map<String, MetadataStoreRoutingDataReader>
_routingDataReaderMap;
+ protected final Map<String, MetadataStoreRoutingDataWriter>
_routingDataWriterMap;
+ protected final Map<String, MetadataStoreRoutingData> _routingDataMap;
+ protected final Map<String, String> _routingZkAddressMap;
// <namespace, <realm, <list of sharding keys>> mappings
- private final Map<String, Map<String, List<String>>> _realmToShardingKeysMap;
+ protected final Map<String, Map<String, List<String>>>
_realmToShardingKeysMap;
+
+ private static volatile ZkMetadataStoreDirectory
_zkMetadataStoreDirectoryInstance;
+
+ public static ZkMetadataStoreDirectory getInstance() {
+ if (_zkMetadataStoreDirectoryInstance == null) {
+ synchronized (ZkMetadataStoreDirectory.class) {
+ if (_zkMetadataStoreDirectoryInstance == null) {
+ _zkMetadataStoreDirectoryInstance = new ZkMetadataStoreDirectory();
+ }
+ }
+ }
+
Review comment:
Remove empty line
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