narendly commented on a change in pull request #908: Make Helix REST realm-aware
URL: https://github.com/apache/helix/pull/908#discussion_r398066168
##########
File path:
helix-rest/src/main/java/org/apache/helix/rest/server/ServerContext.java
##########
@@ -20,42 +20,67 @@
* under the License.
*/
-import java.util.HashMap;
+import java.io.IOException;
+import java.util.List;
import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
import org.apache.helix.ConfigAccessor;
import org.apache.helix.HelixAdmin;
import org.apache.helix.HelixDataAccessor;
+import org.apache.helix.HelixException;
import org.apache.helix.InstanceType;
-import org.apache.helix.rest.metadatastore.ZkMetadataStoreDirectory;
-import org.apache.helix.zookeeper.datamodel.ZNRecord;
+import org.apache.helix.SystemPropertyKeys;
import org.apache.helix.manager.zk.ZKHelixAdmin;
import org.apache.helix.manager.zk.ZKHelixDataAccessor;
-import org.apache.helix.manager.zk.ZNRecordSerializer;
import org.apache.helix.manager.zk.ZkBaseDataAccessor;
-import org.apache.helix.zookeeper.impl.client.ZkClient;
-import org.apache.helix.zookeeper.api.client.HelixZkClient;
-import org.apache.helix.zookeeper.impl.factory.SharedZkClientFactory;
+import org.apache.helix.msdcommon.exception.InvalidRoutingDataException;
+import org.apache.helix.rest.metadatastore.ZkMetadataStoreDirectory;
+import org.apache.helix.rest.metadatastore.accessor.ZkRoutingDataReader;
import org.apache.helix.task.TaskDriver;
import org.apache.helix.tools.ClusterSetup;
+import org.apache.helix.zookeeper.api.client.HelixZkClient;
+import org.apache.helix.zookeeper.api.client.RealmAwareZkClient;
+import org.apache.helix.zookeeper.datamodel.ZNRecord;
+import org.apache.helix.zookeeper.datamodel.serializer.ZNRecordSerializer;
+import org.apache.helix.zookeeper.impl.client.FederatedZkClient;
+import org.apache.helix.zookeeper.impl.client.ZkClient;
+import org.apache.helix.zookeeper.impl.factory.DedicatedZkClientFactory;
+import org.apache.helix.zookeeper.impl.factory.SharedZkClientFactory;
+import org.apache.helix.zookeeper.util.HttpRoutingDataReader;
+import org.apache.helix.zookeeper.zkclient.IZkChildListener;
+import org.apache.helix.zookeeper.zkclient.IZkDataListener;
+import org.apache.helix.zookeeper.zkclient.IZkStateListener;
import org.apache.helix.zookeeper.zkclient.exception.ZkMarshallingError;
import org.apache.helix.zookeeper.zkclient.serialize.ZkSerializer;
+import org.apache.zookeeper.Watcher;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
-public class ServerContext {
+public class ServerContext implements IZkDataListener, IZkChildListener,
IZkStateListener {
+ private static final Logger LOG =
LoggerFactory.getLogger(ServerContext.class);
+
private final String _zkAddr;
- private HelixZkClient _zkClient;
- private ZKHelixAdmin _zkHelixAdmin;
- private ClusterSetup _clusterSetup;
- private ConfigAccessor _configAccessor;
+ private volatile RealmAwareZkClient _zkClient;
+
+ private volatile ZKHelixAdmin _zkHelixAdmin;
+ private volatile ClusterSetup _clusterSetup;
+ private volatile ConfigAccessor _configAccessor;
// A lazily-initialized base data accessor that reads/writes byte array to ZK
// TODO: Only read (deserialize) is supported at this time. This
baseDataAccessor should support write (serialize) as needs arise
private volatile ZkBaseDataAccessor<byte[]> _byteArrayZkBaseDataAccessor;
// 1 Cluster name will correspond to 1 helix data accessor
private final Map<String, HelixDataAccessor> _helixDataAccessorPool;
// 1 Cluster name will correspond to 1 task driver
private final Map<String, TaskDriver> _taskDriverPool;
Review comment:
I understand your concern and where you're coming from. But it's still
difficult. TaskDriver and ConfigAccessor are different APIs by design.
- TaskDriver/HelixManager/HelixDataAccessor -> only serve 1 single Helix
cluster
- ConfigAccessor/ClusterSetup/etc.. -> can serve many Helix clusters
So we need to keep a pool regardless.
To help you understand:
```
public TaskDriver(HelixManager manager) {
}
@Deprecated
public TaskDriver(RealmAwareZkClient client, String clusterName) {
}
@Deprecated
public TaskDriver(RealmAwareZkClient client, ZkBaseDataAccessor<ZNRecord>
baseAccessor,
String clusterName) {}
@Deprecated
public TaskDriver(HelixAdmin admin, HelixDataAccessor accessor,
ConfigAccessor cfgAccessor,
HelixPropertyStore<ZNRecord> propertyStore, String clusterName) {
this(admin, accessor, propertyStore, clusterName);
}
```
You see that every constructor of TaskDriver takes in a cluster name.
Although TaskDriver does not support any ephemeral operations, by design
it's meant to be a single cluster API.
I think what you wanted to see was to pass in some FederatedZkClient into
TaskDriver and use one TaskDriver for all clusters, but 1) that does not work,
and 2) if we wanted to make that work, that's going to require a lot of code
change in TaskDriver.
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