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Posted to reviews@helix.apache.org by GitBox <gi...@apache.org> on 2020/07/29 07:39:02 UTC
[GitHub] [helix] narendly commented on a change in pull request #1178: Feature: ZooScalability Improvements
narendly commented on a change in pull request #1178:
URL: https://github.com/apache/helix/pull/1178#discussion_r462066464
##########
File path: helix-core/src/main/java/org/apache/helix/manager/zk/GenericBaseDataAccessorBuilder.java
##########
@@ -83,7 +82,7 @@ protected RealmAwareZkClient createZkClient(RealmAwareZkClient.RealmMode realmMo
case MULTI_REALM:
try {
zkClient = new FederatedZkClient(connectionConfig, clientConfig);
- } catch (IOException | InvalidRoutingDataException e) {
+ } catch (InvalidRoutingDataException e) {
Review comment:
It was removed from the signature. We don't throw it anymore. It will be thrown in the form of a MultiZkException, and will be a RuntimeException, not a typed exception.
##########
File path: zookeeper-api/src/main/java/org/apache/helix/zookeeper/api/client/RealmAwareZkClient.java
##########
@@ -486,6 +500,13 @@ private void validate() {
throw new IllegalArgumentException(
"RealmAwareZkConnectionConfig.Builder: ZK sharding key must be set on single-realm mode!");
}
+ if ((_routingDataSourceEndpoint == null && _routingDataSourceType != null) || (
+ _routingDataSourceEndpoint != null && _routingDataSourceType == null)) {
+ // For routing data source type and endpoint, if one is set and not the other, it is invalid
Review comment:
If nothing is set, it will try to use the default MSDS endpoint, which is provided in System Properties.
##########
File path: zookeeper-api/src/main/java/org/apache/helix/zookeeper/constant/RoutingSystemPropertyKeys.java
##########
@@ -0,0 +1,38 @@
+package org.apache.helix.zookeeper.constant;
+
+/*
+ * 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.
+ */
+
+/**
+ * This class contains various routing-related system property keys for multi-zk clients.
+ */
+public class RoutingSystemPropertyKeys {
+
+ /**
+ * If enabled, FederatedZkClient (multiZkClient) will invalidate the cached routing data and
+ * re-read the routing data from the routing data source upon ZK path sharding key cache miss.
+ */
+ public static final String UPDATE_ROUTING_DATA_ON_CACHE_MISS =
+ "update.routing.data.on.cache.miss.enabled";
Review comment:
I can rename this and put "routing" in front.
##########
File path: zookeeper-api/src/main/java/org/apache/helix/zookeeper/routing/HttpZkFallbackRoutingDataReader.java
##########
@@ -0,0 +1,81 @@
+package org.apache.helix.zookeeper.routing;
+
+/*
+ * 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.
+ */
+
+import java.util.List;
+import java.util.Map;
+
+import com.google.common.collect.ImmutableMap;
+import org.apache.helix.zookeeper.constant.RoutingDataReaderType;
+import org.apache.helix.zookeeper.exception.MultiZkException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+ * HTTP and ZK-based RoutingDataReader that first tries an HTTP call to MSDS and upon failure,
+ * falls back to ZK for routing data.
+ * HttpZkFallbackRoutingDataReader does not maintain a ZK connection - it establishes for reading
+ * and closes it right away.
+ */
+public class HttpZkFallbackRoutingDataReader implements RoutingDataReader {
Review comment:
The implementations of RoutingDataReader are supposed to be stateless and to be garbage-collected after use. So we should not maintain states. The Javadoc makes that clear.
For example, we don't want to hold onto a ZkFallbackRoutingDataReader since that would mean we hold onto an active ZK connection. We only want a RoutingDataReader instance at initialization, once.
##########
File path: zookeeper-api/src/main/java/org/apache/helix/zookeeper/routing/HttpZkFallbackRoutingDataReader.java
##########
@@ -0,0 +1,81 @@
+package org.apache.helix.zookeeper.routing;
+
+/*
+ * 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.
+ */
+
+import java.util.List;
+import java.util.Map;
+
+import com.google.common.collect.ImmutableMap;
+import org.apache.helix.zookeeper.constant.RoutingDataReaderType;
+import org.apache.helix.zookeeper.exception.MultiZkException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+ * HTTP and ZK-based RoutingDataReader that first tries an HTTP call to MSDS and upon failure,
+ * falls back to ZK for routing data.
+ * HttpZkFallbackRoutingDataReader does not maintain a ZK connection - it establishes for reading
+ * and closes it right away.
+ */
+public class HttpZkFallbackRoutingDataReader implements RoutingDataReader {
Review comment:
The implementations of RoutingDataReader are supposed to be stateless and to be garbage-collected after use. So we should not maintain states. The Javadoc makes that clear.
For example, we don't want to hold onto a ZkFallbackRoutingDataReader since that would mean we hold onto an active ZK connection. We only want a RoutingDataReader instance at initialization, once.
Extending it complicates the design, and you can ask a question of which one it should extend, and you can never do so consistently for other implementations. For that reason, I prefer composition over inheritance.
##########
File path: zookeeper-api/src/main/java/org/apache/helix/zookeeper/routing/ZkRoutingDataReader.java
##########
@@ -0,0 +1,83 @@
+package org.apache.helix.zookeeper.routing;
+
+/*
+ * 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.
+ */
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.helix.msdcommon.constant.MetadataStoreRoutingConstants;
+import org.apache.helix.zookeeper.datamodel.ZNRecord;
+import org.apache.helix.zookeeper.datamodel.serializer.ZNRecordSerializer;
+import org.apache.helix.zookeeper.exception.MultiZkException;
+import org.apache.helix.zookeeper.impl.client.ZkClient;
+import org.apache.helix.zookeeper.zkclient.exception.ZkNoNodeException;
+
+
+/**
+ * Zk-based RoutingDataReader that establishes a ZK connection to the routing ZK to fetch routing
+ * data.
+ * The reading of routing data by nature should only be performed in cases of a Helix client
+ * initialization or routing data reset. That means we do not have to maintain an active ZK
+ * connection. To minimize the number of client-side ZK connections, ZkRoutingDataReader establishes
+ * a ZK session temporarily only to read from ZK afresh and closes sessions upon read completion.
+ */
+public class ZkRoutingDataReader implements RoutingDataReader {
+
+ /**
+ * Returns a map form of metadata store routing data.
+ * The map fields stand for metadata store realm address (key), and a corresponding list of ZK
+ * path sharding keys (key).
+ * @param endpoint
+ * @return
+ */
+ @Override
+ public Map<String, List<String>> getRawRoutingData(String endpoint) {
+ ZkClient zkClient =
+ new ZkClient.Builder().setZkServer(endpoint).setZkSerializer(new ZNRecordSerializer())
+ .build();
Review comment:
If this throws an exception, we should let it throw the exception and not proceed. We should fail early.
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