parakhnr commented on code in PR #2488: URL: https://github.com/apache/helix/pull/2488#discussion_r1195465430
########## meta-client/src/main/java/org/apache/helix/metaclient/recipes/leaderelection/LeaderElectionClient.java: ########## @@ -0,0 +1,125 @@ +package org.apache.helix.metaclient.recipes.leaderelection; + +/* + * 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 org.apache.helix.metaclient.api.MetaClientInterface; +import org.apache.helix.metaclient.factories.MetaClientConfig; + + +/** + * LeaderElectionClient does distributed leader election using CRUD and change notification APIs + * provided by underlying metadata client. Leader election config can provide many + * configs like base path for all participating nodes, sync/async mode, TTL etc. + * + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + * All participants wanted to be elected as leader joins a pool + * LeaderElection client maintains an active leader, by monitoring liveness of current leader and + * re-elect if needed and user no need to call elect or re-elect explicitly. + * This LeaderElection client will notify registered listeners for any leadership change. + */ +public class LeaderElectionClient { + + /** + * Construct a LeaderElectionClient using a user passed in leaderElectionConfig. It creates a MetaClient + * instance underneath. + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, A new + * MetaClient instance will be created and keeps retry connection. + */ + public LeaderElectionClient(MetaClientConfig metaClientConfig) { + + } + + /** + * Construct a LeaderElectionClient using a user passed in MetaClient object + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, user + * will need to create a new MetaClient and a new LeaderElectionClient instance. + */ + public LeaderElectionClient(MetaClientInterface MetaClient) { + + } + + /** + * Returns true if current participant is able to acquire leadership. + */ + public boolean isLeader(String leaderPath, String participant) { Review Comment: Is it like if the participant is able to acquire leadership return true else false, if so can we rename this to `acquireLeadership` ########## meta-client/src/main/java/org/apache/helix/metaclient/recipes/leaderelection/LeaderElectionClient.java: ########## @@ -0,0 +1,125 @@ +package org.apache.helix.metaclient.recipes.leaderelection; + +/* + * 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 org.apache.helix.metaclient.api.MetaClientInterface; +import org.apache.helix.metaclient.factories.MetaClientConfig; + + +/** + * LeaderElectionClient does distributed leader election using CRUD and change notification APIs + * provided by underlying metadata client. Leader election config can provide many + * configs like base path for all participating nodes, sync/async mode, TTL etc. + * + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + * All participants wanted to be elected as leader joins a pool + * LeaderElection client maintains an active leader, by monitoring liveness of current leader and + * re-elect if needed and user no need to call elect or re-elect explicitly. + * This LeaderElection client will notify registered listeners for any leadership change. + */ +public class LeaderElectionClient { + + /** + * Construct a LeaderElectionClient using a user passed in leaderElectionConfig. It creates a MetaClient + * instance underneath. + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, A new + * MetaClient instance will be created and keeps retry connection. + */ + public LeaderElectionClient(MetaClientConfig metaClientConfig) { + + } + + /** + * Construct a LeaderElectionClient using a user passed in MetaClient object + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, user + * will need to create a new MetaClient and a new LeaderElectionClient instance. + */ + public LeaderElectionClient(MetaClientInterface MetaClient) { + + } + + /** + * Returns true if current participant is able to acquire leadership. + */ + public boolean isLeader(String leaderPath, String participant) { + return false; + } + + /** + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + */ Review Comment: nit: Can we add a comment `returns true if participant is able to join the pool else false` and also the descriptions for the parameters of the function. (Sorry but I couldn't get what is the purpose of `userInfo`). ########## meta-client/src/main/java/org/apache/helix/metaclient/recipes/leaderelection/LeaderElectionClient.java: ########## @@ -0,0 +1,125 @@ +package org.apache.helix.metaclient.recipes.leaderelection; + +/* + * 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 org.apache.helix.metaclient.api.MetaClientInterface; +import org.apache.helix.metaclient.factories.MetaClientConfig; + + +/** + * LeaderElectionClient does distributed leader election using CRUD and change notification APIs + * provided by underlying metadata client. Leader election config can provide many + * configs like base path for all participating nodes, sync/async mode, TTL etc. + * + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + * All participants wanted to be elected as leader joins a pool + * LeaderElection client maintains an active leader, by monitoring liveness of current leader and + * re-elect if needed and user no need to call elect or re-elect explicitly. + * This LeaderElection client will notify registered listeners for any leadership change. + */ +public class LeaderElectionClient { Review Comment: One question for my understanding, do we want the `LeaderElectionClient` to be for a specific `path` or is it like this is one single stop for all the leadership related stuff for multiple paths. I feel that we should make it specific to a path, and sort of have a manager that manages multiple paths if wanted. In this way we keep the `LeaderElectionClient` clean. Can you also add that to the description if possible. ########## meta-client/src/main/java/org/apache/helix/metaclient/recipes/leaderelection/LeaderElectionClient.java: ########## @@ -0,0 +1,125 @@ +package org.apache.helix.metaclient.recipes.leaderelection; + +/* + * 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 org.apache.helix.metaclient.api.MetaClientInterface; +import org.apache.helix.metaclient.factories.MetaClientConfig; + + +/** + * LeaderElectionClient does distributed leader election using CRUD and change notification APIs + * provided by underlying metadata client. Leader election config can provide many + * configs like base path for all participating nodes, sync/async mode, TTL etc. + * + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + * All participants wanted to be elected as leader joins a pool + * LeaderElection client maintains an active leader, by monitoring liveness of current leader and + * re-elect if needed and user no need to call elect or re-elect explicitly. + * This LeaderElection client will notify registered listeners for any leadership change. + */ +public class LeaderElectionClient { + + /** + * Construct a LeaderElectionClient using a user passed in leaderElectionConfig. It creates a MetaClient + * instance underneath. + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, A new + * MetaClient instance will be created and keeps retry connection. + */ + public LeaderElectionClient(MetaClientConfig metaClientConfig) { + + } + + /** + * Construct a LeaderElectionClient using a user passed in MetaClient object + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, user + * will need to create a new MetaClient and a new LeaderElectionClient instance. + */ + public LeaderElectionClient(MetaClientInterface MetaClient) { + + } + + /** + * Returns true if current participant is able to acquire leadership. + */ + public boolean isLeader(String leaderPath, String participant) { + return false; + } + + /** + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + */ + public boolean joinLeaderElectionParticipantPool(String leaderPath, String participant, + Object userInfo) { + return false; + } + + /** + * Any participant may exit the exitLeaderElectionParticipantPool by calling the API. + * If the participant is not the current leader, it leaves the pool and won't be elected as next leader. + * If the participant is the current leader, it leaves the pool and a new leader will be elected if there are other participants in the pool. + * Throws exception if the participant is not in the pool. + */ + public boolean exitLeaderElectionParticipantPool(String leaderPath, String participant) { + return false; + } + + /** + * Releases leadership for participant. + * Throws exception if the leadership is not owned by this participant. + */ + public void relinquishLeader(String leaderPath, String participant) { + } + + /** + * Get current leader nodes. Review Comment: nit: `node` and not `nodes` 😅 ########## meta-client/src/main/java/org/apache/helix/metaclient/recipes/leaderelection/LeaderInfo.java: ########## @@ -0,0 +1,42 @@ +package org.apache.helix.metaclient.recipes.leaderelection; + +/* + * 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 org.apache.helix.metaclient.datamodel.DataRecord; + + +public class LeaderInfo { Review Comment: Can we add some description related to this class. Also should we return `LeaderInfo` when you do `LeaderElectionClient.getLeader()`? ########## meta-client/src/main/java/org/apache/helix/metaclient/recipes/leaderelection/LeaderElectionClient.java: ########## @@ -0,0 +1,125 @@ +package org.apache.helix.metaclient.recipes.leaderelection; + +/* + * 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 org.apache.helix.metaclient.api.MetaClientInterface; +import org.apache.helix.metaclient.factories.MetaClientConfig; + + +/** + * LeaderElectionClient does distributed leader election using CRUD and change notification APIs + * provided by underlying metadata client. Leader election config can provide many + * configs like base path for all participating nodes, sync/async mode, TTL etc. + * + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + * All participants wanted to be elected as leader joins a pool + * LeaderElection client maintains an active leader, by monitoring liveness of current leader and + * re-elect if needed and user no need to call elect or re-elect explicitly. + * This LeaderElection client will notify registered listeners for any leadership change. + */ +public class LeaderElectionClient { + + /** + * Construct a LeaderElectionClient using a user passed in leaderElectionConfig. It creates a MetaClient + * instance underneath. + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, A new + * MetaClient instance will be created and keeps retry connection. + */ + public LeaderElectionClient(MetaClientConfig metaClientConfig) { + + } + + /** + * Construct a LeaderElectionClient using a user passed in MetaClient object + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, user + * will need to create a new MetaClient and a new LeaderElectionClient instance. + */ + public LeaderElectionClient(MetaClientInterface MetaClient) { + + } + + /** + * Returns true if current participant is able to acquire leadership. + */ + public boolean isLeader(String leaderPath, String participant) { + return false; + } + + /** + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + */ + public boolean joinLeaderElectionParticipantPool(String leaderPath, String participant, + Object userInfo) { + return false; + } + + /** + * Any participant may exit the exitLeaderElectionParticipantPool by calling the API. + * If the participant is not the current leader, it leaves the pool and won't be elected as next leader. Review Comment: nit: May be `If the participant is not the current leader, it leaves the pool and thus won't be able to participate in the leader election process moving forward.` cause `won't be elected as next leader sounds like this participant was going to be the next leader` 😅 ########## meta-client/src/main/java/org/apache/helix/metaclient/recipes/leaderelection/LeaderElectionClient.java: ########## @@ -0,0 +1,125 @@ +package org.apache.helix.metaclient.recipes.leaderelection; + +/* + * 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 org.apache.helix.metaclient.api.MetaClientInterface; +import org.apache.helix.metaclient.factories.MetaClientConfig; + + +/** + * LeaderElectionClient does distributed leader election using CRUD and change notification APIs + * provided by underlying metadata client. Leader election config can provide many + * configs like base path for all participating nodes, sync/async mode, TTL etc. + * + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + * All participants wanted to be elected as leader joins a pool + * LeaderElection client maintains an active leader, by monitoring liveness of current leader and + * re-elect if needed and user no need to call elect or re-elect explicitly. + * This LeaderElection client will notify registered listeners for any leadership change. + */ +public class LeaderElectionClient { + + /** + * Construct a LeaderElectionClient using a user passed in leaderElectionConfig. It creates a MetaClient + * instance underneath. + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, A new + * MetaClient instance will be created and keeps retry connection. + */ + public LeaderElectionClient(MetaClientConfig metaClientConfig) { + + } + + /** + * Construct a LeaderElectionClient using a user passed in MetaClient object + * When MetaClient is auto closed be cause of being disconnected and auto retry connection timed out, user + * will need to create a new MetaClient and a new LeaderElectionClient instance. + */ + public LeaderElectionClient(MetaClientInterface MetaClient) { + + } + + /** + * Returns true if current participant is able to acquire leadership. + */ + public boolean isLeader(String leaderPath, String participant) { + return false; + } + + /** + * Participants join a leader election group by calling the following API. + * The Leader Election client maintains and elect an active leader from participant pool + */ + public boolean joinLeaderElectionParticipantPool(String leaderPath, String participant, + Object userInfo) { + return false; + } + + /** + * Any participant may exit the exitLeaderElectionParticipantPool by calling the API. + * If the participant is not the current leader, it leaves the pool and won't be elected as next leader. + * If the participant is the current leader, it leaves the pool and a new leader will be elected if there are other participants in the pool. + * Throws exception if the participant is not in the pool. + */ + public boolean exitLeaderElectionParticipantPool(String leaderPath, String participant) { Review Comment: nit: If you want you can rename this to `leave` instead of `exit` cause when you join something you leave 😂 -- This is an automated message from the Apache Git Service. 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