[jira] [Commented] (GOSSIP-75) Voting interface

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GOSSIP-75?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16110130#comment-16110130 ] 

ASF GitHub Bot commented on GOSSIP-75:
--------------------------------------

Github user edwardcapriolo commented on a diff in the pull request:

    https://github.com/apache/incubator-gossip/pull/62#discussion_r130770942
  
    --- Diff: gossip-base/src/main/java/org/apache/gossip/lock/LockManager.java ---
    @@ -0,0 +1,311 @@
    +/*
    + * 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
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    + * 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.gossip.lock;
    +
    +import com.sun.org.apache.xpath.internal.SourceTree;
    +import org.apache.gossip.Member;
    +import org.apache.gossip.crdt.Crdt;
    +import org.apache.gossip.event.data.UpdateSharedDataEventHandler;
    +import org.apache.gossip.lock.exceptions.VoteFailedException;
    +import org.apache.gossip.lock.vote.MajorityVote;
    +import org.apache.gossip.lock.vote.Vote;
    +import org.apache.gossip.lock.vote.VoteCandidate;
    +import org.apache.gossip.lock.vote.VoteSelector;
    +import org.apache.gossip.manager.GossipCore;
    +import org.apache.gossip.manager.GossipManager;
    +import org.apache.gossip.model.SharedDataMessage;
    +
    +import java.util.ArrayList;
    +import java.util.Arrays;
    +import java.util.Collection;
    +import java.util.Collections;
    +import java.util.HashMap;
    +import java.util.HashSet;
    +import java.util.List;
    +import java.util.Map;
    +import java.util.Random;
    +import java.util.Set;
    +import java.util.Timer;
    +import java.util.TimerTask;
    +import java.util.UUID;
    +import java.util.concurrent.ConcurrentHashMap;
    +import java.util.concurrent.Executors;
    +import java.util.concurrent.ScheduledExecutorService;
    +import java.util.concurrent.ScheduledThreadPoolExecutor;
    +import java.util.concurrent.Semaphore;
    +import java.util.concurrent.TimeUnit;
    +import java.util.stream.Collectors;
    +
    +public class LockManager {
    +
    +  private final GossipManager gossipManager;
    +  private final GossipCore gossipCore;
    +  private final Map<String, MajorityVote> majorityVoteCache;
    +  private final ScheduledExecutorService cacheUpdateService;
    +  private final ScheduledExecutorService voteService;
    +  private final VoteSelector voteSelector;
    +  private int numberOfNodes = -1;
    +  private int deadlockDetectionThreshold = 2;
    +
    +  public LockManager(GossipManager gossipManager, GossipCore gossipCore, VoteSelector voteSelector) {
    +    this.gossipManager = gossipManager;
    +    this.gossipCore = gossipCore;
    +    this.voteSelector = voteSelector;
    +    this.majorityVoteCache = new ConcurrentHashMap<>();
    +
    +    cacheUpdateService = Executors.newScheduledThreadPool(2);
    +    voteService = Executors.newScheduledThreadPool(2);
    +    cacheUpdateService.scheduleAtFixedRate(this::updateCache, 0,
    +            1000, TimeUnit.MILLISECONDS);
    +    voteService.scheduleAtFixedRate(this::updateVotes, 0,
    +            1000, TimeUnit.MILLISECONDS);
    +  }
    +
    +  public void acquireSharedDataLock(String key) throws VoteFailedException {
    +
    +    gossipManager.merge(generateLockMessage(key));
    +
    +    // TODO: 7/16/17 gather stats, check possibilities of optimizations
    +    int deadlockDetectCount = 0;
    +    while (true){
    +      MajorityVote majorityVoteResult = majorityVoteCache.get(generateLockKey(key));
    +      if(majorityVoteResult == null ){
    +        continue;
    +      }
    +      final Map<String, VoteCandidate> voteCandidatesMap = majorityVoteResult.value();
    +      final Map<String, Boolean> voteResultMap = new HashMap<>();
    +
    +      voteCandidatesMap.forEach((candidateId, voteCandidate)
    +              -> voteResultMap.put(candidateId, isVoteSuccess(voteCandidate)));
    +
    +      long passedCandidates = voteResultMap.values().stream().filter(aBoolean -> aBoolean).count();
    +
    +      String myNodeId = gossipManager.getMyself().getId();
    +      System.out.println("Node "  + myNodeId + " vote map " + voteResultMap + " pass " + passedCandidates);
    +
    +      if(passedCandidates == 0 && isDeadLock(voteCandidatesMap)){
    +        deadlockDetectCount++;
    +        if(deadlockDetectCount >= deadlockDetectionThreshold) {
    +          if(preventDeadLock(voteCandidatesMap)) {
    +            majorityVoteCache.put(generateLockKey(key), majorityVoteResult);
    +          }
    +        }
    +      }else if(passedCandidates == 1 && voteResultMap.containsKey(myNodeId)){
    --- End diff --
    
    Formatting


> Voting interface
> ----------------
>
>                 Key: GOSSIP-75
>                 URL: https://issues.apache.org/jira/browse/GOSSIP-75
>             Project: Gossip
>          Issue Type: New Feature
>            Reporter: Edward Capriolo
>
> Gossip has CRDT support. This is an important building block to doing higher level things. The next piece is being able to act on an object when we receive it. For example lets take the most simple case. I want the cluster to vote on something such as "who asked for this lock first". Currently we replicate objects lazily through a thread, what we want to do is on reception of an object apply some function such that we can modify the object being received.
> The way I want to go about this is voting objects can be injected with a type like VoteContext
> http://stackoverflow.com/questions/27133161/how-to-pass-constructors-parameters-with-jackson  
> Users can register Voter implementations. On receiving an object  the interface allows logic to be run. In the case of a Voting each node appends its vote as the object moves around over time you can poll your local copy and determine the result of the vote. 



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