[ https://issues.apache.org/jira/browse/TEPHRA-215?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15857882#comment-15857882 ] 

ASF GitHub Bot commented on TEPHRA-215:
---------------------------------------

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

    https://github.com/apache/incubator-tephra/pull/32#discussion_r100042435
  
    --- Diff: tephra-hbase-compat-1.1-base/src/main/java/org/apache/tephra/hbase/txprune/PruneUpperBoundWriterSupplier.java ---
    @@ -0,0 +1,78 @@
    +/*
    + * 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.
    + */
    +
    +package org.apache.tephra.hbase.txprune;
    +
    +
    +import com.google.common.base.Supplier;
    +import org.apache.commons.logging.Log;
    +import org.apache.commons.logging.LogFactory;
    +
    +/**
    + * Supplies instances of {@link PruneUpperBoundWriter} implementations.
    + */
    +public class PruneUpperBoundWriterSupplier implements Supplier<PruneUpperBoundWriter> {
    +  private static final Log LOG = LogFactory.getLog(PruneUpperBoundWriterSupplier.class);
    +
    +  private static volatile PruneUpperBoundWriter instance;
    +  private static volatile int refCount = 0;
    +  private static final Object lock = new Object();
    +
    +  private final DataJanitorState dataJanitorState;
    +  private final long pruneFlushInterval;
    +
    +  public PruneUpperBoundWriterSupplier(DataJanitorState dataJanitorState, long pruneFlushInterval) {
    +    this.dataJanitorState = dataJanitorState;
    +    this.pruneFlushInterval = pruneFlushInterval;
    +  }
    +
    +  @Override
    +  public PruneUpperBoundWriter get() {
    +    synchronized (lock) {
    --- End diff --
    
    We can make an `instance == null` check outside the lock. In case instance is not null just increment refCount and return.


> Share PruneUpperBoundWriter across all TransactionProcessors on the same region server
> --------------------------------------------------------------------------------------
>
>                 Key: TEPHRA-215
>                 URL: https://issues.apache.org/jira/browse/TEPHRA-215
>             Project: Tephra
>          Issue Type: Improvement
>    Affects Versions: 0.11.0-incubating
>            Reporter: Gokul Gunasekaran
>            Assignee: Gokul Gunasekaran
>             Fix For: 0.11.0-incubating
>
>
> Currently we start one prune upperbound writer thread per TransactionProcessor coprocessor. Instead we should be able to share only one thread that flushes writes to the prune state table periodically.



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