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From "Joep Rottinghuis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17327) Allow for lazy connection / BufferedMutator creation
Date Sat, 17 Dec 2016 07:17:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15756533#comment-15756533
] 

Joep Rottinghuis commented on HBASE-17327:
------------------------------------------

Yup, that appears to be the issue.
This seems to be the stack when trying to connect to an HBase cluster that is down:
Thread.sleep(long) line: not available [native method]	
Thread.sleep(long, int) line: 340	
TimeUnit$3(TimeUnit).sleep(long) line: 386	
RetryCounter.sleepUntilNextRetry() line: 158	
RecoverableZooKeeper.exists(String, Watcher) line: 232	
ZKUtil.checkExists(ZooKeeperWatcher, String) line: 414	
ZKClusterId.readClusterIdZNode(ZooKeeperWatcher) line: 65	
ZooKeeperRegistry.getClusterId() line: 103	
ConnectionImplementation.retrieveClusterId() line: 484	
ConnectionImplementation.<init>(Configuration, ExecutorService, User) line: 260	
NativeConstructorAccessorImpl.newInstance0(Constructor<?>, Object[]) line: not available
[native method]	
NativeConstructorAccessorImpl.newInstance(Object[]) line: 62	
DelegatingConstructorAccessorImpl.newInstance(Object[]) line: 45	
Constructor<T>.newInstance(Object...) line: 423	
ConnectionFactory.createConnection(Configuration, ExecutorService, User) line: 235	
ConnectionFactory.createConnection(Configuration) line: 122	


See the following test code to demonstrate this:
<code>
/**
 * 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.hadoop.hbase.mapreduce;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseTestingUtility;
import org.apache.hadoop.hbase.client.Connection;
import org.apache.hadoop.hbase.client.ConnectionFactory;
import org.apache.hadoop.hbase.testclassification.LargeTests;
import org.junit.Test;
import org.junit.experimental.categories.Category;

@Category({LargeTests.class})
public class TestConnectionCreation {

  private static HBaseTestingUtility util = new HBaseTestingUtility();

  @Test
  public void test() throws Exception {
    util.startMiniCluster();
    util.shutdownMiniCluster();

    Configuration hbaseConf = util.getConfiguration();
    Connection conn = ConnectionFactory.createConnection(hbaseConf);
    conn.close();
  }
}
<code>

> Allow for lazy connection / BufferedMutator creation
> ----------------------------------------------------
>
>                 Key: HBASE-17327
>                 URL: https://issues.apache.org/jira/browse/HBASE-17327
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Joep Rottinghuis
>
> The SpoolingBufferedMutatorImpl solution (HBASE-17018) solved the use-case when an existing
HBase connection stalls out due to HBase being down, or other transient issues.
> We have a remaining issue that our service will not start up if it cannot initially connect
to HBase.
> This can be solved by letting the SpoolingBufferedMutator create the wrapped BufferedMutatorImpl
later, but the problem has already occurred: we already have to have a connection in order
to create a BufferedMutator to begin with.
> It would be good to be able to initiate a connection and then have a way for multiple
users to wait for the connection to succeed before using it.
> I'm thinking perhaps create a LazyConnection interface that extends the Connection interface.
It would have an additional waitFor(long timeout, TimeUnit unit) method where clients can
wait for the connection to be established before they start using the connection.
> Or perhaps the ConnectionFactory can have a createLazyConnection method.



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