[ 
https://issues.apache.org/jira/browse/PHOENIX-3654?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16039107#comment-16039107
 ] 

ASF GitHub Bot commented on PHOENIX-3654:
-----------------------------------------

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

    https://github.com/apache/phoenix/pull/236#discussion_r120392963
  
    --- Diff: 
phoenix-queryserver/src/main/java/org/apache/phoenix/loadbalancer/service/PqsZookeeperConfImpl.java
 ---
    @@ -0,0 +1,97 @@
    +/**
    + *
    + * 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.phoenix.loadbalancer.service;
    +
    +import com.google.common.net.HostAndPort;
    +import org.apache.hadoop.conf.Configuration;
    +import org.apache.hadoop.hbase.HBaseConfiguration;
    +import org.apache.phoenix.query.QueryServices;
    +import org.apache.phoenix.query.QueryServicesOptions;
    +import org.apache.zookeeper.ZooDefs;
    +import org.apache.zookeeper.data.ACL;
    +import org.apache.zookeeper.data.Id;
    +
    +import java.util.Arrays;
    +import java.util.List;
    +
    +
    +
    +public class PqsZookeeperConfImpl implements PqsZookeeperConf {
    +
    +        private final Configuration configuration;
    +
    +        public PqsZookeeperConfImpl() {
    +           this.configuration = HBaseConfiguration.create();
    +        }
    +
    +        public PqsZookeeperConfImpl(Configuration configuration) {
    +            this.configuration = configuration;
    +        }
    +
    +        @Override
    +        public String getQueryServerBasePath(){
    +            return 
"/"+configuration.get(QueryServices.PHOENIX_QUERY_SERVER_CLUSTER_BASE_PATH,
    --- End diff --
    
    I think pre-pending the leading '/' is confusing. The user can just provide 
the full path in ZK.


> Load Balancer for thin client
> -----------------------------
>
>                 Key: PHOENIX-3654
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-3654
>             Project: Phoenix
>          Issue Type: New Feature
>    Affects Versions: 4.8.0
>         Environment: Linux 3.13.0-107-generic kernel, v4.9.0-HBase-0.98
>            Reporter: Rahul Shrivastava
>            Assignee: Rahul Shrivastava
>             Fix For: 4.9.0
>
>         Attachments: LoadBalancerDesign.pdf, Loadbalancer.patch
>
>   Original Estimate: 240h
>  Remaining Estimate: 240h
>
> We have been having internal discussion on load balancer for thin client for 
> PQS. The general consensus we have is to have an embedded load balancer with 
> the thin client instead of using external load balancer such as haproxy. The 
> idea is to not to have another layer between client and PQS. This reduces 
> operational cost for system, which currently leads to delay in executing 
> projects.
> But this also comes with challenge of having an embedded load balancer which 
> can maintain sticky sessions, do fair load balancing knowing the load 
> downstream of PQS server. In addition, load balancer needs to know location 
> of multiple PQS server. Now, the thin client needs to keep track of PQS 
> servers via zookeeper ( or other means). 
> In the new design, the client ( PQS client) , it is proposed to  have an 
> embedded load balancer.
> Where will the load Balancer sit ?
> The load load balancer will embedded within the app server client.  
> How will the load balancer work ? 
> Load balancer will contact zookeeper to get location of PQS. In this case, 
> PQS needs to register to ZK itself once it comes online. Zookeeper location 
> is in hbase-site.xml. It will maintain a small cache of connection to the 
> PQS. When a request comes in, it will check for an open connection from the 
> cache. 
> How will load balancer know load on PQS ?
> To start with, it will pick a random open connection to PQS. This means that 
> load balancer does not know PQS load. Later , we can augment the code so that 
> thin client can receive load info from PQS and make intelligent decisions.  
> How will load balancer maintain sticky sessions ?
> While we still need to investigate how to implement sticky sessions. We can 
> look for some open source implementation for the same.
> How will PQS register itself to service locator ?
> PQS will have location of zookeeper in hbase-site.xml and it would register 
> itself to the zookeeper. Thin client will find out PQS location using 
> zookeeper.



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