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https://issues.apache.org/jira/browse/PHOENIX-3654?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Josh Elser updated PHOENIX-3654:
--------------------------------
    Summary: Client-side PQS discovery for thin client  (was: Load Balancer for 
thin client)

> Client-side PQS discovery 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
>            Priority: Major
>             Fix For: 4.12.0
>
>         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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