[jira] [Comment Edited] (CALCITE-5581) Implement Basic client side load balancing in Avatica Driver

["Vaibhav Joshi (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-5581?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17704099#comment-17704099 ] 

Vaibhav Joshi edited comment on CALCITE-5581 at 3/23/23 11:54 AM:
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[~stoty] 

This is good suggestion. But I am seeing some challenges here. We need to consider few aspects.

*Handling failed hosts*

Detecting failures should be easy(I believe try-catch block in connect method), we can even try to maintain some global list of failed hosts.

But identifying and categorizing failed hosts will be challenging.
 * Connection can fail due to transient or non-transient failures. We need to blacklist only hosts with non-transient failures. Retry mechanism should handle transient failures. Challenge here is, how can we identify and categorize failures? Can we safely rely on HTTP error  (e.g. 500 and 503)? Considering that fact that we can have different client implementation, is this a correct assumption?
 * If we some above problem, we can maintain some TTL cache for failed host lookup. TTL cache will make sure that host is not blocked forever. We can keep TTL cache configurable. But this will impact performance i.e. some CPU and memory resource will be consumed to make our client smarter.

*Internal Retries for the failures*

Yes this can be done. I believe we are talking about simple retries e.g.  N retries at interval of M sec, with N and M as configurable parameters. Backoff retries will make our client bulky so we should keep it out of scope.

But it's again tied to nature of failure (transient or non transient). Few points discussed above are applicable. 

In first cut implementation we can keep it simple and retry all failures ( say 6 retries at interval of 10 seconds by default).


was (Author: JIRAUSER291813):
[~stoty] 

This is good suggestion. But I am seeing some challenges here. We need to consider few aspects.

*Handling failed hosts*

Detecting failures should be easy(I believe try-catch block in connect method), we can even try to maintain some global list of failed hosts.

But identifying and categorizing failed hosts will be challenging.
 * Connection can fail due to transient or non-transient failures. We need to blacklist only hosts with non-transient failures. Retry mechanism should handle transient failures. Challenge here is, how can we identify and categorize failures? Can we safely rely on HTTP error  (e.g. 500 and 503)? Considering that fact that we can have different client implementation, is this a correct assumption?
 * If we some above problem, we can maintain some TTL cache for failed host lookup. TTL cache will make sure that host is not blocked forever. We can keep TTL cache configurable. But this will impact performance i.e. some CPU and memory resource will be consumed to make our client smarter.

*Internal Retries for the failures*

Yes this can be done. I believe we are talking about simple retries e.g.  N retries at interval of M sec, with N and M as configurable parameters. Backoff retries will make our client bulky so we should keep it out of scope.

But it's again tied to nature of failure (transient or non transient). Few points discussed above are applicable. 

In first cut implementation we can keep it simple and retry all failures ( 3 retries at interval of 10 seconds by default).

> Implement Basic client side load balancing in Avatica Driver
> ------------------------------------------------------------
>
>                 Key: CALCITE-5581
>                 URL: https://issues.apache.org/jira/browse/CALCITE-5581
>             Project: Calcite
>          Issue Type: New Feature
>          Components: avatica
>    Affects Versions: 1.33.0
>            Reporter: Vaibhav Joshi
>            Assignee: Vaibhav Joshi
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: Avatica Basic client side load balancing.docx
>
>          Time Spent: 1.5h
>  Remaining Estimate: 0h
>
> Implement mechanism to support Client side load balancing by configuring connection properties for load balancing  
> {code:java}
> jdbc:phoenix:thin:
> url=https://<host>:<port>;
> serialization=PROTOBUF;
> authentication=BASIC;
> avatica_user=<userName>;
> avatica_password=<userPw>
> useClientSideLB: [true/false]
> lbStrategy: [RandomDistribution/Sequential/RoundRobin]
> lbURLs: <comma separated URls e.g. URL1, URL2,URL3,...URLn> {code}
> Client should connect to any of the URLs specified in lbURLs ( depending on LB strategy selected).  Please refer to [^Avatica Basic client side load balancing.docx]for more details
>  



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