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From "Erick Erickson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-12767) Deprecate min_rf
Date Thu, 13 Sep 2018 00:18:00 GMT

    [ https://issues.apache.org/jira/browse/SOLR-12767?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16612887#comment-16612887
] 

Erick Erickson commented on SOLR-12767:
---------------------------------------

{quote} #1 is still valuable, but there isn’t much point of making the parameter an integer,
the user is just telling Solr that they want the achieved replication factor, so it could
be a boolean,
{quote}
I question this. The scenario is this:
 * Someone can't re-index from source
 * They need to be really, really, really _sure_ the doc gets indexed

So even being guaranteed that the doc is replicated isn't enough in the unlikely scenario
that the leader and the one replica that the doc happened to replicate to die at the same
time.

Maybe not enough of a window to allow for, but that's the concern.

 

> Deprecate min_rf
> ----------------
>
>                 Key: SOLR-12767
>                 URL: https://issues.apache.org/jira/browse/SOLR-12767
>             Project: Solr
>          Issue Type: Improvement
>      Security Level: Public(Default Security Level. Issues are Public) 
>            Reporter: Tomás Fernández Löbbe
>            Priority: Major
>
> Currently the {{min_rf}} parameter does two things.
> 1. It tells Solr that the user wants to keep track of the achieved replication factor
> 2. (undocumented AFAICT) It prevents Solr from putting replicas in recovery if the achieved
replication factor is lower than the {{min_rf}} specified
> #2 is intentional and I believe the reason behind it is to prevent replicas to go into
recovery in cases of short hiccups (since the assumption is that the user is going to retry
the request anyway). This is dangerous because if the user doesn’t retry (or retries a number
of times but keeps failing) the replicas will be permanently inconsistent. Also, since we
now retry updates from leaders to replicas, this behavior has less value, since short temporary
blips should be recovered by those retries anyway. 
> I think we should remove the behavior described in #2, #1 is still valuable, but there
isn’t much point of making the parameter an integer, the user is just telling Solr that
they want the achieved replication factor, so it could be a boolean, but I’m thinking we
probably don’t even want to expose the parameter, and just always keep track of it, and
include it in the response. It’s not costly to calculate, so why keep two separate code
paths?



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