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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14761) Rename speculative_retry to match additional_write_policy
Date Tue, 13 Nov 2018 16:53:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16685471#comment-16685471
] 

Ariel Weisberg commented on CASSANDRA-14761:
--------------------------------------------

bq. As a user I find this new naming pretty confusing, and I'm curious what other users think.
I think there is significant mind-share in the community and indeed other distributed systems
(e.g. hadoop) around the concept of speculative execution of idempotent operations. If anything
I think it makes sense to do speculative_read_policy and speculative_transient_write_policy.
Even if we keep the additional_read_policy and additional_write_policy naming I worry a user
could easily confuse these somewhat different features (I know that I was confused at first).

We did a speculative name before and it wasn't popular. I think we need to settle on something
and document it. This is the third time we are changing it. Everyone has their own idea of
what is best and none are perfect. 

bq. I think most of the failing dtests are coming from the unconditional check that the objects
are equal even if one isn't set. Perhaps only check they are equal if they are both set?.
Also the string format swaps speculativeRetry with additionReadPolicy (which should probably
be additional).
I'll work on the dtests now.

bq. Did you mean to remove the speculative read option? I think you would want both additional_write
and additional_read in the table?
Yes it's intentional. People shouldn't use the old option. I should add a line saying that
it existed so people are aware one replaces the other.

bq. If I understand speculative transient replica upgrade right, this text no longer applies
to just read coordinators.
Good point I'll update.

bq. AdditionalReadsFailed appears to be inconsistent with the other new in 4.0 metrics (SpeculativeInsufficientRetries
and SpeculativeSampleLatencyNanos). Personally I like the Speculative name across the board
(esp since if we change SpeculativeRetries it's not backwards compatible).
Everything we are doing here should be 100% backwards compatible. It's why the metric is registered
under both old and new names.

I must have had a really bad day because there is a bunch of metric registration that looks
mixed up to me. I'll do a patch to fix the bugs and make it consistent.

> Rename speculative_retry to match additional_write_policy
> ---------------------------------------------------------
>
>                 Key: CASSANDRA-14761
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14761
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Ariel Weisberg
>            Assignee: Ariel Weisberg
>            Priority: Major
>             Fix For: 4.0
>
>
> It's not really speculative. This commit is where it was last named and shows what to
update https://github.com/aweisberg/cassandra/commit/e1df8e977d942a1b0da7c2a7554149c781d0e6c3



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