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https://issues.apache.org/jira/browse/SOLR-13122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16873726#comment-16873726
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Erick Erickson commented on SOLR-13122:
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[~janhoy] You're making me hop in the wayback machine, See SOLR-11218. The use
case goes like this:
* user creates a collection and all of their front-end code points to it. Call
it C1
* user wants to re-index for whatever reason, but must keep serving from the
old collection and switch atomically
* user reindexes into new collection C2
* user switches atomically by creating alias C1 point to C2.
* if they couldn't create an alias they'd have to shut down at least
temporarily after C2 was ready, then delete C1 then create the alias. This is
actually a little scary, one of the selling points is "you can always switch
back if you discover that C2 is flawed"... After the first time they'd have
both collections of course, but the first time would be some risk.
There's a similar pattern for once-a-day indexing and switching your C1 alias
to point to C2 one day, C1 the next, then back to C2 the next etc.
Ideally, of course, C1 starts out as an alias pointing to collection_blue and
the reindex to collection_green then point C1 at collection_green. But I see
this in the field only very rarely, especially first-time users. They just
start with collection C1.
In that JIRA, I put a test specifically to keep from deleting the underlying
collection by following the alias IIRC.
I wouldn't object to prohibiting aliases from having the same name as a
collection, but it needs to deal with the above for users (most) who don't
start with an alias and can't/won't change all their app code when they
discover they need aliases. We'd need to specifically call out the above and
provide some guidance to get them past the problem. Users would complain about
the 5 minute downtime, but I don't think that's a show-stopper.
And if we do prohibit this we need to not only prevent creating an alias with
the same name as a collection, but vice-versa. I think you allude to that with
"enforce uniqueness", but thought I'd call it out specifically.
> Ability to query aliases in Solr Admin UI
> -----------------------------------------
>
> Key: SOLR-13122
> URL: https://issues.apache.org/jira/browse/SOLR-13122
> Project: Solr
> Issue Type: Improvement
> Components: Admin UI
> Reporter: mosh
> Assignee: Jan Høydahl
> Priority: Major
> Labels: UI
> Fix For: 8.2
>
> Attachments: alias-collection-menu-selected.png,
> alias-collection-view.png, alias-collections-menu.png,
> alias-collections-menu.png, alias-delete-dialogue.png, alias-dropdown.png,
> alias-select-double.png, alias-view.png
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> After having recently toyed with Time Routed Alias in SolrCloud,
> we have noticed there is no way to query an alias from the admin UI,
> since the combo box only contains the current collection in the cluster.
> Solr Admin UI ought to have a way to query these aliases, for better
> convenience.
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