Thanks Ilan, this seems good. In addition to addressing practical
concerns, this could also be an opportunity to clarify the semantics
around updateLog/tlog configuration:
In looking closely at this code, my understanding is that the
`<updateLog><str name="dir">${solr.ulog.dir:}</str></updateLog>`
setting in solrconfig.xml currently defines the _parent_ directory
that contains the tlog dir. Except that afaict, the tlog dir is the
_only_ path that's actually relevant. In fact, the portion of the
refguide that mentions this is called "Transaction Log Configuration"
[1].
This muddles the intent of this setting; it would be much clearer if,
rather than a "dir" property (defaulting to `[instanceDir]/data/`)
defining the _parent_ directory of the tlog dir, we simply had a
"tlogDir" property (defaulting to `[instanceDir]/data/tlog/`) that
directly defines the tlog dir. The semantics of this could then be
clarified to indicate that:
1. if tlogDir is relative, it is resolved relative to core
instanceDir, and must resolve to a descendent dir of instanceDir
(i.e., cannot "escape" via ../../../).
2. if tlogDir (whether absolute or relative) resolves to a descendant
of instanceDir, it is already implicitly namespaced by core, and the
property defines the tlog dir directly.
3. if tlogDir is absolute and resolves to a directory _outside_ of the
core instanceDir, it is _not_ implicitly namespaced by core, and the
property therefore defines a parent directory, within which a
core-namespaced tlog dir will be created (for a final tlog file path
of, e.g., `[tlogDir]/[core_name]/tlog.0000000000000001`)
As it stands currently, the above three cases are already ambiguous;
the proposed bugfix PR [2] necessarily resolves this ambiguity, but
even so, the semantics of the "dir" property map poorly onto what
actually needs to be configured.
Does this make sense, and/or am I missing something?
Michael
[1]
https://solr.apache.org/guide/solr/latest/configuration-guide/commits-transaction-logs.html#transaction-log-configuration
[2] https://github.com/apache/solr/pull/1895
On Fri, Sep 8, 2023 at 4:59 PM Ilan Ginzburg <ilans...@gmail.com> wrote:
>
> Re backcompat issue: might be an option to fix that config but use a
> different name for it then, so that any currently existing (and ignored)
> config continues to be ignored.
>
> Ilan
>
> On Thu, Sep 7, 2023, 6:14 PM Michael Gibney <mich...@michaelgibney.net>
> wrote:
>
> > I'd like to call some extra attention to SOLR-16962 [1]. I'm fairly
> > certain that it's been years since it has actually worked to specify
> > tlog dir in solrconfig.xml `<updateLog/>` element. I've opened a PR
> > that fixes this, but it involves making some decisions about edge-case
> > handling, for which I'd appreciate feedback.
> >
> > Of course, if anyone _has_ successfully configured a custom tlog dir
> > location with a recent solr version, I'd be curious to hear about that
> > too!
> >
> > Also worth mentioning: if anyone currently has this latently
> > configured in solrconfig.xml, I wonder if it's possible that fixing
> > this bug could cause a change in behavior that might cause a
> > backcompat issue.
> >
> > [1] https://issues.apache.org/jira/browse/SOLR-16962
> >
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