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https://issues.apache.org/jira/browse/LUCENE-10342?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Uwe Schindler updated LUCENE-10342:
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Priority: Critical (was: Major)
> Add (very limited) java.util.logging to Lucene Core
> ---------------------------------------------------
>
> Key: LUCENE-10342
> URL: https://issues.apache.org/jira/browse/LUCENE-10342
> Project: Lucene - Core
> Issue Type: New Feature
> Components: core/other
> Reporter: Uwe Schindler
> Assignee: Uwe Schindler
> Priority: Critical
> Labels: flamewar, logging
>
> At the moment we have some parts in Lucene where we check for features of the
> JDK and use them, only if available:
> - We only use MMapDirectory, if we can unmap, so sun.misc.Unsafe must be
> available
> - To correctly calculate heap space requirements of data structures for
> caching and other types of buffers, we try to calculate the heap size of
> objects. To do this correctly we need some information like the size of
> ordinal object pointers. If they are 32 bits on 64 bit platforms, the memory
> usage of Object[] arrays (and HashSet/HashMaps) dramatically reduce size by
> factor of 2.
> As those checks require "optional" modules in the java module system, which
> may not even be available by default as they are unsupported, we do the check
> dynamically.
> With the Java module system the problems start, that a user of Lucene may
> need to add those modules to the module descriptor of the application. If he
> misses that or for some other reason it does not work (like feature is not
> available), we silently disable MMapDirectory or for memory usage we may be
> off by an factor of 2.
> My suggestion is now to enable java.util.logging in Lucene's core (maybe also
> in other modules, too - luke is already) and report such warnings using
> java.util.logging. Any downstream code will see the logging then depending on
> the used logging system (log4j, slf4j with correct wrapper module).
> I know this suggestion may cause a bit a flame war because of disagreement
> about pros and cons about if logging is needed, so I'd like to limit this to
> warnings+. We won't ever emit info/debug/trace. To make sure we only log
> "warn" and "error"/"severe" events, I will add a forbiddenapis rule to deny
> all other loglevels.
> As a side effect I will also add an IndexWriter log stream implementation for
> java.util.logging to make it easy to log infostream events during indexing.
> I will provide a PR adding 2 warnings and the InfoStream implementation.
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