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Posted to issues@solr.apache.org by "Eric Pugh (Jira)" <ji...@apache.org> on 2026/08/26 17:59:00 UTC
[jira] [Resolved] (SOLR-14349) Upgrade to slf4j 2x when available and encourage using lambdas for expensive methods called in log statements.
[ https://issues.apache.org/jira/browse/SOLR-14349?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Eric Pugh resolved SOLR-14349.
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Resolution: Not A Problem
The upgrade side of this ticket has been done a long time ago... However, the adoption of the Lambda pattern is something we need to discuss and adopt as a project and worht it's own Jira ;)
> Upgrade to slf4j 2x when available and encourage using lambdas for expensive methods called in log statements.
> --------------------------------------------------------------------------------------------------------------
>
> Key: SOLR-14349
> URL: https://issues.apache.org/jira/browse/SOLR-14349
> Project: Solr
> Issue Type: Improvement
> Reporter: Erick Erickson
> Priority: Major
>
> Log4j2 already supports lazily-evaluated lambda expressions, but slf4j won't support them until slf4j-2.0.0, see: [https://jira.qos.ch/browse/SLF4J-371|https://jira.qos.ch/browse/SLF4J-371.]. (thanks M. Drob for finding this!)
> Why it matters:
> A line like *log.trace("stuff {}", object.someMethod())* will execute object.someMethod() regardless of the log level, leading to unnecessary work. One example is SOLR-12353.
> Uwe Schindler pointed out that in the log4j2 context, constructs like: *log.info("stuff {}", () -> object.someMethod(param))* are evaluated lazily, i.e. the *object.comeMethod(param)* method is called if (and only if) the log level includes "INFO".
> Until slf4j2.0 comes out, we'll handle these expensive calls on a case-by-case basis, the simplest way is to wrap expensive calls in an if clause, e.g. *if (log.isTraceEnabled)* *\{log.trace....}*. Ugly, but it works. Once we can upgrade to slf4j2.0, we should encourage using lambdas for any expensive method call that's part of a log message.
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