[jboss-jira] [JBoss JIRA] (LOGTOOL-132) Support low-metaspace bundles/classes

[David Lloyd (JIRA)]

    [ https://issues.jboss.org/browse/LOGTOOL-132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13523380#comment-13523380 ] 

David Lloyd commented on LOGTOOL-132:
-------------------------------------

Re-reading the analysis, I guess that the vtable/itable savings would only occur if we actually rewrote the interface itself into a final class so that there is no inheritance going on at all.

We could retain basic compatibility with older {{jboss-logging}} just by providing a constructor which accepts only a Logger and assumes Locale.ROOT.  It would defeat I18n in this case but I think that's OK: when running with an older {{jboss-logging}} than what the project was compiled for, one must expect problems.

> Support low-metaspace bundles/classes
> -------------------------------------
>
>                 Key: LOGTOOL-132
>                 URL: https://issues.jboss.org/browse/LOGTOOL-132
>             Project: Log Tool
>          Issue Type: Enhancement
>            Reporter: David Lloyd
>            Priority: Critical
>
> Metaspace is at a premium in the application server environment, and the number one consumer is presently generated log classes.
> Introduce a leaner variation on generated classes with the following requirements:
> * The generated class must be {{final}}
> * The generated class must contain no message strings
> * The generated class must accept both a {{Logger}} and a {{Locale}}, and load its resources from a file based on that information
> * The usage of Java 8's locale lookup functionality should be considered, to support language tags etc.; a helper utility could be introduced into {{jboss-logging}} for this
> Here are some implementation ideas:
> * Option 1: The resource files contain only messages, one per line, loaded directly into a {{String[]}} instance field in the implementation class; each logging method uses a hard-coded array index to access its message
> ** A key advantage is that the implementation class is very small, and consumes very little metaspace; also, it is fast, requiring only an array lookup to acquire the string
> ** A disadvantage is, any change to the message set invalidates all the locale files, which must then be regenerated
> ** Also, each locale file must contain all messages, unless a fallback mechanism is used (e.g. an empty line signifies that the string should come from the parent locale)
> * Option 2: The resource files contain key-value pairs, with the key being equal to the method name
> ** Advantage: the file is not invalidated if a key is added, and sub-locales can inherit more easily from parent locales
> ** Disadvantage: the added overhead of mapping lines to methods (for example, using a switch statement to map method names to fixed indexes, or loading the messages into a hash table e.g. {{HashMap}}) will fill metaspace or impact performance, or both



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