[jira] [Updated] (LOG4J2-3469) Create new AppenderComponentBuilder from existing Appender

["Jody Garnett (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/LOG4J2-3469?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jody Garnett updated LOG4J2-3469:
---------------------------------
    Summary: Create new AppenderComponentBuilder from existing Appender  (was: Override configuration file properties and appenders with programmatic configuration)

> Create new AppenderComponentBuilder from existing Appender
> ----------------------------------------------------------
>
>                 Key: LOG4J2-3469
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-3469
>             Project: Log4j 2
>          Issue Type: New Feature
>          Components: Configuration, Configurators, Core
>    Affects Versions: 2.17.2
>            Reporter: Jody Garnett
>            Priority: Minor
>         Attachments: DEFAULT_LOGGING.xml
>
>
>  
> The documentation covers both [Initialize Log4j by Combining Configuration File with Programmatic Configuration|https://logging.apache.org/log4j/2.x/manual/customconfig.html#Hybrid] and [Programmatically Modifying the Current Configuration after Initialization|https://logging.apache.org/log4j/2.x/manual/customconfig.html#Programmatically_Modifying_the_Current_Configuration_after_Initialization]. 
> However both these techniques are limited as to what they can accomplish:
>  * MyXMLConfiguration.doConfigure() is shown adding an appender, via addLogger method
>  * A custom configuration super.setup() method is shown using config.addLogger() and then ctx.updateLoggers().
> My challenge is to programatically update the configuration to:
>  * Override logfile output location, either directly modifying appender, or modifying config property used by appender.
>  * Optionally Filter out any RollingFileAppender or FileAppender appenders
>  * Optionally suppress (filter out) any Console loggers if asked
> I am seeking an api used to pre-process configuration objects if one is available.
> In the past when using a fluent / builder API there is an option to jump-start a builder with the configuration of an existing object. This approach would allow a builder to be loaded with an existing appender; revised, and a new appender generated as a replacement.
> {code:java}
> ConfigurationBuilder<BuiltConfiguration> builder = ConfigurationBuilderFactory.newConfigurationBuilder();
> Appender appender = config.getAppenders("geoserverlogfile");
> if( appender instanceof RollingFileAppender){
>     RollingFileAppender fileAppender =(RollingFileAppender) appender;
>     
>     AppenderComponentBuilder appenderBuilder = builder.
>         newAppender("geoserverlogfile", fileAppender)
>             .addAttribute("fileName", "${GEOSERVER_LOG_LOCATION}.log");
>     
>     config.getAppenders().remove("geoserverlogfile");
>     addAppender((Appender) appenderBuilder.build());
> }{code}
> The alternative is quite verbose and prone may miss copying new parameters added over time.
>  
> Candidates:
> *MyXMLConfiguration.setup()* prior to super.setup(): Unclear how easy/safe it is to to modify _rootNode_ structure directly? Is this what is intended?
> {code:java}
> public void setup() {
>     for( Node child : rootNode.getChildren()){
>         if ("Properties".equals(child.getName())){
>             for( Node property : child.getChildren() ){
>                 if( property.getAttributes().containsKey("name") &&
>                         property.getAttributes().get("name").equals("GEOSERVER_LOG_LOCATION")) {
>                     // override value with current GEOSERVER_LOG_LOCATION
>                     property.setValue("foo.log");
>                 }
>             }
>         }
>     }
>     super.setup();
> }{code}
> *MyXMLConfiguration.doConfigure()* before super.doConfigure(): should be able to modify _rootNode_ and make any changes required. Unclear how easy/safe it is to to modify node structure directly?
> *MyXMLConfiguration.doConfigure()*  after super.doConfigure(): is too late:
>  - Can add loggers and appenders
>  - Modifications to config.getProperties() are not reflected in appender configuration.
>  - Modifications to existing appenders cannot be accomplished
> {*}MyXMLConfiguration.{*}{*}preConfigure(Node){*} allows xml to be rewritten just-in-time:
> {code:java}
> @Overrideprotected void preConfigure(Node node) {
>     if( !node.isRoot() && node.getName().equals("Property")){
>         if( node.getAttributes().containsKey("name") &&
>                 node.getAttributes().get("name").equals("GEOSERVER_LOG_LOCATION")) {
>             // override value with current GEOSERVER_LOG_LOCATION
>             node.setValue("foo.log");
>         }
>     }
>     super.preConfigure(node);
> } {code}
> For reference see attached {*}DEFAULT_LOGGING.xml{*}.



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