Improve InfoStream class in trunk to be more consistent with logging-frameworks
like slf4j/log4j/commons-logging
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Key: LUCENE-3598
URL: https://issues.apache.org/jira/browse/LUCENE-3598
Project: Lucene - Java
Issue Type: Improvement
Components: core/index
Affects Versions: 4.0
Reporter: Uwe Schindler
Followup on a [thread by Shai Erea on
java-dev@lao|http://lucene.472066.n3.nabble.com/IndexWriter-infoStream-is-final-td3537485.html]:
I already discussed with Robert about that, that there is one thing missing.
Currently the IW only checks if the infoStream!=null and then passes the
message to the method, and that *may* ignore it. For your requirement it is the
case that this is enabled or disabled dynamically. Unfortunately if the
construction of the message is heavy, then this wastes resources.
I would like to add another method to this class: abstract boolean
isMessageEnabled() that can also be implemented. I would then replace all null
checks in IW by this method. The default config in IW would be changed to use a
NoOutputInfoStream that returns false here and ignores the message.
A simple logger wrapper for e.g. log4j / slf4j then could look like (ignoring
component, could be enabled):
Loger log = YourLoggingFramework.getLogger(IndexWriter.class);
{code:java}
public void message(String component, String message) {
log.debug(component + ": " + message);
}
public boolean isMessageEnabled(String component) {
return log.isDebugEnabled();
}
{code}
Using this you could enable/disable logging live by e.g. the log4j management
console of your app server by enabling/disabling IndexWriter.class logging.
The changes are really simple:
- PrintStreamInfoStream returns true, always, mabye make it dynamically
enable/disable to allow Shai's request
- infoStream.getDefault() is never null and can never be set to null. Instead
the default is a singleton NoOutputInfoStream that returns false of
isMessageEnabled().
- All null checks on infoStream should be replaced by
infoStream.isMessageEanbled(component), this is possible as always != null.
There are no slowdowns by this - it's like Collections.emptyList() instead
stupid null checks.
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