Hello Ed,
As mentioned in my comment, if you need to create just a single appender at
application launch, then what you have done will probably work OK. However, if
you need to create appenders via configuration file, then the programmatic
approach you outlined will require a lot more workt. Moreover, if you need to
create multiple file appenders, one for each thread, then things are going to
get even more complicated.
As long as you stick to programmatic configuration, and a single thread per
application, you should be fine.
In any case, SiftingAppender provides an elegant solution tailored exactly for
the kind of problem you're facing.
Cheers,
Bridges, Ed (Citco) wrote:
Hello,
Following up from a comment from Ceci on StackOverflow:
http://stackoverflow.com/questions/1239227/dynamically-creating-destroying-logging-appenders
I'd like to get context around his point that it is not possible, since
it appears not only possible but quite easy. Likely I'm just missing
something and would like to get more background about how to approach
this problem.
I quote here my original question:
I have a legacy PSVM application which I'd like to redirect its logging
output to unique files per execution. So, if I invoke it at 10:00, then
have it redirect it's output to {thread-id}-10:00.log; and another
thread of execution may begin an execution at 10:01, and its output
would go to {thread-id}-10:01.log. I understand that this is not elegant.
My questions are:
· is this possible?
· does someone have an idea of how to approach?
· is it possible to release/destroy an appender when it's no
longer needed?
A suggestion I received on this posting proposed simply extending
FileAppender. Based on that I created a simple (naïve?) class named
"DynamicRuntimeFileAppender" like so:
public class DynamicRuntimeFileAppender extends FileAppender {
private static Logger log =
Logger.getLogger(DynamicRuntimeFileAppender.class);
public DynamicRuntimeFileAppender() {
}
public DynamicRuntimeFileAppender(
Layout layout,
String filename,
boolean append,
boolean bufferedIO,
int bufferSize) throws IOException {
super(layout, filename, append, bufferedIO, bufferSize);
}
public DynamicRuntimeFileAppender(
Layout layout,
String filename,
boolean append) throws IOException {
super(layout, filename, append);
}
public DynamicRuntimeFileAppender(
Layout layout,
String filename) throws IOException {
super(layout, filename);
}
public static Appender configuredInstance(String filename) throws
IOException {
if(null == filename || filename.length() < 1) {
throw new IllegalArgumentException("filename cannot be empty.");
}
HTMLLayout layout = new HTMLLayout();
layout.setTitle(filename);
boolean append = false;
DynamicRuntimeFileAppender appender = new
DynamicRuntimeFileAppender(layout, filename, append);
appender.setName(filename);
appender.setBufferedIO(false);
appender.setEncoding("UTF-8");
appender.setImmediateFlush(true);
appender.setThreshold(Level.ALL);
return appender;
}
}
When I run it using a test like this, it appears to work fine:
private static final Logger log = Logger.getLogger(Log4JTest.class);
@Test
public void testAddAppender() throws Exception {
Appender a = DynamicRuntimeFileAppender.configuredInstance(
buildFilename("target/Log4JTest")
);
log.addAppender(a);
log.info(format("test message using appender [%s]", a.getName()));
log.removeAppender(a);
a.close();
}
Thank you very much.
Ed
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Ceki Gülcü
Logback: The reliable, generic, fast and flexible logging framework for Java.
http://logback.qos.ch
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