public String toString() {
        return ArchiverHandler.class.getName() + ": root=" + absoluteRootDir;
    }
Generate prefix for log filenames based on log message.
<p>
<EM>This message is <code>public</code> only because we need
access to it in unit tests.  For all practical purposes this
method does not exist to you, the application programmer, OK? :-)</EM>
<p>
XXX optimize!
logserver/src/main/java/com/yahoo/logserver/handlers/archive/ArchiverHandler.java