001/**
002 * Logback: the reliable, generic, fast and flexible logging framework.
003 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
004 *
005 * This program and the accompanying materials are dual-licensed under
006 * either the terms of the Eclipse Public License v1.0 as published by
007 * the Eclipse Foundation
008 *
009 *   or (per the licensee's choosing)
010 *
011 * under the terms of the GNU Lesser General Public License version 2.1
012 * as published by the Free Software Foundation.
013 */
014package ch.qos.logback.core.sift;
015
016import ch.qos.logback.core.spi.LifeCycle;
017
018/**
019 * Implement this interface in order to compute a discriminating value for a
020 * given event of type <E>.
021 * 
022 * <p>The returned value can depend on any data available at the time of the
023 * call, including data contained within the currently running thread.
024 * 
025 * @author Ceki G&uuml;lc&uuml;
026 * 
027 * @param <E>
028 */
029public interface Discriminator<E> extends LifeCycle {
030
031    /**
032     * Given event 'e' return a discriminating value.
033     * 
034     * @param e
035     * @return
036     */
037    String getDiscriminatingValue(E e);
038
039    /**
040     * The key or variable name under which the discriminating value should be
041     * exported into the host environment. 
042     *
043     * @return
044     */
045    String getKey();
046}