storm-core/src/jvm/backtype/storm/metric/IEventLogger.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package backtype.storm.metric;

import backtype.storm.task.TopologyContext;

import java.util.Date;
import java.util.Map;

/**
 * EventLogger interface for logging the event info to a sink like log file or db
 * for inspecting the events via UI for debugging.
 */
public interface IEventLogger {

    /**
     * A wrapper for the fields that we would log.
     */
    public static class EventInfo {
        String ts;
        String component;
        String task;
        String messageId;
        String values;
        EventInfo(String ts, String component, String task, String messageId, String values) {
            this.ts = ts;
            this.component = component;
            this.task = task;
            this.messageId = messageId;
            this.values = values;
        }

        /**
         * Returns a default formatted string with fields separated by ","
         *
         * @return a default formatted string with fields separated by ","
         */
        @Override
        public String toString() {
            return new Date(Long.parseLong(ts)).toString() + "," + component + "," + task + "," + messageId + "," + values;
        }
    }

    void prepare(Map stormConf, TopologyContext context);

    /**
     * This method would be invoked when the {@link EventLoggerBolt} receives a tuple from the spouts or bolts that has
     * event logging enabled.
     *
     * @param e the event
     */
    void log(EventInfo e);

    void close();
}