/*
 * 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 org.apache.storm.loadgen;

import com.esotericsoftware.kryo.io.Output;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Arrays;
import java.util.Collection;
import java.util.Map;
import org.apache.storm.metric.api.IMetricsConsumer;
import org.apache.storm.serialization.KryoValuesSerializer;
import org.apache.storm.task.IErrorReporter;
import org.apache.storm.task.TopologyContext;

/**
 * Listens for all metrics and POSTs them serialized to a configured URL.
 *
 * <p>To use, add this to your topology's configuration:
 * ```java
 *   conf.registerMetricsConsumer(HttpForwardingMetricsConsumer.class, "http://example.com:8080/metrics/my-topology/", 1);
 * ```
 *
 * <p>The body of the post is data serialized using {@link org.apache.storm.serialization.KryoValuesSerializer}, with the data passed in
 * as a list of `[TaskInfo, Collection&lt;DataPoint&gt;]`.  More things may be appended to the end of the list in the future.
 *
 * <p>The values can be deserialized using the org.apache.storm.serialization.KryoValuesDeserializer, and a correct config + classpath.
 *
 * <p>@see org.apache.storm.serialization.KryoValuesSerializer
 */
public class HttpForwardingMetricsConsumer implements IMetricsConsumer {
    private transient URL url;
    private transient IErrorReporter errorReporter;
    private transient KryoValuesSerializer serializer;
    private transient String topologyId;

    @Override
    public void prepare(Map<String, Object> topoConf, Object registrationArgument, TopologyContext context, IErrorReporter errorReporter) { 
        try {
            url = new URL((String)registrationArgument);
            this.errorReporter = errorReporter;
            serializer = new KryoValuesSerializer(topoConf);
            topologyId = context.getStormId();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void handleDataPoints(TaskInfo taskInfo, Collection<DataPoint> dataPoints) {
        try {
            HttpURLConnection con = (HttpURLConnection) url.openConnection();
            con.setRequestMethod("POST");
            con.setDoOutput(true);
            try (Output out = new Output(con.getOutputStream())) {
                serializer.serializeInto(Arrays.asList(taskInfo, dataPoints, topologyId), out);
                out.flush();
            }
            //The connection is not sent unless a response is requested
            int response = con.getResponseCode();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void cleanup() { }
}
