/*** 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.flume.interceptor;import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.List;
import java.util.Map;
import org.apache.flume.Context;
import org.apache.flume.Event;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import static org.apache.flume.interceptor.HostInterceptor.Constants.*;/*** Simple Interceptor class that sets the host name or IP on all events* that are intercepted.<p>* The host header is named <code>host</code> and its format is either the FQDN* or IP of the host on which this interceptor is run.*** Properties:<p>**   preserveExisting: Whether to preserve an existing value for 'host'*                     (default is false)<p>**   useIP: Whether to use IP address or fully-qualified hostname for 'host'*          header value (default is true)<p>**  hostHeader: Specify the key to be used in the event header map for the*          host name. (default is "host") <p>** Sample config:<p>** <code>*   agent.sources.r1.channels = c1<p>*   agent.sources.r1.type = SEQ<p>*   agent.sources.r1.interceptors = i1<p>*   agent.sources.r1.interceptors.i1.type = host<p>*   agent.sources.r1.interceptors.i1.preserveExisting = true<p>*   agent.sources.r1.interceptors.i1.useIP = false<p>*   agent.sources.r1.interceptors.i1.hostHeader = hostname<p>* </code>**/
public class HostInterceptor implements Interceptor {private static final Logger logger = LoggerFactory.getLogger(HostInterceptor.class);private final boolean preserveExisting;private final String header;private String host = null;/*** Only {@link HostInterceptor.Builder} can build me*/private HostInterceptor(boolean preserveExisting,boolean useIP, String header) {this.preserveExisting = preserveExisting;this.header = header;InetAddress addr;try {addr = InetAddress.getLocalHost();if (useIP) {host = addr.getHostAddress();} else {host = addr.getCanonicalHostName();}} catch (UnknownHostException e) {logger.warn("Could not get local host address. Exception follows.", e);}}@Overridepublic void initialize() {// no-op
  }/*** Modifies events in-place.*/@Overridepublic Event intercept(Event event) {Map<String, String> headers = event.getHeaders();if (preserveExisting && headers.containsKey(header)) {return event;}if(host != null) {headers.put(header, host);}return event;}/*** Delegates to {@link #intercept(Event)} in a loop.* @param events* @return*/@Overridepublic List<Event> intercept(List<Event> events) {for (Event event : events) {intercept(event);}return events;}@Overridepublic void close() {// no-op
  }/*** Builder which builds new instances of the HostInterceptor.*/public static class Builder implements Interceptor.Builder {private boolean preserveExisting = PRESERVE_DFLT;private boolean useIP = USE_IP_DFLT;private String header = HOST;@Overridepublic Interceptor build() {return new HostInterceptor(preserveExisting, useIP, header);}@Overridepublic void configure(Context context) {preserveExisting = context.getBoolean(PRESERVE, PRESERVE_DFLT);useIP = context.getBoolean(USE_IP, USE_IP_DFLT);header = context.getString(HOST_HEADER, HOST);}}public static class Constants {public static String HOST = "host";public static String PRESERVE = "preserveExisting";public static boolean PRESERVE_DFLT = false;public static String USE_IP = "useIP";public static boolean USE_IP_DFLT = true;public static String HOST_HEADER = "hostHeader";}}