Flume学习（五）：Flume Channel Selectors使用

转载：http://blog.csdn.net/xiao_jun_0820/article/details/38116103

前几篇文章只有一个项目的日志，现在我们考虑多个项目的日志的收集，我拷贝了一份flumedemo项目,重命名为flumedemo2,添加了一个WriteLog2.java类，稍微改动了一下JSON字符串的输出，将以前requestUrl中的"reporter-api"改为了"image-api",以便和WriteLog类的输出稍微区分开来，如下：

 package com.besttone.flume;

 import java.util.Date;

 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;

 public class WriteLog2 {
     protected static final Log logger = LogFactory.getLog(WriteLog2.class);

     /**
      * @param args
      * @throws InterruptedException
      */
     public static void main(String[] args) throws InterruptedException {
         // TODO Auto-generated method stub
         while (true) {
             logger.info(new Date().getTime());
             logger.info("{\"requestTime\":"
                     + System.currentTimeMillis()
                     + ",\"requestParams\":{\"timestamp\":1405499314238,\"phone\":\"02038824941\",\"cardName\":\"测试商家名称\",\"provinceCode\":\"440000\",\"cityCode\":\"440106\"},\"requestUrl\":\"/image-api/reporter/reporter12/init.do\"}");
             Thread.sleep(2000);

         }
     }
 }

现在有这么一个需求描述：要求flumedemo的项目的log4j日志输出到hdfs,而flumedemo2项目的log4j日志输出到agent的log日志中。

我们还是采用log4jappender来配置log4j输出给flume的souce,现在的需求明显是有两个sink了，一个sink为hdfs,一个sink为logger。于是现在的拓扑结构应该是这样的：

需要实现这么一个拓扑接口，就需要使用到channel selectors，让不同的项目日志通过不同的channel到不同的sink中去。

官方文档上channel selectors 有两种类型:

Replicating Channel Selector (default)

Multiplexing Channel Selector

这两种selector的区别是:Replicating 会将source过来的events发往所有channel,而Multiplexing 可以选择该发往哪些channel。对于上面的例子来说，如果采用Replicating ,那么demo和demo2的日志会同时发往channel1和channel2,这显然是和需求不符的，需求只是让demo的日志发往channel1,而demo2的日志发往channel2。

综上所述，我们选择Multiplexing Channel Selector。这里我们有遇到一个棘手的问题，Multiplexing 需要判断header里指定key的值来决定分发到某个具体的channel，我们现在demo和demo2同时运行在同一个服务器上，如果在不同的服务器上运行，我们可以在 source1上加上一个 host 拦截器（上一篇有介绍过），这样可以通过header中的host来判断event该分发给哪个channel，而这里是在同一个服务器上，由host是区分不出来日志的来源的，我们必须想办法在header中添加一个key来区分日志的来源。

设想一下，如果header中有一个key:flume.client.log4j.logger.source,我们通过设置这个key的值，demo设为app1,demo2设为app2,这样我们就能通过设置：

tier1.sources.source1.channels=channel1 channel2
tier1.sources.source1.selector.type=multiplexing
tier1.sources.source1.selector.header=flume.client.log4j.logger.source
tier1.sources.source1.selector.mapping.app1=channel1
tier1.sources.source1.selector.mapping.app2=channel2

来将不同项目的的日志输出到不同的channel了。

我们按照这个思路继续下去，遇到了困难，log4jappender没有这样的参数来让你设置。怎么办？翻看了一下log4jappender的源码，发现可以很容易的实现扩展参数，于是我复制了一份log4jappender代码，新加了一个类叫Log4jExtAppender.java,里面扩展了一个参数叫：source,代码如下：

 package com.besttone.flume;

 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.nio.charset.Charset;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Properties;

 import org.apache.avro.Schema;
 import org.apache.avro.generic.GenericRecord;
 import org.apache.avro.io.BinaryEncoder;
 import org.apache.avro.io.DatumWriter;
 import org.apache.avro.io.EncoderFactory;
 import org.apache.avro.reflect.ReflectData;
 import org.apache.avro.reflect.ReflectDatumWriter;
 import org.apache.avro.specific.SpecificRecord;
 import org.apache.flume.Event;
 import org.apache.flume.EventDeliveryException;
 import org.apache.flume.FlumeException;
 import org.apache.flume.api.RpcClient;
 import org.apache.flume.api.RpcClientConfigurationConstants;
 import org.apache.flume.api.RpcClientFactory;
 import org.apache.flume.clients.log4jappender.Log4jAvroHeaders;
 import org.apache.flume.event.EventBuilder;
 import org.apache.log4j.AppenderSkeleton;
 import org.apache.log4j.helpers.LogLog;
 import org.apache.log4j.spi.LoggingEvent;

 /**
  *
  * Appends Log4j Events to an external Flume client which is decribed by the
  * Log4j configuration file. The appender takes two required parameters:
  * <p>
  * <strong>Hostname</strong> : This is the hostname of the first hop at which
  * Flume (through an AvroSource) is listening for events.
  * </p>
  * <p>
  * <strong>Port</strong> : This the port on the above host where the Flume
  * Source is listening for events.
  * </p>
  * A sample log4j properties file which appends to a source would look like:
  *
  * <pre>
  * <p>
  * log4j.appender.out2 = org.apache.flume.clients.log4jappender.Log4jAppender
  * log4j.appender.out2.Port = 25430
  * log4j.appender.out2.Hostname = foobarflumesource.com
  * log4j.logger.org.apache.flume.clients.log4jappender = DEBUG,out2</p>
  * </pre>
  * <p>
  * <i>Note: Change the last line to the package of the class(es), that will do
  * the appending.For example if classes from the package com.bar.foo are
  * appending, the last line would be:</i>
  * </p>
  *
  * <pre>
  * <p>log4j.logger.com.bar.foo = DEBUG,out2</p>
  * </pre>
  *
  *
  */
 public class Log4jExtAppender extends AppenderSkeleton {

     private String hostname;
     private int port;
     private String source;

     public String getSource() {
         return source;
     }

     public void setSource(String source) {
         this.source = source;
     }

     private boolean unsafeMode = false;
     private long timeout = RpcClientConfigurationConstants.DEFAULT_REQUEST_TIMEOUT_MILLIS;
     private boolean avroReflectionEnabled;
     private String avroSchemaUrl;

     RpcClient rpcClient = null;

     /**
      * If this constructor is used programmatically rather than from a log4j
      * conf you must set the <tt>port</tt> and <tt>hostname</tt> and then call
      * <tt>activateOptions()</tt> before calling <tt>append()</tt>.
      */
     public Log4jExtAppender() {
     }

     /**
      * Sets the hostname and port. Even if these are passed the
      * <tt>activateOptions()</tt> function must be called before calling
      * <tt>append()</tt>, else <tt>append()</tt> will throw an Exception.
      *
      * @param hostname
      *            The first hop where the client should connect to.
      * @param port
      *            The port to connect on the host.
      *
      */
     public Log4jExtAppender(String hostname, int port, String source) {
         this.hostname = hostname;
         this.port = port;
         this.source = source;
     }

     /**
      * Append the LoggingEvent, to send to the first Flume hop.
      *
      * @param event
      *            The LoggingEvent to be appended to the flume.
      * @throws FlumeException
      *             if the appender was closed, or the hostname and port were not
      *             setup, there was a timeout, or there was a connection error.
      */
     @Override
     public synchronized void append(LoggingEvent event) throws FlumeException {
         // If rpcClient is null, it means either this appender object was never
         // setup by setting hostname and port and then calling activateOptions
         // or this appender object was closed by calling close(), so we throw an
         // exception to show the appender is no longer accessible.
         if (rpcClient == null) {
             String errorMsg = "Cannot Append to Appender! Appender either closed or"
                     + " not setup correctly!";
             LogLog.error(errorMsg);
             if (unsafeMode) {
                 return;
             }
             throw new FlumeException(errorMsg);
         }

         if (!rpcClient.isActive()) {
             reconnect();
         }

         // Client created first time append is called.
         Map<String, String> hdrs = new HashMap<String, String>();
         hdrs.put(Log4jAvroHeaders.LOGGER_NAME.toString(), event.getLoggerName());
         hdrs.put(Log4jAvroHeaders.TIMESTAMP.toString(),
                 String.valueOf(event.timeStamp));

         // 添加日志来源
         if (this.source == null || this.source.equals("")) {
             this.source = "unknown";
         }
         hdrs.put("flume.client.log4j.logger.source", this.source);
         // To get the level back simply use
         // LoggerEvent.toLevel(hdrs.get(Integer.parseInt(
         // Log4jAvroHeaders.LOG_LEVEL.toString()))
         hdrs.put(Log4jAvroHeaders.LOG_LEVEL.toString(),
                 String.valueOf(event.getLevel().toInt()));

         Event flumeEvent;
         Object message = event.getMessage();
         if (message instanceof GenericRecord) {
             GenericRecord record = (GenericRecord) message;
             populateAvroHeaders(hdrs, record.getSchema(), message);
             flumeEvent = EventBuilder.withBody(
                     serialize(record, record.getSchema()), hdrs);
         } else if (message instanceof SpecificRecord || avroReflectionEnabled) {
             Schema schema = ReflectData.get().getSchema(message.getClass());
             populateAvroHeaders(hdrs, schema, message);
             flumeEvent = EventBuilder
                     .withBody(serialize(message, schema), hdrs);
         } else {
             hdrs.put(Log4jAvroHeaders.MESSAGE_ENCODING.toString(), "UTF8");
             String msg = layout != null ? layout.format(event) : message
                     .toString();
             flumeEvent = EventBuilder.withBody(msg, Charset.forName("UTF8"),
                     hdrs);
         }

         try {
             rpcClient.append(flumeEvent);
         } catch (EventDeliveryException e) {
             String msg = "Flume append() failed.";
             LogLog.error(msg);
             if (unsafeMode) {
                 return;
             }
             throw new FlumeException(msg + " Exception follows.", e);
         }
     }

     private Schema schema;
     private ByteArrayOutputStream out;
     private DatumWriter<Object> writer;
     private BinaryEncoder encoder;

     protected void populateAvroHeaders(Map<String, String> hdrs, Schema schema,
             Object message) {
         if (avroSchemaUrl != null) {
             hdrs.put(Log4jAvroHeaders.AVRO_SCHEMA_URL.toString(), avroSchemaUrl);
             return;
         }
         LogLog.warn("Cannot find ID for schema. Adding header for schema, "
                 + "which may be inefficient. Consider setting up an Avro Schema Cache.");
         hdrs.put(Log4jAvroHeaders.AVRO_SCHEMA_LITERAL.toString(),
                 schema.toString());
     }

     private byte[] serialize(Object datum, Schema datumSchema)
             throws FlumeException {
         if (schema == null || !datumSchema.equals(schema)) {
             schema = datumSchema;
             out = new ByteArrayOutputStream();
             writer = new ReflectDatumWriter<Object>(schema);
             encoder = EncoderFactory.get().binaryEncoder(out, null);
         }
         out.reset();
         try {
             writer.write(datum, encoder);
             encoder.flush();
             return out.toByteArray();
         } catch (IOException e) {
             throw new FlumeException(e);
         }
     }

     // This function should be synchronized to make sure one thread
     // does not close an appender another thread is using, and hence risking
     // a null pointer exception.
     /**
      * Closes underlying client. If <tt>append()</tt> is called after this
      * function is called, it will throw an exception.
      *
      * @throws FlumeException
      *             if errors occur during close
      */
     @Override
     public synchronized void close() throws FlumeException {
         // Any append calls after this will result in an Exception.
         if (rpcClient != null) {
             try {
                 rpcClient.close();
             } catch (FlumeException ex) {
                 LogLog.error("Error while trying to close RpcClient.", ex);
                 if (unsafeMode) {
                     return;
                 }
                 throw ex;
             } finally {
                 rpcClient = null;
             }
         } else {
             String errorMsg = "Flume log4jappender already closed!";
             LogLog.error(errorMsg);
             if (unsafeMode) {
                 return;
             }
             throw new FlumeException(errorMsg);
         }
     }

     @Override
     public boolean requiresLayout() {
         // This method is named quite incorrectly in the interface. It should
         // probably be called canUseLayout or something. According to the docs,
         // even if the appender can work without a layout, if it can work with
         // one,
         // this method must return true.
         return true;
     }

     /**
      * Set the first flume hop hostname.
      *
      * @param hostname
      *            The first hop where the client should connect to.
      */
     public void setHostname(String hostname) {
         this.hostname = hostname;
     }

     /**
      * Set the port on the hostname to connect to.
      *
      * @param port
      *            The port to connect on the host.
      */
     public void setPort(int port) {
         this.port = port;
     }

     public void setUnsafeMode(boolean unsafeMode) {
         this.unsafeMode = unsafeMode;
     }

     public boolean getUnsafeMode() {
         return unsafeMode;
     }

     public void setTimeout(long timeout) {
         this.timeout = timeout;
     }

     public long getTimeout() {
         return this.timeout;
     }

     public void setAvroReflectionEnabled(boolean avroReflectionEnabled) {
         this.avroReflectionEnabled = avroReflectionEnabled;
     }

     public void setAvroSchemaUrl(String avroSchemaUrl) {
         this.avroSchemaUrl = avroSchemaUrl;
     }

     /**
      * Activate the options set using <tt>setPort()</tt> and
      * <tt>setHostname()</tt>
      *
      * @throws FlumeException
      *             if the <tt>hostname</tt> and <tt>port</tt> combination is
      *             invalid.
      */
     @Override
     public void activateOptions() throws FlumeException {
         Properties props = new Properties();
         props.setProperty(RpcClientConfigurationConstants.CONFIG_HOSTS, "h1");
         props.setProperty(RpcClientConfigurationConstants.CONFIG_HOSTS_PREFIX
                 + "h1", hostname + ":" + port);
         props.setProperty(
                 RpcClientConfigurationConstants.CONFIG_CONNECT_TIMEOUT,
                 String.valueOf(timeout));
         props.setProperty(
                 RpcClientConfigurationConstants.CONFIG_REQUEST_TIMEOUT,
                 String.valueOf(timeout));
         try {
             rpcClient = RpcClientFactory.getInstance(props);
             if (layout != null) {
                 layout.activateOptions();
             }
         } catch (FlumeException e) {
             String errormsg = "RPC client creation failed! " + e.getMessage();
             LogLog.error(errormsg);
             if (unsafeMode) {
                 return;
             }
             throw e;
         }
     }

     /**
      * Make it easy to reconnect on failure
      *
      * @throws FlumeException
      */
     private void reconnect() throws FlumeException {
         close();
         activateOptions();
     }
 }

然后然后将这个类打了一个jar包：Log4jExtAppender.jar，扔在了flumedemo和flumedemo2的lib目录下。

这时候flumedemo的log4j.properties如下：

 log4j.rootLogger=INFO


 log4j.category.com.besttone=INFO,flume,console,LogFile

 #log4j.appender.flume = org.apache.flume.clients.log4jappender.Log4jExtAppender
 log4j.appender.flume = com.besttone.flume.Log4jExtAppender
 log4j.appender.flume.Hostname = localhost
 log4j.appender.flume.Port = 44444
 log4j.appender.flume.UnsafeMode = false
 log4j.appender.flume.Source = app1


 log4j.appender.console= org.apache.log4j.ConsoleAppender
 log4j.appender.console.Target= System.out
 log4j.appender.console.layout= org.apache.log4j.PatternLayout
 log4j.appender.console.layout.ConversionPattern= %d{yyyy-MM-dd HH:mm:ss} %5p %c{1}: %L - %m%n

 log4j.appender.LogFile= org.apache.log4j.DailyRollingFileAppender
 log4j.appender.LogFile.File= logs/app.log
 log4j.appender.LogFile.MaxFileSize=10KB
 log4j.appender.LogFile.Append= true
 log4j.appender.LogFile.Threshold= DEBUG
 log4j.appender.LogFile.layout= org.apache.log4j.PatternLayout
 log4j.appender.LogFile.layout.ConversionPattern= %-d{yyyy-MM-dd HH:mm:ss} [%t:%r] - [%5p] %m%n

flumedemo2的如下：

 log4j.rootLogger=INFO


 log4j.category.com.besttone=INFO,flume,console,LogFile

 #log4j.appender.flume = org.apache.flume.clients.log4jappender.Log4jExtAppender
 log4j.appender.flume = com.besttone.flume.Log4jExtAppender
 log4j.appender.flume.Hostname = localhost
 log4j.appender.flume.Port = 44444
 log4j.appender.flume.UnsafeMode = false
 log4j.appender.flume.Source = app2


 log4j.appender.console= org.apache.log4j.ConsoleAppender
 log4j.appender.console.Target= System.out
 log4j.appender.console.layout= org.apache.log4j.PatternLayout
 log4j.appender.console.layout.ConversionPattern= %d{yyyy-MM-dd HH:mm:ss} %5p %c{1}: %L - %m%n

 log4j.appender.LogFile= org.apache.log4j.DailyRollingFileAppender
 log4j.appender.LogFile.File= logs/app.log
 log4j.appender.LogFile.MaxFileSize=10KB
 log4j.appender.LogFile.Append= true
 log4j.appender.LogFile.Threshold= DEBUG
 log4j.appender.LogFile.layout= org.apache.log4j.PatternLayout
 log4j.appender.LogFile.layout.ConversionPattern= %-d{yyyy-MM-dd HH:mm:ss} [%t:%r] - [%5p] %m%n

将原来的log4j.appender.flume 由org.apache.flume.clients.log4jappender.Log4jExtAppender改为了我重新实现添加了source参数的com.besttone.flume.Log4jExtAppender

然后flumedemo的log4j.appender.flume.Source = app1，flumedemo2的log4j.appender.flume.Source = app2。

运行flumedemo的WriteLog类，和和flumedemo2的WriteLog2类，分别去hdfs上和agent的log文件中看看内容，发现hdfs上都是app1的日志，log文件中都是app2的日志，功能实现。

完整的flume.conf如下：

 tier1.sources=source1
 tier1.channels=channel1 channel2
 tier1.sinks=sink1 sink2
 tier1.sources.source1.type=avro
 tier1.sources.source1.bind=0.0.0.0
 tier1.sources.source1.port=44444
 tier1.sources.source1.channels=channel1 channel2
 tier1.sources.source1.selector.type=multiplexing
 tier1.sources.source1.selector.header=flume.client.log4j.logger.source
 tier1.sources.source1.selector.mapping.app1=channel1
 tier1.sources.source1.selector.mapping.app2=channel2
 tier1.sources.source1.interceptors=i1 i2
 tier1.sources.source1.interceptors.i1.type=regex_filter
 tier1.sources.source1.interceptors.i1.regex=\\{.*\\}
 tier1.sources.source1.interceptors.i2.type=timestamp
 tier1.channels.channel1.type=memory
 tier1.channels.channel1.capacity=10000
 tier1.channels.channel1.transactionCapacity=1000
 tier1.channels.channel1.keep-alive=30
 tier1.channels.channel2.type=memory
 tier1.channels.channel2.capacity=10000
 tier1.channels.channel2.transactionCapacity=1000
 tier1.channels.channel2.keep-alive=30
 tier1.sinks.sink1.type=hdfs
 tier1.sinks.sink1.channel=channel1
 tier1.sinks.sink1.hdfs.path=hdfs://master68:8020/flume/events/%y-%m-%d
 tier1.sinks.sink1.hdfs.round=true
 tier1.sinks.sink1.hdfs.roundValue=10
 tier1.sinks.sink1.hdfs.roundUnit=minute
 tier1.sinks.sink1.hdfs.fileType=DataStream
 tier1.sinks.sink1.hdfs.writeFormat=Text
 tier1.sinks.sink1.hdfs.rollInterval=0
 tier1.sinks.sink1.hdfs.rollSize=10240
 tier1.sinks.sink1.hdfs.rollCount=0
 tier1.sinks.sink1.hdfs.idleTimeout=60
 tier1.sinks.sink2.type=logger
 tier1.sinks.sink2.channel=channel2