log4j:ERROR Flume append() failed.(flume-ng-log4jappender-1.4.0.jar bug)

       日志出现“log4j:ERROR Flume append() failed.”，发现flume-ng-log4jappender-1.4.0有一个bug。详细，请查阅：https://issues.apache.org/jira/browse/FLUME-2186。

       解决方法：修改flume-ng-log4jappender中的append方法。修改为：

 @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.    boolean ready = true;    String errorMsg = "Cannot Append to Appender! Appender either closed or" +              " not setup correctly!";    if (rpcClient == null) {      LogLog.error(errorMsg);      if (unsafeMode) {          activateOptions();          if(rpcClient == null || !rpcClient.isActive()) {              ready = false;          }      }else {          throw new FlumeException(errorMsg);      }    }    if(unsafeMode && !ready) {        return;    }    if(!rpcClient.isActive()){      reconnect();    }    if(rpcClient == null || !rpcClient.isActive()) {        if(unsafeMode) {              return;          } else {              LogLog.error(errorMsg);              throw new FlumeException(errorMsg);          }    }    //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.getTimeStamp()));    //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);    }  }