先说两句：
公司最近需要做一个数据分析平台，主要功能就是收集app中用户的行为日志，然后通过日志分析出一些通用的报表数据、用户行为预测等等，便于运营。
日志怎么接入：
接入的日志服务器端开发用的C++，日志打印用的log4cplus，使用java的同学可能比较熟悉log4j，其实都一样。Just so so。直接上配置文件：
#flume_log
log4cplus.appender.R6=log4cplus::SocketAppender
log4cplus.appender.R6.host=10.132.34.12
log4cplus.appender.R6.port=44444
log4cplus.appender.R6.layout=log4cplus::PatternLayout
log4cplus.appender.R6.layout.ConversionPattern=%m
直接采用SocketAppender发送日志到远程服务器，从上面的配置可以得到，10.132.34.12就是Flume接受日志的服务器，44444就是Flume的端口号。
Flume配置：
由于采用的是SocketAppender，Flume这边可以采用SyslogTcpSource，直接上配置文件：
a1.sources = s1
a1.sinks = k1
a1.channels = c1
a1.sources.s1.type = syslogtcp
a1.sources.s1.host = 10.132.34.12
a1.sources.s1.port = 44444
a1.sources.s1.channels = c1
a1.channels.c1.type = memory
a1.channels.c1.capacity = 10000
a1.channels.c1.transactionCapacity = 100
a1.sinks.k1.type = logger
a1.sinks.k1.channel = c1
开始配置的时候感觉一切怎么都这么顺利呢，So Easy有没有。后来测试的时候才发现现在才刚刚开始。
问题1：消息怎么没有换行呢？
消息接入的时候log4cplus里面的配置为：log4cplus.appender.R6.layout.ConversionPattern=%m，是不是加上'%n'就ok了，加上'%n'后测试发现问题没有解决，尝试手动在日志后面加上'\n'呢，还是不行。但是消息打印到本地磁盘，一些都那么美好，通过SocketAppender就是没有换行，崩溃中...
问题2：为什么Flume接收的日志总有乱码？
Flume通过logger Sink打印的日志中总有乱码，通过tcpdump发现tcp包中确实包含一些无关信息。难道是发送的时候数据就有问题，反复检查C++代码发现没有问题。
咋办呢？
本猿是一名java程序员，对C++不太了解。查看了下org.apache.log4j.net.SocketAppender的源码。发现了一些端倪。
首先在SocketAppender中声明了一个ObjectOutputStream oos;的变量，
在connect方法内部对oos进行了实例化，oos=new ObjectOutputStream(newSocket(address,port).getOutputStream());
在append方法内部调用的是:oos.writeObject(event);其中event类型是org.apache.log4j.spi.LoggingEvent。
到此为什么出现乱码，为什么消息里的换行符不起作用看起来就明了了。
原来SocketAppender发送的是一个序列化后的对象，而Flume的SyslogTcpSource接收到tcp包后没有进行反序列化，而是直接将收到的消息作为日志内容进行解析，出现乱码就不奇怪了。
随后网上download了一份log4cplus的源码，发现里面的实现基本和java一致，SocketAppender发送的消息也是序列化后的对象。具体代码如下：
其中convertToBuffer的代码如下：
解决：
1、客服端修改logcplus源码重新编译安装，在append方法内部修改发送内容，直接将消息内容发送到Flume（需要修改代码bool ret = socket.write(msgBuffer);），联系客户端 同学，说难度比较大，扩展性不好，放弃了。
2、重写Flume的SyslogTcpSouce源码，在Flume端解析对象内容。C++端解析的源码如下：
通过上面的代码，可以很容易的写出java的实现版本。
注意：java解析到消息内容后，如果消息不是'\n'结尾，需要手动添加'\n'，否则Flume无法正常解析日志内容。由于SyslogTcpSource的消息默认长度为2500Byte，所以当日志达到最大值的时候会切断消息内容。
由此所有的问题看似都完美解决了。附修改后的完整代码一份，如下：
packagecom.mirror.game.flume.source;
importorg.apache.flume.ChannelException;
importorg.apache.flume.*;
importorg.apache.flume.conf.Configurable;
importorg.apache.flume.conf.Configurables;
importorg.apache.flume.source.AbstractSource;
importorg.apache.flume.source.SyslogSourceConfigurationConstants;
importorg.apache.flume.source.SyslogUtils;
importorg.jboss.netty.bootstrap.ServerBootstrap;
importorg.jboss.netty.buffer.ChannelBuffer;
importorg.jboss.netty.buffer.ChannelBufferFactory;
importorg.jboss.netty.buffer.ChannelBuffers;
importorg.jboss.netty.channel.Channel;
importorg.jboss.netty.channel.ChannelFactory;
importorg.jboss.netty.channel.*;
importorg.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
importorg.slf4j.Logger;
importorg.slf4j.LoggerFactory;
importjava.net.InetSocketAddress;
importjava.nio.ByteOrder;
importjava.util.Map;
importjava.util.Set;
importjava.util.concurrent.Executors;
importjava.util.concurrent.TimeUnit;
/**
*@Author: 小胖墩
*@Description:
* 接受log4cplus序列化后的对象，并对tcp包反序列化得到日志内容。log4cplus序列化和反序列化的过程参考socketappender.cxx的源码。
*
* 序列化过程如下：
* void convertToBuffer(SocketBuffer & buffer, const spi::InternalLoggingEvent& event, const tstring& serverName)
* {
*
* buffer.appendByte(LOG4CPLUS_MESSAGE_VERSION);
* #ifndef UNICODE
* buffer.appendByte(1);
* #else
* buffer.appendByte(2);
* #endif
*
* buffer.appendString(serverName);
* buffer.appendString(event.getLoggerName());
* buffer.appendInt(event.getLogLevel());
* buffer.appendString(event.getNDC());
* buffer.appendString(event.getMessage());
* buffer.appendString(event.getThread());
* buffer.appendInt( static_cast(event.getTimestamp().sec()) );
* buffer.appendInt( static_cast(event.getTimestamp().usec()) );
* buffer.appendString(event.getFile());
* buffer.appendInt(event.getLine());
* buffer.appendString(event.getFunction());
* }
*
* 反序列化过程如下：
* spi::InternalLoggingEvent readFromBuffer(SocketBuffer& buffer)
* {
* unsigned char msgVersion = buffer.readByte();
* if(msgVersion != LOG4CPLUS_MESSAGE_VERSION) {
* LogLog * loglog = LogLog::getLogLog();
* loglog->warn(LOG4CPLUS_TEXT("readFromBuffer() received socket message with an invalid version"));
* }
*
* unsigned char sizeOfChar = buffer.readByte();
*
* tstring serverName = buffer.readString(sizeOfChar);
* tstring loggerName = buffer.readString(sizeOfChar);
* LogLevel ll = buffer.readInt();
* tstring ndc = buffer.readString(sizeOfChar);
* if(! serverName.empty ()) {
* if(ndc.empty ()) {
* ndc = serverName;
* }
* else {
* ndc = serverName + LOG4CPLUS_TEXT(" - ") + ndc;
* }
* }
* tstring message = buffer.readString(sizeOfChar);
* tstring thread = buffer.readString(sizeOfChar);
* long sec = buffer.readInt();
* long usec = buffer.readInt();
* tstring file = buffer.readString(sizeOfChar);
* int line = buffer.readInt();
* tstring function = buffer.readString(sizeOfChar);
*
* spi::InternalLoggingEvent ev (loggerName, ll, ndc,
* MappedDiagnosticContextMap (), message, thread, internal::empty_str,
* Time(sec, usec), file, line, function);
* return ev;
* }
*
*@Date: 2017/10/21 16:53
*@ModifiedBy :
*/
public classMirrorSyslogTcpSourceextendsAbstractSourceimplementsEventDrivenSource,Configurable {
private static finalLoggerlogger= LoggerFactory.getLogger(MirrorSyslogTcpSource.class);
private intport;
privateStringhost=null;
privateChannelnettyChannel;
privateIntegereventSize;
privateMapformaterProp;
privateCounterGroupcounterGroup=newCounterGroup();
privateSetkeepFields;
public classsyslogTcpHandlerextendsSimpleChannelHandler {
privateSyslogUtilssyslogUtils=newSyslogUtils();
public voidsetEventSize(inteventSize){
syslogUtils.setEventSize(eventSize);
}
public voidsetKeepFields(Set keepFields) {
syslogUtils.setKeepFields(keepFields);
}
public voidsetFormater(Map prop) {
syslogUtils.addFormats(prop);
}
@Override
public voidmessageReceived(ChannelHandlerContext ctx,MessageEvent mEvent) {
ChannelBuffer buff = (ChannelBuffer) mEvent.getMessage();
while(buff.readable()) {
try{
intlength = buff.readInt();//消息总长度
ChannelBuffer eventBuffer = buff.readBytes(length);//消息你内容，log4cplus将InternalLoggingEvent封装序列化后的结果
intmessageVersion = eventBuffer.readByte();//消息版本号，log4cplus默认消息版本号为3
intsizeOfChar = eventBuffer.readByte();//char的字节长度，unicode=1，否则=2
intserverNameLength = eventBuffer.readInt();//获取server name
ChannelBuffer serverNameBuffer =null;
if(serverNameLength >0){
serverNameBuffer = eventBuffer.readBytes(serverNameLength * sizeOfChar);//serverName
}
intloggerNameLength = eventBuffer.readInt();
ChannelBuffer loggerNameBuffer =null;
if(loggerNameLength >0){
loggerNameBuffer = eventBuffer.readBytes(loggerNameLength * sizeOfChar);//loggerName
}
intlogLevel = eventBuffer.readInt();//日志级别
intndcLength = eventBuffer.readInt();// ndc
ChannelBuffer ndcBuffer =null;
if(ndcLength >0){
ndcBuffer = eventBuffer.readBytes(ndcLength * sizeOfChar);
}
intmessageLength = eventBuffer.readInt();//消息内容
ChannelBuffer messageBuffer =null;
if(messageLength >0){
intlen = messageLength * sizeOfChar;
messageBuffer = eventBuffer.readBytes(len);
/**
* 必须在消息末尾添加‘\n’，否则消息解析失败.
*/
byte[] messageArray = messageBuffer.array();
if(messageArray[len-1] !='\n'){
byte[] newArray =new byte[len+1];
System.arraycopy(messageArray,0,newArray,0,len);
newArray[len] ='\n';
messageBuffer = ChannelBuffers.buffer(ByteOrder.LITTLE_ENDIAN,newArray.length);
messageBuffer.writeBytes(newArray);
}
}
if(logger.isDebugEnabled()){
intthreadLength = eventBuffer.readInt();//线程名字
ChannelBuffer threadBuffer =null;
if(threadLength >0){
threadBuffer = eventBuffer.readBytes(threadLength * sizeOfChar);
}
inttimeStampSec = eventBuffer.readInt();//时间戳
inttimeStampUsec = eventBuffer.readInt();
intfileLength = eventBuffer.readInt();//打印日志的文件
ChannelBuffer fileBuffer =null;
if(fileLength >0){
fileBuffer = eventBuffer.readBytes(fileLength * sizeOfChar);
}
intline = eventBuffer.readInt();//代码中的行数
intfuncLength = eventBuffer.readInt();//打印日志的方法名
ChannelBuffer functionBuffer =null;
if(funcLength >0){
functionBuffer = eventBuffer.readBytes(funcLength * sizeOfChar);
}
StringBuilder sb =newStringBuilder("{");
sb.append("length=").append(length).append(",")
.append("messageVersion=").append(messageVersion).append(",")
.append("serverNameLength=").append(serverNameLength).append(",")
.append("serverName=").append(serverNameBuffer==null?"null":newString(serverNameBuffer.array(),"utf-8")).append(",")
.append("loggerNameLength=").append(loggerNameLength).append(",")
.append("loggerName=").append(loggerNameBuffer==null?"null":newString(loggerNameBuffer.array(),"utf-8")).append(",")
.append("logLevel=").append(logLevel).append(",")
.append("ndcLength=").append(ndcLength).append(",")
.append("ndc=").append(ndcBuffer ==null?"null":newString(ndcBuffer.array(),"utf-8")).append(",")
.append("messageLength=").append(messageLength).append(",")
.append("message=").append(messageBuffer ==null?"null":newString(messageBuffer.array(),"utf-8")).append(",")
.append("threadLength=").append(threadLength).append(",")
.append("thread=").append(threadBuffer==null?"null":newString(threadBuffer.array(),"utf-8")).append(",")
.append("timeStampSec=").append(timeStampSec).append(",")
.append("timeStampUsec=").append(timeStampUsec).append(",")
.append("fileLength=").append(fileLength).append(",")
.append("file=").append(fileBuffer==null?"null":newString(fileBuffer.array(),"utf-8")).append(",")
.append("line=").append(line).append(",")
.append("funcLength=").append(funcLength).append(",")
.append("func=").append(functionBuffer==null?"null":newString(functionBuffer.array(),"utf-8")).append(",")
.append("}");
logger.debug(sb.toString());
}
Event e =syslogUtils.extractEvent(messageBuffer);
if(e ==null) {
logger.warn("Event is null, Parsed partial event, event will be generated when rest of the event is received.");
continue;
}
try{
getChannelProcessor().processEvent(e);
counterGroup.incrementAndGet("events.success");
}catch(ChannelException ex) {
counterGroup.incrementAndGet("events.dropped");
logger.error("Error writting to channel, event dropped",ex);
}
}catch(Exception e){
logger.error("read message error,",e);
}
}
}
}
@Override
public voidstart() {
ChannelFactory factory =newNioServerSocketChannelFactory(Executors.newCachedThreadPool(),Executors.newCachedThreadPool());
ServerBootstrap serverBootstrap =newServerBootstrap(factory);
serverBootstrap.setPipelineFactory(() -> {
syslogTcpHandler handler =newsyslogTcpHandler();
handler.setEventSize(eventSize);
handler.setFormater(formaterProp);
handler.setKeepFields(keepFields);
returnChannels.pipeline(handler);
});
logger.info("Mirror Syslog TCP Source starting...");
if(host==null) {
nettyChannel= serverBootstrap.bind(newInetSocketAddress(port));
}else{
nettyChannel= serverBootstrap.bind(newInetSocketAddress(host,port));
}
super.start();
}
@Override
public voidstop() {
logger.info("Mirror Syslog TCP Source stopping...");
logger.info("Metrics:{}",counterGroup);
if(nettyChannel!=null) {
nettyChannel.close();
try{
nettyChannel.getCloseFuture().await(60,TimeUnit.SECONDS);
}catch(InterruptedException e) {
logger.warn("netty server stop interrupted",e);
}finally{
nettyChannel=null;
}
}
super.stop();
}
@Override
public voidconfigure(Context context) {
Configurables.ensureRequiredNonNull(context,SyslogSourceConfigurationConstants.CONFIG_PORT);
port= context.getInteger(SyslogSourceConfigurationConstants.CONFIG_PORT);
host= context.getString(SyslogSourceConfigurationConstants.CONFIG_HOST);
/**
* 默认每条日志记录的大小，默认2500字节。由于序列化的过程中会占用大量的空间，此处将默认大小设置为10*DEFAULT_SIZE
*/
eventSize= context.getInteger("eventSize",SyslogUtils.DEFAULT_SIZE*10);
formaterProp= context.getSubProperties(SyslogSourceConfigurationConstants.CONFIG_FORMAT_PREFIX);
keepFields= SyslogUtils.chooseFieldsToKeep(
context.getString(
SyslogSourceConfigurationConstants.CONFIG_KEEP_FIELDS,
SyslogSourceConfigurationConstants.DEFAULT_KEEP_FIELDS));
}
}