学习笔记：分布式日志收集框架Flume

1. 业务现状分析
   • WebServer/ApplicationServer分散在各个机器上，想在大数据平台hadoop上进行统计分析，就需要先把日志收集到hadoop平台上。
   • 思考：如何解决我们的数据从其他的server上移动到Hadoop之上？
     • 脚本shell，用cp拷贝到hadoop集群上，再通过hadoop fs -put xxxx存储到hdfs上，但是这种方式会有如下问题：
       • 如何做监控？如果拷贝过程中某台机器断掉了怎么做到很好的监控？
       • 采用cp方式，需要设定一个复制的间隔时间，这样做时效性如何？
       • log一般存为txt文本文件，如果把文本格式的数据直接通过网络传输，对i/o的开销很大
       • 如何做负载均衡，压缩等等
2. Flume概述
   • Flume is a distributed, reliable, and available service for efficiently collecting（收集）, aggregating（聚合）, and moving（移动） large amounts of log data. It has a simple and flexible architecture based on streaming data flows. It is robust and fault tolerant with tunable reliability mechanisms and many failover and recovery mechanisms. It uses a simple extensible data model that allows for online analytic application.
   • Flume设计目标：可靠性，扩展性，管理性
   • 业界同类产品的对比
   1. • Flume:Cloudera/Apache  java
      • Scribe:Facebook  c/c++  不再维护
      • Chuka:Yahoo/Apache java 不再维护
      • kafka:
      • Fluentd:Ruby
      • Logstash:ELK
3. Flume架构及核心组件
   • 　
   • Source ：收集，常用的Source：Avro Source，Exce Source，Spooling，NetCat TCP Source，Kafka Source
   • Channel ： 聚集，常用的Channels：Memory Channels，File Channels，Kafka Channels
   • Sink ：输出，常用的Sink：HDFS Sink，Hive Sink，Logger Sink，Avro Sink，Hbase,Kafka
   • 设置multi-agent flow（可参看官网）
4. Flume环境搭建
   • 安装JDK
   • 安装Flume
5. Flume实战案例
   • 案例一的需求：从指定网络端口采集数据输出到控制台

     # example.conf: A single-node Flume configuration
     
     #使用Flume的关键就是写配置文件
     #配置Source
     #配置Channel
     #配置Sink
     #把以上三个组件串起来
     #a1:agent名称；r1:source名称；k1:sink名称；c1:channels的名称
     # Name the components on this agent
     a1.sources = r1
     a1.sinks = k1
     a1.channels = c1
     
     # Describe/configure the source
     a1.sources.r1.type = netcat
     a1.sources.r1.bind = localhost
     a1.sources.r1.port = 
     
     # Describe the sink
     a1.sinks.k1.type = logger
     
     # Use a channel which buffers events in memory
     a1.channels.c1.type = memory
     a1.channels.c1.capacity =
     a1.channels.c1.transactionCapacity = 
     
     # Bind the source and sink to the channel
     a1.sources.r1.channels = c1
     a1.sinks.k1.channel = c1

     启动agent：

     bin/flume-ng agent --name a1 -c $FLUME_HOME/conf  --conf-file xxx(刚刚定义的example.conf) -Dflume.root.logger=INFO,consol

   • 案例二的需求：监控一个文件实时采集新增的数据输出到控制台

     #agent选型：exec source + memory channel + logger sink
     #文件名：exec-memory-logger.conf
     
     a1.sources = r1
     a1.sinks = k1
     a1.channels = c1
     
     a1.sources.r1.type = exec
     a1.sources.r1.command= tail -F  /home/hadoop/data.log#要监控的文件
     
     a1.sinks.k1.type = logger
     
     a1.channels.c1.type = memory
     
     # Bind the source and sink to the channel
     a1.sources.r1.channels = c1
     a1.sinks.k1.channel = c1

     启动agent命令同上：

     bin/flume-ng agent --name a1 -c $FLUME_HOME/conf  --conf-file exec-memory-logger.conf

   • 案例三的需求：将A服务器上的日志实时采集到B服务器上

     #技术选型：
     #exec source + memory channel + avro sink
     #avro source + menory channel + logger sink
     
     #第一个conf文件内容如下：exec-memry-avro.conf
     exec-memory-avro.source = exec-source
     exec-memory-avro.sink = avro-sink
     exec-memory-avro.channels = memory-channel
     
     exec-memory-avro.sources.exec-source.type=exec
     exec-memory-avro.sources.exec-source.command=tail - F /home/hadoop/data.log
     
     exec-memory-avro.sinks.avro-sink.type=avro
     exec-memory-avro.sinks.avro-sink.hostname=hadoop000
     exec-memory-avro.sinks.avro-sink.port=
     
     exec-memory-avro.channels.memory-channel.type = memory
     
     exec-memory-avro.source.exec-memory.channels=memory-channel
     exex-memory-avro.sinks.avro-sinks.channel = memory-channel
     
     #第二个conf文件内容如下：avro-memory-logger.conf
     avro-memory-logger.source = avro-source
     avro-memory-logger.sink = logger-sink
     avro-memory-logger.channels = memory-channel
     
     avro-memory-logger.source.exec-source.type=avro
     avro-memory-logger.source.exec-source.bind=hadoop000
     avro-memory-logger.source.exec-source.port=
     
     avro-memory-logger.sinks.logger-sink.type=logger
     
     avro-memory-logger.channels.memory-channel.type = memory
     
     avro-memory-logger.source.avro-memory.channels=memory-channel
     avro-memory-logger.sinks.logger-sinks.channel = memory-channel

     启动两个对应的conf文件：

     bin/flume-ng agent --name avro-memory-logger  -c $FLUME_HOME/conf --conf-file avro-memory-logger.conf

     bin/flume-ng agent --name exec-memory-logger  -c $FLUME_HOME/conf --conf-file exec-memory-logger.conf

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