03_Flume多节点Failover实践

1、实践场景

模拟上游Flume Agent在发送event时的故障切换 （failover）

1）初始：上游Agent向active的下游节点Collector1传递event

2）Collector1故障： kill该进程的方式来模拟， event此时发送给Collector2，完成故障切换

3）Collector1恢复：重新运行该进程，经过最大惩罚时间后，event将恢复发送给Collector1

2、配置文件

Agent配置文件

# flume-failover-client
# agent name: a1
# source: exec with given command, monitor output of the command, each line will be generated as an event
# channel: memory
# sink: k1 k2, each set to avro type to link to next-level collector

#  define source,channel,sink name
a1.sources = r1
a1.channels = c1
a1.sinks = k1 k2

#  define source
a1.sources.r1.type = exec
a1.sources.r1.command = tail -f /root/flume_test/server.log

# 03 define sink,each connect to next-level collector via hostname and port
a1.sinks.k1.type = avro
a1.sinks.k1.hostname = slave1   # sink bind to remote host, RPC(上游Agent avro sink绑定到下游主机）
a1.sinks.k1.port = 4444

a1.sinks.k2.type = avro
a1.sinks.k2.hostname = slave2   # sink band to remote host, PRC（上游Agent avro sink绑定到下游主机）
a1.sinks.k2.port = 4444

# 04 define sinkgroups,only 1 sink will be selected as active based on priority and online status
a1.sinkgroups = g1
a1.sinkgroups.g1.sinks = k1 k2
a1.sinkgroups.g1.processor.type = failover

# k1 will be selected as active to send event if k1 is online, otherwise k2 is selected
a1.sinkgroups.g1.processor.priority.k1 = 10   # 基于优先级进行选择，优先级高的被选中active; 优先级相同则根据k1,k2出现的先后顺序进行选择
a1.sinkgroups.g1.processor.priority.k2 = 

# failover time,milliseconds
# if k1 is down and up again, k1 will be selected as active after  seconds
a1.sinkgroups.g1.processor.priority.maxpenality = 1000  # 回切时间

#  define channel
a1.channels.c1.type = memory
# number of events in memory queue
a1.channels.c1.capacity =
# number of events for  commit(commit events to memory queue)
a1.channels.c1.transactioncapacity = 

#  bind source,sink to channel
a1.sources.r1.channels = c1
a1.sinks.k1.channel = c1

a1.sinks.k2.channel = c1

Collector1配置文件

#  specify agent,source,sink,channel
a1.sources = r1
a1.sinks = k1
a1.channels = c1

# 02 avro source,connect to local port 4444
a1.sources.r1.type = avro        # 下游avro source绑定到本机，端口号要和上游Agent指定值保持一致
a1.sources.r1.bind = slave1
a1.sources.r1.port = 4444

#  logger sink
a1.sinks.k1.type = logger 

#  channel,memory
a1.channels.c1.type = memory
a1.channels.c1.capacity =
a1.channels.c1.transactionCapacity = 

#  bind source,sink to channel
a1.sources.r1.channels = c1
a1.sinks.k1.channel = c1

Collector2配置文件

#  specify agent,source,sink,channel
a1.sources = r1
a1.sinks = k1
a1.channels = c1

# 02 avro source,connect to local port 4444
a1.sources.r1.type = avro      # 下游avro source绑定到本机，端口号要和上游Agent指定值保持一致
a1.sources.r1.bind = slave2
a1.sources.r1.port = 4444

#  logger sink
a1.sinks.k1.type = logger 

#  channel,memory
a1.channels.c1.type = memory
a1.channels.c1.capacity =
a1.channels.c1.transactionCapacity = 

#  bind source,sink to channel
a1.sources.r1.channels = c1
a1.sinks.k1.channel = c1

3、启动Collector1,2 以及Agent

启动Collector1

# ./bin/flume-ng agent --conf conf --conf-file ./conf/flume-failover-server.properties --name a1 -Dflume.root.logger=INFO,console

解读：根据当前目录下的conf目录中的flume-failvoer-server.properties配置文件启动flume agent; agent名称为a1;

flume向终端打印INFO级别及以上的日志信息

启动Collector2

 # ./bin/flume-ng agent --conf conf --conf-file ./conf/flume-failover-server.properties --name a1 -Dflume.root.logger=INFO,console

 启动Agent

# ./bin/flume-ng agent --conf conf --conf-file ./conf/flume-failover-client.properties --name a1 -Dflume.root.logger=INFO,console

注意：

1）要先启动下游Collector，再去启动Agent;  否则Agent启动后就会进行下游有效站点的选择，此时Collector如果还没有启动，则会出现报错

2）3个Agent正常启动后， Agent会建立和所有下游站点的连接： 经历 open -> bound -> connected 三个阶段

4、故障模拟及恢复

1） 故障发生前： 首先向log文件，管道方式添加数据，查看event是否在Collector1的终端被打印

Collector1所在的Slave1节点收到并向终端打印event

2） 故障模拟： kill collector1进程

 3）再次尝试发送数据

Collector2所在的Slave2节点收到并向终端打印event

与此同时，Agent将一直尝试重新建立和Collector1的连接

4）重新启动Collector1进程，模拟故障恢复

# ./bin/flume-ng agent --conf conf --conf-file ./conf/flume-failover-server.properties --name a1 -Dflume.root.logger=INFO,console

5）向log中再次追加数据，查看event是否重新被发送给collector1, 并被打印到终端

此时Collecot1收到并打印事件 (回切时间在Agent的配置中设置为1秒）

 6) 考虑所有下游节点全部down掉，之后下游节点恢复的情况，数据最终给谁？

由于Flume有基于event的事务机制，当下游节点全部down掉时，Flume会将event保留在channel中

当下游节点重新恢复，Agent会再次进行active节点选择，然后将evnet再次发送

当下游节点收到event后，Agent才将event从channel中移除

如果是Collecotr2先恢复， 则event会发送给Collector2;  并且Collecot1之后并不会收到发给Collector2的数据，因此event此时已经从Agent的channel中被移除