flume默认提供以下Selectors：

Replicating Channel Selector

a1.sources = r1

a1.channels = c1 c2 c3
a1.sources.r1.selector.type = replicating
a1.sources.r1.channels = c1 c2 c3
a1.sources.r1.selector.optional = c3


Multiplexing Channel Selector
a1.sources = r1
a1.channels = c1 c2 c3 c4
a1.sources.r1.selector.type = multiplexing
a1.sources.r1.selector.header = state
a1.sources.r1.selector.mapping.CZ = c1
a1.sources.r1.selector.mapping.US = c2 c3
a1.sources.r1.selector.default = c4


Custom Channel Selector
自定义selector,需要实现ChannelSelector接口
a1.sources = r1
a1.channels = c1
a1.sources.r1.selector.type = org.example.MyChannelSelector