Database Reference
In-Depth Information
Figure 14-3. Using a second agent tier to aggregate Flume events from the first tier
Tiers are constructed by using a special sink that sends events over the network, and a cor-
responding source that receives events. The Avro sink sends events over Avro RPC to an
Avro source running in another Flume agent. There is also a Thrift sink that does the same
thing using Thrift RPC, and is paired with a Thrift source.
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WARNING
Don't be confused by the naming: Avro sinks and sources do not provide the ability to write (or read)
Avro files. They are used only to distribute events between agent tiers, and to do so they use Avro RPC
to communicate (hence the name). If you need to write events to Avro files, use the HDFS sink, de-
scribed in
File Formats
.
Example 14-4
shows a two-tier Flume configuration. Two agents are defined in the file,
named
agent1
and
agent2
. An agent of type
agent1
runs in the first tier, and has a
