Flume Overview

Apache Flume is a highly available, distributed, and configurable tool/service that collects and aggregates large amounts of data such as logs and events from different sources. It is designed to collect data flows (e.g., log data) from various web servers and store them in centralized data storage system like HDFS and HBase.

Flume Architecture

A Flume event is defined as a unit of data flow. A Flume agent is a JVM process that contains the components required for completing a task. Among them, Source, Channel, and Sink are the core ones.

• Source
  It consumes an event passed to it by an external source (e.g., web servers or other sources) and save it to one or more channels.
• Channel
  Located between a source and a sink, a channel is used to cache incoming events. After the sink successfully sends the events to the channel at the next hop or the final destination, the events are removed from the channel.
• Sink
  A sink is responsible for transferring the events to the next hop or final destination and removing them from the channel upon transfer completion.

Instructions

Preparations

• Create an EMR cluster. When creating the EMR cluster, you need to select the Flume component on the software configuration page.
• Install Flume in the /usr/local/service/flume path on the core and task nodes (CVM instances) of the EMR cluster. The installation path for master nodes is /usr/local/service/apps/.

Configuring Flume

Go to the /usr/local/service/flume folder and create a file named example.conf.

# example.conf: A single-node Flume configuration

# 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 = 44444

# 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 = 1000
a1.channels.c1.transactionCapacity = 100

# Bind the source and sink to the channel
a1.sources.r1.channels = c1
a1.sinks.k1.channel = c1

Starting Flume

bin/flume-ng agent --conf conf --conf-file example.conf --name a1 -Dflume.root.logger=INFO,console

Configuring a test sample

After successful configuration, you will see the Flume agent started previously printing to the terminal.

telnet localhost 44444
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
Hello world! <ENTER>
OK