Avro end to end in hdfs – part 2: Flume setup

This is a series of posts aiming at explaining how and why to set up compressed avro in hdfs. It will be divided in a few posts, more will be coming if relevant.

  1. Why avro?
  2. How to set up avro in flume (this post)
  3. How to use avro with hive
  4. Problems and solutions

Set up flume

Believe it or not, this is the easy part.

On the source, there is nothing specific to add, you can carry on as usual.

On the sink here is a sample with comments:

# Very important, *DO NOT* use CompressedStream. Avro itself will do the compression
# *MUST* be set to .avro for Hive to work
# Of course choose your own path
# The magic happens here:

Note the hdfs.path. “some_key” might be timestamp, for instance, which could create a new directory every hour. This will be used later in Hive.

Using this configuration will use the default Avro schema, which you can find defined in the flume source:

 "type": "record",
 "name": "Event",
 "fields": [{
   "name": "headers",
   "type": {
     "type": "map",
     "values": "string"
 }, {
   "name": "body",
   "type": "bytes"

If you want to use your own custom schema, you need to extend AbstractAvroEventSerializer. This is not very complex, and the default avro event serializer actually extends it already, hardcoding a schema. This is a good example to carry on. You would typically out the schema at an place reachable by the sink, being either hdfs itself or an url. The path could be hardcoded in your class if you have one schema only, or could be passed as a flume header.

If, as in the example, you are using snappy, first make sure that snappy is installed:

# RedHat world:
yum install snappy
# Debian world:
apt-get install libsnappy1

And that’s really it, there is nothing more to do to use the default schema.


3 thoughts on “Avro end to end in hdfs – part 2: Flume setup

  1. Pingback: Avro end to end in hdfs – part 1: why avro? | This DWH guy

  2. Pingback: Avro end to end in hdfs – part 3: Hive | This DWH guy

  3. Pingback: Avro end to end in hdfs – part 4: problems and solutions | This DWH guy

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s