Flume HDFS Sink generates lots of tiny files on HDFS

Question

I have a toy setup sending log4j messages to hdfs using flume. I'm not able to configure the hdfs sink to avoid many small files. I thought I could configure the hdfs sink to create a new file every-time the file size reaches 10mb, but it is still creating files around 1.5KB.

Here is my current flume config:

a1.sources=o1
a1.sinks=i1
a1.channels=c1

#source configuration
a1.sources.o1.type=avro
a1.sources.o1.bind=0.0.0.0
a1.sources.o1.port=41414

#sink config
a1.sinks.i1.type=hdfs
a1.sinks.i1.hdfs.path=hdfs://localhost:8020/user/myName/flume/events
#never roll-based on time
a1.sinks.i1.hdfs.rollInterval=0
#10MB=10485760
a1.sinks.il.hdfs.rollSize=10485760
#never roll base on number of events
a1.sinks.il.hdfs.rollCount=0

#channle config
a1.channels.c1.type=memory
a1.channels.c1.capacity=1000
a1.channels.c1.transactionCapacity=100

a1.sources.o1.channels=c1
a1.sinks.i1.channel=c1

Answer 1

It is your typo in conf.

#sink config
a1.sinks.i1.type=hdfs
a1.sinks.i1.hdfs.path=hdfs://localhost:8020/user/myName/flume/events
#never roll-based on time
a1.sinks.i1.hdfs.rollInterval=0
#10MB=10485760
a1.sinks.il.hdfs.rollSize=10485760
#never roll base on number of events
a1.sinks.il.hdfs.rollCount=0

where in the line 'rollSize' and 'rollCount', you put il as i1. Please try to use DEBUG, then you will find like:

[SinkRunner-PollingRunner-DefaultSinkProcessor] (org.apache.flume.sink.hdfs.BucketWriter.shouldRotate:465)  - rolling: rollSize: 1024, bytes: 1024

Due to il, default value of rollSize 1024 is being used .

Answer 2

HDFS Sink has a property hdfs.batchSize (default 100) which describes "number of events written to file before it is flushed to HDFS". I think that's your problem here.

Consider also checking all other properties: HDFS Sink .

Answer 3

This can possibly happen because of the memory channel and its capacity. I guess its dumping data to HDFS as soon as its capacity becomes full. Did you try using file channel instead of memory ?