How to fanout an AWS kinesis stream?

Question

I'd like to fanout/chain/replicate an Input AWS Kinesis stream To N new Kinesis streams, So that each record written to the input Kinesis will appear in each of the N streams.

Is there an AWS service or an open source solution?

I prefer not to write code to do that if there's a ready-made solution. AWS Kinesis firehose is a no solution because it can't output to kinesis. Perhaps a AWS Lambda solution if that won't be too expensive to run?

Answer 1

There are two ways you could accomplish fan-out of an Amazon Kinesis stream:

• Use Amazon Kinesis Analytics to copy records to additional streams
• Trigger an AWS Lambda function to copy records to another stream

Option 1: Using Amazon Kinesis Analytics to fan-out

You can use Amazon Kinesis Analytics to generate a new stream from an existing stream.

From the Amazon Kinesis Analytics documentation:

Amazon Kinesis Analytics applications continuously read and process streaming data in real-time. You write application code using SQL to process the incoming streaming data and produce output. Then, Amazon Kinesis Analytics writes the output to a configured destination.

Fan-out is mentioned in the Application Code section:

You can also write SQL queries that run independent of each other. For example, you can write two SQL statements that query the same in-application stream, but send output into different in-applications streams.

I managed to implement this as follows:

• Created three streams: input, output1, output2
• Created two Amazon Kinesis Analytics applications: copy1, copy2

The Amazon Kinesis Analytics SQL application looks like this:

CREATE OR REPLACE STREAM "DESTINATION_SQL_STREAM"
(log VARCHAR(16));

CREATE OR REPLACE PUMP "COPY_PUMP1" AS
  INSERT INTO "DESTINATION_SQL_STREAM"
    SELECT STREAM "log" FROM "SOURCE_SQL_STREAM_001";

This code creates a pump (think of it as a continual select statement) that selects from the input stream and outputs to the output1 stream. I created another identical application that outputs to the output2 stream.

To test, I sent data to the input stream:

#!/usr/bin/env python

import json, time
from boto import kinesis

kinesis = kinesis.connect_to_region("us-west-2")
i = 0

while True:
  data={}
  data['log'] =  'Record ' + str(i)
  i += 1
  print data
  kinesis.put_record("input", json.dumps(data), "key")
  time.sleep(2)

I let it run for a while, then displayed the output using this code:

from boto import kinesis

kinesis = kinesis.connect_to_region("us-west-2")
iterator = kinesis.get_shard_iterator('output1', 'shardId-000000000000', 'TRIM_HORIZON')['ShardIterator']
records = kinesis.get_records(iterator, 5)
print [r['Data'] for r in records['Records']]

The output was:

[u'{"LOG":"Record 0"}', u'{"LOG":"Record 1"}', u'{"LOG":"Record 2"}', u'{"LOG":"Record 3"}', u'{"LOG":"Record 4"}']

I ran it again for output2 and the identical output was shown.

Option 2: Using AWS Lambda

If you are fanning-out to many streams, a more efficient method might be to create an AWS Lambda function:

• Triggered by Amazon Kinesis stream records
• That writes records to multiple Amazon Kinesis 'output' streams

You could even have the Lambda function self-discover the output streams based on a naming convention (eg any stream named app-output-*).